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July 8

Paddy Mouse

What is Paddy mouse?70.73.145.207 (talk) 01:07, 8 July 2009 (UTC)

Paddy is a rice field. I've seen Mus booduga being referred to as a "rice paddy mouse", but I guess any murid living in a paddy may qualify as a "paddy mouse"... --Dr Dima (talk) 01:39, 8 July 2009 (UTC)

Total guess here, but is "paddy mouse" something akin to Welsh rabbit; that is it really isn't mouse, but the term is used as a perjorative towards Vietnamese cuisine? --Jayron32.talk.contribs 02:33, 8 July 2009 (UTC)

No, the Vietnamese cuisine article clearly talks about the paddy mouse meat sensu stricto. --Dr Dima (talk) 03:53, 8 July 2009 (UTC)

Well then, why not eat them? Not a lot of meat, I'd imagine, but get a few dozen together and the right spices, and it sounds like a fine dinner. --Jayron32.talk.contribs 04:33, 8 July 2009 (UTC)

I would actually very much like to try what a well-prepared paddy mouse dish tastes like. From personal experience, a platter of frog legs is a fine dinner to say the least, miniature size of the said legs notwithstanding. Never tried a roasted rodent, though. Do you know of any Vietnamese restaurants in US or in Western Europe that serve a paddy mouse dish? --Dr Dima (talk) 07:59, 8 July 2009 (UTC)

I was imagining a pejorative toward something Irish. —Tamfang (talk) 18:05, 21 July 2009 (UTC)

Do birds have an equivalent to the navel, as seen in mammals?

In mammals, the navel/bellybutton is the point at which the umbilical cord was attached while in the womb. Is there something similar in birds, i.e. at the point at which the bird was connected to the yolk, while in the egg? I've seen cross-sectional pictures of fertilized eggs and it looks as though the bird foetus is connected to the outside of the yolk by something similar to an umbilical cord. --84.69.51.112 (talk) 01:12, 8 July 2009 (UTC)

No. Not even all mammals have them. We are a part of the "Placental Mammal" sub-group - the umbilical cord connects to the placenta. No placenta - no cord. Hence, Duck billed platipus and Kangaroos don't have belly buttons because, while they are mammals, they are not placental mammals. Birds lay complicated eggs with all sorts of membranes and stuff in them - but I don't think there is a similar connection. See image at right of a 1 week old chick embryo - I don't see any kind of cord there... SteveBaker (talk) 02:48, 8 July 2009 (UTC)

the Vitelline duct or the vitelline system is the thing that connects the yolk to the embryo.--Lenticel ^(talk) 03:58, 8 July 2009 (UTC)

Dislocated knuckles

Just read an article in my local newspaper about a policeman suffering a dislocated knuckle while attempting to arrest someone. I've never heard of such an injury before; is it very common? Joint dislocation makes me guess that it's not the same as any of the dislocated finger pictures (can't remember which joint is the knuckle, and our article is very poor quality, but I expect that these would also be captioned "dislocated knuckle" if it were the same thing), so I'm assuming that this is not a dislocated finger. Nyttend (talk) 02:09, 8 July 2009 (UTC)

Knuckle is a common term for the any of the three joints on each of your fingers (well, two on your thumb). A dislocated knuckle is identical to a dislocated finger. The two bones that meet at one of the knuckle joints can become disarticulated just as any other joint can. --Jayron32.talk.contribs 02:31, 8 July 2009 (UTC)

Animal intelligence and attempts to escape captivity

Is there any evidence on whether more intelligent animals in captivity are more or less likely to attempt to escape? NeonMerlin 02:12, 8 July 2009 (UTC)

Depends how you define intelligence. A hamster is more likely to escape than a dolphin; can you claim that the hamster is more intelligent? A male cat with its balls still attached is more likely to attempt to escape than a neutered one; does the feline intelligence reside in the scrotum? I don't think so... --Dr Dima (talk) 04:00, 8 July 2009 (UTC)

