Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

September 18

Water and the Human Body

If there was a video camera which could only film the movement of water inside people's bodies what would the footage look like of people going about their daily lives? Would it look like fluid sloshing all over the place or would it be mostly static except for arteries and veins? TheFutureAwaits (talk) 08:20, 18 September 2009 (UTC)

Given that most of the water is contained in individual cells and the bloodstream, the only "sloshing" would be water that has just been consumed or has gathered in the bladder. In the bloodstream, it would be "flowing" rather than "sloshing". Baseball Bugs ^{What's up, Doc?} carrots 14:04, 18 September 2009 (UTC)

Sloshing is generally a Bad Thing. To get 'sloshing', you need to have free liquid and open air in the save cavity within the body. Usually this doesn't happen (or happens rarely and is quickly remedied). You can get a mixture of gas and liquid in the upper gastrointestinal tract by swallowing air with your food or drink, or by consumption of carbonated beverages; either way, this gas is released through belching. Gas further down in the system (generated by the action of digestion) usually comes out the other end.

You can accumulate air/fluid mixtures in the digestive system if there is some sort of obstruction or bowel perforation, and in the lungs due to inflammation or inhalation of liquids. [1] shows a person with a bowel perforation. The description is on this page. The pelvic bone is visible at the bottom of the frame, the lower edge of the lungs is at the top, and the spine runs up the center. Arrowheads indicate multiple air-liquid interfaces in the bowel. TenOfAllTrades(talk) 14:31, 18 September 2009 (UTC)

Okay....um why don't we steer away from the bowels. The water in people's cells, is it moved around when someone is walking, jumping or falling? TheFutureAwaits (talk) 14:43, 18 September 2009 (UTC)

There should not be any air bubbles in cells, and the interior of cells is partly water and partly other stuff, as I recall from biology class, so you might get smooth motion of the cells themselves, in response to body movements, but no "sloshing" as such. In fact, the same presumably should hold true of the bladder and stomach - there should be no air at all in the bladder, and not much in the stomach - so you would see "rolling" as a result of change of position of the containing organ due to body movement - but no real "sloshing" in the bladder and not much in the stomach. And the rest of the body, I think, would be smoothe motion. Baseball Bugs ^{What's up, Doc?} carrots 14:46, 18 September 2009 (UTC)

In Cells tehmselves the Cytoskeleton keeps things from moving around. Or even keeps them moving. The liquid just flows around them. Even though cells are somewhat flexibile, human cells (except for a few kinds) are pretty rigid things. --212.6.123.204 (talk) 16:47, 18 September 2009 (UTC)

There are other places where fluids move around besides the circulatory system, though. Besides the contents of the digestive tract there's also bile, lymph, tears, urine, semen (for some of us), and probably others I've forgotten. However, in all cases these things are produced in small quantities and normally move slowly (with obvious exceptions), so they'd hardly be noticeable in the original poster's scenario. --Anonymous, 18:43 UTC, September 18, 2009.

Don't forget cerebrospinal fluid. As you say, though, all of those are generally small volumes, moving quite slowly relative to blood. (For CSF, you make about 500 mL (two cups) per day, and the brain and CNS hold about 150 mL (a little over half a cup). It's a modest trickle.) TenOfAllTrades(talk) 22:32, 18 September 2009 (UTC)

Technically there would be constant movement within intra and extra-cellular fluids as there is constant movement of micro-particles in the body. Be it minerals/lipids/protein you name it. Water goes where particles go, specially saline. It would be a bit complicated to explain here. But you should read on hypertonic and hypotonic solutions within the human body and the fluid shift it causes and that might give you a better idea on the subject. The marieb or Tortora physiology manuals are quite thorough on the subject.

Energy eigenfunctions of a free particle

If someone could help me with this it'd be much appreciated - the more help I can get the better.

"Find the energy eigenfunctions ψ_E(x) for a free particle of mass m subject to the periodic boundary condition

ψ_E(x) = ψ_E(x + L).

What are the allowed values of E? What are the degeneracies of the energy levels? Comment on the limit L → ∞."

For the eigenfunctions, I think they're the f satisfying -(h²/2m)$\nabla ^{2}$f(x) = E * f(x) - working in 1 dimension.

This means our functions have to be of the form Asin(kx)+Bcos(kx) with k^2=2mE/(h^2), and the periodicity implies kL=2npi, right? In which case we can find the values of E in terms of n,L etc.

I'm not really sure if I'm at all right on this, or what the 'allowed values' are, and I'm clueless about the degeneracies too.

If anyone could walk me through some of it i'd really appreciate it!

Thanks :) Spamalert101 (talk) 12:54, 18 September 2009 (UTC)

If the boundary condition is periodic then the function (solution) must be periodic too, as you guess. But shouldn't you consider higher harmonics as part of the function. eg Function = Sum over n ( A_nsin(knx)+B_ncos(knx) ) maybe that's implicit and you already have

Your equation for k looks right.

Don't you also need to state the nature of the boundary to get a solution eg the potential energy that relates to the boundary

(h2/2m)$\nabla ^{2}$f(x) = (E-boundary energy function) * f(x) maybe you are expected to ignore this and just assume an approximate solution?

With that you can then attempt to get a full solution. But as far as you have got what you have written seems basically not wrong.83.100.251.196 (talk) 13:08, 18 September 2009 (UTC)

You've already got allowed values - these are values - from kL=2npi gives k=2npi/L so you have a range of solutions to try with n=1,2,3,4 etc - these will be your allowed values - solving for E_function for each n gives the allowed values of E (these are called the eigenvalues I think)83.100.251.196 (talk) 13:16, 18 September 2009 (UTC)

You're most of the way there. n has to be an integer, and it follows (using the equations you wrote above) that E can only have certain discrete values for a given L. The degeneracy comes from the fact that different values of A and B with the same k give different solutions with the same energy. (Only the ratio of A and B matters, since the overall scaling factor on the wave function is irrelevant.) -- BenRG (talk) 13:16, 18 September 2009 (UTC)

Does it tend to a continuous function as L goes to infinity, or something else? Spamalert101 (talk) 14:16, 18 September 2009 (UTC)

Assuming that the boundaries are potential barriers, and do not dissapear - I think part of the solution would be to make the assumption that the wavefunction goes to zero at +/- infinity. Maybe I'm missing something, but I think a little more info about the boundaries is needed...83.100.251.196 (talk) 14:28, 18 September 2009 (UTC)

83.100.251.196, you are missing the fact that there are no boundaries (Or rather the boundary condition is just periodicity and nothing else). The problem is perfectly fine the way it is stated whithout any other conditions at +- infinity os anywhere else. Dauto (talk) 15:21, 18 September 2009 (UTC)

Incinel, inkinel, ...?

I was watching an episode of World's Toughest Fixes where they were working on an aircraft. The vertical fin was attached with bolts made of a metal that sounds like inkinel ("a metal harder than steel, harder than titanium"). I tried a couple of spellings but found little on google. What is that metal? Do we have an article on it? 62.78.198.48 (talk) 18:01, 18 September 2009 (UTC)

Inconel ? 83.100.251.196 (talk) 18:16, 18 September 2009 (UTC)

Inconel is used for high temp applications. I would question why the bolts on the vertical stabilizer of an airplane would need that (unless perhaps it was supersonic), but it sounds like 83.100 might have it. Googlemeister (talk) 18:43, 18 September 2009 (UTC)

It seems like inconel has similar properties to Kovar (which is a brand-name, I believe, for particular nickel-iron-cobalt alloys). Kovar is a useful alloy because its coefficient of thermal expansion matches that of glass. It's possible that Inconel's thermal expansion matches that of the carbon-fiber, fiber-glass, or other synthetic or composite material that the vertical stabilizer is made of. It would be extremely undesirable if the metal tail portion thermally expands at a different rate than the vertical stabilizer - potentially leading to cracking, fissuring, and other disaster scenarios for an airframe. I would guess that Inconel is used for this reason, rather than its high melting point. One of the most complicated mechanical challenges in a modern airframe is making all the exotic materials (carbon fiber, phenolic paper, fiber-wrap, exotic metal alloys, plastics and other synthetics) play nice together. Remember that hardness used in lay-person-speech may not be the correct usage - they may actually be referring to a wide variety of material properties - toughness, ductility, hardness, impact strength, compressive strength, etc. Nimur (talk) 21:27, 18 September 2009 (UTC)

This search seems to confirm it http://www.google.co.uk/search?hl=en&q=inconel+boeing+767&meta=&aq=f&oq= it looks like they had problems with the standard stainless steel bolts (as well as some other parts), so went for the 'best alloy' they could get for bolts - it's probably not a specific design requirement for inconel - they just will have wanted an alloy that would be trouble free.83.100.251.196 (talk) 21:53, 18 September 2009 (UTC)

[2] ".. replacement of all H-11 steel alloy barrel nuts and bolts with Inconel nuts and bolts, which ends the repetitive inspections. " 83.100.251.196 (talk) 21:56, 18 September 2009 (UTC)

Inconel is used for three reasons: 1) it's very strong, 2) it retains its strength at high temperatures better than other metals, and 3) it's resistant to chemical attack. --Carnildo (talk) 01:05, 23 September 2009 (UTC)

remove reproductive organs

I'm writing a book about a woman who hates her reproductive organs and wants them gone. She absolutely hates the idea of pregnancy, sex with men or any implication that her body could produce a child if she was raped or something. What scientific things could she do to either remove or destroy her reproductive organs without causing damage to herself? What medical procedures would be most efficient and safe for her to undergo to achieve this? Any and all suggestions are welcome, this book is a wacky tale so weird and wonderful ideas are welcome, as long as they actually work in real life. Thanks.

For starters, you want to read hysterectomy. --Anonymous, 18:46 UTC, September 18, 2009.

Oh, you already posted about that on the Miscellaneous Desk. Okay, it's not the same question, but... --Anon, 18:52 UTC, Sep. 18.

Yes, similar question although I thought this aspect of the question would be better suited to the science desk

Also look at Oophorectomy - remove the ovaries and there are no eggs, just like spaying female cats and dogs.  Ronhjones  ^(Talk) 20:40, 18 September 2009 (UTC)

You can sterilise a women without removing the ovaries - you just need to cut/partially remove the fallopian tubes. --Tango (talk) 01:30, 19 September 2009 (UTC)

True, but if she hates her reproductive system so much, then ovary removal will also stop her periods - which if left might remind her about her sexuality.  Ronhjones  ^(Talk) 18:49, 19 September 2009 (UTC)

Phalloplasty? Presumably without the other aspects of gender reassignment. Not sure about efficient, but it's certainly wacky. 84.12.138.49 (talk) 22:09, 18 September 2009 (UTC)

Tying the tubes is the way to go. The female equivalent of vasectomy. You don't want to mess around with innards too much - the more you do, the more risk of complications. Tie the tubes and leave everything else intact. Especially leave the ovaries, as the source of female hormones and such - unless you want your protagonist to develop a mustache. Baseball Bugs ^{What's up, Doc?} carrots 02:15, 19 September 2009 (UTC)

This seems like a good option. Is there a specific name for female phalloplasty or cutting the fallopian tubes which I could look up? Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)

Yes, it's called Tubal ligation. Baseball Bugs ^{What's up, Doc?} carrots 09:22, 19 September 2009 (UTC)

People's feelings change over time - it would be a serious mistake to do something irreversible even if it seemed like a good idea today. SteveBaker (talk) 02:21, 19 September 2009 (UTC)

Since the book is supposedly a fantasy, maybe instead of having them tied she could have a valve installed in each tube, which could be turned open or closed under certain circumstances. Baseball Bugs ^{What's up, Doc?} carrots 02:32, 19 September 2009 (UTC)

No, she wants any possibility of becoming pregnant gone for good. This will NEVER change. Tempoaryrefdeskaccount (talk) 08:36, 19 September 2009 (UTC)

Then tying the tubes is the best bet, as it's the least invasive and traumatic to the body and is fully effective in preventing pregnancy. Baseball Bugs ^{What's up, Doc?} carrots 09:19, 19 September 2009 (UTC)

Thanks everyone! I'm going to read up on this, if I have any more questions I hope it will be ok to ask again.

1,2 diketones and ascorbic acid

I know 1,3-diketones rapidly convert into their enol forms because of hydrogen bond stabilisation. But what about ascorbic acid? Why is it predominantly in enol form? Here, the inductive effect seems more important than any hydrogen bonding effect (you'd have to form a four-membered ring for the alcohol proton to hydrogen bond with the ketone.) Is it carbonyl-carbonyl repulsion and also the fact that the alkene bond stabilises the carbons next to the alcohol groups? John Riemann Soong (talk) 20:20, 18 September 2009 (UTC)

very short answer - enol form includes a conjugated pi system: an enone - which gains additional stabilisation from interaction of the C=C and C=O pi systems. (also see diketone)

1,3 diketones are predominately in the enol form for this reason eg 1,3 dioxocyclohexane (cyclohexane-1,3-dione) has increased acidicity too, despite being unable to form the hydrogen bond. For unconstrained 1,3 diones the potential for hydrogen bonding (or coordination to a metal) is 'icing on the cake'.83.100.251.196 (talk) 23:45, 18 September 2009 (UTC)

Why is diacetyl found predominantly as a diketone though, and not in enone form? Is it because the terminal alkene is destabilised? (Wow, hyperconjugation gives a large enough stabilisation to determine whether something is found in enone form or not?) John Riemann Soong (talk) 15:23, 19 September 2009 (UTC)

Um, anyone? John Riemann Soong (talk) 01:29, 22 September 2009 (UTC)

Natural walking speed?

Hi. I know that I swing my arms while walking, kind of like a pendulum. The swinging of my arms is coordinated, more or less, with the speed of my gait. (The right arm goes forward as the left leg steps forward.) I also know that a pendulum has, at least at a decent first approximation, a natural period that depends on the pendulum's length. Therefore, since my arms are of fixed length, they must have a natural period. Therefore, I have a natural walking speed determined by the lengths of my arms.

Does that make any sense? If so, do people tend to walk at this pace, or not? Would it be more efficient if we did? -GTBacchus^(talk) 23:38, 18 September 2009 (UTC)

yes it makes sense - but I don't think that the arms are free oscillators - specifically consider the rotating motion of the hips (and to a lesser extent torso) as you walk (eg think about those 'speed walkers' at the olympics) - so the motion of the arms, can serve also to provide a small amount of additional thrust or drive to the walking motion. I'm sure a human locomotion expert will be along soon>.83.100.251.196 (talk) 23:50, 18 September 2009 (UTC)

Clarify - it's not clear to me whether the arm motions helps thrust, or serves to reduce impulse or control balance when walking.. It does seem that the movement of the arms is related to walking motion and is muscular in nature [3], nor is it clear whether this reflex muscle motion of the arms is helpful, or an evolutionary throwback to quadrupeds , or a safety mechanism, or a bit of all. [4]83.100.251.196 (talk) 00:37, 19 September 2009 (UTC)

This seems convincing to me:

During rhythmic movement, arm activity contributes to the neural excitation of leg muscles. These observations are consistent with the emergence of human bipedalism and nonhuman primate arboreal quadrupedal walking.[5]

This seems to confirm that swinging arms is beneficial to reducing impulsive forces:

Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it. Walking with opposite-to-normal arm phasing required minimal shoulder effort but magnified the ground reaction moment, causing metabolic rate to increase by 26 per cent. Passive dynamics appear to make arm swinging easy, while indirect benefits from reduced vertical moments make it worthwhile overall.[6]

Also from the same place "The shoulder muscles contribute to active swinging (Fernandez-Ballesteros et al. 1965)" see link above.83.100.251.196 (talk) 00:45, 19 September 2009 (UTC)

After all that sigh see [7]

..A vast majority of people exhibited an actual angular velocity exceeding the expected theoretical angular velocity calculated for a virtual pendulum of similar mass and length characteristics..

This suggests that people swing their arms faster than that expected from a pendulum, but doesn't answer if it would be more efficient to walk slower.83.100.251.196 (talk) 00:50, 19 September 2009 (UTC)

You might find the graph: figure 8.19 page 212 "Muscles, reflexes, and locomotion" by Thomas A. McMahon [8] helpful - note that at below 5mph (a good walking speed) that energy use is not linear with speed (ie not E=k x Speed ) - but that the energy use remains almost constant for motion between 1 and 5 mph - though it does decrease a little at lower speeds - the obvious conclusion to this is that it is not more efficient to walk slower than a standard walking pace (assuming a power=force x velocity law).83.100.251.196 (talk) 00:58, 19 September 2009 (UTC)

Try walking while holding your arms stiff at your sides, and you'll see the value in arm motion. It's not like a pendulum, it's fully-body coordination. Baseball Bugs ^{What's up, Doc?} carrots 11:54, 19 September 2009 (UTC)

Sure, I think that's clear enough, but I don't see why that full body coordination can't be reinforced by (or alternatively have to work against) something inherent about the swinging arm. I don't think the value in arm motion has been brought into question, just whether or not there might be a most natural period for it. If arm motion weren't an important part of walking, the question would be meaningless. -GTBacchus^(talk) 01:33, 22 September 2009 (UTC)

September 19

Alcohol by volume myths

In college a friend told me that the difference between 3.2% ABV beer and 4.5% (or whatever other beer is) was very small and only amounted to a difference of a beer per case. After doing the math though, this seems clearly untrue (it should take 2 three-percent beers to equal one six-percent). First, is my math reasoning correct and if I am, what is the origin of this myth? I've heard it from lots of people but the math seems easy (double the percent, double the amount). I need help knowing where people are making the mistake.

Well, let's see. there are 24 beers in a case and there are 12oz in a beer, then that is 288oz of liquid per case. For a 3.2% alcohol beer, that is 9.2 oz of alcohol per case and 0.38oz of alcohol per beer. So the "extra beer" in this exact case would be in increments of 0.38oz of pure ethanol...follow me? Let's look at the 4.5% case, it has 13oz of alcohol per case. This is a difference of 3.8oz!! In terms of "extra beers" as we defined earlier, that is 10 more beers! Looks like the difference is bigger than even I thought before I walked myself thought it.Mrdeath5493 (talk) 03:10, 19 September 2009 (UTC)

Now after doing some more math I see that if you want to find a rough one "extra beer" beer increment then multiply the ABV of any beer by 0.04 (4%) and that represents the 1 beer "step." So for the previous example if I multiply 3.2% by 0.04 I get 0.128ABV...this means that every 0.128% ABV difference between my reference beer and a different one represents an "extra beer." So, looking at the previous example I can just say 4.5-3.2 = 1.3% abv difference. 1.3/0.128 = ~10 extra beers. Cheers!Mrdeath5493 (talk) 03:20, 19 September 2009 (UTC)

As far as I can tell, you're absolutely correct and I don't know why people would say it's 1 beer worth ((4.5/3.2)*24 = 33.75 beers, so about 10 extra per case of 24). There are other things to take into account besides just the amount of alcohol when considering how drunk someone will get, for example you'll get more drunk on an empty stomach. However that seems to work in the favor of the higher alcohol beer, since you'll have less non-alcohol stuff in you for the same amount of alcohol. Maybe it has to do with perception? How drunk people act might be related to how drunk they think they should be, so if they've had more beers they might feel more drunk even if they've had less total alcohol? Rckrone (talk) 03:44, 19 September 2009 (UTC)

Thank you for the responses. I agree, I don't understand how people believed it was less. Thank for confirming that my math was right. Part of my question is how others could have come to the opposite conclusion. I wonder now if it was due to someone using addition and not multiplication on the numbers. Although even after doing those numbers it doesn't make sense. Does anyone else have any info on the myth (thank you for confirming those numbers are right).

Possibly due to someone noting the shrinkage effect on dilution - take 50ml pure ethanol and 50ml pure water - you won't get 50% ABV - as the mix will be around 97ml total (IIRC), so the strength is 50/97*100 = 51.5%. But for low figures, any effect is negligible.  Ronhjones  ^(Talk) 18:45, 19 September 2009 (UTC)

Alkene Nomenclature

Hello. Is it internationally acceptable to name 1-alkenes larger than propene with one carbon double bond by simply their parent chain? For example, could 1-butene be simply called butene since there are no other isomers? Thanks in advance. --Mayfare (talk) 02:27, 19 September 2009 (UTC)

There's also 2-butene (with cis and trans isomers) and isobutene. You should stick with calling 1-butene by its proper name, and not just "butene" -- the latter could be any of 4 different things. 98.234.126.251 (talk) 02:59, 19 September 2009 (UTC)

There's also cyclobutane and methylcyclopropane which are isomers of butene (though, not themselves alkenes). And to confirm the above response, the name "butene" is ambiguous, because it does not indicate where the double bond occurs. You would need to specify 1-butene or 2-butene. For shorter chains (propene, ethene), there is exactly 1 version of the molecule, so it does not have to be numbered, because "propene" and "ethene" can ONLY be one structure. --Jayron32 05:55, 19 September 2009 (UTC)

Just a small addition, the IUPAC name is actually but-1-ene. Rkr1991 ^{(Wanna chat?)} 07:47, 19 September 2009 (UTC)

No it's not. eg shell (company) does this http://www.shell.com/home/content/chemicals/products_services/our_products/lower_olefins/1_butene/index_1_butene.html 83.100.251.196 (talk) 11:06, 19 September 2009 (UTC)

Lots of companies (and people, etc) don't use the current standard naming conventions...as long as the name is unambiguous enough for the speaker to communicate to the desired audience, it's not important to be formally "correct". I get lots of ads for "alpha olefins" even though they are properly called "alkenes" and positions should be specified with numbers:) IUPAC makes an official ruling, and only people who care about being formally correct bother to listen:) Interestingly, the infix-numbering is the one used in our article about IUPAC scheme for alkenes, but I think the IUPAC Blue Book uses prefix-notation for simple cases. DMacks (talk) 20:51, 19 September 2009 (UTC)

It's work noting that for industrial chemical processes the distinction bewteen 1 and 2 butene is very improtant - since they undergo different chemical reactions giving different products.83.100.251.196 (talk) 12:30, 19 September 2009 (UTC)

Just ignore these ugly IUPAC names. Say ethylene and propylene and butylene like God intended. --Trovatore (talk) 20:32, 19 September 2009 (UTC)

But which butylene? There's four of'em, y'know, and they're all different... 98.234.126.251 (talk) 04:56, 21 September 2009 (UTC)

Sure, and they all have names. Don't see the problem. --Trovatore (talk) 05:21, 21 September 2009 (UTC)

What I mean is, you can't just say "butylene" if you're talking about a particular isomer -- you have to specify "1-butylene" or "2-butylene" or "isobutylene" or something like that (and for 2-butylene you also gotta specify cis or trans unless it's a mixture of both as it often is). 98.234.126.251 (talk) 06:34, 21 September 2009 (UTC)

Does a knife wound to the stomach cause immediate death?

I've just watched the high-quality film Faster Pussycat! Kill! Kill! on TCM. In the course of almost every member of the cast getting murdered, the cute girl with the Italian accent gets stabbed three times in the abdomen and dies immediately.

Would this happen in real life? Assuming a major abdominal artery was severed, how long would it take to bleed out sufficient to lose consciousness? Alternatively, how near the ribcage would the knifeblow need to be to hit the solar plexus and would that produce immediate death? (This is not a homework question :) Franamax (talk) 07:40, 19 September 2009 (UTC)

Depends on where you stabbed and how big the knife was. It's very possible it could happen immediately, for example bullets cause almost instant death if they hit certain areas of the body and they are about as damaging as a knife.--Patton123 (talk) 09:04, 19 September 2009 (UTC)

It was in the mid-lower abdomen area, with an approx. 19mm X 150mm knife, sharp on one side. No bullets, so no sonic shock, just stabbing. Straight thrusts. Slender actress, so the penetration would have been 50-75% of the body width. Now that I think of it, maybe she just fainted from pain, and bled out later. Franamax (talk) 09:50, 19 September 2009 (UTC)

That's dramatic license. Keep in mind that gunshots and stabbings are often presented differently than in real life. Unless a bullet or knife hits you square in the heart, immediate death (or very fast death) from such a wound (as with the "rumble" in West Side Story) seems unlikely. Typically stab and gunshot victims die of loss of blood, which takes a little while. Lee Oswald was shot through the abdomen, the bullet hitting several vital organs, and fell to the ground moaning and groaning, taking a minute or so to pass out, and dying later. John Lennon was hit in a major artery, and had time to cry, "I'm shot!" before passing out. Lincoln and RFK were shot in the back of the head and it took a number of hours before they succumbed. Baseball Bugs ^{What's up, Doc?} carrots 09:17, 19 September 2009 (UTC)

Well, B-dramatic license anyway. ;) How did Oswald get shot through several vital organs? Ruby shot him straight-on, so I would have thought only one would have been pierced! That seems to be the closest to my OQ, about abdomen wounds, but even there you have bullet trauma (supersonic shock). I'm talking straight knife-thrust here. Franamax (talk) 09:54, 19 September 2009 (UTC)

I think he was hit in the spleen, among other things. As I understand it, he wasn't actually hit straight-on, but maybe it would be useful to study the videos. I haven't seen them for awhile. Maybe I need to watch some snuff films to brighten an otherwise dull afternoon. Baseball Bugs ^{What's up, Doc?} carrots 10:28, 19 September 2009 (UTC)

In this photo, at least,[9] it appears Oswald was hit from an angle. Baseball Bugs ^{What's up, Doc?} carrots 10:31, 19 September 2009 (UTC)

That altered photo is actually a joke. I can supply the punch line, if you're interested. This pair of photos [10] suggests he was hit at a significant angle. Baseball Bugs ^{What's up, Doc?} carrots 10:33, 19 September 2009 (UTC)

Well d'uhh! Of course I'll need closure on the punchline. :) Given the musical theme, is it "don't you want me baby?" And yes, Ruby did come from the side and Oswald turned away, which would expose a significant cross-section of organs in the gut. At least that's what every one of the faked photos shows. Can't remember where I saw the real one now. ;) Franamax (talk) 11:17, 19 September 2009 (UTC)

The second set of photos aren't fakes, they're widely circulated. The punch line I've seen to that first (altered and morbidly funny) photo is, "Thank you, Dallas! Good night!" Baseball Bugs ^{What's up, Doc?} carrots 11:29, 19 September 2009 (UTC)

Here's a youtube with a melodramatically-narrated newsreel of the shooting. [11] Notice they freeze-frame it at the moment the famous photo was taken, i.e. when its flashbulb went off and illuminated the moment. One subtlety is that Ruby (real name "Rubinstein", as the narrator points out) fired with his middle finger, as he was missing most of his index finger - subliminally "giving the finger" to Oswald, in deadly fashion. Baseball Bugs ^{What's up, Doc?} carrots 11:37, 19 September 2009 (UTC)

FYI, it took Oswald nearly two hours to die, despite his severe wounds. Baseball Bugs ^{What's up, Doc?} carrots 11:47, 19 September 2009 (UTC)

A bullet wound would knock you unconscious pretty much instantly from shock or whatever, and you'd die very quickly after that. Also bullets do a tremendous amount of damage in a radius much, much larger than the bullet itself. Knives aren't so damaging though, but they could ill you fairly fast (Certainly a powerful stab in the lower abdomen woould kill you within a few seconds, hence why the Romans were taught to "punch" that location with their swords).92.251.186.199 (talk) 09:31, 19 September 2009 (UTC)

Do you have a ref where I could read up on lower abdomen wounds? I could see a sword-stab to the solar plexus, but down farther in the gut it just seems like a fairly slow and painful death would result. What is down there that would result in death in a few seconds? Franamax (talk) 09:56, 19 September 2009 (UTC)

I can't think of anything either but it's what I've read about hte Romans they hit the lower abdomen and it apparently resulted in a swift death.92.251.159.145 (talk) 10:07, 19 September 2009 (UTC)

I guess the issue is what is meant by "immediately". Even if you get your head lopped off, the organs are going to be alive for a few seconds until they run out of oxygen. I was thinking of the scene in West Side Story where one gang member stabs another in the belly with a switchblade (which is not much larger than a pocket knife) and he immediately falls, apparently dead. Dramatic license. Baseball Bugs ^{What's up, Doc?} carrots 09:44, 19 September 2009 (UTC)

With respect Franamax I think you need to brush up on your anatomy a bit. In the lower abdomen there are at least two major arteries that when severed or punctured would lead to pretty rapid internal bleeding and subsequent death. As for Lee Harvey Oswald being shot 'straight on', if you look at realistic abdominal anatomy you will see that several of the organs overlap when viewed front to back (or vice versa!) Talking about 'belly', 'abdomen', 'stomach' or 'thorax' is not very helpful, one needs to be more precise about position and angle. IMHO a quick death would occur from a direct heart stabbing which could be achieved from several directions and angles, but it would mean a front entry either through the hypochondriacal area or intercostally. Equally, using a badly directed fictional example like West Side Story is not really helpful either. Who knows how the director guessed or obtained information about the realism of the stabbing. 86.4.186.107 (talk) 10:11, 19 September 2009 (UTC)

(multi e/c's) I'm talking of course about the movie "fall-to-the-ground-and-never-move-again" thing, but more generally immediate incapacitation (within 5 seconds) from a stab wound with a slender knife to the stomach. And I don't think they ever actually signed the license to rip off West Side Story from Shakespeare anyway. ;) But yes, I was really asking about stab wounds in the stomach, and you would always want to bring a gun to a knife-fight. Incidentally, from what I'm aware, when you get your head lopped off, your head will also stay alive for a few seconds - so when you got guillotined, there would be enough time for you to be conscious of being held up before the crowd as just a head.

I think I've found my answer anyway - fainting due to severe pain, with subsequent henorrhage lowering blood pressure nd inducing shock, leading to loss of life while still in an unconscious state. Certainly in the movies they don't often have EMT's rushing in after those stabby moments. Thanks for the feedback! Franamax (talk) 10:17, 19 September 2009 (UTC)

Indeed, I read about a guy who was going to be beheaded and told his friends to watch him blinking, he blinked for a couple of seconds after decapitation.

I recall reading in On Killing that the quickest and most silent "takedown" knife kill involves stabbing someone through their lower back, into their kidneys, I think? I don't exactly recall the anatomy. It was brought up in the context of how people actually kill with a knife, rather than how they do it in the movies (where they like to "slash" the throat, which is really not the quickest or the most silent approach). --98.217.14.211 (talk) 13:26, 19 September 2009 (UTC)

It seems like what's really needed here is a definition of "immediate". Or more accurately, some information on how fast you (1) go unconscious; and (2) die after various kinds of attacks to various parts of the body. For example, with a malaria mosquito, it takes a while. With a guillotine, it's pretty fast - though maybe not "instantly". Baseball Bugs ^{What's up, Doc?} carrots 13:30, 19 September 2009 (UTC)

I know of a case where a person was stabbed in the heart and was taken to the local casualty unit with the knife still stuck in him. A surgeon who was just going out at the time and saw him called for some stitches to be brought and opened his chest up right there in reception and massaged the heart and stitched it up. A very effective way of clearing patients :) The person was awake and asking for breakfast the next morning and was out in a week. So no even being stabbed in the heart isn't necessarily fatal, though I wouldn't advise such heroic surgery in general even if it worked in this case. Stomach wounds tend to be very nasty because of the stomach juices and bacteria but at least you get a little more time to try and fix the problem. Dmcq (talk) 16:10, 19 September 2009 (UTC)

One of the things that movies most consistently get wrong is the ease with which people die: somebody gets a fatal wound and just immediately flops down and lies there. The only movie I know that comes close to showing what actually happens is Saving Private Ryan. Looie496 (talk) 18:01, 19 September 2009 (UTC)

Maybe that's because they only have 90-120 minutes to cover everything in a film. In Walk the Line, when Johnny Cash's brother gets severely injured by a saw, they portray him dying that afternoon. He actually went through a week of agony before succumbing. Baseball Bugs ^{What's up, Doc?} carrots 18:53, 19 September 2009 (UTC)

In the photo of the Oswald shooting, Ruby was at about a 45 degree angle to Oswald's left. The doctor who performed the autopsy said the bullet entered the "lower left chest" and "it was fairly obvious that the bullet had transgressed virtually every major organ and vessel in the abdominal cavity, which later proved to be the case." These included the aorta and the inferior vena cava. The initial massive blood loss killed him from anoxia. 3 liters of blood (out of 5 in the body) had leaked into the abdominal cavity. The right kidney and liver were hit, as were the stomach, pancreas, and spleen. Despite this, the doctor thought they might have saved him if he had been closer to the hospital. Edison (talk) 19:56, 19 September 2009 (UTC)

Genetically engineered corn seed

What would be the impact of genetically engineered corn seed that required a proprietary germination activator and had a proprietary terminator gene if it became dominant? -- Taxa (talk) 09:14, 19 September 2009 (UTC)

What are you talking about? Baseball Bugs ^{What's up, Doc?} carrots 09:18, 19 September 2009 (UTC)

Watch the documentary, "The Future of Food." -- Taxa (talk) 09:24, 19 September 2009 (UTC)

Where corn (i.e. maize) is concerned, it's not much of an issue, since you can't save selected ears and plant the next generation of hybrid corn anyway. Well, you can, but you won't get hybrid corn, as the Mendel effect will kick in and you'll get a combination of tall plants, short plants, high-yield plants, low-yield plants, etc. Then you'd be back in the business of trying to create your own open-pollinate varieties - which are significantly less hardy than hybrid corn is. Might be more of an issue with other crops like wheat and soybeans. Keep in mind that maize is a thoroughly domestic crop. It does not and cannot exist in the wild in its familiar form. Baseball Bugs ^{What's up, Doc?} carrots 09:41, 19 September 2009 (UTC)

Perhaps not in the US where industrialized production and genetically engineered corn designed specifically for High Fructose Corn Syrup and a mired of other genetically engineered products including spermicide, herbicide, pesticide, pharmaceuticals and plastic has wiped out virtually all other varieties of corn. Not in Mexico, however, where domestic corn is typically open-pollinated to gain or revitalize various strengths which wild varieties may have. Unfortunately the large varieties of corn in Mexico today are a great risk from the thing in the US that special purpose varieties are the only ones that count despite our knowledge that preserving natural bio-diversity is what it is all about unless you want to be setup for a catastrophe worse than the Potato Famine. -- Taxa (talk) 10:07, 19 September 2009 (UTC)

The USA used to use largely open-pollinate varieties. When the drought came along in the early 1930s, those who had planted hybrids got some yield, and those who had planted open-pollinate varieties didn't. That pretty much wrapped it up for the open-pollinate varieties in America. Sure, you can still do open-pollinate varieties. But if you're wanting to sell your grain to the local elevator, you're not likely to make as much money from open-pollinates as from hybrids, simply because the yield likely won't be as high. Lack of genetic diversity is certainly a concern, which is why there are conscious efforts made to maintain some biodiversity. Baseball Bugs ^{What's up, Doc?} carrots 10:23, 19 September 2009 (UTC)

If a genetic variant had a "proprietary germination activator and had a proprietary terminator gene", how do you propose that these genes would become dominant? Wouldn't the variant be selected out in the first generation? I'm not sure where the controversy about gene contamination of indigenous Mexican corn (teosinte) varieties is at nowadays, but that's a little different than the question on gene diversity. The problem there is that agrobusiness tends to favour stable variants and market them heavily. This reduces natural genetic variation within the cropped varieties of plants. But that has been happening long before genetic engineering came along. Most banana plants in the world are a single clone. Apis mellifera is a single widely used species at great risk right now. The basic problem is: which farmers are you going to tell not to use the most productive variety? Which pollination companies are you going to tell not to use the most productive and available bees? Answer those questions and you will have solved the problem of maintaining genetic diversity. :( Franamax (talk) 10:36, 19 September 2009 (UTC)

There is a common conspiracist notion (conspiracy theories being the basis of most of that user's questions on these pages) that somehow companies are "imposing" genetically modified organisms on the market. In fact, they are driven by demand. The farmers want the highest possible yield, and that's what these products deliver. The companies also recognize the risks and try to do something about it. You're right about the banana. Through artificial selection they've got one that's really good, and also vulnerable. This happens in nature also, of course. The pink dogwood has been severely beaten back by a particular disease that apparently hasn't affected the more common white dogwood. But we know a lot more about genetics than we did during the potato famine. In fact, we knew nothing about genetics during the potato famine, except by vague inference. So the potential to prevent a disaster is much better than it was in the 1840s. Baseball Bugs ^{What's up, Doc?} carrots 10:46, 19 September 2009 (UTC)

I'll have to temper this now. There are at least two "conspiracy" theories which arise quite naturally from market forces but nonetheless pose a threat:

• Contrary to most of recorded history, in the last 20-30 years the producers of plant seed and the producers of pesticide (primarily herbicide) have converged. So now we have companies such as Syngenta, Monsanto and Pioneer/DuPont whose economic incentive is to produce crop varieties synergic with their own pesticide products. Admittedly, as far as herbicides go, Roundup is a least-awful one and genetically-engineered Roundup-ready seed (soybean and canola especially) may (or may not) have reduced environmental impact (key assumption being that crop acreage stayed the same and use of more toxic herbicides decreased, but at least one of those assumptions is broken). The really big problem here is the corporate conbination of pesticide research and seed research. Who ever said that was a good idea? Instead, the space was captured by profit-seeking interests in a free market. But it's not necessarily true that the pursuit of profit always results in a net benefit to society. As always, what external costs are generated?
• And genetically-modified organisms to a degree enjoy a "free ride" in that if they are deemed harmless, they get sold within the existing system, undifferentiated. All of the canola and soybeans get mixed together in the grain elevator, so the consumer is not even given a choice. The natural consequence of this is that producers have an incentive to adopt the most profitable commodity practice, rather than the one which delivers the most desirable benefit to the consumer. In similar fashion, US consumers get recombinant BST-stimulated milk, whereas we in Canada do not. Is there any difference? I'm not sure, but I'd sure like to have the choice.

In summary, no it's not a huge conspiracy - but market forces aren't always beneficial. The cheapest food isn't always beneficial either. Food is pretty fundamental and it needs extra scrutiny, since it's, like, what we need to survive. Franamax (talk) 12:32, 19 September 2009 (UTC)

There's much more scrutiny now than there was a hundred years ago. Baseball Bugs ^{What's up, Doc?} carrots 12:37, 19 September 2009 (UTC)

True. Hardly anyone dies of dropsy or scrofula nowadays. I think my points stand though. Franamax (talk) 13:06, 19 September 2009 (UTC)

People could always plant their own crops like they used to. But the natural trend seems to be away from small farms and towards big ones, as with other types of industries. You get more efficiency in trade for less diversity. Baseball Bugs ^{What's up, Doc?} carrots 13:14, 19 September 2009 (UTC)

It's only a "natural trend" because of the way agricultural subsidies are handed out. Honestly, if you want to take a "free-market" approach, big aggro is possibly the worst example you can find, as it is one of the most highly subsidized government industries there is in the United States. It has about as much to do with the free market as does Social Security. --98.217.14.211 (talk) 13:47, 19 September 2009 (UTC)

Agriculture is one thing the USA does very well. We seem to outsource everything else. If we outsource our core agriculture, we're doomed. I'm fine with my tax dollars going to support the ag industry. Baseball Bugs ^{What's up, Doc?} carrots 13:54, 19 September 2009 (UTC)

I suggest that you might not have a full grasp on the pertinent issues. Basically the entire industry is vastly warped by government involvement—that's why corn is so cheap, and so high fructose corn syrup is so cheap, and why it is everything. It's not good for us, and it's not a legitimate economy—it's government propped up subsidies that vastly encourage large farms run by a small number of people and production of gigantic monocultures. You can't simultaneously appeal to the importance of the free market and then use as your example something that is a completely government-mandated situation, one that has major economic and health implications. --98.217.14.211 (talk) 21:50, 19 September 2009 (UTC)

Not to drag this out more, but genetically engineered food is a huge boon and vastly safer than the alternative; The problem of corn in America has little to do with genetics, as is being said. The problem has everything to do with post-Depression era policies and a Nixon era racist named Earl Butz. Agribusiness is just that, a business, and diversity is bad for mass production. Say what you will about the current system, but without it a lot of people would die. As Bugs says, it's an industry worth subsidizing. We're doing it backwards (Butz pulled the rug out) but it usually works. That being said, there are tons of other problems, mostly related to nitrogen and antibiotics. ~ Amory (user • talk • contribs) 20:37, 19 September 2009 (UTC)

You seem to be implying that the alternatives are "everybody starves" or "we subsidize the industry the way we are currently doing it." That is not even remotely true, and it's a ridiculous false dilemma, and there are plenty of well-thought-out suggestions as to better ways to do it, both in terms of crop health and public health. Who are all of these people who would die without the current system? --98.217.14.211 (talk) 21:50, 19 September 2009 (UTC)

Plumbing - tap not running properly

I'm not sure if this is the best place to ask this question but here goes anyway.

The hot water tap on the sink in my bathroom isn't working properly. Even when fully turned on, there is only a trickle of water. The hot tap on the adjacent bath works fine. I have traced the pipework as far as I can but I can't trace it all the way back to the hot water tank because it goes into the concrete floor. The tank is located the other side of the wall from the offending tap. I am pretty sure that there is NOT one of those mini stop valves on the pipe feeding the tank as I can't see one and the pipework looks like it is original from the installation (1960s), when those valves were not commonplace. The HW tank outlet pipe has a red tap on it but as there is only one outlet then that can't be the issue if the bath HW supply is fine.

I also thought the tap itself might have seized up so I removed the screw and the head and that all looks fine. I have attempted to remove the main part of the tap but it is reluctant to come off (the whole tap moves rather than the part that is supposed to unscrew. I don't want to apply too much force in case it damages the ceramic basin. If there is anything that might be causing it then I will have another go at removing it but I'm not sure if there is any benefit from doing so. I have a book on basic plumbing and it has lots on dealing with a dripping tap but nothing about the opposite problem!

Any ideas please?

It certainly sounds like the pipe is clogged somehow. I would think the hot water feed to both the sink and the tub would be a common pipe that splits somewhere near the two. Does your book say anything about mineral buildup in pipes or anything like that? Baseball Bugs ^{What's up, Doc?} carrots 10:01, 19 September 2009 (UTC)

Thanks. Could well be limescale as I live in a hard water area but I've never heard of hot water pipes getting clogged in this way. My book mentions how to install a water softener but no mention of dealing with clogged pipes - I will look online later. 78.33.180.73 (talk) 10:08, 19 September 2009 (UTC)

The only thing you can do short of calling a plumber is to cut the water and the heater off and take the valve apart. If its clogged from build up then simply clean it good. Sometimes soaking in vinegar will help loosen lime build up. Rust buildup requires a little more aggressive chemistry. Try manual cleaning first. DISCLAIMER: This is not plumbing advice. For plumbing advice, please consult a plumber. Some States have laws. -- Taxa (talk) 10:13, 19 September 2009 (UTC)

They're obviously trying to avoid calling a plumber, as that can run into money. But unless they want to take their pipes apart, which is a risky thing to do if you don't know what you're doing, it's best to call a professional. Baseball Bugs ^{What's up, Doc?} carrots 10:16, 19 September 2009 (UTC)

About unscrewing, it may unscrew in the opposite direction. There's bits of plumbing that do that though I haven't touched any for a year or two so I've forgotten which. Dmcq (talk) 15:02, 19 September 2009 (UTC)

9 times out of 10 the tap will try to turn (rather than the top section), one has to use something like a large adjustable spanner to hold the spout of the tap - if that don't work, then it's mole grips or strap spanner on the tap body, but it's then difficult not to mark the tap body!  Ronhjones  ^(Talk) 18:39, 19 September 2009 (UTC)

Often the flow decreases because the aerator is clogged with scale.See [12]. This is a little combination of wire screen and plastic discs with hole in them, which screws onto the outlet of the faucet. If the flow is much greater (though maybe splashy) when the aerator is unscrewed, then either clean and reassemble the aerator as described in the site linked, or take the aerator to a hardware store (plumbing supply) and there should be a screwthread checker which you can try it on to determine the thread, then buy a replacement and install it. A plumber once quoted me a $3000 pipe replacement job to correct low flow, when the clogged screen in the aerator was the problem. It is the weakest link in the whole system, and the cheapest/easiest to correct. Edison (talk) 19:42, 19 September 2009 (UTC)

To get a feel for what is going on I would try to stop the water flow with a finger. If the pressure is high so that it's impossible to hold back the water, but still the water only trickles then there is a blockage in the tap or pipe leading to it. 1960's plumbing in a hard water area will almost certainly have scaling. Call a plumber. They have tools, muscles and experience to deal with this, including replacing the tap IF that is called for. Cuddlyable3 (talk) 22:16, 19 September 2009 (UTC)

If you do find that the pipes are hopelessly clogged with scale, it will be rather expensive to extract them from the concrete floor and replace them. A much cheaper alternative is to abandon the existing pipes and replace them with PEX tubing (flexible plastic tubing). You can drill a hole in the wall and run the tubing through there. Connecting the PEX tubing to the water heater and faucet may still require a plumber, but this should be far less disruptive and expensive than ripping up the floor. Another advantage is that, when the PEX tubing eventually clogs up, it will be far easier to replace. StuRat (talk) 03:34, 20 September 2009 (UTC)

A useful diagnostic test in this case is to turn the hot water off at the tank, remove what you can at the sink, and open the tap at the bath. blow in the pipe to see if the block is between the basin and the bath. Note that lots of taps wont let fluids go "backwards" through them. Polypipe Wrangler (talk) 06:27, 22 September 2009 (UTC)

Wave functions

Hi all! Another one from me again - thanks for all the help yesterday.

I'm trying to get my head around QM as best I can before the start of the year but i'm more of a pure mathematician at heart - it'd be great if I could get a hand with this!

Consider the time-independent Schrodinger equation given and show that for any real k, in 1 dimension,

ψ(x) = e^ikx(tanh(x) − ik)

is a solution for the potential $V=-{\frac {h^{2}}{m}}sech^{2}(x)$(I've done this bit), and find its (scaled) energy ε. Show that this is the wavefunction of a scattering state where the reflection probability vanishes. Find the transmission amplitude, and verify that the transmission probability is 1. Consider the extension (analytic continuation) of this solution to positive imaginary values of k. Show that for the value of k corresponding to the bound state at ε = −1, ψ(x) reduces to the bound state wavefunction, and that the transmission amplitude has a simple pole.

I'm fine with the first part and finding the scaled energy - the only way I can think of to do the next part is to consider a reflective potential barrier of height U(x,y) for some parameter y s.t. U -> V as y -> 0, wherein the limit of the wavefunction in this potential is ψ(x), but I'm not sure if that would work. After that, how do I go about finding the transmission amplitude/probability? I'm not meant to consider the integral of |ψ(x)^2| from 0 to infinity, because it's not normalisable, but I'm not sure how else to approach the rest of the question - thanks in advance for any help :)

Spamalert101 (talk) 11:50, 19 September 2009 (UTC)

For the real k case, I think you can just look at the limits of what ψ does as x goes to ±infinity, and make an argument based on that. I don't know about the imaginary k case. Rckrone (talk) 17:38, 19 September 2009 (UTC)

Obviously ψ behaves badly if k isn't real because of the e^ikx part, but maybe they just want you to consider what |tanh(x) − ik| does? That would produce a bound state at ε = -1, although I don't really know what it would all mean in terms of the physics. Rckrone (talk) 17:57, 19 September 2009 (UTC)

Oh I see. In that specific case where ε = -1, things don't go bad since the decay of |tanh(x) − ik| stops e^ikx from blowing up. ψ = sech(x). Still don't know what the physical interpretation of that is. Sorry about the rambling multiple posts. Rckrone (talk) 18:15, 19 September 2009 (UTC)

If you have a 1D wavefunction that looks like Ae^ikx before scattering and Be^ikx after scattering then the transmission amplitude is (by definition) B/A, and the transmission probability is the squared modulus of the transmission amplitude. Here "before" is to the left (−x) and "after" is to the right, since the wave is rightward-moving everywhere. -- BenRG (talk) 00:07, 20 September 2009 (UTC)

Blu Tack properties

Anyone have the thermal properties such as MP, thermal conductivity, flammability and hazards (when heated) of Bostick Blu-Tack? Also, whats it made from?--79.75.113.153 (talk) 14:58, 19 September 2009 (UTC)

[13] starts to give a description.

It's non conductive (I'm fairly sure), when heated the hydrocarbons will be driven off, (and can burn), when calcined the blue tack synthetic polymers also decompose leaving the mineral filler behind, as a friable white shape (the same as the original piece of blutak)

I don't know thermal conductivity.

You can search for "BluTak MSDS" , a MSDS] is a material safety data sheet which will give standard warnings and hazards for use. Found here [ http://www.bostik.co.uk/diy/safetyData/product/89] 83.100.251.196 (talk) 17:23, 19 September 2009 (UTC)

Galileo and gravity

The page on Galileo says that he did a thought experiment about dropping objects of different masses to see that they would all fall at the same rate. My question is, how would he have been able to have even thought about gravity since gravity wasn't discovered until Isaac Newton was hit on the head by a falling apple many years later? --70.129.185.53 (talk) 16:11, 19 September 2009 (UTC)

See gravity. What Galileo (might have) thought about was "dropping objects of different masses", regardless of whether he had a concept of "gravity". Nobody "discovered" gravity. What Newton did was develop a theory and give the concept a name.--Shantavira|^{feed me} 16:23, 19 September 2009 (UTC)

The key thing Newton did was work out a universal theory of gravity - that is, he worked out that what makes apples fall off trees is the same thing that keeps the Moon in orbit around the Earth. People knew that things fell down before that. --Tango (talk) 17:52, 19 September 2009 (UTC)

The real story about Galileo and dropping differently-massed objects does not involve him tossing cannonballs from the Leaning Tower of Pisa.

Galileo's actual area of expertise, both before and after his telescopic discoveries, was in the field of falling objects, usually balls rolling down an inclined plane. It hardly took someone of Galileo's brains to notice that, unless caught by the wind, objects fall downward. Aristotle's theory of gravity, in part, stated that solid objects fell toward the center of the Earth because they shared an "Earthly" nature. His followers now almost two thousand years after his time, added the corollary that the more massive the object was, the faster it would fall. Galileo (who, in fact, was an Aristotelian himself) knew from his experiments that, to the best that could be measured, this wasn't so. There were two possible alternate corollaries.

1. Suppose a heavy cannonball were chained to a much lighter one, and the combination were dropped from a height. The standard theory said that the combo should fall faster than the heavy one alone, as the lighter one's weight should be added to that of the heavy one. However, since the lighter one, under the same theory, would not be attracted to the Earth as much (notice that they hadn't yet distinguished between weight and mass), the combo should fall more slowly than the heavy one alone, as the lighter one would be holding it back. Since the same theory and reasoning resulted in contradictory and opposite results, it was clear that the theory itself was invalid.

2. Galileo proposed that the actual mass/weight didn't matter and that given certain constraints, objects experienced the same acceleration downward. (Please do not bother posting anything about terminal velocity, air pressure, the shape or cross-section of the falling object, or inexact timepieces. Don't even think about trying this experiment in a rising elevator with an infinitely long shaft.)

Now what happened is that when Galileo, in Padua published the results of his experiments, a gentleman in Pisa disputed his results. Galileo, in what was for him only a mild rebuke, suggested that the other fellow try thr experiment from his town's cockeyed Bell Tower. As far as is known, the experiment has never been tried. (The Apollo 15 test was done in vacuum.) B00P (talk) 19:31, 19 September 2009 (UTC)

Brainiac did the experiment in one episode - it was quite impressive. They tried various household objects dropped from a crane and found that, as long as both objects were very heavy (so air resistance was minimal), it really did work. A car and a tire fell at almost exactly the same rate. --Tango (talk) 21:15, 19 September 2009 (UTC)

They used to allow people to walk unsupervised to the top of the Leaning Tower. Someone must have tried the experiment at some point. -- BenRG (talk) 22:10, 19 September 2009 (UTC)

All objects with the same air resistance fall at the same rate?

Isn't this claim by Galileo false, since, while Earth would exert the same gravitational force on both objects, the heavier object would exert slightly more gravitational force on Earth, meaning it would fall slightly faster? --75.28.52.196 (talk) 16:25, 19 September 2009 (UTC)

The mass of earth is estimated at 6 * 10**24 kilograms. That's in comparison to, say, a 1 kilogram weight. Think of the difference between 1 kilogram and 10**24 kilograms and you'll get an idea of how negligible such an effect would be - basically unmeasurable. Baseball Bugs ^{What's up, Doc?} carrots 16:34, 19 September 2009 (UTC)

A bit of care with terminology is warranted in this situation. While both bodies see the same gravitational field, the massive object experiences a much stronger gravitational force than the light object, in direct proportion to their two masses. The effect is what we expect — both objects experience indentical acceleration towards the center of mass of the Earth-object system. As the original poster notes, the Earth must experience a reciprocal gravitational force, and therefore by accelerated 'upwards' towards our falling object. (This must happen in order to conserve momentum in the Earth-object system.)

That being said, for nearly any measurement one is likely to perform on or near Earth the increased acceleration will be infinitesimal. As Baseball Bugs notes, the mass of any test object is likely to be many, many, many orders of magnitude smaller than the mass of the Earth. The place where such factors is important is in modelling the interactions of astronomical objects. The Moon, for instance, weighs a little more than 1% of the Earth's mass; its orbit is therefore a little faster that it would be if we were to replace it with a smaller chunk of rock. TenOfAllTrades(talk) 16:53, 19 September 2009 (UTC)

There is no increased acceleration really - at all, not even a small negliable amount - see the link below.83.100.251.196 (talk) 17:15, 19 September 2009 (UTC)

They are talking about a difference in the acceleration of the Earth, not a difference in acceleration of the objects. Rckrone (talk) 18:03, 19 September 2009 (UTC)

The force equation is F= G M_earthM_object / r²

But acceleration is Force/mass ie a = F/M_object

Therefor the acceleration is a= G M_earthM_object / r² M_object

ie a= G Mearth / r2

Which is independent of the mass of the object.

This is the same equation as found at Gravitational acceleration 83.100.251.196 (talk) 17:13, 19 September 2009 (UTC)

You don't understand. The point of the question is that the test mass also accelerates the Earth (at least in principle), which causes the distance between the cetner of masses r to be reduced more rapidly than if you consider only the acceleration of the test mass alone. Hence it is correct, in principle, to say that heavier mass would fall faster (i.e. the separation distance r decreases more rapidly, everything else being equal) because in addition to it's own motion it also drags the Earth towards itself. Of course, in practice, these effects are utterly negligible unless both bodies are of astronomical size. Dragons flight (talk) 18:04, 19 September 2009 (UTC)

Oh I see - the net acceleration - that's easy it's:

acceleration = G ( M_earth + M_object )/ r²

83.100.251.196 (talk) 18:56, 19 September 2009 (UTC)

But the object comes from the earth, and so subtracts from the mass of the earth - thus M_earth + M_object is constant and independent of the mass of the object, making the mass of the object irrelevent.83.100.251.196 (talk) 19:12, 19 September 2009 (UTC)

You are saying that the feather falls just as fast as the hammer because of the attraction caused by the hammer still sitting on the lab bench? I like that answer. Completely irrelevant to the physics of the situation, but I like it. --Tango (talk) 21:18, 19 September 2009 (UTC)

Sort of.. Even weirder is this - two masses m1 and m2 in vacuo on the surface of a much larger earth sized body of mass M , radius R - then raise one of the two smaller masses to height x (x << R)..

The net accelleration of the 'earth' and falling masss bodies towards each other is larger for the smaller mass... ie the smaller mass falls faster. (equation is fairly simple to get taking into account all the forces)83.100.251.196 (talk) 22:19, 19 September 2009 (UTC)

I don't think that Galileo ever said that. It's certainly not true: a baseball and an equal-sized iron ball have the same air resistance, but fall at different rates, as Galileo knew very well. Looie496 (talk) 17:53, 19 September 2009 (UTC)

In any case, a baseball and an equal-sized smooth and round object should not have the same air resistance, due to the seams and other irregularities on the surface of a baseball. But in a vacuum, they would drop at the same rate. Baseball Bugs ^{What's up, Doc?} carrots 19:12, 19 September 2009 (UTC)

I agree that even if two objects are the same size and shape, with the same surface texture, therefore having the same "air resistance", the heavier one will fall faster in air. Edison (talk) 19:34, 19 September 2009 (UTC)

Could you expand on the justification for that - is it contrary to the inverse square law of gravitation? I got no change in acceleration for different densities as a first, and second approximation (taking in to account the motion of the earth as well see above)>83.100.251.196 (talk) 20:27, 19 September 2009 (UTC)

Let's try a thought-experiment, although the first part is easy enough to actually do. Take two idendical pieces of typing-paper. Crumple one into a ball. Hold them at arm's-length from your body, one in each hand. I would be willing to bet large amounts of money that the crumpled sheet hits the floor first.

The theoretical version takes place in a vacuum; air resistance is, therefor zero. I would imagine that most people would be willing to concede that under those circumstances the two sheet would land ximultaneously.

Now it doesn't take much to move from "same-mass, different shape" to "same-shape (and volume, thus congruenr)", but "different mass." B00P (talk) 19:54, 19 September 2009 (UTC)

An object falling with air resistance has two forces acting on it: gravity and friction. Two objects with the same shape and different masses both have equal acceleration due to gravity, caused by unequal forces (the forces are proportional to their respective masses). On the other hand the objects have equal force acting on them due to friction (assuming the same velocity), which produces unequal accelerations. Thus the net accelerations are not the same. Rckrone (talk) 21:05, 19 September 2009 (UTC)

That makes sense - so for a given velocity (same shape/size different density) the air resistance is the same, but relatively less than the accelerating force on the heavier object.83.100.251.196 (talk) 21:13, 19 September 2009 (UTC)

In a vacuum, acceleration is the same no matter the mass or shape of the object. The experiment is high school physics was a ball and a feather. Obviously they drop at different rates in air, due to air resistence. In a vacuum tube, they drop at identical rates. So far so good. Now consider a hollow pingpong ball and one filled with something. I'm trying to figure why they should drop at different rates in air. I'm supposing it's because the lighter ball has trouble "cutting through" the air - kind of like the feather. But if you take two fairly heavy balls of somewhat different sizes and drop them, they should hit the ground at pretty close to the same time. I think Aristotle claimed if one ball was twice as heavy, it would it the ground in half the time. However, it's only a small difference - the difference caused by a little more air resistance on the smaller (lighter) ball. And in a vaccuum, they fall at the same rate. Have I got it right now? Baseball Bugs ^{What's up, Doc?} carrots 21:27, 19 September 2009 (UTC)

The force of air resistance only depends on shape and speed, but the acceleration also depends on mass because a=F/m. -- BenRG (talk) 22:17, 19 September 2009 (UTC)

Something doesn't make sense here. Two objects of different masses, dropped at the same time from the same height in a vaccuum, will hit bottom together. Their acceleration is the same, regardless of their mass. Baseball Bugs ^{What's up, Doc?} carrots 05:47, 20 September 2009 (UTC)

It does make sense. Gravity depends on mass, acceleration depends on mass, air resistance does not. --194.197.235.240 (talk) 12:03, 20 September 2009 (UTC)

Are there any pleasant wildernesses left in the world?

I saw a tv programme about a man travelling on foot through the Yukon in Alaska, USA. The Yukon has I believe extremely cold temperatures in winter, and looked like it may have mosquito or midge problems. Are there any wildernesses left in the world that are pleasant places to be in, without much danger, health risks, or extreme climate? Or have all these areas now been settled by large human populations and hence are not wildernesses? 78.144.252.66 (talk) 18:54, 19 September 2009 (UTC)

I think it unlikely that there has ever been such a thing as a "pleasant" wilderness from the human viewpoint. If the climate is "pleasant", it will be teeming with life, including a variety of life forms that would be very happy and eager to consume you, or parts of you. That's why we build houses. With screens to hopefully keep the bugs out. Baseball Bugs ^{What's up, Doc?} carrots 18:57, 19 September 2009 (UTC)

The most pleasant areas are the most attractive for settlement. So no. Vranak (talk) 19:03, 19 September 2009 (UTC)

Woody Allen said it best: "Nature... is basically a gigantic restaurant." Baseball Bugs ^{What's up, Doc?} carrots 19:09, 19 September 2009 (UTC)

Parts of Tasmania or some of the cooler parts of Australia perhaps? 78.144.252.66 (talk) 19:10, 19 September 2009 (UTC)

What degree of "wilderness" are you looking for? There are certainly many national and state parks in the US that are pleasant to hike in. Rckrone (talk) 19:31, 19 September 2009 (UTC)

Likewise, depends how you define pleasant. Still, I'd recommend enormous portions of the American Northeast (NYS especially) and definitely the Rockies in the West (Wyoming in particular). They are breathtaking, and as long as you have a map, compass, and some rope for a bear hang, you'll be fine. I've never been happier than when I was out there. ~ Amory (user • talk • contribs) 20:23, 19 September 2009 (UTC)

There are wildernesses both with warm (africa, S america) and cold winters (wear a bear skin etc) , but I can't think of any that lack large predators - possibly a small island somewhere - maybe madagascar, or somewhere in indonesia. Even so there are still likely to be stinging flies, tropical diseases and possibly snakes.83.100.251.196 (talk) 20:31, 19 September 2009 (UTC)

Most of the Northwestern third of the state of Maine in the U.S. is relatively wild; there aren't even any state-maintained roads or anything, its probably the closest thing to untouched wilderness in the northeatern U.S. that there is. See Maine North Woods and Maine Highlands. --Jayron32 21:32, 19 September 2009 (UTC)

There are several areas of nice moorland in England, does they count? --Tango (talk) 21:40, 19 September 2009 (UTC)

I have to make a minor correction to your post. The Yukon isn't "in Alaska", it's a Canadian territory which is adjacent to the US state of Alaska. StuRat (talk) 03:17, 20 September 2009 (UTC)

The Yukon is also the name of a river that runs through both the state of Alaska, and the Yukon Territory. I assume they were referring to the river. Googlemeister (talk) 13:29, 21 September 2009 (UTC)

Hmm, in that case "...traveling on foot through the Yukon..." river would lead to some mighty wet and cold feet, unless it was frozen over, in which case that would be traveling "over" the Yukon river, not "through" it. StuRat (talk) 19:31, 21 September 2009 (UTC)

The Olympic Wilderness is quite pleasant and generally lacks in mosquitoes and extreme weather/climate, etc. Pfly (talk) 04:30, 20 September 2009 (UTC)

English (and Scottish) moorland is pleasant but you're never far from habitation. I'd go with Tasmania. One neat thing about Tassie is that you can look up at a clear sky; unless you're north of Hobart airport there are no flightpaths overhead and therefore no contrails.--Shantavira|^{feed me} 07:34, 20 September 2009 (UTC)

+1 for Tasmania. Come and say hello too. You'd be silly to go for a wander in the south west without the right equipment and so on though. Noodle snacks (talk) 09:27, 20 September 2009 (UTC)

Scotland - You could plump for the Outer Hebrides, fairly quite - unless you go way out to St.Kilda (uninhabited) - I find you tend to get rather too many biting midges in the summer in West Scotland.  Ronhjones  ^(Talk) 19:07, 21 September 2009 (UTC)

My guess isw there are pleasant wildernesses in South America, as previously mentioned, and probably in the warmer southern parts of the former Soviet Union. As they have few people and are undeveloped (thank goodness), then necessarily they will not create much publicity. I expect that even in hot areas such as Africa or Mexico, there must be pleasant areas where altitude makes it cooler. The far east must have many wilderness areas, with a tropical climate. 84.13.198.33 (talk) 10:15, 20 September 2009 (UTC)

I may be a little biased, but I have to put in a vote for New Zealand, in the south in winter it can be a bit unpleasant but everywhere else for most of the year is very nice.

I would opt for the island of Kahoolawe in Hawaii. It was traditionally used as a bombing range, but not anymore and is not inhabited. Granted it has little in the way of fresh water, but if the intended population is very small, that is less of a concern. One note is there might be unexploded ordinance laying around. Whether it would be enough to constitute danger... Googlemeister (talk) 13:34, 21 September 2009 (UTC)

Antihallucinogenics

Is there a name or category for drugs which cure hallucinations? Now that I think about it, do any such drugs exist? Vimescarrot (talk) 22:39, 19 September 2009 (UTC)

antipsychotic drugs are one recourse for poeple who are having a 'very bad trip', though I don't know if this is to prevent panic psychosis etc, or if they actually stop the hallucinations. - though there are typically supposed to be active on the same neurological sites that are thought to be related to psychosis and halluncinations (serontin receptors etc). Looking at hallucinogen and the various receptors responsible for hallucinations might be helpful in your research as well.83.100.251.196 (talk) 22:51, 19 September 2009 (UTC)

On the web I've seen Ziprasidone described as an anti-hallucinogen - but it seems that it is conventionally classed as an anti-psycotic.83.100.251.196 (talk)

There are so many types of hallucination I think there may be other drug types that can deal with them.83.100.251.196 (talk) 22:56, 19 September 2009 (UTC)

For hallucinations induced by 5-HT2A receptor agonists (LSD and most other psychedelics), a 5-HT2A antagonist should work (which many antipsychotics are). For deliriant-induced hallucinations, muscarinic receptor agonists should work. If you have been convinced that cannabis causes hallucinations, then I guess you should believe a cannabinoid receptor antagonist will cure those hallucinations. --Mark PEA (talk) 00:31, 20 September 2009 (UTC)

Neither Wikipedia, nor her editors, nor the Wikimedia Foundation, nor any affiliates thereof assume any liability for any injury, harm, or fatality, to you or others, that may result from misuse of these medications based on advice given herein. Intelligentsium 02:41, 20 September 2009 (UTC)

I don't think any antipsychotic drug will "cure" a hallucination. They are usually part of a long-term psychological monitoring and medication process. It's very doubtful that they would have an immediate effect to "stop a bad trip" as might have been implied above. Nimur (talk) 02:50, 20 September 2009 (UTC)

Ah I just remembered the drug that is often given to "screaming lunatics" picked up by the police (a doctor does this, not the police obviously) was Temazepam which is not an anti-psychotic - but I believe is given to calm them down and prevent them harming themselves or others. Another reason to not take anecdotal evidence from strangers on the internet - sorry if that misled anyone.

Nevertheless anti-psychotics are/were used as medication for conditions that include medication, and do (in some cases) prevent the hallucinations. This can be checked via studies, I remember that Oliver Sacks described such a case in one of his popular books.83.100.251.196 (talk) 22:43, 20 September 2009 (UTC)

The situation is complicated by the fact that some hallucinations may not be 'chemical' but 'wiring' problems - synaesthasia might be an example of this, hallucinations brought on by brain damage or unusual brain structure are unlikely (?) to be dealt with by drugs.83.100.251.196 (talk) 09:41, 20 September 2009 (UTC)

September 20

Breath-Controlled Automobiles (not the toy cars)

Either my google-foo has vanished or I dreamt this up. Somewhere in a long investigation of adaptive devices for paraplegics and quadraplegics/tetraplegics who are drivers, I seem to remember reading about investigations of and even prototypes of breath-controlled cars. There certainly are breath-controlled and voice-controlled wheelchairs, but I can't find anything on automobiles. Does anyone know where I could find some information? // BL \\ (talk) 03:32, 20 September 2009 (UTC)

Not strictly relevant but Hilary Lister just sailed round Britain in a breath-controlled boat. If you google her you might find out about something relevant about her control system. Tinfoilcat (talk) 10:58, 20 September 2009 (UTC)

Suck and puff switches, or Sip-and-puff, e.g. these, are found on many quads' wheelchairs. Nimur (talk) 15:30, 20 September 2009 (UTC)

In the L'il Abner comic strip, he once drove the "Nomoto Car," invented by a "Mr. Nomoto." It had no engine, and was powered by the driver breathing in and out, with the chest motion coupled to the wheels. With fast enough huffing and puffing, Abner could go quite fast. Edison (talk) 18:53, 20 September 2009 (UTC)

This seems like an awfully dangerous idea! Sure, you could have some kind of interface that would allow steering, gas, brake and gearshifter (plus lights, windshield wipers, turn signals, etc) to be driven by some kind of breath-controlled menu-based interface - but how fast could someone with so little dexterity actually get from (say) turning on their windshield wipers to pressing on the brake, releasing the gas and steering out of the way in the event that a little kid runs out between two parked cars right in front of the vehicle? Worse still - if the person is so disabled that they cannot turn their head and body to control the car - what hope is there that they'd be able to adequately look out of the side windows or look towards the rear when joining traffic from a freeway ramp or something?

A suck/blow switch is essentially a single analog input - and because of the necessity of ceasing to blow when you run out of breath or need to swallow saliva or lick your lips - you don't even have full control of that single input. With something as slow as a powered wheelchair - you can simply have the thing stop when the breath input ceases to be applied. You could easily imagine a wheelchair that travelled slowly forwards as long as pressure is applied to the breath tube, turns left when more pressure is applied, turns right when you suck gently on the tube and reverses when you suck hard on it. As soon as you cease sucking or blowing, the wheelchair could simply stop. That kind of an interface works fine at 2 miles per hour with everyone around the user being aware that they are severely disabled and need to be given space to manouver.

But you can't have a car travelling at 70mph go into a full-scale emergency stop every time the user needs to take a breath! Sure, it is technologically possible to slowly control a car with such a minimal interface - but is it sane to attempt it? Hell no!

What is required to give such people the mobility they'd like to have is something like the cars in the DARPA Grand Challenge that can essentially drive themselves. The user would then only be required to use the suck/blow interface to make high level decisions - like "turn left at the next intersection" that could be made in plenty of time to let the robotic systems handle the details of changing speed, steering, avoiding other cars, etc. Better still - design it so the car knows where it's going and is capable of driving the entire way without any driver input whatever - then all the user has to do with the breath interface is select between entries within a list of pre-determined destinations...just like you select your destination with a navigation computer.

But those DARPA vehicles are a LONG way from being safe enough to let loose on the roads.

SteveBaker (talk) 19:21, 20 September 2009 (UTC)

I wouldn't say "a LONG way..." It's not so very uncommon around these parts. Last summer while biking over by the Horse Farm and Robot Car Ranch, I saw a team of computer science nerds in a chase-car holding an SUV-mounted HD camera and going after Stanley, who was out driving, unmanned, on a very real and very public roadway... as far as I know, it was no accident, but then again Stanley might have escaped... Nimur (talk) 20:19, 20 September 2009 (UTC)

It's hard to imagine how that could possibly be legal. Heck, you can't legally drive a car (in the USA) where the engine starts itself without a direct command from the driver! With that degree of legal luddism - I can't see fully autonomic cars being legal for an awfully long time. Nor should they be! The potential for tiny software bugs to kill people in large numbers is too high to be tolerable. There would need to be much more extensive testing and certification by some kind of federal agency before these things could be trusted on our roads. SteveBaker (talk) 21:52, 20 September 2009 (UTC)

Well, cars with human drives manage to kill people in large numbers. But yes, there should be much more extensive testing and certification [...] before these people should be trusted on our roads. ;-) --Stephan Schulz (talk) 16:58, 22 September 2009 (UTC)

instantaneous speed question

An object is moving with uniformly increasing speed. It's speed at time zero is 0m/s. If it's average speed during the first second is 14m/s at what time will it's instantaneous speed be 14 m/s?

I know the answer is 0.50 seconds, but i don't know how you get it.

Average speed = (v_initial + v_final) / 2 for constant acceleration. Therefore v_final = 28 m/s, and its velocity would be 14 m/s halfway through. Not an instantaneous answer, but what do you expect for free? Clarityfiend (talk) 04:32, 20 September 2009 (UTC)

v = v_initial + a*t. 14 = 0 + 28*t -> t=0.5 if you want more specifics. Clarityfiend (talk) 04:49, 20 September 2009 (UTC)

how did you get 28? isn't it supposed to be 0m/s plus 14m/s divided by 2 which equals 7?

It's (0 + v_final)/2 = 14 m/s. v_final = 28 m/s. Rckrone (talk) 05:59, 20 September 2009 (UTC)

same answer told a different way

Uniformly increasing speed means constant acceleration - thus v=at , the average speed = ʃat.dt /t = 0.5at

So 14 = 0.5a1 which gives a=28m/s^2

So for v=14m/s you need to solve v=at , or t = v/a =14/28 =0.5s

The main problem is knowing how to calculate the average speed which requires integration (the area under the speed/time graph) - did all of that make sense.83.100.251.196 (talk) 09:34, 20 September 2009 (UTC)

i still don't see how you got 28.

Step by Step solution

Step 1. "uniformly increasing speed" is "constant acceleration"

Step 2. V_initial = 0 m/s

Step 3. V_average = 14 m/s

Step 4. V_average = ( V_initial + V_final )/2

Step 5. Delta_t = 1 s

Step 6. Acceleration = (V_final - V_initial) / Delta_t

step 7. V(t) = V_initial + Acceleration * t

Step 8. Find t when V(t) = 14 m/s

202.147.44.84 (talk) 02:56, 21 September 2009 (UTC)

Here is how I did it:

v=at 14m/s=a(1s) 14m/s/1s=a a=14m

14m/14m/s=1s

so shouldn't the answer be 1 second?

Your "14m/s=a(1s)" line is assuming that it is travelling at 14m/s after 1 second, so of course that is the answer you are going to get. It is the average speed over the first second that is 14m/s, not the speed after 1 second. --Tango (talk) 03:04, 21 September 2009 (UTC)

but I don't know the speed of the object after 1 second, so don't I have to assume it?

The reason that you know the speed after one second is that your question said uniformly increasing. This means that the speed after one second is double the speed after half a second (and also double the average because it starts from rest). If the rate of speed increase (acceleration) is not uniform, then the calculations are more complicated. Dbfirs 07:57, 21 September 2009 (UTC)

transistor

1.What is the need of biasing a transistor? 2.What are the different types of biasing in the transistor ,Explain them in detsil? 3.What are the advantages of the biasing types ,one over the other?

Main use of biasing a transistor is for the teacher to have some questions for your homework. 95.112.150.86 (talk) 07:36, 20 September 2009 (UTC)

We have an article: Bipolar transistor biasing. See what you can learn! Graeme Bartlett (talk) 12:31, 20 September 2009 (UTC)

Most transistor equations that circuit designers want to use are actually small signal model approximations. This means that they only describe a rough approximation to the total transfer function of the device. The bias point is the region where those particular approximations are valid - usuallyalways, this means the transistor must be configured with a particular DC voltage to each input and output; the circuit equations describe fluctuations around that point. Nimur (talk) 15:28, 20 September 2009 (UTC)

Not that we should be doing homework, but Electronic_amplifier#Power_amplifier_classes is the article the OP wants. Tevildo (talk) 19:02, 21 September 2009 (UTC)

About particle accelerator

I have a question about difficulty to accelerate particles.

I have often read newspapers writing about large particle accelerators with pictures of them (though recently there seems to be not many).

Do they need a lot of energy to accelerate particles? I tried calculation, Particle accelerator#Synchrotrons says "To reach still higher energies, with relativistic mass approaching or exceeding the rest mass of the particles (for protons, billions of electron volts GeV), it is necessary to use a synchrotron." A textbook of physics at hand says 1eV = (about)1.6*10^(-19)J, so 1GeV = (about)1.6*10^(-10)J. If we accelerate 10^13 (1 trillion) protons, we need 1.6kJ.

It seems to me that facilities in pictures are too massive to provide only 2kJ or maybe 10kJ of energy. What is the difficulty in accelerating them? Like sushi (talk) 08:42, 20 September 2009 (UTC)

• The large diameter is more to do with the Gyroradius of a high energy charged particle than some difficulty in accelerating them. Noodle snacks (talk) 09:13, 20 September 2009 (UTC)

Thank you.

Looking at Gyroradius, the reason seems to be so small charge. I can not try calculation for it, because I do not know how to handle magnetic field and what the units for it. (Could somebody do it for me?)

One more question is not the diameter, but heavily equipped tube (the one particles go through). Why is it so heavily equipped?

Like sushi (talk) 11:02, 20 September 2009 (UTC)

• The idea here is to capture as much information about the particle interaction as possible, you would not want to miss any of the products, especially if the reaction was a rare one! Graeme Bartlett (talk) 12:30, 20 September 2009 (UTC)

On newspapers, there is usually only one picture. Is the tube covered with the heavy equippment everywhere? Or those are just one of heavily equipped places?

Like sushi (talk) 14:40, 20 September 2009 (UTC)

The synchrotron beam line has "equipment" all over it - for comparison, take a look at SLAC's beam line (which is a linear accelerator, not a synchrotron), going off about a mile each direction from this photo. Those red things are klystrons, which add energy to the particle beam; and there's a lot of coolant and so forth. Then, there are "taps" where particles are plumbed off the main beam line into special-purpose experiments. In those special regions, there is more, different "equipment" - lots of detectors, sensors, coolant plumbing, etc. Nimur (talk) 15:18, 20 September 2009 (UTC)

I was recently talking to a guy from SLAC (who had also worked at the LHC, and knows something about enormous synchrotrons). My question was about how much energy is actually stored in the "ring" at the LHC. The individual particles may reach TeV, but I was interested in the total energy in the facility. When working with large RADARs, we often use an onsite power station, because we might be consuming 3 or 5 megawatts static power, plus peaking; so I wanted to see how a particle accelerator compares. It seems like the actual energy in the highly accelerated particles is very small (e.g. kilojoules, as pointed out above); the particles themselves have long lifetimes without colliding with walls, and can basically hold that kilojoule of stored energy for hours or days. Then, for a particular experiment, the ring "bleeds off" its energy tank to shoot particles in to one of the connected experiment housings. But while in "storage" (orbiting in the synchrotron), the high-energy particles are not really needing to be "restored" with a significant amount of power. However, that's because they're in essentially a collisionless medium, thanks to the enormous electromagnets which make up the accelerator ring. These magnets, (which were the cause of the infamous fire when the magnets quenched), do require a lot of energy (I never got exact numbers and couldn't find any on the web). But, I'm told that CERN is hooked in to the local energy grid - to me, this tells me that "a lot of power" is actually less than a standard military RADAR or aviation RADAR (which often has its own electric generator). I would really be interested to see a "pie chart" breakdown of the electric consumption of SLAC or CERN - how much is used for basic facilities; how much is for the enormous computer data center(s), and how much energy is actually used for the accelerator (during a science run, of course - the accelerators typically do not operate at full power 24/7/365!) Nimur (talk) 15:13, 20 September 2009 (UTC)

The nominal annual electricity consumption for the CERN facility is roughly 1000 GWh; only 8% of that is for infrastructure (heat and lights). All the rest goes to the accelerator facilities. In addition to the actual energy required to accelerate particles, there is massive consumption of electricity required to maintain the vacuum systems (the LHC alone contains more than fifty kilometers of ultrahigh-vacuum pipe) and the cryogenic plants (the LHC holds roughly a hundred tons of liquid helium). The nominal annual consumption of the LHC alone is about 390 GWh, which averages out to about 40 MW continuous &dmash; but the beamline isn't actually on for the whole time [14]. The LHC will usually be shut down in the winter months due to high electricity costs (the Swiss use a lot of electric heat), and even during the rest of the year it will not operate at full power continuously. Based on that, I would expect a fully-powered-up LCH to be pulling 100 MW or so out of the local grid. TenOfAllTrades(talk) 17:49, 20 September 2009 (UTC)

That would be a lot of power - enough to warrant its own electric generator. 100 MW of average continuous power is about 10% of a large nuclear station's peak output capacity - enough energy for a large town or city. I suspect that if the draw is that large (and it may well be), then there must be significant on-site generation capacity. Also, thanks to TenOfAllTrade's great link, I found my pie-chart. According to that page, the electricity is jointly supplied by three separate power distributors in France and Switzerland. I imagine the technical challenge of load-balancing that quantity of power (not to mention the politics of billing it) is huge. Nimur (talk) 20:03, 20 September 2009 (UTC)

There's some more figures here [15] - it makes the point that most of the energy consumption is refrigeration. The LHC is quoted at 120MW.83.100.251.196 (talk) 20:51, 20 September 2009 (UTC)

I suppose it's impossible to properly insulate the electromagnets since that would get in the way of their interaction with the 'pipe' - can anyone say anymore about this - is it very difficult to insulate the electromagnets on the inside part?83.100.251.196 (talk) 21:01, 20 September 2009 (UTC)

what can I grow in a vase ~5" by ~30" ?

So someone unloaded a bunch of vases on me from a wedding reception. I've given a few away but am stuck with 4. They're very tall, very skinny cylinders. About 5" x 30". Ideally, I'd like to grow vegetables in them, but failing that I'd settle for a regular ol' houseplant. I've looked around a bit and there are certain species that would benefit from the depth (tomatoes...) but would really have a hard time with the width (also tomatoes...). Does anyone have any ideas? inb4 "put cut flowers in them" 74.115.162.11 (talk) 10:29, 20 September 2009 (UTC)

Drainage is going to be a problem unless you're able to make holes in the bottoms and stand them in saucers. Given that, perhaps you could grow something that requires hilling, such as leeks, gradually building up the soil as they grow.--Shantavira|^{feed me} 10:47, 20 September 2009 (UTC)

carrots ? 83.100.251.196 (talk) 10:50, 20 September 2009 (UTC)

OP here. Thanks! They're ceramic so I can put holes in the bottom without much difficulty. I'll read up on leeks. Hadn't thought about carrots - maybe I could tie em all together and make a carrot patch! That's a lot of soil for only 4 carrots though... there's gotta be something else. 74.115.162.11 (talk) 11:51, 20 September 2009 (UTC)

The dimensions you describe sound more like they are designed to display cut flowers than grow them. I'd fill them with fully grown tall flowers or plants. Some don't even need water, like cat tails. Other could benefit from water, like lillies. However, even with water, the cut flowers will only last a few days, so just toss them, and the water, when they go limp. StuRat (talk) 12:06, 20 September 2009 (UTC)

What is WELS?

During the translation of Saint John River (New Brunswick) I have encountered this sentence: "There is an Abenaki burial site containing a large number of graves where the Big Black River joins the Saint John in township 18, range 13, WELS." The bold text should be the location of the site, however I do not understand any of it. So, please describe "township", "range" and "WELS" to me. Thank you! - Xbspiro (talk) 11:36, 20 September 2009 (UTC)

The article on Public Land Survey System has the answer. --Cookatoo.ergo.ZooM (talk) 12:09, 20 September 2009 (UTC)

Since New Brunswick is a Canadian province, you might find the answers at Dominion Land Survey. However, I would guess that the WELS term is the same as in the US, where it means "West of the Easterly Line of the State" (except that in Canada it would be the province or territory). See Wels_(disambiguation). StuRat (talk) 12:19, 20 September 2009 (UTC)

Aw, think a bit. Why would "state" be used to refer to a province? (Or territory, but there are no territories anywhere near there and never have been.) And anyway, if you read the DLS article, you'll see that that survey system wasn't used in the older parts of Canada (just as the PLSS wasn't used in the olest parts of the US), and that where it was used, things were referred to the various principal meridians, not to political boundaries.

In fact I expect Cookatoo had it right -- because the confluence of those rivres is not in New Brunswick, but in northwestern Maine, about 15 miles east of St-Pamphile, Quebec. But it wasn't the PLSS. See the Historical Atlas of the United States published in 1988 by National Geographic (ISBN 0-87044-747-5, not to be confused with any other atlas by the same name). On page 98 is a map in 6 colors showing where the different land survey systems were used, which I happen to have a photocopy of here; and for northern Maine, what it shows is "Rectangular survey, local or state".

Considering the reference to ranges of townships, I imagine that the survey used some principles similar to the PLSS, but it was not part of the PLSS. If the "easterly line" means the north-south part of the international border, then the townships cannot have been the 6-mile squares of the PLSS, as the location is less than 80 miles from that line; but maybe it refers to a line drawn north from a point farther east in southern Maine. I can't say.

--Anonymous, 22:55 UTC, September 20, 2009.

It's not inconceivable that parts of Canada near the US might share some of the same systems with the US. For example, Canada has dollars, quarters, dimes, nickels, and pennies, just like in the US. They don't use pounds or euros as in the UK. However, the sight actually being in Maine makes even more sense. StuRat (talk) 19:25, 21 September 2009 (UTC)

The PLSS plan was indeed copied in Canada as the DLS, but it was a different survey. In both countries, the act of surveying land not previously owned by anyone who counted into lots to be made available to settlers was an important exercise of sovereignty, first by the colonial powers and later by the independent countries that succeeded them. The methods of one country's survey might be copied in the other, but the survey itself would not cross the border, which was my point. --Anonymous, 19:55 UTC, September 21, 2009.

Also note that the US/Canadian border has changed at times (going all the way back to when both were colonies). Thus, if a survey was already done by one country, and that land is then acquired by another country, they might tend to go with the previous surveys rather than re-invent the wheel (and upset many locals who find their house is no longer entirely on their land). StuRat (talk) 20:20, 21 September 2009 (UTC)

Fair point. Normally one would want the border to be agreed on before surveys happen, because people also don't like to learn that their house is in the wrong country. But it doesn't always happen that way. Maine's border with what is now Canada, by the way, was defined unclearly in the original Treaty of Paris (1783) and didn't finally get settled until the Webster-Ashburton Treaty of 1842. I don't know when the areas around there were surveyed. --Anonymous, 07:32 UTC, September 21, 2009.

Thanks to your suggestions, I have found the answer in this article. Thanks again for all three of you! - Xbspiro (talk) 19:08, 21 September 2009 (UTC)

The "easterly line of the state" in Aroostook County, eh? So then they're not 6-mile square townships. Thanks. --Anonymous, 19:58 UTC, September 21, 2009.

Genetically engineered meat growing plant?

Would it be possible to genetically engineer a plant or tree to produce animal tissue for human consumption? For example a tree that grew chicken drumsticks on its branches?Trevor Loughlin (talk) 13:23, 20 September 2009 (UTC)

Theoretically it would probably be easier to genetically modify an animal that was nothing but tissue growth (you would be making an "artificial animal" of sorts), than it would be to engineer a vegetable to make animal tissue (totally different cell types, metabolisms, etc.). So for example you'd modify the DNA (and other things) of an embryo of a pig, for example, to create something that would just generate pig flesh (no head, no brain, no bones) if you put it in a solution of oxygen and nutrients, or something along those lines. It would still technically be an "animal" all the way, though it wouldn't have any nervous system (and hence no ability to suffer, and relatively simplified needs). But from a plant? I don't know—probably not. Plant and animal DNA is just way too different and probably is not in any way compatible. The closest you could probably get is plant flesh that somewhat simulated animal flesh (sort of a tofu plant) but getting something that really simulated its composition and flavor... I dunno, that's pretty hard to imagine even with very highly advanced capabilities. Much easier to just make meat from meat. --98.217.14.211 (talk) 14:11, 20 September 2009 (UTC)

A fictional treatment of 98's "artificial animal" features in Frederik Pohl & C. M. Kornbluth's classic 1953 science-fiction novel (previously a 1952 magazine serial entitled Gravy Planet), The Space Merchants. Cheap Gallina chicken meat, marketed as "Chicken Little", is harvested from an eponymous "grey-brown, rubbery hemisphere some fifteen yards in diameter . . ." - essentially an immortal cancer tumour. Yum! 87.81.230.195 (talk) 17:37, 20 September 2009 (UTC)

It should be possible to grow a food product which tastes like meat and has the texture of meat from plants, even is it is not genetically meat. See [16] for some existing plant-derived meat substuitutes. Genetic engineering might start with tofo growing from soy and seitan (sp?)growing from wheat, both very meat like. Mushrooms already yield the meat-like Quorn™. "GoodBite," made from peas and wheat, is already meatlike. Scientists already can insert animal genes into plants, per [17]. Edison (talk) 18:46, 20 September 2009 (UTC)

Nothing is impossible, but getting plants to produce animal cells is about as difficult a task as could be imagined. Basically you would have to combine the plant and animal genomes in one cell, add a "master expression controller" that switches a cell between plant and animal phenotype, add machinery to control the controller, and add some machinery that would pump sugars and other nutrients from the plant part to the animal part. At best it would take a heck of a lot of plant tissue to support even a little bit of animal tissue. Looie496 (talk) 22:45, 20 September 2009 (UTC)

Dark meat is different than light because it is excercised more. All forms of meat in a vat/grown flesh that doesn't move even a little would be the ultimate light meat and taste bad. Sagittarian Milky Way (talk) 02:19, 21 September 2009 (UTC)

Could you simulate exercise by attaching electrodes and giving the muscle tissue small shocks? --Tango (talk) 02:34, 21 September 2009 (UTC)

It worked for Galvani.. But on a plant? We got all these wires, stems, blood vessels.. it's the Borgified Frankenstein plant. Sagittarian Milky Way (talk) 02:54, 21 September 2009 (UTC)

The advantage of such a plant-animal hybrid would be that it would use photosynthesis and basic soil nutrients/fertilizer to cut out all the energy inefficiencies in the plant to animal chain, along with the labour of animal husbandry. As for exercise, the chicken legs could have a natural pacemaker to make them pulsate and also circulate blood.Perhaps a placenta like interface could convert plant proteins into blood for the muscle tissue.Trevor Loughlin (talk) 06:10, 21 September 2009 (UTC)

You're hinting at the key issue of why someone would want to do this, which is cost-effectiveness. It might be technologically possible, but if the end product isn't cheaper than raising real chickens, it would be hard to find a market for it. →Baseball Bugs ^{What's up, Doc?} carrots 06:20, 21 September 2009 (UTC)

There's no way to compete with the cost of raising chickens in, say, the current US ag environment (where the overall costs of raising the chickens in a factory setting—e.g., to the environment, or in the case of health care—are not picked up by the producer, but by the government or the consumers). One could, I guess, imagine a world where factory farming of the sort done now is illegal, and that these other costs are paid for by producers, which might make the price a bit more competitive. But that would require the actual R&D of the chicken-plant to be quite low, as the production costs are probably comparable to regular chickens... yeah, I don't know if I see it happening any time soon, to be sure. --98.217.14.211 (talk) 12:50, 21 September 2009 (UTC)

your premises are wrong, your argument is invalid, but your conclusion is correct.

any historical examples of such?

Not sure of historical examples, but argument from fallacy is related to this and contains some hypothetical examples. --Mark PEA (talk) 14:21, 20 September 2009 (UTC)

Perhaps Fermat's Last Theorem? He did say that "I have discovered a truly marvellous proof of this, which this margin is too narrow to contain" - which, given the actual proof, is probably wrong. Tim Song (talk) 14:34, 20 September 2009 (UTC)

Pretty much any failed scientific theory is an example of that.

• Alchemy - for example - starts with the premise that the universe is made from Earth, Air, Fire and Water - proceeds to argue that (say) burning wood in air drives out the water and air and adds fire (which has negative mass in this scheme of things) - concluding that you'd wind up with some dry, Earth-like material with much less mass than the original wood (which is a fair description of wood-ash) and that you could condense water out of the gasses ("air") that are produced in the wood-smoke. The conclusion fits observations - but the premise and argument are quite utterly bogus.
• Aristotle's theories of motion - says that when you push something, it gradually slows down and stops because being stationary is it's natural state, to which it seeks to return - and that heavy objects fall faster than light ones. This is completely incorrect - but turns out to work reasonably well down here on earth where we have air resistance and friction pretty much everywhere you look. (Dirty little secret: Several computer games use Aristotle's laws of mechanics rather than Newton's because they are easier to work with and produce pretty convincing results most of the time!)

SteveBaker (talk) 14:40, 20 September 2009 (UTC)

How about Phlogiston theory - apparently there isn't any phlogoston - but things still burn.83.100.251.196 (talk) 17:38, 20 September 2009 (UTC)

The Bohr model of hydrogen is a good one. It got the correct spectral lines despite having nearly all the details wrong. In Bohr's model the nth energy level was a circular orbit with n units of the fundamental angular momentum, but in reality the energy doesn't depend on the angular momentum at all (to a first approximation). One thing these all have in common, though, is that their predictions are really retrodictions—they were concocted to match existing experimental results. It's harder to think of totally wrong theories that successfully predicted new phenomena. I guess the Dirac sea model counts (it predicted the positron), and maybe Einstein's static universe (predicted a positive cosmological constant). -- BenRG (talk) 19:01, 20 September 2009 (UTC)

For more background on the Bohr model, the important work was done by Johannes Rydberg (see Rydberg formula) who discovered that the spectral lines of Hydrogen (see Balmer series) could be described via a simple inverse square law. That is, the wavelength difference between the lines matched, exactly, a very simple equation with simple variables. Rydberg had no idea about the electronic structure of the atom (he devised his equation in 1888, the electron would not be discovered until 1897), indeed he had no idea how his simple equation related to the actual structure of the atom. It was Bohr who connected the dots between Rydberg's equation and the organization of electrons in an atom. It turns out that Rydberg's equation is really a special case of the Schrödinger equation for a one-electron system; likewise the Bohr model only holds for a one-electron system. This is because of the problem with an n-body problem. A one electron system is a two-body problem (electron and nucleus), and as such, the interactions can be descibed by simple inverse square laws, like the Rydberg equation. Once you have more than two interactions, such as between many electrons and the each other and the nucleus, it becomes impossible to use simple mechanics to describe the state of the electrons. The relationship between the Bohr/Rydberg model and the Schrödinger model is EXACTLY analogous to the relationship between Newtonian mechanics and Quantum mechanics. As such, though it is not directly applicable in most cases, it is still a very useful model in the same way that Newtonian physics is a useful, if incorrect, model. --Jayron32 02:00, 21 September 2009 (UTC)

The Titius–Bode law is a good one - it provides a simple equation that describes the distances of the planets from the sun. It's an utterly beautiful result - and it fitted the positions of the planets that were known at the time (circa 1715) - almost perfectly. Even after Uranus was discovered - 70 years later - it fitted the rule perfectly. Sadly, Neptune and Pluto are nowhere near their predicted places - and in truth it's more or less a coincidence that the rule works so well for the inner planets. SteveBaker (talk) 21:38, 20 September 2009 (UTC)

I think it's a bad example because it doesn't meet the OP's first two requirements: "your premises are wrong" and "your argument is invalid". Being an empirical law, it had no premises; being an empirical law, the only argument supporting it was that it matched known solar system distances. The scientists hundreds of years ago didn't know why it worked, but that doesn't mean they made invalid assumptions or logical fallacies. --99.237.234.104 (talk) 23:20, 21 September 2009 (UTC)

On a similar note Kepler's Mysterium Cosmographicum gives pretty good results for planetary distances using methodology that would be indistinguisable from witchcraft to many modern scientists.83.100.251.196 (talk) 21:55, 20 September 2009 (UTC)

Sure. Even the wrong people can be right sometimes. Imagine Reason (talk) 01:13, 22 September 2009 (UTC)

Caloric theory: The premises were wrong, but the conclusions were good enough to form the basis of modern thermodynamics. --Carnildo (talk) 01:32, 23 September 2009 (UTC)

Those who espouse hidden variable theory consider the premises of quantum mechanics wrong, despite the ability of quantum mechanics to accurately predict many phenomena. However, they have yet to provide a better explanation which supersedes the quantum mechanical treatment. Nimur (talk) 21:40, 25 September 2009 (UTC)

Inexpensive LCD display that is relatively good for photo editing work — recommendations?

Does anyone know of an inexpensive (no more than $500 US) LCD display that is relatively good for photo editing work? I'm looking for one that's able to show the difference between different shades of colors near both the low end and the high end of the dynamic range.

I never realized how good my Komodo Sceptre was until I got a cheap VGA LCD monitor to put side-by-side with it. The color fidelity, contrast ratio, and overall high quality of the Komodo is fantastic, and I bought it five years ago for under $250. Your price-point will largely depend on the viewable area you want. Definitely stick to DVI (digital connection) if you are aiming for color fidelity. Nimur (talk) 15:22, 20 September 2009 (UTC)

radioactive decay: kinetics v. thermodynamics

I see with some interest (let's use isotopes of thorium as an example) that half-life has a funny correlation with decay energy. It doesn't seem to fit the Arrhenius equation model, or anything that would go with exp(). Th-231 has an incredibly short half-life, even though the decay energy is only 0.39 MeV. The decay energy for Th-232 is 4.0 MeV, though it has a half-life of 11.4 billion years, but the half-life of the next most stable isotope is six orders of magnitude smaller, even though the decay energy only decreased by 0.7 MeV. John Riemann Soong (talk) 16:28, 20 September 2009 (UTC)

Nuclear decay requires a quantum mechanical treatment, properly adjusted for the large number of interacting nucleons. Have you analyzed the decay from that point of view? Classical atomic theory and even the simplifications of quantum theory that work well for "electron clouds" are rarely rigorous enough to solve the nuclear reactions such as fission and decay. Nimur (talk) 16:57, 20 September 2009 (UTC)

The decay ernergy wouldn't be the right quantity anyway - the Arrhenius equation uses activation energy not reaction enthalpy.

You'd need the energy of the transition state between starting nucleotide, and deacy products, and as Nimur says a classical treatment might not still be good - at the very least I'd would expect something like the equivalent of quantum tunnelling to be important (since I expect the nucleus to be very small)

That said there might be a classical relationship between energy of decay, and the activation energy (and hence half life) - however this would be complicated by the structure of the nucleus... (what ever that is exactly)

If you want to try a classical comparison that might work - I'd suggest comparing half lifes of nucleotides differing by 2n+2p (since I already know that that is a significant number..)

It's a bit like comparing properties of transistion elements - just as you need to take into account electron configuration for those, you'll probably need to take into account (or look for patterns) in nuclear structure as the atomic number increases..83.100.251.196 (talk) 17:35, 20 September 2009 (UTC)

Leaving aside the quantum mechanical considerations for a moment, the trick to using the Arrhenius equation is that E_a is defined as the activation energy of the reaction in question. The decay energy that you're looking at is related to the net energy change of the reaction; it doesn't tell you anything about the activation energy of the decay 'reaction'. What the change in energy will tell you is the ratio of reactants to products (as a function of temperature) after the system reaches equilibrium; see Boltzmann distribution. TenOfAllTrades(talk) 18:02, 20 September 2009 (UTC)

Almost forgot - are you comparing the same decay processes - there are a lot of different types beta decay, alpha decay etc that would complicate an already complicated relationship.83.100.251.196 (talk) 20:33, 20 September 2009 (UTC)

Victoria Falls swimmers

Tourists swimming at the edge of Victoria Falls

htf is this possible? — Preceding unsigned comment added by 86.162.106.217 (talk)

The brownish area between the swimmers and the falls is a rock lip just beneath the surface. See Snopes for more info. DMacks (talk) 19:22, 20 September 2009 (UTC)

The image description page states "It is possible to swim at the edge of the falls in a naturally formed safe pool, accessed via Livingstone Island." and from our article on Victoria Falls "A famous feature is a naturally formed pool known as the Devil's Armchair, near the edge of the falls, accessed via Livingstone Island. When the river flow is at a safe level, usually during the months of September and December, people can swim as close as possible to the edge of the falls within the pool without continuing over the edge and falling into the gorge; this is possible due to a natural rock wall just below the water and at the very edge of the falls that stops their progress despite the current." Nanonic (talk) 19:25, 20 September 2009 (UTC)

That does not mean that these tourists are participating in a "safe" activity. Nimur (talk) 19:58, 20 September 2009 (UTC)

It's dangerous, just not as dangerous as it looks. Although, given the way waterfalls work, that rock lip could shatter at any time. For a more daring similar illustration, go to this NG page [18] and scroll to the right about three times. Look for a thumbnail of an African in silhouette. That's dangerous. Baseball Bugs ^{What's up, Doc?} carrots 20:24, 20 September 2009 (UTC)

Took me ages to realize you weren't talking about the baby playing with cobras. ~ Amory (user • talk • contribs) 22:32, 20 September 2009 (UTC)

Well, that doesn't seem too safe either. But I was referring to the photo of the African standing on the lip of that pool. One little slip and you'd be fish food... after a nice 30-story drop. Baseball Bugs ^{What's up, Doc?} carrots 22:36, 20 September 2009 (UTC)

(According to the text, the cobras are defanged. So that's not sooo bad...) --98.217.14.211 (talk) 12:55, 21 September 2009 (UTC)

Declining bee population?

Human carnivorous behaviour has reduced flora/plants and in turn is threatening the bee population. Is this true? I don't read it on Wikipedia and I don't know if other sources are good or just there is two of everything on the internet... Anybody know about bees? ~ R.T.G 20:21, 20 September 2009 (UTC)

Sort of this was in the news in the UK [19] [20] [21] - there seemed to be an unexplained number of colony collapses Colony collapse disorder which may be unrelated to farming methods.

Excluding the potential for a bee virus, increased levels of monoculture, lack of wild flowers, various insecticides, etc are a problem for bees - topics briefly mentioned in the above newspaper links.83.100.251.196 (talk) 20:27, 20 September 2009 (UTC)

I think we should be linking this colony collapse disorder to bee because in Ireland there is an apparent 50% decline and according to some here that only follows a similar happening in America and now from this we see it is a world phenomenon. Thank you. ~ R.T.G 20:32, 20 September 2009 (UTC)

CCD is linked to bees, and vice versa. What link do you think is missing? --Tagishsimon (talk) 18:03, 21 September 2009 (UTC)

Colony collapse disorder does mean "declining bee population." It is a specific type of loss of bees. Most claims of colony collapse disorder turn out to be something different. If you read the article colony collapse disorder, it details that much of the "world-wide" claims of CCD are not in any way CCD or still unsubstantiated. -- kainaw™ 20:38, 20 September 2009 (UTC)

I don't know what you mean but the article seems to confirm that bees are mysteriously dying in large numbers around the world? ~ R.T.G 20:40, 20 September 2009 (UTC)

The CCD article makes is painfully clear that many cases that are initially classified by farmers as CCD turn out to be population loss for another reason. Therefore, your request that the CCD article be linked directly to the main bee article because it is a "world phenomenon" requires some substantial evidence that it is a world phenomenon. I think you are using CCD as a synonym for "population loss". CCD is one cause of population loss. There are many others that are not CCD. -- kainaw™ 21:27, 20 September 2009 (UTC)

I have to disagree. Much like the term AIDS was used to mean any unexplained deficiency in the human immune system, prior to the identification of an agent (HIV, in this case), CCD is currently used to mean any unexplained loss in bee population. Many possible agents have been identified, in this case, so CCD really doesn't yet have a specific meaning. StuRat (talk) 17:16, 21 September 2009 (UTC)

And beside that, going by the article claims all we would need is incidents in China and we would have circled the globe. Will that do for a broader implication of "worldwide"? Seriously it says Canada, 25 USA states, 7 or 8 European countries and suspicious reports from Brazil and India, that is quite considerable and completely overlooked on the bee article as well as by the experts here on the "everything dies if the bees die" ~ R.T.G 17:51, 21 September 2009 (UTC)

That's overstating it a bit. Everything wouldn't die even if bees all went extinct (which is extremely unlikely, as they will mutate and adapt to handle whatever threatens them). There are other pollinators for flowers, such as birds and other insects. As far as people are concerned, we can manually pollinate plants (or possibly build machines for that purpose), or we can eat foods that don't require pollination (such as those which reproduce asexually). Life goes on. StuRat (talk) 19:13, 21 September 2009 (UTC)

Sorry Stu but that is the naive view. Is it fair for us to say "They'll mutate and cope with it!"? Well, I think the problem must be a bit more serious than that! ~ R.T.G 01:19, 22 September 2009 (UTC)

No, it's not naive at all. Insects have very short lifespans and high mutation rates, allowing them to develop resistance far more quickly than us. So, while it took humans centuries to develop resistance to the Black Plague, bees could likely do it in a few years. StuRat (talk) 16:03, 22 September 2009 (UTC)

If anyone has any citations that state CCD has lost any and all meaning and currently means "any reason for a bee to die", then please update the article. Otherwise, I will continue to stick with the cited article over claims otherwise. CCD has a very specific meaning. As the article states: "a major part of the subsequent analysis of the phenomenon hinges upon distinguishing between true CCD losses and non-CCD losses." What is happening in this discussion is a rationalization that any loss is CCD. We might as well claim that cars cause CCD when they hit bees while driving down the road. I sincerely hope that the absurdity of such a claim is obvious and, I hope, makes it clear that making up your own definition of CCD is just as absurd. If you want to show concern over declining bee population, that is fine. Trying to redefine CCD to be anything you want it to mean takes away from the message and makes it sound absurdly alarmist. -- kainaw™ 04:01, 22 September 2009 (UTC)

You changing the def of CCD from "any unexplained death of a bee colony" to "any death of a bee" is a straw man argument. Nobody is arguing that an explained cause of death, like a car hitting a bee, is CCD. When you refute an argument, please stick with the actual argument, and don't just exaggerate it to make fun of it, that's not at all helpful. StuRat (talk) 16:03, 22 September 2009 (UTC)

Please, do not detract from the important factor one more time. CCD? Who cares. The bees are dying. There is speculation that such a thing would be frighteningly dangerous to life as we know it. There is not so much as a scare mongerer on the topic to inform us about that problem. The closest we have on Wikipedia, apparently so far, is the CCD article. Defining CCD is a secondary almost irreleveant topic unless you have zero real interest in the important topic, the bees are mysteriously dying all over the place and nobody seems to know about it. It is so unheard of, I imagine people saying "You made that up". If you can think of a more relevant subject than CCD please share with us. If you want to discuss disparity between language and expert speculation on CCD, try Talk:Colony collapse disorder. I can see no topic more worthy of linking to the article Bee wether they aren't sure if it was CCD or not unless it is a hoax article? ~ R.T.G 12:52, 22 September 2009 (UTC)

It appears that you now understand my point: CCD is a type of mass-death in a bee hive. It is not the term used to define any and all mass-deaths in a bee hive. Understanding that point, I hope you understand why I disagree with your claim that we should "link" CCD to bee. It may very well be that your definition of "link" is different than mine. It appears to me that you are claiming that we should take the article on bees and replace it with the article of CCD. My only intention in this entire thread has been to point out that CCD is a type of mass-death for bees. It is not a definition of bee. Therefore, if someone wants to learn about bees, getting an article about CCD will not be very helpful. If you mean something completely different by "link", please explain yourself further. -- kainaw™ 19:25, 22 September 2009 (UTC)

Sure Kainaw, the article about bees dying is completely irrelevat to the subject of bees. I am glad, in a way, that you can see how I understand you because my OP would not have been answered satisfactorily if only for you perhaps, wouldn't you say so? Like you say, if learning about bees, knowledge of CCD would not be very helpful even though it was the most useful addition to this thread so far, we will take your word for it until you add something better, right? Oh, I can see you understand me too so that is all settled, yay. ~ R.T.G 10:00, 23 September 2009 (UTC)

In true American fashion, Yanks assume that because they have just about destroyed THEIR OWN bee colonies through rapacious greed, the same is true EVERYWHERE else. It is not. In Australia, our bees are disease-free, healthy, happy, and producing the world's best honey. But then we don't drive them around in trucks for thousands of miles, forcing them to fertilise different fields day after day, and thus multiplying over and over again their chances of contracting a disease, and making their lives unbearable because they have to learn new geographies and new flowers just as they become familiar with the old ones. Nor do we force them to eat stuff from genetically modified foods. And in reward, by letting them feed on the pollen of a particular flower at their own leisure, our contented bees produce honey with the exquisite taste and aroma of THAT flower, and other countries beat a path to our door to buy jars of it. The destruction of American bee colonies, with genetic diseases leading to malformed bees, and the collapse of their immune systems through being forced to exist in highly unnatural slave type conditions has been well documented. Myles325a (talk) 05:06, 26 September 2009 (UTC)

Hmm Australia? You mean a possible source of Diseases of the honey bee#Israel acute paralysis virus (IAPV) which has been linked to CCD? [22] (yes I'm aware this raises doubt on the claim Australian bees is what brought it to the US) [23] [24] [25] Incidentally, I doubt anyone forces bees to 'eat stuff from genetically modified foods' they choose to do it themselves. Also the idea this is solely an American problem doesn't explain why it's a problem in parts of Europe (as mentioned in the CCD article and in the Wired article), which don't have many of the causes you mentioned above. Incidentally I'm doubtful of the claim Australian honey is the world's best. Jellybush honey aka Australian Mānuka honey is not as well known as (real New Zealand) Mānuka honey, in fact it isn't even mentioned in Monofloral honey and the fact that it's sometimes called Australian Mānuka honey should given an idea too. Nil Einne (talk) 07:55, 26 September 2009 (UTC)

This sounds like the same anti-American rhetoric I'd heard when AIDS was first documented in the US (note that it had apparently existed for years in Africa before that, without being documented). People in other countries argued that they didn't have to do anything about it since "it's just an American disease". Now it's a serious threat in many of those nations which chose to ignore it. StuRat (talk) 12:01, 26 September 2009 (UTC)

Myles325a back here. Sturat, argument by analogy is a poor way to discuss anything, and is not counted as evidence. Nil Einne, yes there have been attempts to blame Australian bees for American bee problems, but informed sources have discounted that, and many put forward the idea that such a slander has been promoted to avert attention from the rapacious practices that have led to the decline of the bee in the US. How is it that even now there appears to be NO clear answer as to what has caused these major epidemics, so dangerous to the fertilisation of crops? Could it be that big business has hushed it all up to protect their own pockets? Your other comments are amongst the silliest I have read here for quite a while (and that's saying something.) "Bees choose to [eat what they eat] themselves", do they? Yeah, my cat doesn't eat meat...I don't give it any. Bees are not window-shopping credit card carrying flits from Sex and the City. When they are put into some huge field with identically cloned and genetically modified sunflowers, they have to eat that, don't they? And Australia has hundreds of differnt honeys. How does asserting that ONE brand of honey (Manuka) is actually a New Zealand honey go towards rebutting my claim that our honey is the best in the world? Of course New Zealand's is 2nd best, and I wouldn't eat the stuff from your place if they tied me down and poured honey down a funnel wedged in my throat. Myles325a (talk) 23:06, 27 September 2009 (UTC)

Long time later, but my point is that Mānuka honey is arguablly far more likely to be considered the best honey then anything from Australia. There's good evidence from this from the fact monofloral honey mentions 3 monofloral honeys from Australia. One of them is Mānuka honey which as I said is generally considered more of a New Zealand thing and is well known enough to have an article. Another is Eucalyptus where the article barely mentions the honey. A third is a subtype of the former Eucalyptus marginata where again the article barely mentions the honey. Incidentally, it sounds like you don't know how science works, but from your history, I guess this isn't surprising. Your reply BTW is pretty silly. My cat eats meat sometimes it will even eat meat I leave lying around if I'm careless. What it will not eat (unlike dogs) is chocolate probably because it can't taste sucrose. The only way I could get it to eat chocolate would be either by really forcing it. Giving it meat to eat isn't forcing it to eat meat, just the same as putting bees in a field containing GM crops isn't forcing them. It's simply what we give them. The use of the word 'force' implies an unnecessary degree of coercion which isn't suited to the realities of the situation. Bees will eat whatever is similar enough to what they've evolved to eat that's in the environment. Incidentally, you still seem to be ignoring the fact that CCD is not a problem unique to the US. Nil Einne (talk) 08:48, 5 July 2012 (UTC)

Jupiter's gravity protecting Earth from comet impacts

I've read that Jupiter's gravity protects the Earth from comet impacts. How does this work? --Halcatalyst (talk) 21:20, 20 September 2009 (UTC)

Jupiter is big and has a large gravity field. As a result, it's got a good chance of interacting with passing comets such that they either get flung out of the solar system or, more rarely, collide with Jupiter directly. It's also possible that Jupiter's gravity tweaks a comet just so and causes a collision with Earth, but those odds are substantially lower given that the Late Heavy Bombardment is past and most remaining space bits are in stable orbits). To a lesser extent, the other gas giants provide similar protection, but they're both less massive (thus less gravitational influence) and farther away (thus covering proportionally less of the solar system). — Lomn 21:43, 20 September 2009 (UTC)

The idea being that over time Jupiter will vacuum up or toss out many of the random space objects in orbits around the sun that cross Jupiter's orbit. Those same objects tend to be the ones that could potentially hit Earth. Sometimes the interaction between Jupiter and a comet might just redirect the comet to some other orbit, which on average probably doesn't hurt or help our chances of being hit, but when a comet collides with Jupiter or gets flung out of the sun's orbit, then we have one less comet in the solar system to worry about. Rckrone (talk) 22:07, 20 September 2009 (UTC)

It's of note that at Jupiter#Impacts it says that actually it's unclear whether Jupiter actually does this. --98.217.14.211 (talk) 00:19, 21 September 2009 (UTC)

I too think this idea is one that sounds straightforward but is less so when you give it more thought. Sure, comets and other stuff will collide with Jupiter and thus be mopped up, and no longer be a danger. And its immense gravity will make other coments deviate from their paths. But wouldn't such deviations be divided between those comets which are expelled from the Solar System and those which are propelled inwards where they are more of a danger to Earth than ever? We might expect that many comets' orbits are around the sun. If those orbits are very eccentric, they will pass the Earth again and again, each time from a different direction and by a different distance. This is what Halley's comet does now. And eventually the comet could hit Earth. A large gas giant like Jupiter could have the effect of disturbing that orbit on one of the comet's visits to our Solar System. That disturbance could well mean the connection between the comet and the Sun was changed and there would be a good chance that it would be thrown out of the sytem. That would be better for the Earth. In the early days of the Solar System, there was a lot of debris around, and we can see by the Moon's surface that there were a lot of collisions. It is thought that our moon was formed after a major collision between the Earth and another body ( which also gave the Earth its tilt). Some planets have been knocked sideways by immense collisions. But over time, these potentially dangerous bodies have been either mopped up, herded into roughly circular orbits or thrown out of the System. Planets like Jupiter may have been quite important for this process. Incidentally, it has been proposed that the Earth has had additional protection from the moon which circles it, in a local and smaller version of what Jupiter is thought to do. Myles325a (talk) 00:44, 21 September 2009 (UTC)

Two points. First: Comet Halley's orbit doesn't come anywhere near Earth's orbit. Second: Comets sent by Jupiter into the inner solar system are likely to have a second encounter with Jupiter later on when it might be ejected. If it doesn't get ejected then it is likely to have a third encounter and than a fourth one , etc... On the other hand, once a comet gets ejected it never comes back, and that's the point of the "Jupiter mops up comets" theory. Dauto (talk) 01:13, 21 September 2009 (UTC)

To draw an analogy, its like cars driving on a snowy road. As the tires scatter the snow, some of the snow lands somewhere else on the road, where the next car can still drive through it. However, any snow that gets thrown from the road will never have any mechanism to get back on the road, so it is gone forever. As hundreds of cars drive along the road, it will gradually clear of snow, since each car clears some of the snow. Likewise, Jupiter does not actually have to clear every comet the first time it encounters it. It only has to clear it from the solar system once; and Jupiter has had millions of orbits to "clear the snow" as it were. Even if there is only a tiny chance on any one encounter that Jupiter will eject any one object, after many thousands of such encounters, they all become cleared out. --Jayron32 01:42, 21 September 2009 (UTC)

You are ignoring the fact that nearly all comets crossing the inner solar system are "new", meaning that they were scattered into the inner solar system due to Oort cloud and interstellar interactions within the last few million years. So, in our mature solar system, the population of inner solar system crossing comets is a balance between processes that scatter comets into the inner solar system (from the practically limitless population beyond Neptune) and processes that destroy or scatter them out again. It is not the case that Jupiter could ever destroy all the comets. Dragons flight (talk) 02:05, 21 September 2009 (UTC)

Halley's Comet has an aphelion of 35.1 AU and a perihelion of 0.586 AU, so it must cross the Earth's orbit occasionally (every few thousand orbits, maybe - its orbit is highly inclined compared to Earth's orbit, so we have to wait for them to precess so the nodes coincide). A collision is extremely unlikely, but not impossible. --Tango (talk) 01:55, 21 September 2009 (UTC)

Given that we passed through Halley's tail in its 1910 sighting, a collision with that one is certainly within the realm of possibility. Baseball Bugs ^{What's up, Doc?} carrots 02:56, 21 September 2009 (UTC)

The tail is literally millions of times longer than the solid part and thousands of times wider. No big iffy. Your death has only a 1 in 25000 chance of being by comet or asteroid. Sagittarian Milky Way (talk) 03:10, 21 September 2009 (UTC)

No question about it. But it's still possible. Millions of miles sounds like a lot, but it's a blip in interstellar space. It came relatively close once. It might be millions of years before it comes that close (or closer) again. But it could happen. Baseball Bugs ^{What's up, Doc?} carrots 03:37, 21 September 2009 (UTC)

Tango, as you said, Halley's orbit has a high inclination and that's why its orbit does not come anywhere near earth's orbit as I had originally stated. That's all I said. Slow processes such as chaotic orbit precession could conceivably over a large amount of time change that orbit into a different one where the comet might get closer to earth's orbit, but that is impossible to predict with any certainty. Dauto (talk) 15:57, 21 September 2009 (UTC)

• Thank you all for your responses. --Halcatalyst (talk) 00:17, 25 September 2009 (UTC)

Masturbation

Removed request for a medical prognosis based on a change in activity. -- kainaw™ 22:21, 20 September 2009 (UTC)

To the person who asked the question: if you ask for facts without relating them to yourself, you may have better luck getting answers. And you should start by reading masturbation. Looie496 (talk) 22:25, 20 September 2009 (UTC)

September 21

Visually sexing non-sexually diamorphic parrots?

Is this possible, if you're familiar with the species? Without waiting for one of them to lay an egg or to see which one is on top during mating, I mean. Are there any subtle features that might not be obvious to most people that you can look for to determine male from female?

There may also be behavioral ways to tell the gender. What species are we talking about ? StuRat (talk) 15:37, 21 September 2009 (UTC)

Methods for parrot gender determination Cuddlyable3 (talk) 17:04, 21 September 2009 (UTC)

Voltage ratings for light bulbs?

I've got a full-spectrum incandescent bulb for warming reptiles bought in the US that has 120V printed on it. I'm in China now and wondering if I can use it. I know from accidental experience that 120V appliances are sent to their graves on 220V, but I'm wondering about light bulbs. As far as I can recall, this is the first bulb I've ever seen that even HAS a voltage rating. Have I just not noticed all this time? Will using it blow-out the filament inside? Or do voltage ratings not really apply to bulbs? The easy solution is to just try it, but these are expensive and extremely hard to find in China so... (thank you) 218.25.32.210 (talk) 00:56, 21 September 2009 (UTC)

I've done it so you don't have to experiment (25 years ago). It will burn very brightly for a few minutes, then ... poof. No more light. The reptiles might get too warm, too, then too cold. Acroterion _(talk) 01:01, 21 September 2009 (UTC)

Thank you! 218.25.32.210 (talk) 01:20, 21 September 2009 (UTC)

And while you may never have noticed, it is quite standard for light bulbs to carry a voltage rating. --Anonymous, 05:00 UTC, September 21, 2009.

If you happen to have two identical 120v bulbs, they will work fine from 240v if connected in series (and at slightly reduced output from 220v), but don't attempt this unless you know what you are doing. These voltages are dangerous. There are step-down transformers available for a safe solution. Other solutions include connecting your single bulb across one half of a resitive load such as a room heater (or two room heaters in series), but only a qualified electrician should attempt this. Dbfirs 07:38, 21 September 2009 (UTC)

As a lightbulb is not very expensive, you should just buy one locally for the correct voltage. Googlemeister (talk) 13:14, 21 September 2009 (UTC)

Is it legal to bring reptiles bought in the US to China ? Cuddlyable3 (talk) 16:56, 21 September 2009 (UTC)

A lightbulb connected to twice the specified voltage might explode, or it might just burn very brightly for a short while before it failed, Two bulbs connected in series ((NOT PARALLEL) to twice the specified voltage should function, but when the filament in one fails, if it shorts or arcs across, the other would be subject to about twice the specified voltage, and then it might explode. The filament supports may be physically different in high and low voltage bulbs, and arrangements for breaking the arc when a filament opens might not work well at much higher voltage. Edison (talk) 23:47, 21 September 2009 (UTC)

How could a lamp filament fail in a way that short circuits the lamp ? How does fairly undramatic fusing at 4x rated heating become an explosion ? Cuddlyable3 (talk) 07:34, 23 September 2009 (UTC)

Furry *green* animals?

It occured to me on the way to work this morning that I can't think of a single fur-bearing animal that's green. Perhaps there's a small monkey species out there or another, but I can think of no grazing animals, and certainly no predators. In the upper latitudes such coloration would be a hindrance in winter, but in the subtropics and tropics I would think that shades of green would be a useful adaptation. There are plenty of green birds, reptiles, and amphibians. What's with the furries? 218.25.32.210 (talk) 01:00, 21 September 2009 (UTC)

You're quite right. Amazingly, this point has received no discussion whatsoever in any of the evolution literature that Google Scholar finds. Looie496 (talk) 01:09, 21 September 2009 (UTC)

(edit conflict)Heh well, does this count? In all seriousness, I don't know of any, and according to Mammal#Integumentary system there are none with either green or blue. If we think about it, though, there's a good reason. You mention adaptation, but what is green that a mammal hangs out around? Leaves are already way off the ground, and out of the way of most predators. If the creature ever went on the ground, a brown or white color would certainly be very favorable so as to blend in, whereas green would hinder them when on the ground. ~ Amory (user • talk • contribs) 01:13, 21 September 2009 (UTC)

I'm guessing you're from the higher latitudes. Growing up in Florida, and having traveled through Central America and northern South America, the underbrush is always exceedingly green. 218.25.32.210 (talk) 01:21, 21 September 2009 (UTC)

There is no such a thing as a green fur pigment. Evolution cannot make one magically appear. Dauto (talk) 01:25, 21 September 2009 (UTC)

Not magically, but why couldn't it occur by random mutation? It is suggested below that it would be harmful, but that seems strange to me - green pigments exist in nature without doing any harm to other types of lifeforms. --Tango (talk) 03:06, 21 September 2009 (UTC)

If you scroll down the page here it gives the simple answer that most animals (not just mammals) simply are unable to synthesize the colors blue or green. It says that the blues and greens seen in birds and amphibians aren't actually blue and green, but are due to "structural effects." That is, air sacs in feathers scatter light that make them appear blue, for example, and frogs use multiple layers. ~ Amory (user • talk • contribs) 13:52, 21 September 2009 (UTC)

AFAIK, birds 'do' green by overlaying the structural effect that creates blue upon a yellow feather. If the yellow pigment isn't present (as in the case of the blue budgerigar mutation), you end up with blue feathers in the areas that would normally be green. --Kurt Shaped Box (talk) 20:38, 21 September 2009 (UTC)

Indeed, which is why a lot of mammals have mottled and patterned fur - it breaks up the view of predators/prey and makes them harder to detect against the multi-colored and discontinuous background. ~ Amory (user • talk • contribs) 02:00, 21 September 2009 (UTC)

Outdent -- but such pigments apparently exist for feathers and skin, which brings me back to the original question - why aren't there (or why can't there be) green fur-bearing animals? 218.25.32.210 (talk) 01:33, 21 September 2009 (UTC)

The Three-toed sloth can have algae growing in their fur, which will give it a greenish color. Probably the closest to green fur you will find. --Jayron32 01:37, 21 September 2009 (UTC)

The link I provided above actually has some information, albeit unsourced. It mentions in passing that there's some evidence that producing a green pigment in fur would actually harm the animal; I can imagine this wouldn't be the case for feathers. Also, most birds that have green not only pretty much spend all their time in the air or high in trees amongst leaves, but are usually along the lines of birds of paradise. Those animals have such an immense source of resources that they have developed seemingly absurd sexual rituals, often involving incredibly bright coloring, that can in fact be a hindrance to them. Mammals (with the exception of human males) tend to be more logical in their choice of mates due to resource conservation. ~ Amory (user • talk • contribs) 01:58, 21 September 2009 (UTC)

The readers should be aware that vast majority of mammals do not possess the trichromatic color vision; only humans, some simians, and, curiously, marsupials do. Most other mammals are dichromats, therefore they can not tell green from some other colors of same perceived brightness. While this does not answer the question per se, this certainly helps explain the obvious lack of evolutionary pressure on the small mammals to turn green. There obviously is a pressure to turn white in winter, but apparently there is little or no pressure to turn green in summer. Indeed, most predators can tell white from non-white, but probably very few can tell green from some shades of grey or brown. Now, I have no idea what kind of color vision the diurnal birds of prey are capable of; I know their retinas are somewhat different from those of the mammals, but I do not know what classes of photoreceptors they have and how many. If they can tell green from grey and brown, then my hypothesis is probably wrong :( --Dr Dima (talk) 09:31, 21 September 2009 (UTC)

OK, I did a little reading and it looks like birds do have a very good color vision. However (at least in a starling) the sensitivity peaks of the different classes of cones are all far apart in wavelengths, while in humans the L and M cone sensitivity peaks are close. This suggests that birds can see some colors that we can't (in near UV, for example), but probably can not tell shades of red from shades of green very well. The latter requires the L and M cone sensitivity peaks to be close to each-other -- like it is in humans -- in order to enhance the selectivity over a relatively narrow spectral band between 560 and 600 nm. So my hypothesis may be right after all. --Dr Dima (talk) 09:56, 21 September 2009 (UTC)

The animals that tend to have good color vision are the ones that depend upon being able to tell whether fruit is ripe by sight alone. Those are not carnivores - so the prey of carnivores don't need green fur. But in any case, camoflage isn't so much about being the right color as in breaking up the shape of the animal. Think about animals like Zebra and Tigers - they have those big, bold, high-contrast stripes - which you'd think would stick out like a sore thumb. But they don't. Those patterns break up the shape of the animal and make it surprisingly hard to see. SteveBaker (talk) 13:32, 21 September 2009 (UTC)

This link backs up your theory about vision playing a role as well. ~ Amory (user • talk • contribs) 13:52, 21 September 2009 (UTC)

A couple thoughts. First, humans and some other mammals can have green eyes, so we are able to make that pigment. It's just a matter of making it in our skin rather than our eyes. And while I agree that solid green wouldn't be the best camo, perhaps green and brown stripes or mottling would be good, such as the clothes and face paint soldiers sometimes use. Next point: since the Q was about green furry animals, not just mammals, I'd include fuzzy green caterpillars. StuRat (talk) 15:02, 21 September 2009 (UTC)

Green eyes have no green pigment on them. Dauto (talk) 17:47, 21 September 2009 (UTC)

To answer the OP, the Green Monkey and the Squirrel Monkey come immediately to mind - the Green Monkey isn't really _that_ green, but the Squirrel Monkey is. :) Tevildo (talk) 19:21, 21 September 2009 (UTC)

Bunches of doctors in an emergency room...

I was looking at some pictures of emergency patients getting operated on and I noticed there were somewhere around six to seven people working with the same patient at once. What are they all doing? I am asking for a likely role breakdown for doctors/nurses/clinicians tending to the patient. (e.x. one lead surgeon, two assisting him in holding tissue away from where the main surgeon is working, one to fiddle with the IV, three residents watching to learn... something like that) Do this many doctors work on a single person for non-emergency surgery too? 66.57.240.8 (talk) 05:15, 21 September 2009 (UTC)

Well, of course, it depends on the particular surgery and the setting (large teaching hospital, small community hospital), etc., but typical roles would include the following:

1. anesthesiologist or nurse anesthetist - provide anesthesia and monitor vital signs and respiratory status
2. attending surgeon - to perform the surgery proper, supervise resident
3. surgical resident(s) - learning, may open or close incision, or perform other parts of the surgery
4. medical student(s) - learning, may run errands to lab etc.
5. scrub nurse - gives instruments to surgeon, maintains sterile operating field, keeps track of instruments and sponges, etc.
6. circulating nurse - provides supplies to scrub nurse, labels & sends pathological specimens, other tasks not requiring sterility

-Nunh-huh 06:24, 21 September 2009 (UTC)

Nurse quickly, give me suction!

And the scrub nurse can't have any kids...because she's sterile. :) DRosenbach ^{(Talk | Contribs)} 17:11, 21 September 2009 (UTC)

And the head nurse isn't likely to get pregnant either, but for an entirely different reason. :-) StuRat (talk) 20:12, 21 September 2009 (UTC)

Are you talking about an emergency room or an operating theatre? They are different things. What you may be describing as surgery may actually be resuscitation - that's what is done when a trauma patient is first brought to the ER. --Tango (talk) 20:46, 21 September 2009 (UTC)

I was looking at a bunch of different pictures from Flickr and several of them still have a lot of staff in the room when it is pretty clear that the patient is not being resuscitated. (I'm assuming that the surgeon would not be fiddling with the person's innards with forceps or tubes or whatever they are holding while resuscitating someone.) In several of the photos, the rooms were also pretty small which makes me think they are ERs and not theaters. Part of the reason I asked was because I was curious if having so many doctors crammed into one rather small room was normal and what they all were doing. I was wondering if I was mistaken in thinking that for most surgeries only three or four people were actually needed at most once the patient was stable (i.e. not being resuscitated). Thank you Nunh-huh for your detailed answer by the way. 66.57.240.8 (talk) 23:45, 21 September 2009 (UTC)

An interesting story here. Bus stop (talk) 17:19, 23 September 2009 (UTC)

an adiabatic enclosure, 2 mol of Cu...

I'm trying to get this concept. So there's one mol of Cu at 0 C, and one mol of Cu at 100 C, in thermal contact. They are both in an "adiabatic enclosure". AFAIK there is no phase transition, but their equilibrium temperatures are not 50 C. I'm trying to figure out why this is. So since it's adiabatic, I take it no energy is being lost to the environment or anything and the energy gets transferred to some other mode besides kinetic energy. (The Cp given is 33.64 + 6.28×10^-3 T J/mole K.)

This is an entropy issue I think -- it occurs to me that the volume of the two mols of Cu will change at different rates w/respect to each other, and as a result, one mol of Cu will have more energy stored in the form of internal potential energy (seen as difference in volume) than the other, so the equilibrium temperature will be below 50 C. Is there any way to calculate this equilibrium temperature? John Riemann Soong (talk) 05:36, 21 September 2009 (UTC)

Is the 'T' in the formula for Cp temperature? If the heat capacity is temperature dependent, then the temperature won't be linear in the amount of heat energy. In this case the equilibriums temperature would be over 50 C, although the amount over would be pretty negligible. Rckrone (talk) 07:31, 21 September 2009 (UTC)

Hmmm, the nonlinear part of heat capacity is because of potential energy, right? Okay, is the equilibrium temperature higher because the entropy of the system has increased? Where does the additional enthalpy come from? John Riemann Soong (talk) 07:39, 21 September 2009 (UTC)

OOHHHHH I think I get it now. I was thinking differential volume expansion (does that factor in Cp?) and work being done by the heat transfer, but in heat transfer from hot to cold, S always increases. I wasn't really thinking about Debye heat capacity and such, but I realise it probably kicks in for copper. So let's get an extreme-ish case -- 1 K helium and say, 100K helium (let's choose a suitable pressure where we can ignore phase transitions). Basically, for a system with very little disorder, transferring a fixed amount of heat from a system with much more disorder will increase the disorder of the first system by a lot more than it would decrease the disorder of the much-disordered system? And thus, disorder as a whole increases, increasing temperature? John Riemann Soong (talk) 08:23, 21 September 2009 (UTC)

Lymphocytes

how we can separate lymphocytes from blood sampleAnkita.roshni (talk) 05:37, 21 September 2009 (UTC)

By googling 'separating lymphocytes' I got many results. This[26] was the first, which you may find helpful. 86.4.186.107 (talk) 06:05, 21 September 2009 (UTC)

The standard laboratory method for isolating lymphocytes, is by ficoll centrifugation, as described in our article. You then get a mixture of lymphocytes and monocytes, called peripheral blood mononuclear cells. If you start out with anticoagulated blood, there will be platelets in the mixture as well. If you start out with defibrinated blood, there will be few platelets, and also fewer monocytes. Defibrinated blood is produced by shaking blood containing no anticoagulant in a bottle filled with glass beads. If you need to remove monocytes, specialized centrifugation techniques exist, or you may take advantage of the tendency of monocytes to adhere to plastic, e.g. in a petri dish. Other methods for isolating lymphocytes include fluorescence-activated cell sorting and immunomagnetic separation. The standard method for removing lymphocytes (and other white blood cells) from red cell or platelet concentrates for transfusion, is by filtration. --NorwegianBlue ^talk 08:30, 21 September 2009 (UTC)

Combustion

Is combustion always with oxygen? From the combustion article it appears not, but everywhere I've looked the definition is a reaction with oxygen. What's the actual definition? --wj32 ^t/c 08:04, 21 September 2009 (UTC)

You could probably combust something with anything electronegative like a halogen like chlorine, but note that oxygen is the most abundant atmospheric electron acceptor, whereas diatomic nitrogen is quite stable and not very electrophilic. In fact, oxygen is prolly the most abundant oxidiser because all the more reactive ones don't survive as long at ambient temperatures, while you need a little more "oomph" to get something to combust with oxygen. The idea of combustion essentially is that the item being combusted is being oxidised, and the oxidiser is getting reduced. John Riemann Soong (talk) 08:39, 21 September 2009 (UTC)

So... the oxygen-only definition is wrong (technically)? --wj32 ^t/c 08:42, 21 September 2009 (UTC)

Well it works most of the time. And if you're doing some chemical process where you're halogenating something or making some exotic acid, then you could say, "yeah I'm combusting it in fluorine"... I suppose to distinguish "combustion" and "oxidation", one would say that the primary method of combustion is via free radical formation and propagation and homolytic cleavage, whereas with ambient oxidation it doesn't always this way. John Riemann Soong (talk) 08:51, 21 September 2009 (UTC)

OH -- one more important point. Oxygen is unique among most oxidisers in that it is a diradical, usually found in triplet oxygen state. Hence the emphasis on radical formation -- diatomic oxygen cannot participate in many classic reactions in organic chemistry, like nucleophilic lone pair donation, or electrophilic electron acceptance, since diatomic oxygen's highest energy electrons are not paired ... and O2's lowest LUMOs (in the not fully occupied orbital sense) are half-occupied by one electron each.

Other electronegative species (like chlorine) generally react via electrophilicity/nucleophilicity-driven mechanisms which involve the movement of electron "pairs". These species react via radical mechanisms at room temperature only under special conditions (like a radical catalyst, due to light, peroxide, etc.). So that's why chlorine, although is less electronegative than oxygen on the Pauling scale (chlorine is the electron donor to oxygen in perchlorate), is far more reactive and electrophilic at room temperature. Diradicals react best with other radicals and it happens to be that most of the biosphere, most of the time, is made up of non-radical substances -- unless you of course suddenly turn up the heat (like in a forest fire) and suddenly start breaking molecular bonds homolytically to get your radicals. Chlorine, not being a radical, reacts readily with "normal" electron donors.

So I guess the refinement of the definition is that combustion is "free radical oxidation". Oxygen is the most abundant free radical oxidiser out there. There are of course derivatives like peroxides, perchlorates and other oxygen-containing things. And then there are probably free radical oxidisers that don't involve oxygen atoms, but they are considerably less abundant. John Riemann Soong (talk) 09:02, 21 September 2009 (UTC)

Gunpowder uses potassium nitrate instead of molecular oxygen as the oxidiser. Dauto (talk) 11:58, 21 September 2009 (UTC)

I'm not sure the precise technical definition as distinct from other sorts of oxidation. May be speed (iron rusting vs on fire) or the presence of some sort of flame? Magnesium (and other active metals I assume) burn with a bright flame under a pure carbon-dioxide atmosphere. I don't know whether that involves free-radical (probably). And thermite is another mixture that contains its own oxidizer agent. DMacks (talk) 13:29, 21 September 2009 (UTC)

Likewise, Magnesium will burn in pure carbon dioxide, which while possibly not "technically" a combustion (since it does not involve oxygen) still amounts to burning to any reasonable person. See this video for a demonstration. --Jayron32 13:29, 21 September 2009 (UTC)

The mystery of the defunct scientific journal

I have sought an article from a journal entitled 'Current Research in Molecular Therapeutic' (ISSN: 1367-6275). The article, printed in 1998, is not listed on PubMed. I contacted the author and was sent a copy in PDF format. The author himself was not sure why the article never appeared on PubMed. Could it be that the journal did not meet PubMed's standards for inclusion and has since gone out of publication? There is only a little evidence on the Internet that it even existed. ----Seans Potato Business 11:04, 21 September 2009 (UTC)

I've been poking around, and so far can't find any references to publications in Curr. Res. Mol. Therapeut. that aren't from 1998. To be fair, I haven't been digging very deep, but it's possible that the journal didn't last long enough to meet the longevity requirements for review and inclusion in Medline/PubMed: Journal selection FAQ. Moreover, if the editors/publisher anticipated winding up the journal after a few issues, they might not have bothered to submit their journal for Medline indexing, or continued to shepherd their application through the Medline process. The Medline FAQ indicates that about three-quarters of submitted journals aren't selected for indexing; a two-year waiting period is imposed before a reapplication is permitted. Again, if the journal missed the cutoff on its first evaluation, it may not have survived long enough to apply again. TenOfAllTrades(talk) 13:47, 21 September 2009 (UTC)

One possibility is that this was a fake journal. Often somebody hawking some product will set up a fake journal so they can claim they are endorsed by the scientific community. What was the article in question ? StuRat (talk) 14:46, 21 September 2009 (UTC)

The odd title lends immediate (weak) support to StuRat's idea. Comet Tuttle (talk) 16:49, 21 September 2009 (UTC)

The grammatically correct title would be http://www.google.co.uk/search?hl=en&q=%22current+research+in+molecular+therapeutics%22&btnG=Search&meta= with an S ...83.100.251.196 (talk) 17:09, 21 September 2009 (UTC)

The current publisher seems to be "Nature America Inc." does that help?83.100.251.196 (talk) 17:13, 21 September 2009 (UTC)

That does sound rather suspicious. Looking through those Ghits, it looks like they got a reputable scientist willing to sell out her reputation to endorse a questionable product. If so, the "journal" may have only lasted long enough to endorse all the products of the parent company. Once this was done, it no longer served any purpose. StuRat (talk) 20:24, 21 September 2009 (UTC)

Inclusion in PubMed and inclusion in Medline are not the same.[27] It's easy to get a journal listed in PubMed, just have a half-decent editorial board and don't look like a total fly-by-night operation. Medline is a whole other ball game. You need consistently good publication levels for about 18 months, and each journal goes through a vetting procedure. If it fails to get indexed it needs to wait two years before reapplying. Fences&Windows 03:23, 23 September 2009 (UTC)

Ha, this was a tricky one to figure out. Apparently there is a company called "Current Drugs Ltd" (recently acquired by Thompson Reuters) that does research on drug development, creating reports that they sell to corporate clients. This Google Scholar search will show you a whole bunch of them. "Current Research in Molecular Therapeutics" is the title of a report they published in 1998. I'm not absolutely certain of what I just wrote but I think it is probably close to correct. In any case, an article that appeared there would not be a valid source for Wikipedia. Looie496 (talk) 00:13, 22 September 2009 (UTC)

Current Drugs Ltd. was then part of the Current Science Group,[28] now the Science Navigation Group. Current Research in Molecular Therapeutics may be related to Current Opinion in Molecular Therapeutics, which was launched in late 1998.[29] It could be a typo, an early title, or an abortive journal, but assuming it is a "fake journal" isn't correct. Fences&Windows 03:19, 23 September 2009 (UTC)

Why don't I sneeze when I'm asleep?

Why is it that, when I have a cold, I don't sneeze or cough while asleep? (I know there are instances when we do, but the symptoms are always at least reduced.) Does it come of the mechanism that paralyses us so we don't act out our dreams? If so, it seems odd, because as far as I can tell, the paralysis stops voluntary movements, not involuntary ones, and I imagine big convulsive sneezes are involuntary...

I wonder if there's a way we can harness whatever causes this to reduce the symptoms of a cold...

thanks Adambrowne666 (talk) 11:20, 21 September 2009 (UTC)

How do you know you don't sneeze in your sleep? Also, while sneezing is semi-involuntary, it may also controled by the somatic nervous system and NOT the autonomic nervous system, and so any control over your conscious movements while asleep would also likely regulate sleeping. --Jayron32 13:24, 21 September 2009 (UTC)

We should also talk about why we sneeze and why it might be suppressed during sleep. The purpose of a sneeze is to clear the airways of irritants or blockages. While awake this works well. However, when asleep, excessive sneezing may interfere with sleep, and thus may cause more harm than good. So, the sneeze response is somewhat repressed, but not totally. If someone blew pepper up your nose while you were asleep, you would wake up sneezing. In this case the harm done by sleeping all night with such an irritant in your airways would be greater than the harm done by waking up. Of course, this system does fail at times, as when we have allergies or asthma. In such cases the response to a minor irritant (or none at all) is all out of proportion. StuRat (talk) 14:30, 21 September 2009 (UTC)

We are able to sleep when there is no apparent danger or immediate demand for activity. While we sleep the body needs only to maintain breathing at a low level since there is only a small constant muscle activity. In contrast, when awake the body needs a higher intake of oxygen to give the ability to react quickly to sudden dangers and to make necessary efforts. It actively resists anything that impairs breathing such as bronchial or nasal congestion by a sneeze or cough reaction. Cuddlyable3 (talk) 15:09, 21 September 2009 (UTC)

The sneeze article mentions this, search for the word "sleep". Googling for sneeze sleep reveals e.g. this and this. 88.112.60.134 (talk) 19:38, 21 September 2009 (UTC)

Well then. So what would be the effect of artificially relaxing the part of the brain responsible for the sneeze reflex as a way of reducing sneezes? Adambrowne666 (talk) 08:32, 22 September 2009 (UTC)

I doubt if it would work, as the chemical which suppresses sneezes likely also represses all other voluntary movements. So, not being able to walk would be a rather serious downside. But, if it was a separate chemical, it could still be harmful by allowing irritants to remain in the air passages, leading to inflammation, infection, etc. On the other hand, it could be useful in reducing the spread of airborne diseases, like the flu and colds. In that case it would have a similar logic with vaccines, since they protect both the person who takes them and those around them, but the person who takes them assumes all the risk. StuRat (talk) 14:12, 22 September 2009 (UTC)

trauma

I am in Africa Botswana and was recently involved in a car accident with my girlfriend, the accident left her traumatised such that she is afraid to get in a car ! The part where we are doesnt have counseling services so how do i help her get through this????

You need to contact a medical professional or counselor. You need to contact a psychologist working in Botswana, and not random strangers on the internet, whose advice may or may not be reliable. this search in Google lists some psychologists... -Jayron32 13:20, 21 September 2009 (UTC)

The questioner said they have no access to counselling services, Jayron. Adambrowne666 (talk) 08:36, 22 September 2009 (UTC)

Try to get in touch with your insurance company. Hopefully you have some kind of travel insurance (either you bought it conciously or you have it, for example, through a credit card you paid with). Ask them if they can provide any help over the phone, if they can refer you to someone, or if they have any other advice. Jørgen (talk) 20:42, 22 September 2009 (UTC)

Virial Theorem & Quantum Mechanics

Hi all -

I'm looking at a proof of the virial theorem and trying to work out where a term disappears to, and was wondering if anyone could explain it for me. (I've done all of the question except the very last line of the last step!)

The Hamiltonian operator for a particle in one dimension is H = T +U where T = p²/2m, and U is any potential.

Show that the expectation value "{T}" is positive in any (normalized) state. By considering {H} show that the energy of the lowest bound state (assuming there is one) has energy above the minimum of U.

Suppose ψ is an eigenstate of H with energy E. Show that, for any operator A, and in the state ψ, {[H,A]} = 0.

By taking A = x,show that {p}=0. Now let U(x) = kxⁿ for constants k and n; by taking A = xp, derive the virial theorem

2{T} = n{U}.

(p is the momentum operator, [a,b] is the commutator ab-ba, and {_} is the expectation, throughout the question.)

Now by fiddling around with [H,xp] I've managed to get to:

${\frac {p^{2}}{2m}}+{\frac {Uxp}{2}}={\frac {nU}{2}}\,\Rightarrow \,2\{T\}\,+\,\{Uxp\}=n\{U\}$

for the given 'U', at which point the {Uxp} is meant to disappear, but there's no explanation in the proof - but why? Is it because {p}=0? If so, why does that imply {Uxp}=0? Since there's no explanation in an otherwise detailed proof, I'd assume it's fairly obvious with little calculation.

I don't need much explanation but just a rough idea of why the expectation of kxⁿ⁺¹p should be 0, e.g. a symmetry argument, would be brilliant.

Thanks a lot! Spamalert101 (talk) 13:51, 21 September 2009 (UTC)

I think you’ve made a mistake in computing the commutator. I get [H,xp] = -iħ(p²/m–knxⁿ) = -iħ(2T-nU), from which the result follows immediately. If you calculate the commutator correctly, the kxⁿ⁺¹p term that comes from (kxⁿ)(xp) cancels out the -kxⁿ⁺¹p term that’s one of the two terms that comes from the -(xp)(kxⁿ) term. Red Act (talk) 11:20, 22 September 2009 (UTC)

Extreme Trees

Where can you find the northernmost and southernmost trees (not mosses, grasses, etc) in the world? What species are they? My first thought was evergreen but surely there is a hardier stock than that! TheFutureAwaits (talk) 14:39, 21 September 2009 (UTC)

The Arctic willow grows up to N80, but it is more a shrub then a tree. Granted, at extreme elevation, an 80 year old tree might only be 1 ft tall. If being in the extreme north also has that effect, it would not be trivial to differentiate shrubs and trees since they would probably be the same size. As far as south goes, Tierra Del Fuego has beavers, so I would presume they have trees. There could be islands further south then that with trees. Googlemeister (talk) 16:01, 21 September 2009 (UTC)

Northermost tree: 72°30'N at Ary-Mas (102°27' E) on the Central Siberian Plateau, see Tree line. Southermost tree: Look around 55°58'S 67°16' W Cape Horn on Tierra del Fuego because there are no trees on Antarctica. Cuddlyable3 (talk) 16:10, 21 September 2009 (UTC)

Ah, found it. Dahurian Larch TheFutureAwaits (talk) 16:11, 21 September 2009 (UTC)

Star Trek Voyager & Beaming Stuff Aboard

On Star Trek: Voyager, they seem to routinely lock on to things on other ships and beam them aboard. Wouldn't this be a more effective way of destroying an enemy ship than the proton torpedoes they use to just make the ship rock and the people on board fall against the walls? If they could just beam the engine of the enemy ship (or other essential parts) and put them somewhere else, wouldn't that completely disable the ship once and for all with minimal effort? Or do proton torpedoes just look better? --KageTora - SPQW - (影虎) (talk) 15:22, 21 September 2009 (UTC)

The pretense, as I recall, is that they can't beam stuff through the shields. Generally, though, it's that torpedoes look better. Additionally, transporter-based battles would be remarkably dull: who can beam out the opponent's power system first? OK, you win. — Lomn 15:42, 21 September 2009 (UTC)

I think the OP means photon torpedoes because proton torpedoes are only used by aliens disguised as actors in latex masks. Beaming people around is handy for plot development. Someone put effort into making the stardust fade effect so why not use it in every episode as often as possible? BTW the ship doesn't really rock, they shake the camera and the people just pretend to fall against the walls. Cuddlyable3 (talk) 15:54, 21 September 2009 (UTC)

Also, there is probably some kind of maximum size of object that can be beemed. Otherwise, why not just beem the whole ship into the nearest star, planet, moon, asteroid whatever. Googlemeister (talk) 15:56, 21 September 2009 (UTC)

They actually tried that in one episode using an alien transporter - it turned out not to be compatible with their hardware (something to do with anti-neutrinos). --Tango (talk) 16:24, 21 September 2009 (UTC)

Indeed, they usually have to use conventional weapons to disable the shields before they can transport anything. Once they have done that, it only takes one photon torpedo to destroy the ship, so why bother with the transporter? --Tango (talk) 16:24, 21 September 2009 (UTC)

In Stargate Atlantis they use beamining technology to beam nuclear devices aboard Wraith hive ships to destroy them, until the Wraith learn to use a "jamming frequency". I've always wondered why they didn't simply beam a whole part of the ship out instead of wasting a valuable nuclear explosive - they've been shown to beam objects the size of skyscrapers (well, they've been shown to beam actual skyscrapers) before. On a slightly less tangental note, in Star Trek, beamining tech could easily be used to harmlessly cripple an enemy ship who is, perhaps, only partially disabled (remove, say, the weapons array, or a small yet vital component of the warp drive). I agree...They don't seem to use it as often as they should. Vimescarrot (talk) 16:46, 21 September 2009 (UTC)

If there is anything I learned from Stargate, it's that each and every problem can be solved with a sufficiently big explosion somewhere. Why would you break that basic law of that universe? --Stephan Schulz (talk) 22:56, 21 September 2009 (UTC)

A major reason to bother with the transporter is the preserving of life, presumably a Federation priority; and a second is improved salvage ability, though that would probably be only for museum purposes. Comet Tuttle (talk) 16:48, 21 September 2009 (UTC)

It's basically down to the shield factor. To use Star Trek transporters against an enemy ship you first have to get their shields down, then you have to drop your own shields too - which of course renders you vulnerable to the enemy's transporters or any remaining conventional weapons they may have. Also as far as I'm aware the transporters are specifically calibrated to make it hard to beam out parts of objects for safety reasons - you don't want to chop people in half by accident. Exxolon (talk) 21:16, 21 September 2009 (UTC)

As for actual science, I see no reason why we can't eventually develop a transporter, provided a scanner and transmitter is at one end and a receiver and replicator at the other end. Such a transporter should have an unlimited range, as far as you can send a signal. On the other hand, I see no possible way to do a transport without the devices at each end. How exactly would that work ? So, unless the enemy was kind enough to give you access to their transportation equipment, such sabotage wouldn't work. I suppose there could be a code they use to gain remote access to it, and you could break the code; that might make for a more realistic plot.

A weapon system I always thought they should use is antimatter missiles that drop out of warp drive right on the target. I believe I saw them in one episode. I seriously doubt if any ship-to-ship or face-to-face combat would occur then, it rarely even occurs now, as our offensive weapons are far more effective than any defenses we have. In the future, what "shield" could stand up against, say, black holes launched at the enemy ? StuRat (talk) 23:01, 21 September 2009 (UTC)

As a practical matter, transporting even inert objects would be problematic, and transporting living things would likely kill them. Maybe those details could be worked out. But before anyone gets too confident about matter transportation, find a copy of The Fly (1958 film), where matter transport worked... sort of.

It's a little known fact that at the end of the film, David Hedison is saved by one last matter transport, and finds himself on the bridge of the Seaview. :) →Baseball Bugs ^{What's up, Doc?} carrots 23:20, 21 September 2009 (UTC)

As I recall from The Physics of Star Trek, there are two main problems with transporting a human. The first is data - in order to store sufficient information about all the unique particles in a unique human body to successfully be able to reassemble it from scratch, at the time of writing's storage limits (which have not improved that much) you would need a hard drive approximately 150 million miles across. The second is the Heisenberg Uncertainty Principle which posits "it is impossible to measure simultaneously both position and velocity of a microscopic particle with any degree of accuracy or certainty." - Star Trek transporters actually have "Heisenberg Compensators" to deal with this problem! Exxolon (talk) 00:03, 22 September 2009 (UTC)

Neither of those is the problem. The problem is the physical disassembly and reassembly. It just can't be done. -- BenRG (talk) 00:24, 22 September 2009 (UTC)

Well if I recall the passage I read was assuming that the principle problem of matter-energy-matter conversion was solvable and was looking at the ancillary problem. To put the hard drive problem into perspective - if you centred the centre of the hard drive platter at the centre of the Sun, the outer edge of the disk would be beyond the orbit of Mars! Exxolon (talk) 00:45, 22 September 2009 (UTC)

With modern hard drives, I reckon we're down to about half way to Mercury! We're getting there! --Tango (talk) 00:56, 22 September 2009 (UTC)

I do not see living people ever able to be transported, because there is very very little room for error but something inert, like furniture could if you could get the scanning time down and some great data compression algorithms. Who really cares if a couple of the molecules are off by 30um? It will still be a functional bookcase or table. Googlemeister (talk) 13:19, 22 September 2009 (UTC)

BenRG touches on the main objection to transporting humans in the way Star Trek envisages it. Think about what it does - it scans you, disassembles you, send the information about you to another location, and reassembles you. Note the disassembling bit. You're dead, ripped into pieces, and then a copy of you is reconstructed elsewhere. Nice for the copy, not so great for you. See Second Chances (Star Trek: The Next Generation). Apparently the physics just doesn't work either.[30] Fences&Windows 02:53, 23 September 2009 (UTC)

The concept of converting the atoms to energy, transmitting them, and then changing them back into atoms at the other end always seemed silly to me. All you need to transmit is the pattern (information). The copy can be assembled from stockpiles of various atoms at the target location. As for the old object, just destroy it in whatever way is most convenient (and less painful, if it's alive).

An object made of certain uniform materials could be transported now. A stereolithography (STL) machine makes a 3D object out of a type of plastic, and laminated object manufacturing (LOM) creates a type of wooden object. So, all that's needed is to scan such an object, transmit the dimensions to a remote STL or LOM machine, and create it there. There will be some error in the process, and it will take minutes or hours to complete, but the result should be close enough to the original to be recognizable. StuRat (talk) 13:42, 22 September 2009 (UTC)

That's not transporting it's remote duplicating. Try that with a person and the clone arrives dead with no internal momentum, and the original asks When will something happen? Cuddlyable3 (talk) 07:21, 23 September 2009 (UTC)

They are one and the same. As for restarting the heart, that's a relatively simple matter compared with teleportation. StuRat (talk) 12:27, 23 September 2009 (UTC)

Remote duplication is exactly what the Star Trek teleporter does. Except it kills the original. Fences&Windows 18:42, 23 September 2009 (UTC)

Seemingly forgotten in all this is that Roddenberry invented the matter transporter simply as a plot device to get people from one place to another quickly without having to take a shuttle every time. He also used other far-fetched ideas, such as backwards time travel, which is impossible also, but undeniably makes for interesting storylines. →Baseball Bugs ^{What's up, Doc?} carrots 09:34, 23 September 2009 (UTC)

Backwards time travel may be possible, as long as it's not into your own time line, where it leads to paradoxes. The infinite universes hypothesis (redlink ?) has some serious support, and that means there are also an infinite number of universes exactly like ours. There's no reason you couldn't go back in time in one of those (or appear to do so, if you find a universe which is delayed by the required amount from ours). StuRat (talk) 12:27, 23 September 2009 (UTC)

Pendulum's bob

Does is make any difference for the swinging of a pendulum if we put water inside a hollow bob (physics) instead of other solid material with the same mass?--Quest09 (talk) 16:14, 21 September 2009 (UTC)

No difference to the swing frequency (added) provided the water fills the bob. Turbulence will not occur. Assume you do not burst the bob by freezing or boiling the water Cuddlyable3 (talk) 16:23, 21 September 2009 (UTC)

If there was some water and some air in the bob then you would get movement of the water, which would result in less constant motion, I guess. There may also be a damping effect due to friction of the water with the sides of the bob. --Tango (talk) 16:26, 21 September 2009 (UTC)

Water motion creates a dampening effect, not just turbulence, correct? I remember seeing a documentary on some skyscraper which used drums half-filled with water to dampen the swaying of the buildings (the same concept as motion of a pendulum). -- kainaw™ 16:37, 21 September 2009 (UTC)

Once in motion the water does not move.its all part of being a pendulum83.100.251.196 (talk) 20:15, 21 September 2009 (UTC)

The water in the filled bob rotates. The pendulum swing is damped (pun!) by the mechanical energy loss that goes to heat the water. Vanes could be added inside the bob to prevent this. Cuddlyable3 (talk) 20:22, 21 September 2009 (UTC)

no, the acceleration of the pendulum means that the water inside is stationary with respect to the bucket.83.100.251.196 (talk) 20:43, 21 September 2009 (UTC)

I don't think that is true. At the peak on either side the pendulum is stationary, so the water will just fall down. Down is in a different direction on each side (relative to the pendulum). --Tango (talk) 21:27, 21 September 2009 (UTC)

At the peak the body is accelerating (down) - as the water sloshes down so does the container - result no net motion relative. Try calculating forces and acceleration on the water - same as the container. Same motion.83.100.251.196 (talk) 23:35, 21 September 2009 (UTC)

It isn't true that the forces on the water are the same as those on the container. First of all, the whole container experiences a uniform force from the arm of the pendulum since it's a rigid body, but the water doesn't. Different parts of its volume are affected differently by the normal forces of the walls of the container and since the water isn't rigid, that'll cause the shape to deform. But even if that weren't the case, for example if we replaced the water with a rigid frictionless weight, we still wouldn't have a normal pendulum. The bob and the weight would still experience different forces, since the direction of the force that the bob exerts on the weight depends on the weight's relative position, and so is not necessarily in the direction of the pendulum arm. What we'd have is something like the double pendulum. Notably the double pendulum does have some normal modes that behave nicely like what you're talking about, but usually the motion is chaotic. Rckrone (talk) 05:31, 22 September 2009 (UTC)

If you consider the spherical shells (around the pivot point) of water - it seems to me that each shell experiences uniform force (increasing with radial distance from the pivot) - so that makes me think that the pressure in the water increases with radial distance (just like in a standing column), and that there is no net tangential force on an part of a shell (relative to it's neighboring molecules in the same shell).. Assuming the 'bukcet' doesn't buckle I'm still not convinced that there will be any motion, but I'll have to give it more thought. (the actual pressure @ depth does change over the pendulum period - but I don't see a point when the forces cause motion in the water)83.100.251.196 (talk) 11:11, 22 September 2009 (UTC)

Correcction due to the width of the bucket in the direction of oscillation the equipressure surfaces will not be perfectly spherical - but I still don't have any 'inversion' or reason for motion.83.100.251.196 (talk) 11:14, 22 September 2009 (UTC)

Ah the top surface will 'hollow'! this would cause shearing in the body of liquid (not turbulence I think) - this would inevitably dissipate some energy83.100.251.196 (talk) 11:16, 22 September 2009 (UTC)

wait a minute no shear, just a non-flat surface - cant anyone actually answer this definitively without arm waving? :)

Well, so if the bob were half-filled with water and half-filled with air, the pendulum would swing less and not be simply less predictable, right? And, if we could avoid turbulence, would it still make a difference? --Quest09 (talk) 16:39, 21 September 2009 (UTC)

Are we approaching tuned mass damper territory?

No difference under pendulum motion - the liquid undergos the same forces as the rest of the pendulum - thus is stationary with respect to the vessel which holds it. There won't even be any turbulence.83.100.251.196 (talk) 20:15, 21 September 2009 (UTC)

A container filled with water and subject to angular acceleration (like a pendulum bob) will have the water rotate. This could be seen if a sealed glass container with bits of paper suspended in the water were suddenly turned one way or the other. The water nearest the sides of the container would, due to friction with the sides, start to turn with the container, more than the water in the center. When the rotation is reversed (as in a pendulum bob starting to swing the other way), there will be turbulence and it will then start to follow the sides in the other direction. This is besides any sloshing around in a partially filled container. This work should affect the movement of the pendulum slightly, but slight effects on period could be important in a timekeeping device. Edison (talk) 23:39, 21 September 2009 (UTC)

Right, except that there would only be turbulence if the rotation were fast enough. I don't know for sure, but I bet you'd find that the friction created by the water rotation would cause the pendulum to slow down noticeably quicker. Looie496 (talk) 23:49, 21 September 2009 (UTC)

I do not agree that that there would be no turbulence with "slow" rotation, whatever "slow" means in terms of a pendulum, just less than with greater angular acceleration. If the pendulum were very long, the period would be quite long, but there would still be some turbulence. (I must be off to file a research grant for a snow globe full of water and floaty bits and a very long pendulum.) Edison (talk) 01:13, 22 September 2009 (UTC)

"Turbulence" has a very specific meaning in fluid dynamics - I'm fairly sure there would be motion in the water, but it wouldn't necessarily be turbulent. (It depends on Reynolds numbers and other things I don't understand!) --Tango (talk) 01:19, 22 September 2009 (UTC)

Could the actual motion be estimate using that fact that pendulums of different lengths have different time periods (an extension of the double pendulum idea suggested above by Rckrone) ?

I think I can 'derive' shearing motion in the water as the top water level surface changes (see above Ah and above) - if you know what reynualds numbers are you know more than me, maybe you could look at it^^ and say if it sounds reasonable.83.100.251.196 (talk) 11:27, 22 September 2009 (UTC)

I know the words "Reynolds number" and that it has something to do with determining when a flow becomes turbulent, that's about a far as I go! --Tango (talk) 13:21, 22 September 2009 (UTC)

Just googling... There appear to be specific classes of water dampers for pendulums such as "sloshing" and "tuned column" dampers. -- kainaw™ 23:45, 21 September 2009 (UTC)

A tuned liquid column damper isn't quite the same thing as a swinging pendulum- here's a simple picture [31] , a tuned mass damper is also not a simple pendulum.83.100.251.196 (talk) 11:03, 22 September 2009 (UTC)

My 2-year old wanted to play and I thought this was easier to simply try instead of guess at. It is rather simple: Hang a rod from a hook on the back porch railing. Fasten a cup to the bottom of the rod. Test it - does it swing without flopping around and hitting things? Yes. It acts like a nice pendulum. Pour a tiny bit of water in the cup. No noticeable change in the action of the pendulum - but the water does slosh around a lot. Fill the cup half full. The pendulum doesn't swing anymore. It goes to one side, then has extremely noticeable resistance attempting to reach the same elevation on the return swing. After a few swing, went into another motion. The water kept sloshing around, causing motion in the pendulum. Then, fill the cup almost full. The water sloshes out and it ends up half full and acts as it did previously. If anyone else wants to do this experiment, please let me know if your results are different. -- kainaw™ 19:20, 22 September 2009 (UTC)

It would be good to try that last experiment with a lid to stop the water sloshing out. --Tango (talk) 03:40, 23 September 2009 (UTC)

Is that cup fastened rigidly to the rod or is it hinged at the fastening point ? Cuddlyable3 (talk) 07:15, 23 September 2009 (UTC)

I will have to switch cups to put a lid on it. I may try this afternoon when I get back from work. As for hinging - the cup was fastened to the rod on top and on bottom, so it couldn't swing separately. I didn't want to create two pendulums, which I already know have a very odd swinging pattern. -- kainaw™ 13:00, 23 September 2009 (UTC)

I couldn't get it completely full because all of my cups with lids have a wider diameter on top than on bottom. So, the cup is tilted on the rod. I got is almost full with a lid on it. The pendulum doesn't slow down much as it swings. I did 5 tries with no water and 5 tries with it almost full. They are about the same. The almost full of water version shows loss of momentum after a minute, but not what you'd notice if you weren't measuring it. -- kainaw™ 23:43, 23 September 2009 (UTC)

Turning into another creature

In the movie, District 9, Wilkus accidently consumes an alien fluid and slowly is transforming into one. I know it doesn't exist, however what would have to happen on a cellular level in order for this to happen? Also, what would happen if you took, say, frog DNA and tried to change my DNA cells with it? Forgive my absolute ignorance on this subject. --Reticuli88 (talk) 17:43, 21 September 2009 (UTC)

My level of knowlege on this subject is very limited, but I will give my own speculation on the subject. I also don't believe there's any major research on transformation of living creatures like this. If it were to happen though, you would suffer severe adverse effects as your body's cells are slowly replaced with those of a (very likely) genetically incompatible creature. I imagine that you would be in incredible pain and feel incredibly sick while this is taking place. This is assuming that you can survive as even human to human transplants (with only a TINY amount of genetic difference) requires anti-rejection drugs to be taken continuously. In some ways, you could think of it as a cancer that covers your entire body where incompatible cells are reproducing alongside, and replacing existing human cells. Granted, once again, this is pure speculation based on my limited knowlege of cellular biology. Caltsar (talk) 18:11, 21 September 2009 (UTC)

Think of the body as a collection of cells with one DNA that are specialized to particular purposes and structures. Now imagine the difficulty of spreading new cells with new DNA throughout the body, while simultaneously replacing existing structures and cell-types. It's bad form to speculate about future potentialities, but I would say, "probably not." We can imagine being able to change an entire body's DNA in the future by means of viruses that would modify existing cells, and even that sounds very hard (your body's immune system would likely say "ack, that's not me!"). One would imagine doing this as part of gene therapy—to get your body to stop producing an incorrect hormone, for example. But to simultaneously change body size and structure? It seems a little far-fetched to me. Certainly if one is imagining not only going between species, but species with no shared evolutionary history (e.g. an alien). --98.217.14.211 (talk) 20:07, 21 September 2009 (UTC)

There is nothing called a DNA cell. DNA is the coded double-string of molecules that make up chromosomes in living cells. See the Wikipedia article Introduction to genetics for explanation. Trying to replace your DNA with frog DNA would cause your human cells to reject the intruder, just as they are doing all the time to cells that get damaged by radiation or infection. Cuddlyable3 (talk) 20:11, 21 September 2009 (UTC)

(EC) Unless the alien DNA is encapsulated by some sort of vector which allows penetration to the nucleus, and also contains enzymes which destroy the original DNA, it won't work. We consume DNA all the time in our food, I believe it is just broken down into nucleotides which can be recombined to our own DNA. --Mark PEA (talk) 20:12, 21 September 2009 (UTC)

When thinking about the logistics behind this kind of thing, remember that your bones are basically mineralized deposits; they're not changing for anyone without a whole lot of effort. In the movies, I suppose it doesn't matter because every alien happens to look exactly like a human with a blob of putty on their forehead, but it's the kind of thing you'll need to work out while working on your frog-men. ;-) I loved ST:The Next Generation, but their episode where the crew all starts "de-evolving" just bugged the hell out of me. I'm sure it was news to biologists to learn that spiders are in the family tree... how would the switch from endoskeleton to exoskeleton even work? Matt Deres (talk) 20:32, 21 September 2009 (UTC)

I can imagine a simpler way such a transformation could occur, if the parasitic organism simply eats the host from the inside out. The fungus that takes over the body of an ant works in this way. While, in this case, the exoskeleton remains intact and in "ant form", it's not too much harder to imagine that an organism could digest the existing skeleton and create a new one to it's own liking, and then create organs, a brain, etc. However, note that much of the digested host would be needed for energy, so the final organism would likely be much smaller than the host, unless it ate additional food. I'd also expect all this transition to take far longer than it does in the typical sci-fi thriller, where it can happen in seconds, minutes, or hours. I'd expect it to take weeks, months, or even years. StuRat (talk) 22:44, 21 September 2009 (UTC)

Medicine

I would like to know about the latest oral iron preparations ( new molecules ) for anaemia that are available in India along with the brand names and names of pharma companies that manufacture them. I also want to know about the latest calcium preparations available in India similarly. Ritamacwan (talk) 18:04, 21 September 2009 (UTC)

Here are thousands of search results for Iron[32] and Calcium[33] preparations. Cuddlyable3 (talk) 19:58, 21 September 2009 (UTC)

ideal gas

is Chlorine (Cl2) an ideal gas at -20F? Googlemeister (talk) 20:44, 21 September 2009 (UTC)

Ideal for what? Poisoning someone? Exxolon (talk) 21:11, 21 September 2009 (UTC)

I assume Googlemeister means ideal gas. DMacks (talk) 21:13, 21 September 2009 (UTC)

My (very old) chemistry book only says: "Ideal gas heat cap: 0.144BTU/lb-°F @ 75F." -- kainaw™ 21:16, 21 September 2009 (UTC)

There's no such thing as an ideal gas. Chlorine boils at -30F, so at -20F it will be close to that - which isn't the best condition for ideal gas properties.

The ideal gas law is an extension of experimentally discovered gas laws. Real fluids at low density and high temperature approximate the behavior of a classical ideal gas. However, at lower temperatures or a higher density, a real fluid deviates strongly from the behavior of an ideal gas, particularly as it condenses from a gas into a liquid or solid. The deviation is expressed as a compressibility factor.

So the compressibility factor aka "Z factor" is what you need (at -20F) to see how far off it is.83.100.251.196 (talk) 23:22, 21 September 2009 (UTC) [34] gives "Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F)) : 0.9867" - that's fairly ideal - it is after all a non-polar molecule. There are even equations for estimating Z-factor (search) - but I don't understand/not familiar with them.83.100.251.196 (talk) 23:31, 21 September 2009 (UTC)

Car steering problem

For a math word problem, I had an idea from a problem with a car I had as a teenager. The steering wobbled a bit when I had the car. Over time, it got worse. Eventually, it pulled hard to the right. I corrected by pulling it left. Then, it pulled hard to the left. I correct by turning right. Then, it pulled hard to the right. So, I junked it. For this word problem, I want to state that a part in the steering has failed at X%. This makes it Y% undrivable. What part in steering would reasonably cause this sort of problem as it degraded? -- kainaw™ 20:49, 21 September 2009 (UTC)

I would guess it was the steering rack - the central part of the rack had worn away so it would only engage to the left or the right. Exxolon (talk) 21:09, 21 September 2009 (UTC)

Not everything can be described in terms of percentages. I don't see how drivability can be quantified like that. --Tango (talk) 21:22, 21 September 2009 (UTC)

On math exams, everything in the world can be quantified to a clear percentage. -- kainaw™ 21:24, 21 September 2009 (UTC)

On badly written maths exams, maybe. I would hope you would write good maths exams... --Tango (talk) 21:28, 21 September 2009 (UTC)

You're describing a form of oversteer. The fault, as noted, is probably with the steering rack, or the mounting of the steering rack (although there are many other potential causes). You can probably make up some sort of algorithm describing the extent to which the input (your turning the wheel) relates to the outcome (the extent of oversteer), and state that within certain parameters the oversteer is acceptable, and outside those parameters, unacceptable. But it does sound as if you'll have to make a great deal of the problem and evidence up. --Tagishsimon (talk) 21:34, 21 September 2009 (UTC)

If there was an ECU operating the hydraulic power steering, any number of electrical, software, or mechanical failures might have been responsible for the trouble Kainaw described. I also vote against using "percentage of steering" because it is an unintuitive concept. Can't you rephrase as, say, "percentage that the steering wheel was rotated", and "percentage that the wheels actually turned"? Those are direct, and I think it's what you were trying to describe in the first place, just worded in a confusing way. Nimur (talk) 15:36, 24 September 2009 (UTC)

housing ideas for wiring in a heated enviroment?

im making a mini hot-plate (from a soldering iron taken apart) that should sit in the center of a glass dome. and i need to know how and what to us to place it there with out the heat being made, melting the wires. i was thinking maybe it put them in a glass up-stim to the mini hot-plate. any advise?

Use wires with high heat tolerance? Googlemeister (talk) 21:00, 21 September 2009 (UTC)

How hot? How long a time? Any other factors to consider for your system (high humidity)? Any physical requirements (permanent vs temporary, must allow repositioning vs can be fixed in one position)? DMacks (talk) 21:10, 21 September 2009 (UTC)

My soldering irons always had wires inside them that were protected from the heat of the iron. Why not use wires like those? -- kainaw™ 21:11, 21 September 2009 (UTC)

Some low wattage soldering irons have mains voltage flowing through an insulated resistance wire in the tip. More powerful soldering guns, which might have trigger selectable power up to 100 watts, have a transformer in the handle which steps low current mains voltage electricity down to very low voltage very high current electricity which flows through the noninsulated metal tip. Electrocution is likely to result if things are constructed from these disassembled devices and no distinction is made. The questioner has posted twice about this and never specified the temperature or purpose of the device. Putting mains voltage on something which gets very hot is a good way for the technical novice to injure someone or start a fire. High enough heat will melt insulation and cause wires to short. Ceramic insulators might crack if it gets hot enough. This projects sounds like a recipe for disaster. An adult with sound knowledge of electricity and the safe design of heating devices, so they comply with ANSI standards and the National Electrical Code (or any country's equivalent) should supervise any such work. Edison (talk) 14:03, 22 September 2009 (UTC)

i thought i mentioned how hot it was going to get. it should get around 320'-360' Degrees F. im not so worryed about the glass, the only thing im not sure about is the wiring. i was thinking of using a lead free solder to hold the plate to the soldering iron. becouse i have no need to get it hotter them 360'F im not worryed about it melting agien. im just not sure how to get it in the center of the glass without damaging the parts and wiring.

Ok to throw fermented waste in my compost?

Hi all,

I have a composted heap that is pretty well balanced with greens and browns, is well aerated, and doesn't smell. I had previously told my neighbor, who has a little air-tight kitchen compost bin, that she was welcome to dump her waste in my compost -- the more the merrier! (No meat etc. though). Well, the other day I guess she did so, because it reeked across the whole yard. When I opened the composter to turn it, I was a little light-headed. I'm guessing that her waste had been piling up for weeks in that air-tight container and had started to ferment.

My question is: is it ok to put fermented waste in my composter, or should I tell her not to bother if it gets over-ripe? The smell, by the way, was gone by the next day.

Thanks! — Sam 76.24.222.22 (talk) 22:51, 21 September 2009 (UTC)

My view: it's fine. A random website confirms this. --Tagishsimon (talk) 22:56, 21 September 2009 (UTC)

That web site is mostly about a specific kind of "fermented composting" using Bokashi, so I'm a little unsure if they're knowledgable about regular composting, but you're right that they do say you can just dump it in your regular compost. There's no reason anyone can think of why the byproducts of the fermenting would be harmful to the bacteria doing to composting, or that different kinds of bacteria might compete? — Sam 76.118.181.97 (talk) 00:31, 22 September 2009 (UTC)

September 22

Soap vs Hand Sanitizer

I'm going to be living in an apartment for a while and was shocked to see them only having hand sanitizer and no other kinds of soap. Hand Sanitizer says it kills 99.99% of bacteria but I know that .01% are probably the dangerous ones. Would you suggest going out and buying bar soap, hand soap, or is the hand sanitizer good enough for daily use? Also, I brought with me some dish soap and wouldn't mind using that but is it affective as a hand wash? -- penubag  (talk) 00:02, 22 September 2009 (UTC)

I hate to break it to you, but your skin is crawling with microorganisms, most of which are harmless. There's simply no way to eliminate 100% of germs, some will always survive. As for effectiveness, soap, antibacterial soap, sanitizers etc are all equally effective - it's far more important how you use them than the product you choose. Exxolon (talk) 00:06, 22 September 2009 (UTC)

Yes, I know there are probably more than a billion microorganisms on my body and probably more in my mouth, but would you say hand sanitizer is just as affective as hand wash? If not, which? -- penubag  (talk) 00:09, 22 September 2009 (UTC)

Washing your hands with soap and water is the best and cheaper, soap stops organisms such as C. difficile as well as everything that's killed by the hand sanitizer, which I'm assuming to be alcohol gel. But then again, you would notice if you or someone in your apartment had a C. difficile infection. Although the article on hand sanitizer states that its the most effective against viruses. But again I'd still think it a bit excessive to have alcohol gel in your house instead of soap... MedicRoo (talk) 00:23, 22 September 2009 (UTC)

Clear advice from this website says hand sanitizer can not and should not take the place of proper cleansing procedures with soap and water. There you have it. --Tagishsimon (talk) 00:25, 22 September 2009 (UTC)

Indeed. It is designed to be used when it isn't practical to use soap and water. It certainly shouldn't be used when you have reason to expect your hands are dirty - it should be used purely as a precaution. --Tango (talk) 03:21, 22 September 2009 (UTC)

My understanding is that no product is good at killing viruses (or deactivating them if you prefer), it is mechanical action of washing your hands that dislodges them (the same is largely true for bacteria - soap is primarily a surfactant, not an antiseptic). --Tango (talk) 03:21, 22 September 2009 (UTC)

A plain bar of soap cleans, and is so cheap (cents for several month's worth of supply) that getting it should be a no-brainer. But yes, dish soap will work as well (although it may be a bit harder on your skin), as will shower gel, or, in a pinch, hair shampoo. For maximum benefit, be sure to rub the soapy hands for 30 seconds, including the space between the fingers, then rinse and dry on a clean towel. Both rinsing and drying contribute significantly to the effect. --Stephan Schulz (talk) 12:16, 22 September 2009 (UTC)

Thanks for thoroughly answering my questions -- penubag  (talk) 19:03, 22 September 2009 (UTC)

As a follow-up (I've only just come across this question), no product will say that they kill 100% of germs, as this can't be proved. The "kills 99.9% of known germs" is a cop-out for advertising the product - if you use their product, and end up dying from a germ which should have been killed by the product, when your family sue the company they can just say "whooaah! We didn't say it would kill all germs... this must have been one of those 0.1% we don't kill". Also, notice that they generally talk about killing "known germs" - you had better hope that you don't get any of those pesky unknown ones, as who knows if the product will kill it? -- PhantomSteve (Contact Me, My Contribs) 08:06, 24 September 2009 (UTC)

anyone have a picture of solid chlorine?

I can't believe I can't find a photo of this online ... I get retarded photos of pool disinfection crystals instead. Chlorine freezes at around -100 C, so I think it should be achievable. John Riemann Soong (talk) 01:33, 22 September 2009 (UTC)

P.S. why are manufacturers allowed to call their crystalline chlorinating agents "solid chlorine"? It really makes life in academia hard. Is it possible to file a lawsuit against these people for misleading product labelling and for misleading the public? John Riemann Soong (talk) 01:36, 22 September 2009 (UTC)

We're not allowed to give legal advice, but I've heard it said that anyone can sue anyone for anything. Doesn't mean your suit will go very far. If I were a juror I wouldn't be very impressed by the claim that consumers would be expecting a cryogenic product to put in their pools. --Trovatore (talk) 02:34, 22 September 2009 (UTC)

I looked very hard for a picture but came up empty handed. Someone needs to make some and take a picture for the good of the internet. Apparently it freezes in liquid nitrogen if any lab tech has a vial handy and an afternoon of free time to make some liquid chlorine. A description from an ancient book says the solid is initially a vivid yellow but goes clear which is odd. I don't know how reliable it is given the text's age and my potential for misinterpretation. I filtered out most of the junk by excluding words like "pool", "spa", and "filter". 66.57.240.8 (talk) 02:58, 22 September 2009 (UTC)

Liquid chlorine is still yellow-green. Is there a reason to believe that frozen chlorine won't just look like yellow-green ice? If not, why would it be something that people would think to snap a photo of and post on the Internet? I'm not saying nobody has done it, but if it just looks like frozen urine, why would it be that interesting? -- kainaw™ 05:07, 22 September 2009 (UTC)

Oh come on. There must be a picture of froze urine somewhere on the internet... — Sam 63.138.152.155 (talk) 19:47, 22 September 2009 (UTC)

It might change color depending on what form it assumes, i.e. if it looks like ice or if it assumes some kind of crystalline structure or something. Keep in mind solid ice (H2O) can look clear or somewhat opaque or even kind of blue, so who knows. I wonder what solid nitrogren looks like, for that matter? Maybe like dry ice? Someone asked me recently how you get liquid nitrogen, and I said, that's easy, you just take solid nitrogen and melt it. That didn't seem like a totally satisfactory answer, though. In any case, I would think there would be a reference, somewhere, that would illustrate various elements and compounds in their solid and liquid states? →Baseball Bugs ^{What's up, Doc?} carrots 08:57, 22 September 2009 (UTC)

This doesn't answer the question, but it does have an illustration of liquid Chlorine.[35] It was produced under pressure. I'm no chemist, but various sources point out that standalone solid Chlorine is not found in nature, but only salts. →Baseball Bugs ^{What's up, Doc?} carrots 09:09, 22 September 2009 (UTC)

It's most certainly not misleading, since 'chlorine' in common speech has meant 'chlorine bleach' (sodium hypochlorite) for quite some time. Saying 'solid chlorine' for crystalline sodium hypochlorite makes perfect sense. Don't be ridiculous. Also, actual frozen chlorine shouldn't really look much different than a yellowish dry ice. It won't likely change color when frozen since only weak van der Waals forces hold the stuff together. --Pykk (talk) 14:13, 22 September 2009 (UTC)

Since solid chlorine is not observable in nature, and probably has little usage otherwise, perhaps it's not surprising that it's hard to find a picture of it. If you google [chlorine solid] you typically end up at pages talking about crystalline compounds like you would add to swimming pools. →Baseball Bugs ^{What's up, Doc?} carrots 14:36, 22 September 2009 (UTC)

It's misleading to scientists and students of science who have to work with halogens and halogenating agents. Can't they just say solid chlorinating agents? I could see solid chlorine as potentially useful for a few organic syntheses (favouring stereochemical selection, e.g. syn addition, for electrophilic or nucleophilic attack). John Riemann Soong (talk) 05:02, 23 September 2009 (UTC)

Again, don't be ridiculous. Any and every chemist and student of chemistry should know perfectly well that common and trade names are not the same as scientific names. There's a whole myriad of compounds this is true for. If a scientist is mislead by this, then he or she is an incompetent chemist. If you don't know that 'chlorine' in everyday speech (in several languages, even) is sodium hypochlorite solution, you've got no business being in a lab. You're a potential danger to yourself and others if you know that little. --Pykk (talk) 12:11, 23 September 2009 (UTC)

But this is the google generation. There is no "technical" or specialised name for chlorine that one could search for, and therefore these companies are squandering the name. John Riemann Soong (talk) 12:41, 23 September 2009 (UTC)

http://www.mrs.org/s_mrs/bin.asp?CID=7587&DID=193420&DOC=FILE.PDF solid cl2 pale green as per gas.83.100.251.196 (talk) 23:20, 23 September 2009 (UTC)

Video proof that Hyacinth Macaw x Ara macaw cross-breeding works (not a question)...

Not a question, rather a delayed response to something that's been mentioned on here a few times in the past.

See this video. The bird is apparently a Hyacinth Macaw x Military Macaw hybrid. I know that some posters here were sceptical that such inter-generic hybridization was possible. I'd actually only ever seen still photos myself until now - some of which may have been 'shooped. Just posting this here FYI. --Kurt Shaped Box (talk) 01:35, 22 September 2009 (UTC)

What kind of medical problems are astronauts in orbital space stations equipped to handle?

I suppose evacuating an astronaut back to earth before the planned return is not something that you want to do unless it is necessary, so what kind of medical problems are orbital space stations equipped to handle? What type of problems would be just serious enough to warrant medical evacuation from space?

Google found me this page, which looks useful. --Tango (talk) 03:16, 22 September 2009 (UTC)

It's not space, but perhaps as close to the isolation and danger of space that we have on Earth, and so perhaps of interest to you: Jerri Nielsen was a physician wintering at the South Pole when she discovered that she had breast cancer. She was the only doctor, and they had no cancer drugs. She actually did surgery on herself and coached fellow crew members on how to administer chemotherapy drugs which had to be airdropped under very dangerous conditions. Her memoir of the time is interesting. --Sean 15:02, 22 September 2009 (UTC)

More like medical emergencies, not problems. DRosenbach ^{(Talk | Contribs)} 19:35, 22 September 2009 (UTC)

Intestinal fortitude....

Are human intestines just loose in the abdominal cavity or are they attached in some way (other than the obvious attachments to the stomach and rectum) ? If attached, this leads to another Q: During surgery they sometimes pull the intestines out of the abdominal cavity. How do they do this if they are attached ? StuRat (talk) 04:00, 22 September 2009 (UTC)

Various portions of the intestines are joined to the (muscular) abdominal walls by loops of fascia or omentum - some portions, for example of the colon are retroperitoneal and not free to move, while others are relatively mobile. The portions of intestines that you may see during surgery when the surgeon "runs the bowel" to look for perforations and such are either found free in the peritoneal cavity, or have been freed up during surgery. The intestine article is a little short on the gross anatomy, but you might get a better idea of the situation looking at greater omentum and lesser omentum. - Nunh-huh 04:39, 22 September 2009 (UTC)

Isn't most of the body's interior bound together, to some extent, by various connective tissue? →Baseball Bugs ^{What's up, Doc?} carrots 09:48, 22 September 2009 (UTC)

Well, yes, I guess. Connective tissue connects various organs in various ways. I think the question was about the anatomy of those connections. - Nunh-huh 10:34, 22 September 2009 (UTC)

Here is a link [36]to a diagram which explains it pretty well, it's a diagram but it makes it clear that much of the small intestine is attached to the mesentery, the large intestine is much less mobile. I have seen programmes where young babies have been born with much of their small intestine outside the abdomen, a condition called exomphalos and the paediatric surgeon just pushed the intestine back in through the open umbilicus, it was clearly quite mobile and not firmly attached to any other structure (of course not, otherwise it would not have been left outside the abdomen - doh!) Richard Avery (talk) 11:36, 22 September 2009 (UTC)

Thanks so far. I now have some follow-up Q's. If the intestines are "freed up during surgery", is this done by severing the connective tissue ? If so, do they re-attach it when they replace the intestines or just leave them loose ? And, if they do leave them loose, doesn't this have any negative side-effects ? StuRat (talk) 13:15, 22 September 2009 (UTC)

Yes, if the surgeon needs to get to a specific part of the intestine that requires it, he or she will make an incision through the connective tissue. In general, afterwards it's just left "loose", with no ill effects. - Nunh-huh 22:13, 22 September 2009 (UTC)

Sometimes there are ill-effects, namely scar tissue called adhesions. Fences&Windows 02:27, 23 September 2009 (UTC)

Aren't there side effects from the intestines flopping around loose ? Just offhand I would expect a greater incidence of the intestines getting twisted or moving to a place where they don't belong. StuRat (talk) 12:14, 23 September 2009 (UTC)

"Volvulus." Axl ¤ [Talk] 14:43, 23 September 2009 (UTC)

Hernia. Fences&Windows 18:46, 23 September 2009 (UTC)

OK, so, is there a procedure to reattach the intestines to the omentum, or secure them in some other manner, for those patients who suffer the side effects of intestines left "loose" ? StuRat (talk) 13:39, 24 September 2009 (UTC)

What is the name of this bird?

I saw a bird in North Western WA and I am awfully curious as to what it was. It was all black with a bit of blue on each wing (rectangular in shape really) as well as on the tail. Thanks!! Veronika Stolbikova (talk) 06:17, 22 September 2009 (UTC)

I live very far from NW WA so I'm mostly guessing right now, but you can check any of the following: common grackle, Steller's jay, Blue Bunting, purple martin, Brewer's blackbird, brown-headed cowbird and see if any of those is even close. Some of those are black but have iridescent plumage. You can do a google image search for each one of these birds to see more images. --Dr Dima (talk) 07:29, 22 September 2009 (UTC)

Dr Dima is assuming that by WA you mean Washington. I had been assuming you meant Western Australia, in which case you could be looking at a Rainbow Pitta.--Shantavira|^{feed me} 08:04, 22 September 2009 (UTC)

Judging by the picture on Veronika's user page, I would bet on the US state of Washington. Dismas|^(talk) 09:38, 22 September 2009 (UTC)

Ford Explorere 1998

Could anyone give me some information on why my 1998 Ford Explorer (import) injectors are over fueling. Desparate?

Thank you

Val. —Preceding unsigned comment added by 86.132.102.151 (talk • contribs) 11:54, 22 September 2009

I would guess that they might need cleaning - or perhaps the computer is getting a bad reading from one or more of the oxygen sensors. Do you have a check-engine light? After you get it fixed, check the spark plugs, clean & re-gap them. SteveBaker (talk) 14:49, 22 September 2009 (UTC)

Vitamin D from sunlight during a northern winter

I understand that at for example London England in the summer 20 minutes worth of clothed exposure to sunlight is enough to provide your daily requirement of Vitamin D. I also understand that winter sunshine or evwening sunshine is not effective at producing Vitamin D in the skin. What are the approximate dates during the colder parts of the year when clothed sunshine exposure for say 1/2 hour a day cannot provide the daily requirement of Vitamin D please? 78.144.255.50 (talk) 12:01, 22 September 2009 (UTC)

Our article on Vitamin D says that: adequate amounts of vitamin D3 can be made in the skin after only ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen....but also that this requires UV exposure at levels greater than 3. Unfortunately - this isn't just a matter of time-of-year, time-of-day and latitude - it also depends on cloud cover, pollution, ozone damage - and a host of other things. So we can't give even approximate dates. However, most halfway decent weather forecasting sites will give you predicted and current UV indices. This site, for example, is predicting that over the next 14 days in London, only three will have UV indices above 3 (Sun 27th, Wed 30th, Thu 1st) - so getting two 15 minute exposures per week - even at this time of year - would require you to be outdoors at close to midday on every suitable day with sufficient amounts of skin exposed (no hats, no gloves, wear shorter sleeves - don't wear sunscreen, you don't need it at UV levels 5 and below, and it prevents Vitamin D formation). As winter progresses, there are going to be fewer and fewer days where you'll get what you need. So check your weather forecast. SteveBaker (talk) 14:38, 22 September 2009 (UTC)

Hmmm - this site predicts UV levels of 4 for the whole of this week. Perhaps weather forecasting isn't that good at predicting UV levels. SteveBaker (talk) 14:45, 22 September 2009 (UTC)

A spoonful a day of Cod liver oil is not especially tasty or exciting but takes care of Vitamin A and D requirements. That's more reliable than sunlight. Cuddlyable3 (talk) 19:31, 22 September 2009 (UTC)

You risk Vitamin A overdose doing that. 89.242.104.32 (talk) 09:39, 23 September 2009 (UTC)

"...the Lowest Observed Adverse Effect Level ...for vitamin A, when taken over an extended period of time is 21,600 IU. Most multivitamins contain vitamin A doses below 10,000 IU, therefore multi-vitamins are unlikely to cause vitamin A toxicity when taken at their recommended dosage.":Hypervitaminosis A. Also see Hypervitaminosis D. Fences&Windows 19:31, 23 September 2009 (UTC)

Palladium refining.

Are there any easily available substances excluding Na/K chlorate to precipitate palladium from aqua regia solutions? Renaldas Kanarskas (talk) 12:01, 22 September 2009 (UTC)

Does this have to be in aqua regia, or just post dissolution - ie can the aqua regia be neutralised? Hydrazine might be a precipitant http://www.springerlink.com/content/x3p70967751u5363/ in 2M HNo3, as could be ammonium chloride see Palladium also [37] after neutralisation.

Aqua regia is neutralized with carbamide or with evaporation of nitric acid. IMHO hydrazine will precipitate not only palladium, but gold also. Renaldas Kanarskas (talk) 20:54, 22 September 2009 (UTC)

"Pd(II) salts + hydrazine in the presence of various ligands" is the standard way to make Pd(0) complexes used as organic catalysts. DMacks (talk) 21:29, 22 September 2009 (UTC)

Also does this precipitation have to be selective ie in the presence of Ag,Au etc. Dimethylgloxime can be a good precipitant, but will not be compatable with aqua regia.83.100.251.196 (talk) 12:19, 22 September 2009 (UTC)

Thank you, I knew about DMG, but thought it is used only to test palladium, not to precipitate. Renaldas Kanarskas (talk) 20:54, 22 September 2009 (UTC)

It'll also precipitate nickel if there is any. There's some instructions here [38] p338 (the extraction of the metal in the method given is complicated by the ability of Pd to form Palladium hydride - calcination of the DMG Pd compound, followed by redissolution and electro-winning might be another way)83.100.251.196 (talk) 10:07, 23 September 2009 (UTC)

In slightly acid solution Ni does not interfere, but gold (and selenium) do. [39] - gold is partially reduced to free metal. Pt, Ir, Rh are not precipitated.83.100.251.196 (talk) 12:22, 23 September 2009 (UTC)

As an aside, to separate Pd and Ni when produced in solution by aqua regia dissultion (after neutralisation) - electroplating of the salt solutions might be an option , with Pd2+ being much easier to electroplate (0.925V) than Nickel (-0.25V) (at standard conditions). This won't separate gold from palladium very well. (no reference)83.100.251.196 (talk) 11:21, 23 September 2009 (UTC)

As yet another aside gold salts can be extracted into an organic solvent (eg ethyl acetate incompatible with Nitric acid) after dissolution, it appears that Pd salts are not extracted by organic solvents.83.100.251.196 (talk) 12:36, 23 September 2009 (UTC)

Where did all the universe's energy come from, and where will it go?

Or is this just a mystical question? 78.144.255.50 (talk) 12:11, 22 September 2009 (UTC)

Have you tried reading Big Bang and Universe, and the latter's See also?

It's not even clear whether the concept of energy is a valid one when talking about the universe as whole and even if it is, it is not clear what the total energy of universe is. it might be zero, in which case there is no need to explain where it came from. Dauto (talk) 12:51, 22 September 2009 (UTC)

Where will the energy go? scientifically this is easy - it will spread out - the universe will acchieve thermal equilibrium - everything will be 'luke warm' (this is ignoring the possibility that the universe collapses in on itself see Ultimate fate of the universe).

See also the somewhat emotively title article Heat death of the universe !83.100.251.196 (talk) 12:54, 22 September 2009 (UTC)

Where did the energy come from - this is as fundamental as "why does the universe exist" -one simple answer is that the energy was created as part of the big bang, which is the most popular current scientific theory. What gave rise to that, and questions such as "why was the unverse (and all it's energy created)" is not answerable by science, and is purely mystical, or philosophical.83.100.251.196 (talk) 12:48, 22 September 2009 (UTC)

As I understand it the related question "what gave rise to big bang / where did the big bang come from" is also not answered by science.83.100.251.196 (talk) 12:51, 22 September 2009 (UTC)

"Yet". There are conflicting thoughts about the Big Bang. If it really started as a mathematical singularity, there should be no way of figuring out what happened "before" it. But a real singularity is incompatible with quantum mechanics. See e.g. this popular summary of a Nature Physics paper. --Stephan Schulz (talk) 13:03, 22 September 2009 (UTC)

And keep in mind the "can't be answered by science" stricture just means, "nobody has yet come up with a way to talk about this that would be anything more than a gigantic leap in logic, a bunch of speculation that could not be tested in any way." Over time, many of these questions end up being answerable by science, both as new information comes in and new theories are thrown around. "How big is the universe" is another one of those kinds of questions that is now pretty straightforward to answer. --98.217.14.211 (talk) 13:10, 22 September 2009 (UTC)

That's not true. There is a difference between not knowing something yet and knowing that something is unknowable. If there was a big bang singularity then any empirical evidence of what happened "before" the big bang (before in quotes since it could well have been the start of time itself, so it makes no sense to talk about a "before") would have been "wiped clean" and could be causally disconnected from us, so we can never know anything about it. The only way we can know anything about what happened before the big bang is if we are wrong about the singularity (which is quite likely - singularities really make no sense, so they are probably just mistakes). --Tango (talk) 13:18, 22 September 2009 (UTC)

As I said, under current understanding, it might be unknowable. However, if someone comes up with a better way to look at it, it might actually become knowable. In Copernicus' day it was considered impossible to use math to say anything about the composition of the universe—the latter was considered to be strictly a philosophical question. Our understanding of what science can and can't answer changes over time. Someday, "is there an afterlife" could be a perfectly scientific question. It isn't now. But let's not pretend that our understanding of what's knowable and unknowable is static. If you look at discussions about the origins of the universe from the 1900s, they are pretty amusing in modern eyes—very quickly every one concludes that one really can't know that much about the early history of the universe, and then some clever fellows came along and found ways to start asking scientific questions about it. --98.217.14.211 (talk) 18:06, 22 September 2009 (UTC)

I once read a 19th century science book for high school students, in which the authors asserted that the atom was as indivisible to the chemist as the Moon was to astronomers. This was a literally correct statement: Note that less than 100 years later the atom could be split in the lab, in the powerplant, in the engineroom of a ship or on the battlefield, and pieces of the Moon were brought back to Earth. 2 weeks ago there was a report in a science journal of the isolation of a magnetic monopole. Edison (talk) 13:46, 22 September 2009 (UTC)

It came from God.

Your next question is liable to be, "Define 'God'." At that point, things become circular. →Baseball Bugs ^{What's up, Doc?} carrots 13:26, 22 September 2009 (UTC)

The total energy in the universe can only be estimated from our position, and our best estimates put it somewhere around zero, and certainly within error of zero (noting of course that this margin of error is very large), leaving the possibility that actually is zero. From a dirac-esque "knowing it is right because it is beautiful" poin of view, this certainly appeals. But of course dark energy and all that will probably just mess everything up if or when it is discovered. Elocute (talk) 21:53, 22 September 2009 (UTC)

0 =1-1. so if you start with 0, you can get positive and negative versions of the same thing for free!

Curious -- couldn't this be kind of related to the fate of the universe? If the net energy of the universe is negative, then perhaps the ultimate fate of the universe is a Big Crunch. If it's positive, the universe will just expand itself to death. If it's zero, then perhaps its fate is periodic. John Riemann Soong (talk) 05:08, 23 September 2009 (UTC)

Since there seems to be a huge amount of energy in the Universe - for example the energy of matter E=mc^2 - then where is all the negative energy to balance this if the total energy is zero? I did not think you could have negative energy. 89.242.104.32 (talk) 09:43, 23 September 2009 (UTC)

Gravity is essentially stored negative energy since it is an attractive force whose 'zero point' is at infinity. Elocute (talk) 09:56, 23 September 2009 (UTC)

Archives for Raw Solstice Data

The "Calendar shift with Seasons" graph from 1750 to 2250 shows two (2) specific measurements for the actual date and time of Winter solstices. The 1st is Dec 23, 1903 at 0:18 UT; and, the 2nd is Dec 22, 2003 at 6:59 UT. I would like to know where the Archives for all this data can be found. Thankyou for any help that can be provided. 12:45, 22 September 2009 (UTC)

Where is this graph? Can you supply a link to it please?--Shantavira|^{feed me} 14:39, 22 September 2009 (UTC)

The referenced graph has been under the previous "Gregorian Calendar" heading in Wikipedia for many months. I just checked and it is no longer there. Apparently an entire new entry has been substituted. Now under "Calendar Seasonal Error" a new graph appears entitled "Leap Shifting of the Gregorian Calendar" showing "Date of Summer Solstice over 400 years"; (actually 500 years due to beginning and ending 50 years not being labeled). This is the same type of raw data I am interested in reviewing.-- [[User:Edwrdgmbl]

Craving certain foods

There are times I crave to eat spinach and someone told me that I probably have an iron deficiency and my body is craving it. If that is so, why are there times I crave raw mushrooms or, at one time, anything with vinegar? Is there an article about this? (note: I am not pregnant unless it is by the Holy Ghost) --Reticuli88 (talk) 13:08, 22 September 2009 (UTC)

The mushroom craving may be because you're low on protein (in which case I'd also expect you to crave meat, fish, eggs, milk, and nuts). However, raw mushrooms may be contaminated with the manure in which they grow, which could cause disease, so I sure don't recommend eating them without cooking.

Vinegar contains a weak acid (acetic acid). It's possible that your body detects that it's excessively alkaline and thus craves acid (the two cancel each other out to produce salt and water). Do you also have a craving for fruit or juice at those times (which contains citric acid) ? StuRat (talk) 13:22, 22 September 2009 (UTC)

Incidentally, while spinach is a relatively good iron source as leaf vegetables go, its fantastic reputation in popular culture is mostly due to a misplaced decimal point giving the false impression it has ~10 times the iron content of similar vegetables. AlmostReadytoFly (talk) 13:34, 22 September 2009 (UTC)

I'm not convinced there's necessarily a link between a food craving and a deficiency. That could lead to irrational justifications for eating junk.--Shantavira|^{feed me} 14:44, 22 September 2009 (UTC)

Well said Shantavira. My belief is that food cravings have a psychological basis. I'm not saying that is bad in any way but that is I think the source of our needs for certain flavours or foods. Richard Avery (talk) 15:33, 22 September 2009 (UTC)

I am convinced that there is often a link, but our understanding of how food cravings arise is remarkably weak. We know that the brain contains powerful mechanisms, operating below the level of consciousness, for associating foods with changes in body state that follow eating them, but we have hardly any understanding of how they work. We have a better understanding of how food aversions arise, but even for that there are a lot of puzzles and controversies. (One example of a craving that often strikes me is that people who come to town after a long backpacking trip usually have a tremendous appetite for fruits and vegetables -- they're notorious for "cleaning out the salad bar".) Looie496 (talk) 15:36, 22 September 2009 (UTC)

I'd say that we have an imperfect mechanism for craving foods high in nutrients we need. One way it can fail is with foods designed to fool us. Thus, someone craving fruit juice may settle for some brightly colored sugar-water (or even worse, sugar-substitute-water), which doesn't actually have any of the nutrients we need. Another way it fails us is that our bodies remain designed to prepare for famine, by packing on the pounds by eating high-fat, high-calorie foods whenever we can. Also, since salt is hard to come by in a natural diet, we tend to crave excess salt all the time. StuRat (talk) 19:05, 22 September 2009 (UTC)

After working outside in the North African desert for several weeks, I started realizing that I had been having constant, intense cravings for Chinese food. I didn't make the connection, however, until someone pointed out how little salt we had been eating (compared to what we had been sweating out) and how salty soy sauce is. Then I realized that what I really wanted was just to drink a bottle of soy sauce. — Sam 63.138.152.155 (talk) 19:54, 22 September 2009 (UTC)

Other than a basic craving for something like water or salt, how could it be that someone craves something when they have no clue what that food contains? If one has no idea what foods contain iron, how could you crave an iron-containing food? Sort of a bizarre, bacronym-sort of concept. DRosenbach ^{(Talk | Contribs)} 19:38, 22 September 2009 (UTC)

You body does all sorts of things like that. You don't have to know that air contains oxygen and you need this to burn calories for your body to tell you when it's time to take a breath. Your body keeps track of what happens after you eat various foods and determines for itself when you need those foods. Just like you will despise foods that make you ill, you will crave those that make you feel better by satisfying some deficiency.

Also consider that hardly anyone ever actually dies from a nutritional deficiency in places where a variety of food is available. Why don't we all just eat our single favorite food until we die from whatever it lacks ? Well, some people obviously attempt to follow a healthy diet, but there are also plenty who eat whatever they crave, nutrition be damned. Even those people rarely die of a deficiency, precisely because this "craving" system provides for a minimum level of nutrition. StuRat (talk) 20:39, 22 September 2009 (UTC)

Note also that spinach doesn't have particularly much iron. This bit of folklore is due to a wrong measurement decades ago. --Ayacop (talk) 08:54, 23 September 2009 (UTC)

Are you saying that spinach is nothing more than a placebo to Popeye? Well, blow me down... another core belief demolished. :( →Baseball Bugs ^{What's up, Doc?} carrots 09:29, 23 September 2009 (UTC)

Chopped liver [40], on the other hand, is a good source of iron (seriously). AlmostReadytoFly (talk) 16:03, 23 September 2009 (UTC)

Try this article on food choice in animals. Also see the work of Steve Simpson at the University of Sydney on this. Fences&Windows 19:41, 23 September 2009 (UTC)

Infra-Red rectenna power breaks the Second Law of Thermodynamics?

On a recent television program, an advanced infra-red (as opposed to microwave) rectenna, based on nanotechnology was demonstrated. This device converted heat radiation into electricity even from the ground at night! Could such a device convert the low grade heat at the end of the universe back into high grade energy, breaking the second law of thermodynamics and preventing the ultimate heat death of the universe?Trevor Loughlin (talk) 13:55, 22 September 2009 (UTC)[Trevor Loughlin]

• I'm sure the answer is "No" - but you might like to read our article Nantenna which describes such things in detail. I believe these devices can only operate if kept cooler than their environment - and that's probably the key to why they don't break the laws of thermodynamics. SteveBaker (talk) 14:03, 22 September 2009 (UTC)
• (EC) The ground at night is still probably 270 degrees or so above absolute zero, so there's no lack of energy there to be made use of. As to your second question, err, let me think for a moment ... no. There's no reason to suppose, on the basis of a very poor understanding of the physics involved, that the device could do something as fundamental as that. --Tagishsimon (talk) 14:04, 22 September 2009 (UTC)
• (EC) No. Even if this really exists (and TV programs typically are lousy sources), it would live off the temperature difference between the (warm) ground and the colder atmosphere/antenna at night. --Stephan Schulz (talk) 14:10, 22 September 2009 (UTC)

The amount of energy that it could receive is actually very small, and you will find that the amount is of the order kT_cmbB, k the Boltzmann constant, T_cmb the CMB temperature, B is bandwidth. Any antenna that receives also makes a similar quality transmitter, so it would be transmitting the thermal energy of the rectifier out the antenna. This would be about kT_antennaB. All resisters, and electronics have a background energy, kTB. See Johnson–Nyquist noise. So to receive energy the antenna has to be a lower temperature than the CMB. This means that the 2nd law is not violated, and you won't be able to get free energy from thermal radiation. Graeme Bartlett (talk) 07:37, 23 September 2009 (UTC)

Don't we have an article on antenna temperature? It should be noted that antennas, especially phased arrays or "rectanna/nantenna" systems, are narrow band. The antenna temperature is therefore sort of unintuitive, since we expect a blackbody spectrum if we seek to have a well-defined temperature. According to NASA, "Antenna temperature is a way of expressing the brightness of a radiation source - it is proportional to the power per unit area emitted by the source". Keep this in mind when analyzing second-law-of-thermodynamics - you might be comparing two "temperatures" that cannot actually be compared. The catch-all is that power will not flow into the antenna in signficant quantities, at any band, against the thermal gradient. Nimur (talk) 15:46, 24 September 2009 (UTC)

Neutralizing Acid waste

In order to neutralize the acid in a waste stream (composed of H2SO4and H2O), dry ground limestone (composition 95% CaCO3 and 5% inerts) is mixed in. The dried sludge collected from the process is only partly analysed by firing it in a furnace which results in only CO2 being driven off. By weight the CO2 represents 10%of the dry sludge. What percent of the pure CaCO3 in the limestone did not react in the neutralisation?

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. ~ Amory (user • talk • contribs) 16:44, 22 September 2009 (UTC)

I attempted this experiment in high school, I was troubled by two issues, one was how dry was dry, the hotter the drying the lighter it got, and there seemed to be no completely dry state. And also there were other gases given off such as H₂S. (yuck). You may also strick Selenium, and sulfur dioxide in your case, but I expect your teacher does not want you to consider impure limestone! Graeme Bartlett (talk) 22:50, 22 September 2009 (UTC)

What would happen in space

I'm very curious about the details of what would happen physically to my body if I was, say, ejected from a rocket. I've seen in games and movies that space seems to suck you out of a spaceship if a door leading outside opens. Is that accurate? If I was sucked out into space, what would happen to my body before I died? And I'm not wearing a spacesuit or anything of that nature. Thanks : ] EVAUNIT-666 16:34, 22 September 2009 (UTC)

Try the search available at the top of the page. A quick look reveals this, this, and this. Essentially, you die. Quickly. ~ Amory (user • talk • contribs) 16:51, 22 September 2009 (UTC)

But you don't explode. We have an article on space exposure.--Shantavira|^{feed me} 17:00, 22 September 2009 (UTC)

It would be more accurate to say you get blown out into space, because of the pressurized air (normal air pressure) behind you and no pressure resisting that force on the outside of the ship. StuRat (talk) 19:13, 22 September 2009 (UTC)

I was just about to post the same (ec) and that sucks!Cuddlyable3 (talk) 19:17, 22 September 2009 (UTC)

Most vacuum cleaners just plain suck, but ours both sucks and blows ! StuRat (talk) 20:29, 22 September 2009 (UTC)

My undergrad lab was in an oooold building, running joke was that everything sucked but the fume hoods and everything blew except the ventilation. DMacks (talk) 20:34, 22 September 2009 (UTC)

I've heard this line before (I think Data said it on Star Trek), but never understood it. What does it mean to be "sucked out of" something if not that there's a lower air pressure at the destination and the air where you are is blowing you towards it? How is the space example any different from a vacuum cleaner which creates a low-pressure chamber which causes stuff to be "blown" into it by the air behind the stuff? --Sean 13:17, 23 September 2009 (UTC)

I suppose the diff is that a vacuum cleaner itself lowers the pressure versus the ambient pressure, and this lowering of the pressure with predictable results constitutes "sucking". Since space doesn't "lower it's pressure with the goal of causing suction", it doesn't suck (although being in space without a spacesuit would most definitely suck). StuRat (talk) 14:16, 23 September 2009 (UTC)

It is well known that suction is a phallusy fallacy. Ie it doesnt exist: its the air pressure that pushes.--CruelSea (talk) 17:30, 23 September 2009 (UTC)

I believe that is the logic of the "blown not sucked" assertion above. Presumably when someone in that camp falls through the ice, they complain about the quality of the heat, since "cold" doesn't exist, either. --Sean 19:48, 23 September 2009 (UTC)

GREEN HOUSE EFFECT

HOW MUCH TEMPRATURE WE CAN RAISE BY USING GREEN HOUSE EFFECT.

It depends on the conditions. Venus is often considered to have a runaway greenhouse effect and has surface temperatures of some 460 °C. You may also be interested in our articles on global warming and global climate models. — Lomn 18:03, 22 September 2009 (UTC)

It also has roughly 200,000 times as much carbon dioxide per square meter as we do. Which illustrates the point that the greenhouse effect can basically be dialed up as high as you want provided you have sufficient greenhouse gas or in the case of a physical greenhouse that you have enough building materials. It is a matter of diminishing returns though since every increase will provide less extra warming than the one before. Dragons flight (talk) 18:16, 22 September 2009 (UTC)

I don't see any reference to climate in the question so are you sure they are not asking about greenhouses etc? My solar vaccuum tubes get to 200C easily using only the greenhouse effect when they have no coolant in them (if the pump doesn't work the coolant blows off at 140C as I discovered this summer)... --BozMo talk 20:45, 22 September 2009 (UTC)

Does a rotating ring show length contraction?

If a straight rod were to travel past me at a significant fraction of the speed of light, I understand that I would observe it to be length-contracted. And I understand that this relates to relativity of simultaneity: even if I observe that the two ends of the rod are passing two points on the ground at a certain instant, from the frame of reference of the rod, the ground is length-contracted and the front end of the rod will pass the first point before the back end passes the second point.

However, what would I observe if a ring (say a hula hoop) were rotating around me? If it rotates at a high velocity, then it seems to me it should be length-contracted, that markings on it will be closer together. But since it's a continuous ring, it still has to join up. The only way for me to observe all the points closer together would be for the ring to have a smaller radius, right? What makes this complicated for me is that if it's rotating, the parts of the ring are accelerating, and I don't really know how length contraction or the other transformations work in this type of accelerating frame. — Knowledge Seeker দ 19:16, 22 September 2009 (UTC)

The hoop will shrink. Imagine starting with a solid object at rest (with respect to frame S) and then simultaneously (with respect to S) accelerating every part of it by the same amount. The object is now physically stretched in the direction of the acceleration—if you boost into its new rest frame it will be longer by a factor of γ. Since it's a solid, it will shrink back to its preferred size through the action of intermolecular forces (or it will break if you accelerated it too much). The preferred size with respect to frame S is of course 1/γ times the rest size. Essentially the same thing happens with the hula hoop, except that the lowest energy state will be a hoop of smaller radius. It's very much like a metallic object shrinking as it cools. This is different from the length contraction you get from a Lorentz boost, which is just a coordinate change and not a physical change in the object.

(Actually, there is also a centrifugal tension that will tend to make the hoop expand. Which effect dominates will depend on the characteristics of the material, but there aren't many materials that can survive the stresses of relativistic rotation anyway.) -- BenRG (talk) 22:08, 22 September 2009 (UTC)

See Ehrenfest paradox. — DanielLC 22:22, 22 September 2009 (UTC)

The conclusion from the Ehrenfest paradox article is that clocks cannot be synchronized between rotating reference frames. SO this means you won't really be able to tell where that hoop has rotated to in a time interval. Graeme Bartlett (talk) 10:07, 23 September 2009 (UTC)

Thanks for the responses. I'm gratified that there isn't a very clear answer to this, though I was hoping for some nice, simple explanation. The reason I was pondering it was I was reading about how magnetism was a consequence of length contraction — while I can grasp that for a straight wire, if the wire were in a circuit, it seems to me that that...actually, never mind, I've tried rewriting this sentence three times and I can't get my thoughts out right. I think I will have to ponder this some more. I really appreciate the answers and any insights you have. — Knowledge Seeker দ 06:10, 24 September 2009 (UTC)

There is a clear answer to this, the one I gave. It's complicated inasmuch as it depends on the properties of the material, but there's no debate over it. The Ehrenfest paradox is a disagreement about words, specifically about how reference frames ought to be defined. The Sagnac effect is closely related. For some reason it's mostly crackpots who argue about the Sagnac effect and mostly real physicists who argue about the Ehrenfest paradox, but the arguing is equally silly either way. Good article, though. -- BenRG (talk) 11:24, 24 September 2009 (UTC)

There is some interesting physics related to current in a wire. For example, an ordinary neutral object is still neutral under a Lorentz boost. But consider a straight neutral wire with current running in it. Under a Lorentz boost (in any direction other than perpendicular to the wire), the moving charge carriers will change density differently from the stationary opposing charge, so the wire acquires a net charge. How can that be, when charge is supposed to be frame invariant? If the wire is part of a circuit, it has to bend around and go in the opposite direction at some point, and that part will acquire an opposite charge; it all adds to zero. If the wire is transporting charge from one reservoir to another, then the relativity of simultaneity implies that in the boosted frame the sum of the charges in the two reservoirs will be different, and that difference shows up on the wire. If you have a hoop of superconducting wire with a current in it and you start it rotating, charge conservation implies that it can't acquire an overall charge and symmetry implies that no part of it can have a local charge either. However, a measurement device sitting on the wire (and rotating with it) will measure a net charge density in the wire (as you can see by doing a local Lorentz boost). If you walk it slowly around the whole wire it will measure the same charge density everywhere. When you reach your starting point again you might conclude that there's a nonzero charge on the wire as a whole, but you'd be wrong. This is another version of the Ehrenfest/Sagnac effect. -- BenRG (talk) 12:18, 24 September 2009 (UTC)

Behind the navel

What can be found behind the human navel ? Is it possible to feed a person by injecting nutrient at the navel ? Cuddlyable3 (talk) 19:40, 22 September 2009 (UTC)

The human navel (umbilicus) is the remnant of the insertion site of the umbilical cord through which the umbilical vein once provided nutrients to the developing fetus. After birth, the umbilical cord no longer functions and eventually falls off, leaving behind the navel. Behind the navel is the Ligamentum teres hepatis, aka round ligament of the liver, which is essentially a string of connective tissue that connects to the liver. In an adult it's really no more than an anatomic landmark and doesn't do anything. The remnant of the umbilical vein is collapsed and replaced with fibrous tissue. Is it possible to feed a person? Yes and no. Not an adult person -- there really isn't a passage that could be used. However, the umbilical vein is commonly used as an IV access site in neonates, particularly in premature infants, through use of an umbilical line. --- Medical geneticist (talk) 21:32, 22 September 2009 (UTC)

Do Re Me

I hear that Indian [subcontinent] music possesses 8 notes instead of the seven commonly used in the US/Europe/etc. Where does this extra note fit in? Are the other notes shifted to make room, or is there an uneven distribution of space between notes to achieve placement of this extra note between Te and the next Do? I thought I'd find an answer or a direction for the answer at Do Re Me or Solfège, but I could not. DRosenbach ^{(Talk | Contribs)} 20:04, 22 September 2009 (UTC)

See musical scale and swara. Dragons flight (talk) 20:10, 22 September 2009 (UTC)

A major scale (and its wraparound buddies the minor scale and various modes) aren't evenly distributed at all; they're only 7 of the 11 notes in the chromatic scale. Most of the world's musical traditions use scales that take some number of notes from the chromatic scale. While the Solfège major scale sounds nice and even to someone from a western background, that's largely because they're so basically acculturated to it (people have been speaking to them in it since the day they were born); things like a Iwato scale will sound just as consonant to someone from that culture (cf Scientific American article from about 1991). But even that chromatic scale (the notes on a piano) isn't the limit; some music is microtonal, which means it uses notes between the piano keys, and even the notes you might think a piano is tuned to are kinda wrong (see musical temperament), but unavoidably so. -- Finlay McWalter • Talk 20:37, 22 September 2009 (UTC)

Do you mean 12 pitches in the chromatic scale? Rckrone (talk) 22:04, 22 September 2009 (UTC)

oops, yes, 12. -- Finlay McWalter • Talk 23:01, 22 September 2009 (UTC)

And westerners aren't prisoners of the tyrannical major mode either; the harmonic minor scale (which deviates from the modal template by raising its last note) is very common in classical music, and the blues scale (which devilishly flattens the fifth) is dominant (sic) in blues, jazz, and rock music. Plus the scales used for the folk musics of many western places (e.g. Hungarian gypsy scale) use different notes again. -- Finlay McWalter • Talk 20:53, 22 September 2009 (UTC)

It's not just acculturation. There's a preference for small-integer-ratio jumps in frequency, because their overtones reinforce one another in chords. So you have the perfect fifth, the most basic interval after the octave, as a 3/2 ratio, and the fourth at 4/3 and the major third at 5/4. How you fit these into a temperment where you're allowed to change keys, that's less canonical, but these basic intervals, at the very least the octave and the perfect fifth, I would expect to be reinvinted in every musical tradition. --Trovatore (talk) 00:04, 23 September 2009 (UTC)

In fact, except for the octave, none of the intervals that the standard chromatic scale produces are perfectly harmonious, because the ratios aren't precisely integral. The advantage of the system is that it allows switching to a different key without retuning, and key changes are essential to modern western music. This system of tuning is called well-tempering, and became popular in the 1700s -- Bach's Well-Tempered Clavier is a group of pieces written to exploit it. Looie496 (talk) 18:17, 23 September 2009 (UTC)

Gull hypnosis

How does this work? Seems similar to chicken hypnotism, from when I've seen it - but the technique is completely different. Any ideas? --Kurt Shaped Box (talk) 20:37, 22 September 2009 (UTC)

I would refer you to our resident gull expert, but, oops, that would be you. I could guess that they have a "sleep mode" that is triggered by their parents or possibly their mates, and that they are somehow tapping into this. StuRat (talk) 21:47, 22 September 2009 (UTC)

(after ec)I've never seen anything like that before in my life. I wouldn't have thought it possible to flip a gull onto its back like that and touch its belly without getting your fingers mauled. Could whirling it around beforehand cause the gull to become too dizzy to move? Na, that doesn't seem plausible to me. --Kurt Shaped Box (talk) 22:04, 22 September 2009 (UTC)

Some animals pretend to be dead not to be eaten -it does not work with scavengers of course, but not everybody is. Could it be this case too? maybe not.--84.220.118.29 (talk) 22:29, 22 September 2009 (UTC)

Well, I don't hang out with gulls 24/7 - but I've never seen nor heard of them 'playing possum' before. If a gull was cornered, I'd expect it to fight for its life. I do know that covering a gulls eyes (say by putting a piece of cloth over its head, or putting the entire bird in a sack - as the bird ringers do) will render it 'mostly docile' after a couple of minutes - but this is clearly not what happened in the video... --Kurt Shaped Box (talk) 22:51, 22 September 2009 (UTC)

Though the bird was shaken beforehand, and already in the upside down position, it was placed down on the hard surface with notable gentleness. I would imagine that the psychology of the bird already largely accepted the likelihood of defeat in this encounter with the man. Thus it experienced (psychologically) relief when it found itself merely resting on its back on the hard surface, no longer in the grasp of the man. And the stroking of its belly also was gentle, thus it failed to trigger an alarm response, due to the special circumstances of having just been released from what it surely perceived as a life threatening situation. It was choosing to leave well enough alone. I have little doubt that animals have psychological states of mind that are analogous to humans'. The gull is probably not going to go to law school, but I think it shares some version of the human basket of frames of mind. Bus stop (talk) 23:06, 22 September 2009 (UTC)

That's an interesting hypothesis - thanks. I've just been browsing YouTube for similar videos and it seems that doves, pigeons lovebirds and canaries can also go into/be put into the same 'trance state'. --Kurt Shaped Box (talk) 23:46, 22 September 2009 (UTC)

I may be wrong. These other instances don't show how the bird got to be on its back, immobile. Bus stop (talk) 00:00, 23 September 2009 (UTC)

I now suspect that there's a specific method of 'hypnotizing' birds, which works with many different species. Some sort of magician's parlour trick that the performer intentionally doesn't show in the vids. Birds do sometimes play or sleep on their backs - but never with their necks in that position, as far as I'm aware. --Kurt Shaped Box (talk) 00:08, 23 September 2009 (UTC)

Birds, among other animals, seem particularly helpless and vulnerable when on their backs. Cats and dogs for instance can defend themselves and fight while on their backs. But bird's wings would seem to me to be at their most useful only when the bird is upright, but I could be wrong about this. Bus stop (talk) 01:33, 23 September 2009 (UTC)

I think you're all a bit too gullible. Why should this bird have been hypnotized, because it says so on the page? Maybe it hit its head on a ship plank and the guy just had the right timing for his show. Maybe chemicals were involved, fed to a random gull beforehand. --Ayacop (talk) 08:43, 23 September 2009 (UTC)

"Gull"-ible? Dat's fer da boids. Chemicals? Like when a wolf slips a mickey to a gull? My first thought on seeing this video was, "He's not dead! He's just stunned! He's pinin' for the fjords!" Then away he flew (assuming it was actually the same bird), headed for them fjords. →Baseball Bugs ^{What's up, Doc?} carrots 09:27, 23 September 2009 (UTC)

WP:OR: I hypnotized my pet rabbit when I was a kid: you cover its eyes and rub its belly and it goes into a similarly flaccid state. --Sean 13:22, 23 September 2009 (UTC)

I'd be curious to know how those fishermen harmlessly captured a wild seagull while on the water in their rickety craft. Bus stop (talk) 13:29, 23 September 2009 (UTC)

Gulls, whilst normally quick-witted, fast-moving and difficult to catch, do have a habit of tangling themselves up in fishing lines or getting the hooks embedded in their beaks when they're trying to snatch the bait - especially when following boats. Those guys probably just reeled the gull in. --Kurt Shaped Box (talk) 19:37, 23 September 2009 (UTC)

Significant figures

What is the significant figure rule for addition and subtraction?174.6.144.211 (talk) 23:37, 22 September 2009 (UTC)

This should give you all you need to know: Significant figures#Arithmetic. ~ Amory (user • talk • contribs) 23:46, 22 September 2009 (UTC)

Roller Coaster Momentum

How do I determine the momentum of a roller coaster? I know that momentum is mass times velocity. If the height of the roller coaster is 191ft tall, the length is 1204 ft. long and the speed is 65.6 mph, what is the mass?

You can't tell without more information. Rckrone (talk) 00:22, 23 September 2009 (UTC)

Maybe this can be worked out. Let mass of coaster be M. Assume its initial velocity is zero. Force (gravity) = Mass X acceleration

So What is the component of gravity acting along the hypotenuse of a right angled triangle height 191; baseline 1204?

Momentum does not come into the solving of this problem. Enough clues!--CruelSea (talk) 00:50, 23 September 2009 (UTC)

With respect, momentum is what the OP asks for. But you cannot evaluate the mass M from the information given. Cuddlyable3 (talk) 06:49, 23 September 2009 (UTC)

Agree it looks like that if you dont have the time taken from top to bottom. Pity!--CruelSea (talk) 16:06, 23 September 2009 (UTC)

Even if you did have the time, it wouldn't help. Remember the story about Galileo and the Leaning Tower of Pisa? (Yeah, it didn't really happen, but the principle is valid enough.) --Anonymous, 20:27 UTC, September 23, 2009.

Postmature birth

Okay, we all know being born premature is bad for you. Would a 10 month term baby have the brain/mind of a 1 month old or a newborn? I doubt much nonsomatic development (beyond the usual) or experience can occur in an environment less stimulating than Plato's Cave.

Unlike normal newborns, this infant will be able to lift his head at birth. Will he say his first word 1 month "earlier" and remember 1 month earlier and walk 1 month earlier etc. for life, fading into normal bounds (for the choice of age start point that is anamolous)? Or will the brain and/or body play catch up/slow down? What studies are there that attempt to follow postmatures' height/weight and developmental milestone excesses (delays) as deep into life as statistically significant? Sagittarian Milky Way (talk) 23:52, 22 September 2009 (UTC)

BozMo said it is possible for babies to be able to lift their heads at birth. (curious: was your baby some number of days overdue?) If you used enough infants, I bet you could easily find better than chance more likely to lift the head at birth the older they are, at least up to a point (even 13 days overdue is still not outside medical normal yet, so it's harder to make the health complications excuse). Likewise, even after accounting for everything one could possibly think of, finding a correlation likely not from chance in ages of death seems almost impossible. Somewhere in between either we csn't track the discrepencies anymore or the discrepencies even out before then. I'm not expecting to find correlations with menarche or anything.. :) Sagittarian Milky Way (talk) 19:55, 23 September 2009 (UTC)

It is perfectly 'normal' for a child to be able to lift their head at birth, just rather 'unusual'. One of mine could. --BozMo talk 10:46, 23 September 2009 (UTC)

I would suspect that the real issue here is not whether the relative "early" nature matters much, but whether there are health risks involved with pregnancies that late. I would suspect that a much more difficult labor would raise a variety of risk factors for both child and mother. As for being a month more developed than your peers, it can hardly matter—a month is just not enough time to matter. I am born in January, my peer is born in February. Does it matter if I have a February brain? Not at all—it will be indistinguishable, and nobody cares what month you are born in (it's not like I'll be tracked with all of the January births—nobody will say, "gosh, he seems a month smarter than his peers!"). --98.217.14.211 (talk) 01:01, 23 September 2009 (UTC)

Being born prematurely is not bad for you. If the mother is terminally ill and the fetus is induced prior to the mother dying and the mother dies prior to the due date, bring born prematurely would be good. DRosenbach ^{(Talk | Contribs)} 12:41, 23 September 2009 (UTC)

Yes it is, unless you have some unusual definition of "bad". From the preterm baby article:

The shorter the term of pregnancy, the greater the risks of mortality and morbidity for the baby primarily due to the related prematurity. Preterm babies have an increased risk of death in the first year of life (infant mortality), with most of that occurring in the first month of life (neonatal mortality).

It goes on to list a variety of serious complications that premature babies are at higher risk for. --Sean 13:28, 23 September 2009 (UTC)

Your quote fails to take into account my given premise. The most serious complication is being dead, unless you have some unusual definition of "complication" or "death." DRosenbach ^{(Talk | Contribs)} 14:30, 23 September 2009 (UTC)

We're all talking about risk factors here. Being born prematurely raises your chance of dying quite a bit. I imagine that being born postmaturely would increase the risk of complications as well. Statistically speaking, being born prematurely is bad for babies, even if in the case of any given individual, it might not be a problem. There are of course mitigating circumstances, but your "terminally ill mother" example is certainly not very common. In medicine (as in many other realms), talking in terms of what is actually likely to happen (and what is more probable) is more useful than being pedantic about it. --98.217.14.211 (talk) 15:37, 23 September 2009 (UTC)

I agree with Sean. DRosenbach's scenario is unhelpful in the context of the original question. Axl ¤ [Talk] 17:04, 23 September 2009 (UTC)

It's not the frequency of "terminally ill mothers", but the idea that just because there is a worse evil that the lesser one is not "bad" for you. If a thought-experiment demon says he'll kill the baby unless mom drinks and smokes throughout her pregnancy, that greater evil doesn't magically make those behaviors not-bad for the baby. --Sean 19:54, 23 September 2009 (UTC)

My son was born about 2 weeks post-mature. When my wife didn't give naturally give birth on the pre-ordained date, they first decided to induce her - but then changed their minds and scheduled a Caesarian section - but then she got a really nasty cold and so they postponed that even longer. The most noticable side-effect was that my son had lost a significant amount of weight...aside from that...not much. He certainly wasn't born with the abilities of a 2-week-old baby. SteveBaker (talk) 23:24, 23 September 2009 (UTC)

I'm a bit late to the discussion here, but I have to say that, despite a somewhat pointless digression into prematurity, no one has mentioned the article on postmature birth, which lists some potential complications of a post-dates pregnancy. (Isn't this supposed to be a REFERENCE desk?) It's also worth noting that the "dates" of a pregnancy are notoriously prone to error. Since the dates are based on the last menstrual period (also discussed in the pregnancy article), dating can be difficult in women who have an irregular cycle. --- Medical geneticist (talk) 23:46, 23 September 2009 (UTC)

What, you don't use one of those time of ovulation things when trying to get pregnant? I suppose the trial and error method is more fun.

acid battery casing repair

Hi, I have a near new deep cycle acid battery (no warranty) which has a pinhole leak at one end. I was wonderin wether there is any common materials or glues that i could use to seal the leak in the casing cheersGegnus (talk) 23:58, 22 September 2009 (UTC)

Sorry, I don't have an answer - but there was a similar question asked here a couple of weeks ago. Those replies may be of some use to you... --Kurt Shaped Box (talk) 00:14, 23 September 2009 (UTC)

Same questioner double posting!--CruelSea (talk) 00:52, 23 September 2009 (UTC)

polythene is acid resistant, so if you get a polythene glue gun you can probably fill that hole. It will not take too much heat however. Graeme Bartlett (talk) 10:34, 23 September 2009 (UTC)

September 23

British Weights and Measures Act

I am trying to locate the text of a certain British Weights and Measures Act (I think that's what it was called). Here are some things I think I remember from it:

• The document was from sometime in the 19th century.
• The document defined the yard as the length of a certain metal rod, and other measures of length in terms of the yard. As a sort of backup should this metal rod be lost or destroyed, the text also gave the length of a seconds pendulum in inches (as "so many Inches, and so-and-so many ten thousandths of an Inch", rather than using Arabic numerals like a normal person would do).
• The document defined a gallon in terms of the volume of so many (ten?) pounds of water.
• There was another backup, so that should the pound standard be destroyed, the weight of so many cubic inches of water would then be taken as the pound (or some similar rule of that sort).

There is a list of such acts at Weights and Measures Act, but there were eight of them in the C19. This EB article may be the sort of thing you were after - it would point to the 1824 act. More EB here. Good luck. --Tagishsimon (talk) 01:15, 23 September 2009 (UTC)

Possible to sustain adult human entirely intravenously?

As far as I know, people who are in a vegetative state are given nutrients via tubes to the stomach and I guess occasionally IV. Would it be possible to sustain an adult human entirely via IV? Essentially bypassing the entire digestive system? The kidneys & bladder would still be operational, but the esophagus, stomach, and intestines would all be unused.

It certainly wouldn't make for an active lifestyle! But I'm just interested in the feasibility of providing the necessary vitamins, amino acids, sugars, etc. over the long-term.

Can we do that yet? 218.25.32.210 (talk) 02:23, 23 September 2009 (UTC)

Yes. Total parenteral nutrition. - Nunh-huh 02:26, 23 September 2009 (UTC)

Yup. Not much of a life though. By the way, that stuff's insanely expensive. Shadowjams (talk) 07:21, 23 September 2009 (UTC)

I don't know how you all come to the conclusion that the intestines would be unused. Bilirubin, for example, from decay of erythrocytes, is the chemical that is dumped in the highest amount into the intestines, through the gallbladder. It's what makes the color of shit. So, eventually, your intestines have to move from all the stuff that comes through the gallbladder. --Ayacop (talk) 09:19, 23 September 2009 (UTC)

Hernia support

What type of doctor(s) would diagnose and treat an abdominal hernia ? (I truss that you will answer promptly.) StuRat (talk) 03:26, 23 September 2009 (UTC)

The Internist or General Practitioner is a good starting point. A general surgeon (or pediatric surgeon if the patient is young) could do the repair. Hernia good jokes lately? Edison (talk) 04:59, 23 September 2009 (UTC)

It's best to be serious, and not engage in disrupturing. →Baseball Bugs ^{What's up, Doc?} carrots 09:23, 23 September 2009 (UTC)

Any physician can diagnose an abdominal hernia. They can then refer you to a general surgeon for treatment since abdominal hernias rarely heal on their own. Livewireo (talk) 15:07, 23 September 2009 (UTC)

most oftenly mutated genes?

Hello, what are the, say ten genes the mutations of which are the most common ones? Note, I'm not asking for the most common single mutations but cumulatively the genes. That is, mutation r123 on gene X may be the most common mutation around but mutations on gene Y may be more common because there are so many different ones. ----Ayacop (talk) 08:34, 23 September 2009 (UTC)

It sounds like you are asking for the gene with the most diverse alleles. In that case, V(D)J recombination is worth noting although it may not result in the most diverse gene.152.16.15.144 (talk) 16:58, 23 September 2009 (UTC)

You need to specify whether you're asking about germ line mutations or somatic mutations. I'm pretty sure that the most frequent class of somatic mutations that occur in (higher?) vertebrates, is the affinity maturation that occurs in B lymphocytes. If you're asking about germ line mutations, I don't know the answer, but there are so called hot spots, as described in our article, where the mutation rate is up to 100 times higher than at other sites in the genome. The major histocompatibility complex has such hot spots. Whether VDJ recombination is within the scope of your question is a matter of definition (I'd say it isn't), but if it were, the variability introduced in our antigen receptors by this process is so huge — a limited number of genes produces a vast number of receptors; 10^{(pick a number, 14 perhaps)} — that it would would dwarf anything else. VDJ recombination is, AFAIK, the only physiological somatic DNA recombination that occurs in vertebrate cells (or, for that matter, eucaryote cells). If anyone knows about other examples, I'd love to hear about it. --NorwegianBlue ^talk 18:24, 23 September 2009 (UTC)

I'm not really sure that this question can be answered but I'll echo the other two answers above and suggest that the OP clarify the question. For example: "which 10 genes have the highest number of different alleles?" or "what are the 10 most frequently mutated genes in cancer cells?" or "what are the 10 genes that are most frequently involved in a new (de novo) disease-causing mutation?" or "which single nucleotide polymorphisms have the highest population prevalence?" or "what are the 10 most common inherited Mendelian disorders?" --- Medical geneticist (talk) 21:14, 23 September 2009 (UTC)

Thanks for steering me to the right words. I would like to see a list that answers the question

• what are the genes that are most frequently involved in a new (de novo) disease-causing mutation? (say, in Europeans)

OTOH, lists that answer the other questions User:Medical geneticist gave would be interesting as well. --Ayacop (talk) 06:54, 24 September 2009 (UTC)

Since I steered you to the question, I guess I'm obligated to try a response...  ;-) I still don't think I can provide a complete answer, but in general the answer is going to be dictated by two variables: (1) the incidence or prevalence of the disease associated with mutations of the gene in question, and (2) the proportion of cases of that disease that are caused by new mutations (as opposed to inherited from an affected or carrier parent).

• Most autosomal recessive genetic disorders are caused by ancient mutations that are present in the general population at a certain carrier frequency and are not typically caused by new mutations, so we can eliminate that category.
• Autosomal dominant genetic disorders are often later onset conditions that don't necessarily impair reproduction and therefore can be inherited, although there is quite a range in terms of severity and reproductive fitness (for example, Huntington's disease, achondroplasia, some forms of osteogenesis imperfecta, marfan syndrome, polycystic kidney disease). Each of these conditions will therefore have a different new mutation rate. Most cases of achondroplasia are due to new mutations on the paternal copy of the gene and new mutations are not uncommon in marfan syndrome and neurofibromatosis, but new mutations are uncommon (by definition) in familial hypercholesterolemia.
• New mutations make up a significant fraction of isolated cases of X-linked disorders (for example, Duchenne muscular dystrophy).

Ok, so in order to answer the question what you really want is a list of genetic disorders by frequency. I found this one but I can't vouch for the list being comprehensive or the numbers being correct (and there are probably differences among various world populations). Then you want a list of genetic disorders by new mutation rate, which I'm having a hard time finding with Google (it could be that such a list just doesn't exist due to limited knowledge-base). You would then be able to intersect the lists to find the disorders having a combination of relatively high incidence and relatively high new mutation rate. I'll do some OR and see if I can come up with some candidates... --- Medical geneticist (talk) 14:22, 24 September 2009 (UTC)

This database looks like a promising source for data on prevalence of individual disorders. I don't think it can answer the question about new mutation rate, though. --- Medical geneticist (talk) 15:19, 24 September 2009 (UTC)

A pity that mining the literature is still so difficult. Many thanks for your efforts. --Ayacop (talk) 17:06, 24 September 2009 (UTC)

Brain cysts from cat parasites in humans

I remember hearing that these are common in humans, and that they change peoples behaviour to make then more relaxed and more outgoing. Just how true is that? 89.242.104.32 (talk) 09:59, 23 September 2009 (UTC)

Are you talking about toxoplasmosis? --Mark PEA (talk) 13:04, 23 September 2009 (UTC)

I hope you're not hoping to give out cats to all of your uptight and introvert friends -- sort of conjured up the tapeworm diet. DRosenbach ^{(Talk | Contribs)} 14:37, 23 September 2009 (UTC)

Toxoplasmosis may also increase traffic accidents,[41] and Rhesus factor may be protective against this.[42] Fences&Windows 19:52, 23 September 2009 (UTC)

'99% accurate'

I've often seen various positive/negative tests advertised, usually in the media, as being '99% accurate' and suchlike. What is usually meant by this in terms of false positives/false negatives? 94.168.184.16 (talk) 12:54, 23 September 2009 (UTC)

Check out sensitivity and specificity. Presumably giving a single number as in your question depends on the context. For example, let's say you have a cancer test that achieves 99% sensitivity, but only 80% specificity. They will probably quote the 99% figure, since the consequences for a false negative are much more serious than for a false positive: a false negative could cause a patient to dangerously delay treatment, while a false positive will probably just cause some unnecessary followup testing. An employment drug screening test might place the emphasis on specificity, since it might be better to let a few stoners in than to risk a lawsuit over a false positive. --Sean 13:39, 23 September 2009 (UTC)

I think a false positive is pretty serious for a cancer test too - the increased stress on someone who thinks they may die anytime soon is not insignificant - especially if it's multiplied by 20% of the people who are tested. This is why some tests which sound (on the face of it) to be amazingly good are not carried out in practice. SteveBaker (talk) 15:41, 23 September 2009 (UTC)

Tests with so many false positives are usually used for initial screening and there would be a follow up test (which is more expensive or unpleasant or time consuming or whatever than the initial one) to dramatically reduce the number of false positives. This is true, for example, for breast cancer - a large majority of positive results on a standard mammary scan are false, and the people doing the scans are careful to make it clear that they are just testing to see if you need the more thorough test, rather than to find out if you actually have breast cancer. --Tango (talk) 16:19, 23 September 2009 (UTC)

In public advertisements for self-tests, it is just as much a legal issue. For example, a pregnancy test if handled and used correctly is 100% accurate. However, there could be some damage to the test in shipping. The test item could have a shelf-life that expired before it was used. The user could be an idiot and assume that the male is supposed to pee on the stick instead of the female. Further, the user could be dumbfounded by the complexity of what + and - means on the result. So, with all those uncontrollable factors in the test, it cannot claim 100% accuracy. -- kainaw™ 13:46, 23 September 2009 (UTC)

And while we're at it... it's worth noting that 99% is pretty good for some applications, pretty bad for others. 1% multiplied by a lot of people is still a lot, and depending on the consequences, can be worse than not testing at all. --98.217.14.211 (talk) 15:29, 23 September 2009 (UTC)

Indeed. Consider a hypothetical 'terrorist sensor' deployed to airports. Let's assume that it can read minds and judge, with 99% accuracy, which passengers are planning to hijack an aircraft and fly it into a building. Is that good enough? On the one hand, if you have a hundred terrorists, you only lose one building. That sounds pretty good. On the other hand, you have roughly two billion air passengers worldwide, each year — so with 99% accuracy, you will incorrectly detain and torture forty million people. Hm. And those numbers assume that the device performs as well in the field as the manufacturer claims; reality is usually much worse than sales brochures. Meanwhile, the cost of installing those devices in every airport in the world gets deducted from budgets which could have been used to do old-fashioned police work, or deliver aid to war-torn countries that breed terrorists, or just to build schools and hospitals and provide other societal benefits. TenOfAllTrades(talk) 17:09, 23 September 2009 (UTC)

You are blurring two types of error. If a terrorist sensor failed to pick up one out of every 100 terrorists, it would be labeled 99% effective. That does not imply that it will consider one out of every 100 non-terrorists a terrorist. It could never consider a non-terrorist a terrorist. It may consider 50 out of 100 non-terrorists a terrorist. The 99% isn't measuring that in this case. On the other hand, if a terrorist sensor were to consider one out of every 100 non-terrorists a terrorist, calling it 99% effective would be a lie. The effectiveness is based on the purpose. The purpose is to identify terrorists and the measure of 1/100 non-terrorists doesn't imply anything about the effectiveness of identifying terrorists. I feel it is important to clarify this because this sort of incorrect argument is commonly used to sway opinion against things by creating a false fear. Terrorism is one of those areas where people attempt to create false fear in order to argue against anything and everything. -- kainaw™ 17:20, 23 September 2009 (UTC)

Yes, I realize that the positive and negative error rates are distinct, and often confused or conflated. I should have been more specific in my definitions. My point was to amplify on the grandparent poster's comment — that is, a superficially low false-positive rate can give a surprisingly high error rate if one is screening for low-probability events. On the point of false fears and terrorism, in general my experience is that sloppy fear-driven arguments are usually made to encourage (not to discourage) doing anything and everything. (Cover-your-ass and 'gotcha' approaches to politics and government bureaucracy play a role here.) The No Fly List in the United States is a perfect example. As far as I know, there's still been no evidence that it has ever prevented a terrorist attack, yet it inconveniences thousands of people and has reached a cost of roughly one billion dollars. And the No Fly List is screening on something that ought to be quite specific (though not necessarily unique): people's names. TenOfAllTrades(talk) 17:37, 23 September 2009 (UTC)

Well literally speaking it should mean that 99% of results are correct, so that the total of false positives plus false negatives should be only 1% of all tests. To see how this might go in practice, a test for a rare disease might be expected to be positive one in one hundred times it is given. In that case, consider applying the test to 200 people if it has a false negative rate of 0.5% plus a false positive rate of 50%. Then 197 people would test negative (with one false negative) and 3 people would test positive (with one false positive), for a combined error rate of 1%. As the example illustrates a test that gives the right result 99% of the time could actually be very inaccurate in the direction of results that rarely occur. (It should mentioned that sometimes accuracy statements are referring to the accuracy in both directions, i.e. both positive and negative, in which case the situation illustrated by this hypothetical would not apply.) Dragons flight (talk) 16:25, 23 September 2009 (UTC)

There's an interesting side effect to calculating the success rate that way. Suppose only 1% of people have our dread disease. If the black box always lights up and says the patient doesn't have the disease, then its overall results are still 99% accurate: 100% correct on the uninfected 99% of the population, and 0% accurate for the 1% who are infected. Such a magical "everything is okay" box would have an absolutely brilliant success rate (99.9999%+) detecting terrorists at the airport, too. TenOfAllTrades(talk) 17:44, 23 September 2009 (UTC)

Hmmm... I smell a multi-million dollar government contract there. Quick! To the patent office! — Lomn 18:23, 23 September 2009 (UTC)

Speaky of false predicting, apparently James Randi used to write a note every morning and put it into his pocket. It said: "I, James Randi, will die today!" and was signed with that day's date. If he died that day, people would wonder how he predicted it.[43] Fences&Windows 19:58, 23 September 2009 (UTC)

Psst! Read Bayesian statistics. Fences&Windows 19:58, 23 September 2009 (UTC)

Genetics

How can I prove the law of segregation for waxy gene in maize?

I think it was proven when meiosis was discovered. DRosenbach ^{(Talk | Contribs)} 14:08, 23 September 2009 (UTC)

I'm not sure I completely understand the OP's question, but the article waxy corn would be a good place to start, and it gives some references about the genetics of the waxy gene in question. Alternatively, is the OP asking for more practical advice on how to set up an experiment that would demonstrate the Mendelian inheritance of the waxy gene? --- Medical geneticist (talk) 20:51, 23 September 2009 (UTC)

Bird with no legs ?

In the movie The Fugitive Kind, Marlon Brando describes "a bird with no legs, with a blue belly so it's hidden from below, which spends it's entire life flying". Is there any truth to this at all ? I know birds can spend days flying, and could eat insects in the air, and maybe drink water when it rains, and some can even mate in the air and sleep in the air. I can't see how they could lay eggs and raise chicks there, though. StuRat (talk) 15:29, 23 September 2009 (UTC)

Fiction != Reality. SteveBaker (talk) 15:35, 23 September 2009 (UTC)

That's not a very useful comment. There are many works of fiction based at least partially of reality. That's why I'm asking if any part of this is true or not. StuRat (talk) 15:43, 24 September 2009 (UTC)

It's the Huma bird. A myth, an impossible animal, though its existence was taken as a possible reality for a few hundred years (like the Sycthian Lamb). As for giving birth in the air, I imagine the babies would have to be pretty well-grown by the time they hatched! Egg comes out, hatches in mid-air, bird instinctively flies out! A silly idea, but a fun one. --98.217.14.211 (talk) 15:41, 23 September 2009 (UTC)

A real-life bird which was at one time believed to have no legs was the bird of paradise. This was not believed in places where they actually lived, though; see the lead section of the article. --Anonymous, 20:33 UTC, September 23, 2009.

There are birds with no legs, though, due to injury or disease. They can sometimes get around quite successfully on the ground by sliding or hopping around on the bellies propelled by their wings. My grandparents have fed the birds in their garden for decades and they have blackbirds with a congenital defect that makes them kind of club footed and their feet often fall off later in life. They survive just fine, although that gene would probably have been removed from the gene pool had by grandparents not made it so easy for them to get food. --Tango (talk) 16:23, 23 September 2009 (UTC)

- In order to achieve flight, birds run-and-jump or hop-and-jump. Without legs, they couldn't take off.

- A white underbelly would grant greater camouflage than a blue one.

- If the bird never lands, does it lay scrambled eggs?

B00P (talk) 17:06, 23 September 2009 (UTC)

If it never lands, it never needs to take off! QI says pink is actually the best disguise, that is apparently what they used to paint some military planes. --Tango (talk) 18:00, 23 September 2009 (UTC)

While I agree that the bird-with-no-legs-giving-birth-in-the-air thing is purely mythical, a run- or hop-and-jump isn't necessary under all conditions. If the bird made a habit of only landing in breezy areas, it could simply face into the wind and start flapping — the wind could in principle give it an airspeed close to, or even in excess of, its stall speed. The very clever bird would only ever land at the top of trees (difficult to do without legs, I grant you) or near the edge of sheer cliffs. A brisk shove sidways with the wing and he's falling...then flying. TenOfAllTrades(talk) 18:48, 23 September 2009 (UTC)

I've seen gulls with no legs taking off successfully. It looks really clumsy - but they can do it. --Kurt Shaped Box (talk) 20:04, 23 September 2009 (UTC)

The common swift comes pretty close. 95.112.148.48 (talk) 19:00, 23 September 2009 (UTC)

Swallows feed on the wing (on airborne insects), drink by dipping their beaks while skimming low over ponds, and may remain airborne for extended periods. In Mediaeval Europe there were various widespread erroneous beliefs about swallows, including one that they never landed/perched and had no legs (for why would God have given them useless appendages?), hence in heraldic art the swallow (under the name hirondelle) was/is traditionally depicted without legs (and also, for some reason, without a beak). 87.81.230.195 (talk) 19:59, 23 September 2009 (UTC)

There is some Monty Python joke to be made here, but I can't figure it out. John Riemann Soong (talk) 18:06, 24 September 2009 (UTC)

NIGHT VISION GOOGLES

If a man standing in front of a mirror is a pitch black room, is wearing a night vision goggles. Can he see his image on the mirror? Explain. — Preceding unsigned comment added by Great gamer (talk • contribs)

What kind of night vision goggles? Are they infrared goggles or low-light goggles? That makes a huge difference. -- kainaw™ 17:32, 23 September 2009 (UTC)

Modern night vision goggles use an image intensifier to amplify the effect in ambient low light. This requires a minimum level of light. In pitch darkness, there is no light to amplify, so no image is seen. Older generations of devices use active infra-red, which would be visible, partly because the device itself has its own IR source, and partly because the man himself projects IR body heat. Axl ¤ [Talk] 17:40, 23 September 2009 (UTC)

Modern night vision goggles need SOME light - not much, but there has to be some. Most of them are sensitive to near-IR and red light, they don't really see blue light or heat very well - although people sometimes confuse NVG's with FLIR (Forward-looking-infrared) cameras which most definitely CAN see heat, but are unsuitable to wear as "goggles". So, in this case, if there is some tiny amount of light in the room, the man will be able to see his reflection in the mirror. If the room is utterly black - then the goggles will have boosted their amplification levels to the maximum possible and all you'll see is "snow" generated by electrical noise from the electronics (like you get when you disconnect the video from your TV). However, most people underestimate the amount of light amplification these gadgets can generate. In practice, it's almost impossible to get things so dark that you can't see anything through the goggles. Light leaking from the NVG's green display around the edges of the goggles provides enough light to see by. When we had a pair of US military goggles on loan, we tried to get a really, REALLY dark room to observe the 'noise' phenomenon first-hand, we found that light leaking under the wood/sheet-rock walls, shining up through the edge of the carpet from the adjacent corridor was quite enough to see by! An LED on a hard disk drive INSIDE a computer in the room cast enough light that even after bouncing off internal structures and out of some ventilation slots, the light was so bright that you could use it to make shadow puppets on the wall opposite. SteveBaker (talk) 23:13, 23 September 2009 (UTC)

Surely, there could be something in that room you could cover them with that would work? Have a guy lie over the doorjamb. Sagittarian Milky Way (talk) 04:49, 24 September 2009 (UTC)

The doorjamb was something we'd figured out in advance - we turned off all of the lights and other equipment in the adjacent room. But light leaking under the walls was quite unexpected. Certainly, you can force the goggles into complete darkness by putting the lens-caps over them - but we wanted to see how things looked just before things got too dark to see. (At the time, I was working on an accurate computer graphics simulation of night vision goggles and infra-red camaras so we did a lot of messing around with NVG's. Driving at night with your headlights turned off and wearing NVG's is a dangerous and exciting thing!) SteveBaker (talk) 12:34, 24 September 2009 (UTC)

Ha ha. Not in the city it isn't. You could see fingerprints by cloudlight alone. (or maybe there was snow on the ground, don't remember) What kind of floor-wall joint was that? That's very unusual. Sagittarian Milky Way (talk) 16:13, 24 September 2009 (UTC)

As I recall, it was a concrete floor with wooden 'stud' walls sheeted with sheet-rock (aka plaster-board) with skirting boards on both sides. Both the room - and the corridor outside were carpeted. I happened to be the one wearing the goggles at the time - and as we knocked out more and more sources of light by turning off computers, disconnecting the phone, etc, this weird sparkling glow appeared around the bottoms of three walls of the room (it was an interior computer room with no windows and only one door) - the room on the other side of the fourth wall had the lights turned off to prevent light from leaking around the door frame. For a while, I couldn't figure out what the glow was - until someone walked along the corridor outside and their shadow dimmed down the glow as they walked along. We eventually pulled up the carpet and ran a strip of duct-tape between the skirting board and the concrete floor - which got the room pretty amazingly dark. But light leaking around the edges of the goggles themselves was hard to eliminate. Even if you pushed the rubber eye-pieces hard up against your face, the light refracted through your skin and appeared as a dim glow around your eyes to anyone else wearing goggles. Getting rid of every last photon is very hard! SteveBaker (talk) 17:48, 24 September 2009 (UTC)

"What do you see when you turn out the light I can't tell you, but I know it's mine" ~~ from With a Little Help from My Friends Cuddlyable3 (talk) 17:00, 24 September 2009 (UTC)

Time Dialation

When Einstein did his thought experiment showing time dialation (with the photon bouncing between two mirrors), why can we assume that the length between the two mirrors doesn't contract?

{{homework}} Fences&Windows 20:04, 23 September 2009 (UTC)

It's not. I had a homework problem along the lines of calculating the new angle a stick makes with the horizontal when it starts moving. The solution was pretty easy, but to show that the component of the length of the stick perpendicular to the velocity doesn't change I argued that a beam of light travelling the length of this component would take the same amount of time in both reference frames, because while an obvserver moving with the stick will have her/his clock run slower, the path that the light takes is longer by an identical factor. But the time dialation equation stems from Einstein's thought experiment mentioned above, which assumes that the length between two mirrors doesn't change. So the logic seems circular, hence the question.

I'll direct you to Special relativity, Introduction to special relativity, Time dilation#Simple inference of time dilation due to relative velocity and Inertial frames of reference#Special relativity while I wait for the physics cavalry to arrive. p.s. Sign your posts using ~~~~. Fences&Windows 23:34, 23 September 2009 (UTC)

The thought experiments are just meant to demonstrate problems with the classical theory that special relativity addresses. Time dilation isn't the unique way to resolve the specific problem brought up by this specific thought experiment (this is the one with the mirrors on the top and bottom of a moving train car, right?), but it is a solution that's part of a larger self-consistent framework that solves a lot of other problems as well. It's not quite correct to say that the equations were derived from certain thought experiments, although I think a lot times it's taught that way because it makes it easier to understand what some of the rationale is. Rckrone (talk) 02:38, 24 September 2009 (UTC)

Alright, so then why isn't there any length contraction? I see that the Lorentz transformation is y'=y, but where does that come from (it could be y'=ay).

Wait, are you referring to Time dilation#Simple inference of time dilation due to relative velocity? The length between the two mirrors doesn't contract because length contraction only occurs in the direction of motion. Or, put another way, contract with respect to what? Traditional length contraction works by comparing distances in a two frames of reference that are moving with respect to each other. Both the reference frame of the ground and of the train have no movement in the y direction relative to each other, so they will not see any differences in y lengths. — Knowledge Seeker দ 06:21, 24 September 2009 (UTC)

Well in physics it all comes down to whether or not we observe the effect. As far as we can tell, y'=y for inertial frames moving relative to each other in the x direction. You could probably come up with a mathematically consistent transformation that involved y'=ay, but we don't see it, so it likely wouldn't have any meaning in the physical world. Of course, hardly anyone thought that time dilation was real at first, since nobody had observed it yet, but careful measurements showed it was really there. So Einstein's assumption that we can ignore the possibility that the length contracted between the mirrors is ok because the result that follows is what we observe. Also, it is extremely likely that you can show that by starting with the postulates of relativity, and some other facts about physics and math, that y'=y and z'=z, but ultimately, we accept it as true because it fits our observations. Jkasd 07:12, 24 September 2009 (UTC)

There can’t be a contraction perpendicular to the direction of an object’s motion, given that the laws of physics are the same in all inertial frames of reference.

We’ll basically use a proof by contradiction. To contradict observed reality, make the hypothesis that moving objects shrink perpendicular to their direction of travel.

Now consider a bullet which has exactly the same diameter as the barrel of a particular gun. Then if the bullet travels at high speed down the barrel of the gun, the bullet’s diameter shrinks, and the bullet easily passes down through the barrel.

However, a frame of reference in which the gun is at rest isn’t the only possible inertial frame of reference. You could just as legitimately use a frame of reference in which the bullet is at rest, and the gun is moving. In that case, the hypothesis that moving objects shrink perpendicular to their direction of travel would require that the gun barrel would have to become narrower than the bullet, which means that either the bullet would jam in the barrel, or perhaps the barrel would explode.

Thus, the bullet must both pass easily through the gun’s barrel, and the bullet must get jammed in the barrel due to the barrel being too narrow, which is a contradiction. Therefore, one must reject the hypothesis that moving objects shrink perpendicular to their direction of travel. A similar argument can be used to show that a moving object doesn’t expand perpendicular to its direction of travel, either.

The argument above ultimately boils down to experimental evidence. The above argument assumes that the laws of physics are the same in all inertial frames of reference, but that’s only a valid assumption because it’s consistent with the experimental evidence. Red Act (talk) 14:31, 24 September 2009 (UTC)

What is the sun fusing?

I learned a little while ago that you can't fuse normal hydrogen because it would produce a helium atom with no neutrons, and those don't exist because they are too unstable. So is it true that the Sun does not fuse any normal hydrogen? It only fuses deuterium and tritium? I'm only talking about hydrogen btw, not other elements. ScienceApe (talk) 19:00, 23 September 2009 (UTC)

There are various reactions going on in the sun, the ones that dominate in the sun are the ones in the proton-proton chain reaction. It is true that at no point are two hydrogen nuclei fused to make helium-2 (which does not exist). For interests sake the other cycle is the CNO cycle which dominates in larger stars (greater than x1.5 solar mass). Elocute (talk) 19:09, 23 September 2009 (UTC)

But according to that article, you can fuse two hydrogen nuclei into deuterium which can then be fused into other elements. ScienceApe (talk) 20:17, 23 September 2009 (UTC)

That's right (as per the article) - there are intermediate reactions in the overal set of fusion reactions which convert Hs into He

Note that a proton can be converted into a neutron plus an antielectron (positive charge) (and of course some energy either way)

See the neutron article for examples of neutrons converting into protons and vice versa.83.100.251.196 (talk) 21:11, 23 September 2009 (UTC)

Vaporizer gun???

i was reading an ardicle and it mentioned something called a vaporizer gun for alternatice smoking. but there isnt a article on it on wikipedia, anyone know about it?

Perhaps the Vaporizer article is what you're after? -- Finlay McWalter • Talk 19:10, 23 September 2009 (UTC)

Are you thinking of an electronic cigarette, or possibly a metered-dose inhaler? TenOfAllTrades(talk) 19:13, 23 September 2009 (UTC)

im not sure, this was something you put the tabacco in. like a pipe, but you dont burn it?

Rocket Problem

So let's imagine that sand is being shot into a car by a truck behind it. The truck maintains a constant distance from the car. The sand is being shot at a rate of 10kg/s, and at a speed of 5m/s. Initially the car is at rest, with a mass of 2000kg. What is the final velocity of the car after 100s?

I managed to find two "solutions", both which appear to be plausible but give different answers. I started by saying that dp/dt of the car = (10kg/s)*(5m/s) = 50N. This seems to make sense, as the sand will always have a 5m/s greater velocity than the car (the distance bewteen the truck and the car can be discounted). Integrating both sides, I get that p = (2000kg + 10kg/s*100s)*v = 5000,v=1.6m/s.

Second solution: As before, but with the equation adjusted a bit. m*dv/dt = u*dm/dt, dv=u*dm/m...integrating both sides, v=5m/s*ln(3/2) = 2.something. Which answer is right, and why? I suspect the second one, but don't know why it would be better than the first. —Preceding unsigned comment added by 76.68.245.124 (talk • contribs) 19:19, 23 September 2009 (UTC)

So at the end of your second paragraph, you say that p_final = 5000 kg*m/s, but you said in the first paragraph that the car has a mass of 2000kg. By my math, p = mv and v_final is 2.5 m/s. Am I missing something? Can you give some more decimal places for your second solution? 66.178.138.125 (talk) 19:42, 23 September 2009 (UTC)

Never mind, see below. 66.178.138.125 (talk) 19:56, 23 September 2009 (UTC)

The first solution has a problem - it assumes that you have to accelerate all of the sand loaded on to the car from rest. What actually happens is that the sand added later on starts out with some 'free' momentum, as the truck has been accelerating to maintain the same velocity as the car. The second solution looks better:

Acceleration as a function of time t, given a constant force F (of 50 N, per your calculation) and total mass of the car plus sand m(t):

• a(t) = F/m(t)
• a(t) = 50 N / (2000 + 10*t) kg

Integrate (velocity at time t is the integral of acceleration), and you're off to the races. A bit more than 2 is what I get, too (though less than the 2.5 of the above editor — he he didn't account for the mass of the sand on board the car). TenOfAllTrades(talk) 19:52, 23 September 2009 (UTC)

You and the original poster both made the mistake of writing F = ma = m dv/dt in a situation where m is a function of time. The correct formula is F = m dv/dt + v dm/dt. I'm pretty sure 1.6 m/s is the correct answer. -- BenRG (talk) 20:06, 23 September 2009 (UTC)

No, I didn't make that mistake; I explicitly noted that mass is a function of time. 1.6 m/s is the result that you get if you assume (incorrectly) that the mass of the car remains constant at its maximum of 3000 kg. TenOfAllTrades(talk) 20:20, 23 September 2009 (UTC)

Just to clarify everyone agrees that F=50N, and that m=2000+10t (kg) ?- the rest should be simple from there.83.100.251.196 (talk) 20:24, 23 September 2009 (UTC)

Thus I would have written dv/dt = 5/(200+t) - getting the second answer.83.100.251.196 (talk) 20:30, 23 September 2009 (UTC)

it assumes that the sand transfers its extra velocity relative to the car as momentum (and so force), and thus once that is done is travelling at the same speed as the car.83.100.251.196 (talk) 20:35, 23 September 2009 (UTC)

Yes, the first solution is correct, assuming that the speed of 5 m/s is relative to the ground. The formula m*dv/dt = u*dm/dt is incorrect. Ehrenkater (talk) 20:40, 23 September 2009 (UTC)

u*dm/dt=dp/dt=d(mv)/dt=m*dv/dt+v*dm/dt Ehrenkater (talk) 20:44, 23 September 2009 (UTC)

I meant to say 5m/s relative to the car, sorry. What difference would that make?

Actually, I would have to disagree with you. If it were 5m/s relative to the ground, then the momentum transfer of the sand wouldn't always be 50N, because the sand would have to decelerate less later on. So force=10kg/s*(5m/s-v).

There are some ambiguous details about the problem that lead to different answers depending on how they're interpreted.

• Does the sand stick to the car, does it collide inelastically and then fall to the road, or does it collide elastically? It's unclear from the way the problem is worded, but I'm assuming it's supposed to be the first case, since the OP's two solutions seem to make that assumption.
• Is the sand being fired at 5 m/s relative to the road, or 5 m/s relative to the car and truck? In the first case the OP's first solution is correct, and in the second case the OP's second solution is correct (both assuming the sticky sand).

Rckrone (talk) 20:54, 23 September 2009 (UTC)

For the first comment, yes the sand sticks...in retrospect calling it a car was a bad idea. And the sand was supposed to be fired at 5m/s relative to the car at all times...but wouldn't this mean that the force = 10*(5-v), and not 50?

Only the change in momentum of the sand matters, so if the sand is moving at 5m/s relative to the car, when it hits Δv = 5 m/s. So Δp/t is 50N. If it was 5 m/s relative to the ground then it would be (10 kg/s)*(5 m/s - v), but in that case it's easier to just sum up the total momentum and divide by the total mass as in the OP's first solution than to worry about forces. Rckrone (talk) 21:10, 23 September 2009 (UTC)

Sorry, what I meant to say was: the sand was supposed to be fired at 5m/s relative to the car at all times, but if it were fired at 5m/s relative to the ground, wouldn't F=10*(5-v)? You said that if the sand were fired at 5m/s relative to the ground, then my first solution would be corrent. But my first solution used F=50N.

This problem represents a tricky case where the change in momentum per time of the car is not equal to the force that the sand is exerting. That's because in addition to exerting a force on the car, the sand also contributes its own final momentum to the new car+sand system, which is evidenced by the increase in mass of the car. In the case where the sand is going at 5 m/s relative to the road, the cars momentum increases at a constant rate of 50 (kgm/s)/s, however the force the sand exerts is only (10 kg/s)*(5 m/s - v), and the additional (10 kg/s)*v is contributed through the sand (now traveling at a speed of v) staying with the car. In the case where the sand is at 5 m/s relative to the car, the force that the sand exerts is a constant 50 N, but the contribution to the car's momentum per time is more, since it contributes an additional (10 kg/s)*v. The problem can be solved using either change in mometum of the car, or force of the sand on the car, but they shouldn't be confused since they're not equal. The first solution treats the change in momentum per time of the car as 50 N rather than the force. Rckrone (talk) 21:59, 23 September 2009 (UTC)

Okay great, that makes a lot of sense...thanks a lot!

2X solution from 1X solution?

If it says the 1X solution contains some wt/vol of substance A, vol/vol of substance B, and x mM of substance C, how do I make a 2X solution? Do I just multiply every substance by two and put them in the same volume of water? Sorry I have no idea here. 199.76.176.159 (talk) 23:31, 23 September 2009 (UTC)

If what says that? --Tango (talk) 23:40, 23 September 2009 (UTC)

This is homeopathic terminology: a 1X solution is 1 part substance to 10 parts water, a 2X solution is 1:100. So to a close approximation, you make a 2X solution my mixing one part 1X with 9 equal-sized quantities of water. If you keep diluting like this until you reach 24X, you have created a standard homeopathic preparation -- i.e., pure water. Looie496 (talk) 00:32, 24 September 2009 (UTC)

Another usage of this term (probably what the OP is referring to) is the process of making a concentrated stock solution. This is a common lab procedure for storing buffers, etc. It's also a convenient way to make a more complex solution by adding different stock components and then bringing the solution up to the final volume with water. In this usage, 2X is a concentrated solution (either add twice the amount of solute per unit volume, or dissolve in half the water). It's not uncommon to have a 10X, 100X or even 1000X concentrated stock solution, depending on the substance. --- Medical geneticist (talk) 01:17, 24 September 2009 (UTC)

Yep, for example, my lab sometimes uses 10X DMEM. We just dilute it 10-fold. Just double the amount of solute, or use half the water. Tim Song (talk) 02:49, 24 September 2009 (UTC)

DNA Structure

Hi, I'm extremely interested in the field of Cancer Research; I was wondering if anyone out there is a specialist in the structural form of DNA. If so, please leave your e-mail below, for I have a word document with a DNA Model I have drawn which I would like to have looked over and checked. Please Help!

Thanks, 74.184.100.154 (talk) 23:48, 23 September 2009 (UTC)

The ref desk staff only offer help right here on the ref desk pages. Also, not many people are willing to post their email addresses. If you can place your document on a web site someplace - it's likely that someone would be able to take a look at it and reply here. SteveBaker (talk) 23:57, 23 September 2009 (UTC)

Then e-mail me at <redacted> if you have knowledge about DNA. Thanks, 74.184.100.154 (talk) 00:00, 24 September 2009 (UTC)

I assume you have already looked at our DNA article. Noting your e-mail name, can I ask whether your model agrees with our article/s. Kaiwhakahaere (talk) 00:05, 24 September 2009 (UTC)

I think, I would just like to make sure. Thanks, 74.184.100.154 (talk) 00:07, 24 September 2009 (UTC)

You might also want to look at DNA structure, DNA nanotechnology and Molecular models of DNA. If you have read all of those, you should be able to have a good idea if your DNA model is correct. You might also like to read Cancer research. As SteveBaker says, if you can place your document on a website somewhere then someone could perhaps look at it. Incidently, I have removed your email address - responses will be put on this page, rather than e-mailed to you. -- PhantomSteve (Contact Me, My Contribs) 07:36, 24 September 2009 (UTC)

If the OP wishes to allow e-mail from other Wikipedia users, the correct procedure is 1) Register an account with Wikipedia, and 2) tick in "My preferences" at "Enable e-mail from other users". Then others can e-mail you from your User or User talk page by using the "E-mail this user" feature. They will not see your e-mail address but you will see theirs.Cuddlyable3 (talk) 15:51, 24 September 2009 (UTC)

True - but irrelevant. The RefDesk does not provide answers by email - period. The idea is that both question and answers must be available for everyone to read. This is vitally important because that's the only way that errors in answers are caught and fixed by subsequent contributors. It also ensures that once someone has carefully researched the answer and provded a decent reply - nobody else wastes their time doing the work all over again! Furthermore (it is hoped!) people will search the archives to see if their question has already been answered before they ask it...although that's something that doesn't happen half as often as we'd like! If OP's get answers via email, they could be horribly wrong and nobody would ever know about it and maybe 30 different people might end up researching and providing almost identical answers. Both would be a serious subversion of the way we work. So we don't do that...ever...as a matter of policy. SteveBaker (talk) 17:36, 24 September 2009 (UTC)

With respect SteveBaker my post is both true and relevant. It is relevant because the OP has every right to wish for e-mail contact and needed to be told that Wikipedia offers that as a built in optional function. It is less relevant though also true that not everyone wants to release their e-mail address while others, including the OP, don't mind. If and when any user chooses to send the OP an e-mail it will be neither your, mine, the RefDesk's or Wikipedia's business whether that private correspondence is "horribly wrong". PhantomSteve already made the point that the OP's address should not appear here, without making a doom warning about it. The subject is properly covered here.Cuddlyable3 (talk) 19:31, 24 September 2009 (UTC)

are alkenes, alkynes, etc. suitable for making Grignard reagents with?

Hi. I'm wondering if it's legal (according to the laws of chemistry) to make a Grignard reagent from say, chloroethylene (vinyl chloride). Would the electron density in the alkene activate the nucleophilicity of the carbon even further (does a Grignard reagent benefit much from further activation anyway?)) ... would magnesium be less likely to react with an alkene carbon because of polar repulsion?

The same goes for alkynes... also what if the halogen is on an aliphatic ring? (Or say you replaced one of the hydrogens in glucose with sugar. Excluding the hydroxyl ones of course.) John Riemann Soong (talk) 02:27, 24 September 2009 (UTC)

Alkenyl and aryl grigards are easy to make. I assume alkynyl would work, but that's a pretty complicated way to do it...easier just to deprotonate the alkyne-H with a base. Having an oxygen attached to the halogenated atom is not a problem either. However, a hydroxyl anywhere in the structure is likely to quench the grigard as soon as you form it. DMacks (talk) 02:40, 24 September 2009 (UTC)

protic solvents and group I/II metals

It sounds kind of funny, but they never discussed the real mechanism of hydroxide formation in high school and secondary school so now in my 2nd year of college I have this knowledge that magnesium, sodium, potassium, lithium, etc. react violently with water but I actually have no idea how the reaction proceeds. With the Group I metals, I'm having an especially hard time coming up with a viable mechanism because they can only donate a radical electron .... so they can't donate an electron pair to H+, which I think sort of undermines its reactivity.

Would group I metals be more explosive in water if not for the fact that they can only donate radical electrons? (Since radicals react best with radicals?)

So what I think happens is that say, Na donates an electron pair to HOH, making HOH(-), an anion radical. The radical electron goes in an antibonding orbital? So okay, now I have a radical anion. What do I do with it? I mean, part of the problem is that I somehow to form some sort of free hydride, which I don't see happening...

I thought of the metal forming some sort of metal hydride, e.g. NaH or something, which would then react with more water to create a hydroxide anion, but I don't see that very likely. The bond for a metal hydride would be so weak -- wouldn't H+ prefer to stay on the oxygen! Na* + HOH --> NaH + *OH? NaH and OH radical, really? That's the thing ... the kinetic barrier would seem so high I don't know why sodium reacts explosively. John Riemann Soong (talk) 03:28, 24 September 2009 (UTC)

I'm pretty sure they donate a single electron to the H+ ion forming an H· radical, which instantly dimerizes and forms H2 gas. This is an approximation, since the H+ ion (and it's surrogate the H3O+ "hydronium" ion) do not really "exist" in solution, but on the balance, if you are "pushing electrons", that is my best guess as a likely mechanism. The "explosive" nature of the reaction is because of the high exothermic nature of it, because heat + H2 gas = big boom. Being an aqueous-state reaction, it occurs at nanosecond speeds like most such reactions, even aqueous reactions that don't blow up in your face occur at similar rates to sodium + water reactions. It isn't the chemical kinetics that makes it explosive in this case, its the thermodynamics. --Jayron32 03:43, 24 September 2009 (UTC)

Well yes, but the radical kinetics seem prohibitive. Alkynes aren't very reactive at room temperature either, and are harder to attack with halogens, even though they are thermodynamically way more unstable than alkenes and alkanes. Why would HOH*- dimerise -- in fact, how does it do it, and what's the chance that HOH radicals would meet each other especially in dilute solution? (Or is it rapid radical transfer, like rapid proton transfer?) And is H* really such a good leaving group? After all, HOH radical would be a radical anion ... and would radical anions react with each other? They'd be both nucleophiles. John Riemann Soong (talk) 03:58, 24 September 2009 (UTC)

Except that water does contain non-trivial amounts of hydrogen ions free in solution. See Autoionization of water. These are small, but as with any equilibrium situation, per Le Chatelier's principle, once removed via reaction with sodium, they will be nearly instantly replaced; the equilibrium kinetics almost certainly faster than the reaction kinetics. So the radical need not form on H2O, since there will always be some readily availible hydrogen ions to accept the electron to form the radical. If you want to understand why the transfer of the electron from sodium to hydrogen is so exothermic, see the Molar ionization energies of the elements, where the first ionization energy of hydrogen is 1312.0 kJ/mol while it is 495.8 kJ/mol for sodium. Now these are "gas phase" ionization energies, and the presence of water as a solvent is going to be a mitigating factor for this reaction, but I still expect the electron transfer from sodium to hydrogen, by any mechanism, to be massively thermodynamic. --Jayron32 04:24, 24 September 2009 (UTC)

Okay, so I can rule out the HOH*- x HOH*- mechanism.... would the reaction slow down as you accumulate more hydroxide ... I mean, the pH of the solution would increase, resulting in less H+ to go around, e.g. there is both less reagent and more basic product . (Le Chatelier double whammy?) Suppose I had 95% THF, 4% LDA, and 1% water (by molarity). Now I add in some sodium metal. What would happen?

Oops, forgot that LDA reacts almost irreversibly with water. Ummm... I add pyridine instead? John Riemann Soong (talk) 04:39, 24 September 2009 (UTC)

How about concentrated NaOH solution - does it react slower - yes.83.100.251.196 (talk) 17:09, 24 September 2009 (UTC)

The other thing that disturbs me is that H3O* radicals have to "find" each other, which seems sort of improbable, but I suppose rapid proton transfer helps this somewhat? The thing though, I expect that with concentration of 10^-15 * 10^-15 (that's a rough reaction probability rate of 10^-30!), that rapid transfer only partially mitigates the slowness of such a reaction ... it still happens in a blink of an eye, but it would actually seem slower than most other "rapid" reactions, allowing us to significantly slow the reaction under creative conditions? John Riemann Soong (talk) 04:34, 24 September 2009 (UTC)

I don't think electron transfer to "H+" is as likely as electron transfer to "H20" in plain water - (see below) - just because of the low concentration. However in an acidic solution I expect the H+'s will react first. Typically we don't add sodium to acid.. Because we don't get many volunteers..83.100.251.196 (talk) 17:13, 24 September 2009 (UTC)

I have some further questions, since I suddenly am guessing that inhibiting radical formation would dramatically undermine sodium's reactivity. I think some heat catalyses the formation of more radicals, which helps autocatalyse the reaction (as the reaction gets hotter more radicals get formed/propagated).

So I have two hypotheses:

• Adding peroxide would dramatically increase the reactivity of the reaction by catalysing the amount of OH* radical available in solution at any one time (plus, it wouldn't be an anion radical, which might help it a bit react with other anion radicals).
• Doing the reaction in say, a cold solution of -50C (or -78 C? that number seems fun) THF and water. (I assume the THF would keep the water from freezing.) The reaction slows much more than a simple Q10 trend (or the T term in the Arrhenius equation) would predict, because of the inhibition of radical propagation.

Can someone comment? John Riemann Soong (talk) 04:08, 24 September 2009 (UTC)

OK, after all of this discussion, I actually bothered to do a search. this article discusses mass spectrometric analysis of sodium-water solvation clusters formed during the sodium-water reaction. Not sure of the depth of detail you want here, but if you read that article, especially the "background" section, it may likely contain the information you seek, or at least references to said information. here is anothr article on a similar subject. --Jayron32 04:43, 24 September 2009 (UTC)

Sodium definately transfers a single electron at a time - but remember that sodium is typically added in bulk - ie you've got Na's next to Na's - so transferring two electrons isn't a problem. For a little more clarity consider the reaction of alkali metals with liquid ammonia at very low temperatures - the intial (isolateable) product is M+(solvated by ammonia) and 'electrons' [44], only at higher temperatures does the 'free electron' actually reduce and react with ammonia to give amide NH2- it can be expected to be similar for water. Additionally it can be expected that the first step is single electron transfer driven by the very thermodynamically favourable solvation of M+

I don't think radicals will actually catalyse the reaction - it looks like radical combination is a final step, not the beginning step. also I don't think peroxide will act as a catalyst - on the surface of Na the peroxide can be converted to two -O^- in one step with no radical intermediates. Also HOH^·- + RO-OR >>> ROH + OH^- + RO· note there is no net increase in number of radicals (However clearly hydrogen peroxide will be more reactive with sodium...)

I'd suggest something like this:

Nan  bulk surface + HOH >>> [Nan bulk]+[HOH]·- still bound to surface

2 ( "Na+ [HOH]·-" bound to surface ) >>> H2 +2NaOHdissolves

It's possible to believe that H· could separate at the surface and migrate across the surface to another radical or radical anion for further reaction

Also what is "Q10 trend" ?83.100.251.196 (talk) 16:30, 24 September 2009 (UTC)

There's an alternative 'in solution' reaction that can be suggested:

Na+[HOH]·- + HOH >>> Na+HO- + OH· + H2
OH· + Na+[HOH]·- >>> Na+HO- + H2O

83.100.251.196 (talk) 16:55, 24 September 2009 (UTC)

It should be worth investigating "hydrated electrons" - the formulation [HOH]^·- may be a simplification (as H30+ is a simplification) [45] - it's definately possible that the initial reaction of Na with water is formation of Na+ and 'hydrated electrons' followed by various other processes - Many references eg [46] suggest that the solvated electron reacts with water to form hydroxide and H atoms - however I prefer my formulation above in which hydroxyl radicals are formed - until I find something that proves that to be wrong.83.100.251.196 (talk) 17:35, 24 September 2009 (UTC)

September 24

lability of alkyne protons and NMR

Would an alkyne proton be a sharp peak in proton NMR? Since amine and alcohol protons show a wide peak, do alkyne protons undergo labile exchange as well? Like if I placed an alkyne in say some deuterium water (or perhaps deuterium methanol to increase solubility), would I see the alkyne proton replaced by deuterium on NMR? John Riemann Soong (talk) 03:40, 24 September 2009 (UTC)

Read the article on Alkynes, especially the section on Reactions specific for terminal alkynes. The C-H bond on a terminal alkyne is relatively weak, making such terminal alkynes a relatively good weak acid. The pKa lies somewhere between the alcohol hydrogen and the amine hydrogen, which means such a hydrogen will behave chemically somewhere between that of alcohols and amines, and should undergo deuterium exchange. --Jayron32 03:47, 24 September 2009 (UTC)

Yeah I remember covering that in my first semester lol. But what I don't get is that my NMR interpreting table seems to imply that alkyne protons have more shielded peaks than hydrocarbons (and seem just as sharp apparently) because of that anisotropy thing -- that is, alkyne protons apparently aren't labile. Are they labile, or are they not? Is my NMR guide just wrong? John Riemann Soong (talk) 03:55, 24 September 2009 (UTC)

Our Chemical shift article, and also any good orgo text, will discuss the origins of the deshielding effects of various groups. Any good text will also have numerous examples of actual NMR spectra for you to see exactly whether their correlation tables are reasonable. I never rule out textbook-mistakes, but I always cross-check with other sources before thinking "mistake" is the likely explanation for something I don't understand. DMacks (talk) 04:32, 24 September 2009 (UTC)

(EC) No, while they DO undergo deuterium exchange, they are NOT labile. That is because lability is due exclusively to hydrogen bonding; the relatively strong hydrogen bonding in alcohols and amines means that protons are essentially shuffled around freely between neighboring molecules. With alkynes, there is no hydrogen bonding, so neighboring alkyne molecules will not exchange protons. The deuterium exchange with alkynes will only occur with a relatively labile base, such as say water or methanol or ethanol. If you added, say, deuterated acetylene to another non-deutrated terminal alkyne, I would expect no deuterium exchange. --Jayron32 04:34, 24 September 2009 (UTC)

Okay, I noted that the pKa of ammonia (and the rest of the amine family) was 35 (10 more than an alkyne!), and yet I wondered why it still gets such wide peaks on NMR! Hmm ... isn't the electron rich triple bond in alkynes a good H+ acceptor? Or no? (The pi cloud is too delocalised?) Simple water (and not hydroxide) is good enough to induce proton exchange? Seems good enough for me...so would an alkyne proton in an alcohol-aqueous solution show up as a sharp peak on NMR? John Riemann Soong (talk) 04:44, 24 September 2009 (UTC)

Yes. Google is your friend. I just typed in "Proton NMR of Acetylene" and this was hit #1. Here is propyne's proton NMR. I would describe the alkynal proton as producing a "sharp" peak on each of these spectra. --Jayron32 04:56, 24 September 2009 (UTC)

Quite sharp indeed. As Jayron32 said, you need hydrogen bonding to get wide peaks; alkynes simply don't do that. And actually, alkynes are generally less reactive to electrophilic attacks than alkenes. Tim Song (talk) 05:03, 24 September 2009 (UTC)

Yeah, isn't that what I said? Alkynes are less reactive at room temp to halogens, etc. So anyway, doesn't it depend on the solvent? I guess this alkyne was dissolved in TMS (what a great protic solvent!) ... but what if some methanol were added too? Also, if a product with a hydroxyl group was sufficiently dilute in TMS, would the lack of hydrogen bonding resharpen the hydroxyl proton peak? John Riemann Soong (talk) 05:06, 24 September 2009 (UTC)

Tetramethylsilane is not the solvent, its added as a dopant to the sample to act as a standard. The solvent is usually something like carbon tetrachloride or Deuterated chloroform. --Jayron32 05:12, 24 September 2009 (UTC)

Oh okay. What if you used a protic solvent? John Riemann Soong (talk) 05:21, 24 September 2009 (UTC)

And so as not to get signal strength issues, perhaps deuterated methanol or dilute methanol in 95% THF? John Riemann Soong (talk) 05:29, 24 September 2009 (UTC)

Well, that sounds great. What I would do if I were you is to approach the professor in charge of the NMR machine at your school, and ask him. If he knows the answer, he'd likely tell you. If there is an open time slot on the NMR, he may even let you run your own samples. --Jayron32 17:00, 24 September 2009 (UTC)

For lability a low activation energy is needed - lone pairs on N or O allow this since a concerted 'H swap' can occur ie simultaneous exchange of H's with no high energy O^- intermediate. Alkynes lack a lone pair, and so lack the ability to do this concerted reaction. Thus they are much less labile than the corresponding OH or NH compounds. (even for the same acidity...)83.100.251.196 (talk) 17:03, 24 September 2009 (UTC)

Consider this reaction:

  H   Ha                     H   Ha
   \ /                        \   \
    O   O             >>>      O   O     
       / \                      \   \
      Hb   H                    Hb   H

(looks better in 3d) - two arrows required - swaps Ha and Hb - in 3d it's easier to see that the two H20 can be arranged so that the product is formed so that the bond angles are still 109degrees - no strain. Also note that the starting product is already part of the way to the product via hydrogen bonds.

However for the exchange with alkynes - it's impossible to get this conformation - there is only one position for the terminal CH (in a straightline) - so such a concerted reaction would produce a highly strained (bent) alkynes (before relaxation) - thus much higher energy, and much less likely to occur. 83.100.251.196 (talk) 17:58, 24 September 2009 (UTC)

Another way to consider it: pKa is a thermodynamic equilibrium measurement, whereas broadening and exchangeability on the NMR timescale is a kinetic effect. That's a more formal dichotomy for the explanation that the exchange is "hard to do" without H-bonding or similar mechanistic possibilities even if "eventually" it would be likely to occur. DMacks (talk) 18:09, 24 September 2009 (UTC)

can strong acid transform one type of alcohol into another?

I thought of this issue a while ago, but say you start out with 1-butanol or something. I'm purposely reacting it at high heat in aqueous solution with sulfuric acid to rehydrate the first alkene product. So now I would get 2-butanol as a major product, right?

So now, I start out with say, 4-methylcyclohexanol. I add H2SO4 + HOH (and any important surfactants). If I left the reaction running long enough, would I eventually get 2-methylcyclohexanol as a major product? The thing is, the hydration has to occur at least twice (at different positions), so I would get a "migration" of the double bond of the alkene intermediate around the ring? Also, if you dehydrate 3-methylcyclohexanol, what is the major product? Both would depend on secondary carbocation formation -- without hyperconjugative stabilisation, would the double bond prefer to be furthest away from the electron-donating methyl group as possible? What would the effect size (based on (de)stabilisation energy) be?

Also, seeing as I would have a pretty interesting reaction sequence, how would someone determine the relative abundance of the final equilibrium products? (Assuming the system was closed and no water was distilled in the rxn.)

John Riemann Soong (talk) 05:40, 24 September 2009 (UTC)

Assuming your equilibriating methylcyclohexanols - you'd get a fairly broad mixture of 1,2,3 and 4methylcyclohexanols. I'd expect the 2. 3 and 4 isomers to be in about the same amounts. But I'd expect slightly more of the 1methylcyclohexanol.

Also consider that a very small amount of 1(hydroxymethyl) cyclohexanol should be formed to..

The reaction products should be exactly the same for 3methylcyclohexanol if left long enough.

Because you're reacting for a long time the relative proportions of the products should depend on the thermodynamic stabilities of the products, (tertiary>secondary>primary see enthalpies of formation of isomers, or enthalpies of combustion of isomers for proof)

Also consider side reactions - one springs to mind - reaction of carbocation with alcohol to make ether.

"how would someone determine the relative abundance of the final equilibrium products?" - did you mean experimentally or theoretically. Theoretically there are many ways - mostly based on ways of estimating bond strengths in different enviroments - either theoretical, or from spectra, or extrapolated from known examples eg methanol,ethanol,propanol,butanol series83.100.251.196 (talk) 14:43, 24 September 2009 (UTC)

Or set up a bunch of equations with the delta G's. The tertiary is preferred by much; the primary I think we can safely ignore. Tim Song (talk) 19:22, 24 September 2009 (UTC)

History of large SI prefixes

Hi. Does anyone know to which unit was the prefix Giga- applied in its first documented usage? Also, when was the first time the term Gigabyte was used? Thanks. -- Meni Rosenfeld (talk) 06:23, 24 September 2009 (UTC)

I don't know when the "giga-" prefix was first used. It was only standardized in 1960, but it had certainly been in use long before that. "gigabyte" has been a standard term pretty much as long as we've had bytes because the word 'byte' was coined in 1956, along with 'kilobyte' to mean 1024 bytes - which established the convention of (mis-)using metric prefixes for power-of-two numbers when talking about bytes. Although that was four years before SI was standardized, it was long after modern SI prefixes were in common scientific use. The choice to use Latin prefixes for smaller units (milli-, micro-) and Greek prefixes for big units (kilo-, mega-) was made sometime in the 1700's - so the choice of 'giga-' was essentially made back then - even if nobody knew it at the time! But whether anyone actually USED those terms is hard to say. When I was studying for my cybernetics degree back in the mid-1970's, the idea that you could have a gigabyte was a remote future possibility. Computers had kilobytes of memory and megabytes of disk and tape storage space. Perhaps someone might be talking about a roomful of magnetic tapes and use the word "gigabyte" - but it's unlikely. The word was almost certainly used by SOMEONE in the 1950's and 1960's - but more like in a joke - "You have so many punched-cards stacked up in your office, you'll soon be hitting a gigabyte!!". Of course nowadays, you're supposed to say 'gibibyte' instead of 'gigabyte' in order to avoid the 1024/1000 confusion...I don't know anyone who does that! Incidentally, the power-of-two version of the SI prefixes is not restricted to bits and bytes - it is also applied in communications technology to prefix words like 'baud' and 'erlang' (the first being a unit of data bandwidth, the second being a telephony unit relating to the number of telephone conversations that can be simultaneously made). SteveBaker (talk) 12:30, 24 September 2009 (UTC)

For what it's worth, the OED's earliest citation for this use of giga- in English is from the "Compt. Rend. de la 14me Conf. (Internat. Union of Chem.)" in 1947: "The following prefixes to abbreviations for the names of units should be used … G  giga-  10⁹ × ." The earliest citation for the prefix's actual occurrence in a word is from 1960—a use of gigacycles in a discussion of frequencies. Deor (talk) 16:16, 24 September 2009 (UTC)

It's hard to believe that the first "actual occurrence in a word" for "giga-" was in 1960 when the SI standard containing the "giga-" prefix also came out in 1960. It must have been used for years before that - if only because the SI folks took several years to nail down the standard...so they must have been using it at least a year or two before 1960. But (as I said before) the convention to use Latin prefixes for small units and Greek for large units meant that "giga-" was presumably the "pre-ordained" choice at least 150 years before the SI people actually wrote it down. SteveBaker (talk) 17:26, 24 September 2009 (UTC)

The Greek word that giga- comes from simply means "giant"; it has no numerical significance in Greek, so it wasn't really preordained that its root would come to be used as a numerical prefix denoting 10⁹. (Similarly, the words that mega- and tera- come from mean "large" and "monster" respectively; the ancient Greeks had no specific names for numbers greater than 10,000.) Since the OED is dependent on printed sources and only on sources in English, it's quite possible that giga- words were in oral use in English before 1960 or that they were in printed use in other languages before then or that earlier printed uses have escaped the lexicographers' notice. It's also possible, however, that few scientists felt the need for terms denoting such magnitudes even after the prefix was agreed on. It may be significant that the earliest recorded uses in words are in gigacycles, gigawatts (1964), and gigahertz (1966), since the related topics seem to be exactly the ones in which names for such large units would have been useful at the time. Deor (talk) 18:12, 24 September 2009 (UTC)

Actually, there are two different "Gigabytes" depending on the context. If you are dealing with longterm solid-state storage like hard drives and flash memory, then a gigabyte = 1000³ (1,000,000,000) bytes. If you are dealing with chip memory like RAM, then a gigabyte = 1024³ (1,073,741,824) bytes. There's been a movement among pedants to get people to use the term "Gibibytes" to refer to the latter (binary) definition, but this has never caught on in any common usage, so under most usages, we are stuck with the dual meanings. --Jayron32 16:53, 24 September 2009 (UTC)

Thank you for crystallizing in 3 words the "movement" behind popularizing the godawful term "gibibyte". You are correct — it is a movement among pedants. Let us all move along, and ignore the pedants. Comet Tuttle (talk) 17:35, 24 September 2009 (UTC)

A book from 1970 uses gigabyte,[47] and so does this German computer magazine from 1981:[48]. Fences&Windows 16:54, 24 September 2009 (UTC)

Force and gravity

A 80kg woman stands on a scale in an elevator. when it starts to move, the scale reads 700N. (i) is the elevator moving up or down?

(ii) what is the elevators acceleration?

Which science class is this question coming from? Also, being an American, my scale doesn't have N's, it only has LB's. What's an N? →Baseball Bugs ^{What's up, Doc?} carrots 06:56, 24 September 2009 (UTC) P.S. N meaning "Newtons", right? It's been a long time since physics class. →Baseball Bugs ^{What's up, Doc?} carrots 07:25, 24 September 2009 (UTC)

Probably the first physics class on mechanics. In physics we use SI, so yeah, the N stands for Newtons which is the basic unit for force. Oddly enough, the pound (lbf) is also a unit of force, and not mass as people commonly assume. Jkasd 07:29, 24 September 2009 (UTC)

The pound-force is a unit of force, yes. The pound mass is a unit of mass. --Trovatore (talk) 09:03, 24 September 2009 (UTC)

I have a vague recollection that the English System unit of mass is the "slug". If your mass adds up to too many slugs, you might be sluggish. →Baseball Bugs ^{What's up, Doc?} carrots 08:19, 24 September 2009 (UTC)

Indeed: slug (mass). Jkasd 08:15, 24 September 2009 (UTC)

Yep. A slug is equivalent to 32 pounds. A Stone is equivalent to 14 pounds. So the subject in question is about 175 pounds, or about 5.5 slugs, or about 13 stone. →Baseball Bugs ^{What's up, Doc?} carrots 08:19, 24 September 2009 (UTC)

It really has been a long time. If I'm reading the Newton (unit) article correctly, 1 kilogram to 10 newtons is used as a rough estimate, actually 1 to 9.80665. So 80 kilograms would equate to about 785 newtons. So if it's only 700 newtons, that would indicate the elevator is descending, right? Beyond that, I give up. →Baseball Bugs ^{What's up, Doc?} carrots 08:25, 24 September 2009 (UTC)

Well, their weight in pounds actually changes during the acceleration, while their mass in slugs remains constant throughout. (assuming they don't eat or breathe or take into account general relativity...) Also, since this is almost certainly homework, let's wait until they at least show some effort before we do the problem for them. Jkasd 08:28, 24 September 2009 (UTC)

However, the mass in pounds also remains the same. --Trovatore (talk) 09:03, 24 September 2009 (UTC)

So an extra-credit question would be, what if they start out holding a McDonald's Angusburger in their hand and slowly consume it while the elevator moves up and/or down? →Baseball Bugs ^{What's up, Doc?} carrots 08:32, 24 September 2009 (UTC)

Well in that case, a special sort of scale would be needed to measure only the woman's mass, and not anything else. You might even have to take into account such things as the rate of mastication. Jkasd 08:36, 24 September 2009 (UTC)

Hey, let's not delve into her private life or what she does alone on elevators. However, if she started holding the burger and then ate it, I would think her overall mass would be constant. We're assuming the 80 kilograms is her body plus whatever she's wearing or holding. In fact, despite the disparagement, I'm guessing she herself is only about 50 kilograms and the rest is shopping bags full of jewelry. And, apparently, angusburgers. →Baseball Bugs ^{What's up, Doc?} carrots 08:46, 24 September 2009 (UTC)

Try reading the article on acceleration. Also, Newton's laws of motion, especially the second one, may prove useful. If you show some effort towards trying to figure out the problem, we can help you more specifically. Jkasd 07:22, 24 September 2009 (UTC)

Regardless of the above, the only reason a woman would stand on a scale in an elevator would be to convince herself that, for a moment at least, she is a bit lighter. Therefore she sends the elevator down. Unless of course this stupidity has also led her to press the wrong button. How she managed to acquire a scale graduated in Newtons is another question.--Shantavira|^{feed me} 07:38, 24 September 2009 (UTC)

I don't think that your statements will help the OP's understanding, and may even detract from it. Since helping others understand is, as I know it, the primary function of the reference desk, I think you should perhaps retract your comments, or at least make it clear you are joking. Jkasd 08:02, 24 September 2009 (UTC)

Agree with Jkasd here. Shantavira's response is potentially offensive and is unlikely to help the OP. The change in a weight scale in a lift is a not uncommon concept in physics and while it's generally a thought experiment, I'm sure quite a number of people do it each year and there's no reason why a woman can't be interested in physics. Also it's possible e.g. the woman is anorexic and is trying to convince herself she doesn't need to put on weight or perhaps she's using it as a motivational device to stop herself putting on weight. Finally the person who set the question is generally unlikely to consider such issues so it could be either way when it comes to the actual question. Nil Einne (talk) 10:04, 24 September 2009 (UTC)

F=m*a means that Weight = mass * gravity. What's the woman's weight when the lift isn't moving? Is 700 N more or less than her normal weight?

Think about when you're in a lift. When you accelerate upwards, do you feel heavier (more weight than normal) or lighter (less weight than normal)?

The total acceleration is the acceleration of the lift and the acceleration due to gravity. F = m * (a + g). Rearrange to find a and put in the numbers, but make sure you get the signs right, because F, a and g are vectors (they have direction). AlmostReadytoFly (talk) 09:15, 24 September 2009 (UTC)

Yes, but up-down velocity also plays a role. If the elevator had no acceleration but was in a constant speed free-fall, the woman would be weightless, relative to the elevator on which the scale in placed. So, how do we add velocity to that equation ? Specifically, how can we determine how much of the apparent weight reduction is due to downward acceleration and how much is due to downward velocity ? You could even have an upward moving elevator which has arrived at it's destination and is decelerating (that is, accelerating downward), to arrive at a weight of 700N. Thus, I'm plain inclined to think that neither part of this Q can be answered with the info provided. Perhaps if we knew the range of speeds at which the elevator travels and the range of acceleration, we may be able to come up with one or more answers. StuRat (talk) 13:11, 24 September 2009 (UTC)

Yes, we can. You've made a few mistakes in your arguments, Stu... First, an object can't be in "constant speed free fall", cause that's not free fall. Free fall means an acceleration of 9.8m/s² downwards. If it goes down with a constant speed, th reading will be her actual weight, ie, when measured in her house.
Since the weight is reduced, the elevator is definitely accelerating down. Since it has just started moving, it is going down.
Now, Since the weight loss is 100N, the acceleration has caused a weight reduction of 784-700=84N. Now 84=m*a, therefore a = 1.05m/s². This is the acceleration with which the elevator is moving downwards... Rkr1991 ^{(Wanna chat?)} 13:26, 24 September 2009 (UTC)

(after edit conflict) Agreed. StuRat is (unusually) writing nonsense. Velocity doesn't come into the argument! Only acceleration of the lift (relative to the building) is significant here. The question would be unanswerable except that it says "when it starts to move" so we can deduce that the initial acceleration is downwards, and so the lift must be going down. Dbfirs 13:33, 24 September 2009 (UTC)

Oops, I think the problem is my the definition of "acceleration". I was only thinking of acceleration due to the elevator's motor, but there's also acceleration due to gravity to consider. So, I was thinking she could be weightless without any action from the elevator's motor, as if the elevator just dropped. While this is correct, there still is acceleration due to gravity. Upon re-reading the Q, I see they didn't specify why the elevator was accelerating, only what it's accel was. Also, I was confusing two different cases of free-fall. In free-fall without atmosphere, it's correct to say the object is accelerating at one g. In the case where there is atmosphere, and terminal velocity has been reached, then there's no acceleration, but the weight of the lady in the elevator would be normal (other than the weight lost by messing herself). :-) StuRat (talk) 15:36, 24 September 2009 (UTC)

A Newton is 102 gram. Either you learned that or (in the US) probably didn't. So before the elevator moves the scale reads 80 x 0.102 = 785N. When the elevator accelerates down the reading reduces by 85N. Applying Newton's 2nd law F (N) = m (kg) a (sec^-2) shows that the downward acceleration is 85 / 80 = 1.1 meters per second per second, to 2 sig. fig. accuracy.Cuddlyable3 (talk) 15:10, 24 September 2009 (UTC)

A Newton is not any number of grams. Grams measure mass and Newtons measure force. The force of gravity at the earth's surface at sea level makes it so that 102 grams of material will be pulled downward with a force of 1 Newton. --Jayron32 16:48, 24 September 2009 (UTC)

Jayron32, how many elevators with 80kg women standing in them do you know that are not on planet earth ? Just a round figure will do. Cuddlyable3 (talk) 18:54, 24 September 2009 (UTC)

But it is a common mistake in an early physics class to confuse weight with mass, so we need to be absolutely clear for the sake of the OP's understanding. Jkasd 19:06, 24 September 2009 (UTC)

Snows all year round

The map shows areas of the US with permafrost where snow can lie all year without melting.Cuddlyable3 (talk) 15:41, 24 September 2009 (UTC)

What are the parts of the US that snows all year round? --Reticuli88 (talk) 13:02, 24 September 2009 (UTC)

Probably only in northern Alaska or very high altitudes (e.g. the Rockies). --98.217.14.211 (talk) 13:49, 24 September 2009 (UTC)

In much of Canada it can snow any month of the year, but typically doesn't. I would suspect that's the same with a lot of northern US states, specifically Montana, North Dakota etc. Is that what you mean? TastyCakes (talk) 16:18, 24 September 2009 (UTC)

I had a friend who died in Colorado when his car slid off the road during a snowstorm in July. And Colorado is pretty far south. In the high Rockies, it can snow on any day of the year; though I am not sure of anywhere in the lower 48 where there will be snow on the ground all 365 days of the year. Even in Barrow, Alaska there is not year-round snow on the ground. --Jayron32 16:35, 24 September 2009 (UTC)

Snow line. Sagittarian Milky Way (talk) 17:03, 24 September 2009 (UTC)

There are literally hundreds of places in the Rockies, Sierra Nevada, Cascades, and Olympic range where snow sticks all year round. The southernmost that I'm aware of are in central California in Sequoia National Park. Looie496 (talk) 18:26, 24 September 2009 (UTC)

Science Lab Cleaner

I am a new Science teacher in a Jr./Sr. High school. What type of cleaner I should use to scrub beakers and other equipment after use in the lab? Answer needs to be safe for student use, please. —Preceding unsigned comment added by Mleisy (talk • contribs)

What was in them? If they were used for aqueous reactions, then hot water is a good start (and might even be completely sufficient). Alconox is a standard series of cleansers for glassware. DMacks (talk) 15:07, 24 September 2009 (UTC)

The cleaner you should use is called a lab technician.--CruelSea (talk) 15:21, 24 September 2009 (UTC)

If you are new to practical science teaching then for the safety of students and yourself you must be properly aware of how to store and handle (not literally!) dangerous chemicals such as undiluted acids (e.g. never add water to sulphuric acide), phosphorus and mercury; precautions such as using a hood to protect against fumes; which reactions can be explosive and how to avoid risks of poisoning, scalding or electric shocks.Cuddlyable3 (talk) 15:34, 24 September 2009 (UTC)

I agree with Cuddlyable -- it's pretty important to get adequate training yourself before trying to teach a practical lab course. You could try the National Science Teachers Association for more information. --- Medical geneticist (talk) 16:06, 24 September 2009 (UTC)

I also agree. If you have to come here to ask such basic questions then you aren't ready to be a science teacher. Don't do any practical exercises with your classes until you have learned basic lab safety. --Tango (talk) 16:30, 24 September 2009 (UTC)

I used to use Alconox for cleaning glassware. I also used it to scrub down counters and stuff, although I think there's better things for that. I never had a problem with it, and I'm sure there are other similar products. TastyCakes (talk) 16:22, 24 September 2009 (UTC)

I'll second alconox. That stuff will clean the white off of rice. It's good stuff. IIRC, they make a hand-washing version and an automatic dishwasher version that works well too. --Jayron32 16:32, 24 September 2009 (UTC)

Torque Practice Problems

Attempting to lift a 450-lb rock, a 180-lb person stand on the end of a 5-foot pry bar. Hint: The pivot of the pry bar is 4 feet from the end. Can the person lift it?

I know Torque is (force)(Lever Length)

but I do not know where to begin.

Accdude92 (talk) (sign) 17:11, 24 September 2009 (UTC)

For it to move, the torque on the side of the bar with the person standing on it must be greater than the side with the rock (or the bar bends or breaks or something!). Under normal gravity, the force due to a one pound mass is one lbf (pound-force) - so the force on each end is equal to the weight on that end. So if you know the distance of each weight from the fulcrum (pivot) you can calculate the two torques and compare them. SteveBaker (talk) 17:17, 24 September 2009 (UTC)

Enlarged nostrils

We don't pick our noses.Cuddlyable3 (talk) 18:38, 24 September 2009 (UTC)

Does excessive nosepicking contribute to enlargement in the nostrils in any way? This is not a personal medical question, rather more of a curiosity question, owing to the fact that nosepicking is a relatively common, albeit bad, habit amongst a large part of the worlds population. I hope the question made sense enough to answer it. Thank you!

No. Lamarck was wrong. ~ Amory (user • talk • contribs) 18:52, 24 September 2009 (UTC)

This doesn't relate to Lamarckism. It is possible to enlarge the nostrils by constantly stretching them, but it seems extremely unlikely that nosepicking could do it. (And regarding the picture, see this Google Image search.) Looie496 (talk) 19:10, 24 September 2009 (UTC)

is the goverment out to get us?

up for discussion.

iv allways been interested in government conspiracies, and lately iv heard from a person that reads up on all the crap going on with the economy (in the U.S.) . He showed me in a paper, on a discustion, a politic mentioned that we would be out of this recession if we lost a third of the population and i cant help but think what if thay used the swine flu as a way to kill off how ever many people thay want or need to get out of the recession by giving out false vaccines? and if thats the case, then all thay would have to do is sell a true vaccine at a higher price. with the way healthcare is calapsing, all the lower class residents may not be able to afford it. it would be an easy way to kill off poor residence leaving a population of much wealthier people. do you think the U.S. Government would go that far?

No, that seems pretty silly to me. TastyCakes (talk) 17:51, 24 September 2009 (UTC)

That is ridiculous. Even if it would work, they would never do it, and it wouldn't work. If you wipe out a third of the population the economy would completely collapse, it wouldn't recover faster. You can't have an economy without a workforce and a workforce needs to include people doing a wide range of jobs, from street sweeping to bank managing. Even if they could wipe out 1/3 of the population while maintaining per-capita GDP, the country's total GDP would inevitably drop, making the US less influential on the international stage, economically, politically and militarily. --Tango (talk) 17:57, 24 September 2009 (UTC)

well even if its not a likely scenario, its still interesting to think about. Its good to hear the opinion of some one more educated in Government.

This is the reference desk, not a forum or soapbox. --Mark PEA (talk) 18:08, 24 September 2009 (UTC)

The custom here is that nonsense is in small font at the end of a section. Small != Big. End != Beginning. Cuddlyable3 (talk) 18:32, 24 September 2009 (UTC)

Uh, broken window fallacy anyone? More citizens always means more GDP, less citizens always means less GDP. More workers means more GDP. Note that it's far better to have 200 million people with 10% unemployment than it is to have 30 million people with 2% unemployment. In the first case, it just means you're using resources inefficiently. Killing off citizens to get yourself out of a "recession" is like not drinking water in a desert because you know you'll sweat a great deal of it. John Riemann Soong (talk) 18:37, 24 September 2009 (UTC)

There are a lot of problems with the idea. From an economic standpoint, it doesn't work out well—killing off a third of the population would cripple, not stimulate the economy.

From a governance standpoint, it doesn't work out well either. In a democratic government, politicians are mostly interested in things they can point to as something they did, or avoiding things that will later be used as ammunition against them. This particular event would satisfy neither—even if the conspiracy was kept secret, the politicians would not benefit. They'd be accused of grossly mismanaging the outbreak, and even if the economy DID bounce back at a much later date, they would never be able to take credit for it. If it did leak out in any way (and there are many ways that could happen), then they'd be treated like Stalinists.

How would it leak out? Well, it doesn't take many independent researchers to see if a vaccine doesn't work in an outbreak, and to check the vaccine itself to see if that's the problem.

In short: the possibility of exposure is high, the possibility of actually benefitting is low. That's a recipe for not doing it. Now, there are always exceptions—our governmental figures are often less rational about such things than we'd imagine (Nixon provides great examples of this, where his personal psychology got in the way of making the rational political decision). Still, in the absence of ANY evidence that this sort of thing would be going on, I can see NO reason to even entertain it as a realistic possibility.

Be aware—there are people "out to get you." There are people who want to hook you on addictive products, take your money, are happy to ruin your lives and health in the meantime. They have immense political influence and are able to spend literally billions of dollars lobbying our politicians and pushing their bills through Congress. They are probably a far greater threat to the idea of democracy, and to your personal livelihoods and freedoms, than any government conspiracy. --Mr.98 (talk) 19:37, 24 September 2009 (UTC)

Annulenes vs. cycloalkanes

I'm quite confused by the fact IUPAC organic nomenclature apparently makes it compulsory to use annulenes in polycyclic compounds, as I fail to understand the ambiguities alluded to here and here (this probably has to do with how unwiledy the online material is to consult).This policy results in the central ring in Butriptyline being treated as containing double bounds which must be "removed", a rather counterintuitive approach to me.

I'm also confused by the way even a simple single-bound fusion of a cycloheptane and naphthalene must be described as a 7,8,9,10-tetrahydro-6H-cyclohepta[b]naphthalene according to the online tool even though it seems to me that cyclohepta- clearly implies there cannot be double bounds unique to that ring to begin with! (Why not to use annulenes there too, anyway?) Circeus (talk) 18:45, 24 September 2009 (UTC)

I'm not sure I follow what question you are meaning to ask, but the prefix for seven is "hepta-" and not "hept-". The a is dropped before vowels by convention, but if it does not precede a vowel, then the "hepta-" is correct, and does not imply a single- or double- bonding situation in any manner. --Jayron32 18:48, 24 September 2009 (UTC)

Okay, but it still confuses me awfully that the ring is assumed to be maxed in double bounds, but named as an otherwise unqualified cycloheptane: putting two double bounds results in 6H-cyclohepta- being the prefix, which is only possible with the assumption that the ring requires a stated hydrogen (I think that is the proper term), which a mere cycloheptane ring certainly doesn't. Circeus (talk) 19:09, 24 September 2009 (UTC)

Re-opening my refrigerator door

Normally the door on my refrigerator takes about 5 lb. of force to open. At times, depending on how many seconds have passed since I closed it, a considerably larger force is needed. Just now I tried to open the door about five seconds after I closed it, and I had to use 15 - 20 lb. of force. Is air pressure differential causing this, or is something else going on?

I have a side-by-side refrigerator/freezer and there are valves between the fridge and freezer compartments to allow for more efficient cooling (or so says the owners manual). WHat I have found is that if I open and close the freezer, it will "suck some air" out of the fridge and make it much harder to open the fridge. This may be similar to what is happening in your situation. --Jayron32 19:33, 24 September 2009 (UTC)

Is this a refrigerator with a mechanical latch or a plastic strip magnet to hold the door shut? Cuddlyable3 (talk) 19:36, 24 September 2009 (UTC)

My refrigerator is a side-by-side model with magnetic strip (I haven't seen a mechanical latch refrigerator in decades - are they still made?)