The females of the human species thinks that their male counterpart do think with their scrotum and its attached part. :)--Lenticel ^(talk) 04:22, 8 July 2009 (UTC)

You know, NeonMerlin was asking a question, not asserting something. Tempshill (talk) 04:29, 8 July 2009 (UTC)

Well, monkeys will escape if given the slightest opportunity, and they're the most intelligent animals in captivity, so at some level it is true. Looie496 (talk) 05:53, 8 July 2009 (UTC)

The most intelligent animals in captivity are chimps, not monkeys.--80.58.205.37 (talk) 08:08, 8 July 2009 (UTC)

Surely some humans in captivity are smarter than that... Prison escape? Nimur (talk) 15:01, 8 July 2009 (UTC)

I would say that monkeys/chimps are escaping not to necessarily escape, but out of curiosity of the unknown. I know my pet budgerigars are kept captive in a cage and they like it. Whenever I remove them from the cage, they always try to fly back into it. This must be because they know that the cage provides security and necessities for their survival. This would be untrue for a captive wild bird rather than birds that were born in the cage. -- penubag  (talk) 10:27, 8 July 2009 (UTC)

Parrots are fairly notorious for figuring out how to escape from their cages - routinely pulling back bolts, undoing clasps, lifting up sliding panels, butting open hatches, etc. I've personally seen a cockatoo that understood how to open a padlock by turning the key (the cage was actually padlocked to prevent the bird from getting out - the owner left the key in, figuring that she would *never* work that one out!). Budgies, whilst not as intelligent as Macaws, Amazons, African Greys, Cockatoos, etc. do sometimes work out how to get the door open - though it seems to very from individual to individual. Some never appear to consider trying to escape - though I suppose that it may just mean that those particular birds are quite happy to remain in the cage. --Kurt Shaped Box (talk) 10:52, 8 July 2009 (UTC)

Does John Dillinger count as an "intelligent animal?" He made some impressive escapes. Our hamster lifted up the water bottle out of its niche in the seemingly secure Habitrail, escaped, found some colored tissue paper, tore off a 2 foot by 1/2 inch strip of white, and a similar strip of pink, took them back into the cage, and up to his bedroom chamber, where he installed them as decorations. Perhaps the most intelligent animals escape, go shopping, and come back. If they had internet and a credit card, would they just order stuff to be delivered? 24.13.87.201 (talk) 15:00, 8 July 2009 (UTC)

Massless patricles in quantum mechanics

Can they have 0 angular momentum? If not, which system has fewer degrees of freedom, a massless particle or a spinless one? 76.67.78.167 (talk) 04:58, 8 July 2009 (UTC)

According to our article on Spin (physics), photons have a spin and are massless. In fact, the same article notes that the only spinless particle in the Standard Model is the Higgs boson, which if it exists, definately has a mass. So, to answer your question, all particles in the standard model, even those which are massless, and even those which are point particles and lack internal structure or even volume, have spin, except for the Higgs, which has a mass but no spin. Of course, if it turns out that the Higgs does not exist, then the answer would be that all particles have a spin. --Jayron32.talk.contribs 05:04, 8 July 2009 (UTC)

I want to know if it is possible for a massless particle to have no spin, not just whether one exists. For example, it is impossible for a massless particle to have a speed lower than c, not because no massless particle with this ability is in the standard model, but because of special relativity. Does something similar rule out spin 0 massless particles, or are they theoretically possible? 76.67.78.167 (talk) 07:45, 8 July 2009 (UTC)

In today's quantum mechanics there is no rule forbidding the existence of spin 0 massless particles. In fact if you google the term "massless spin-zero" you will find several papers that either propose such particles or ways to detect them, should they exist.

But if it one day turns out that no massless spin-zero particles exist, there will hopefully be a theory explaining why it's impossible. EverGreg (talk) 08:03, 8 July 2009 (UTC)

What would the equivalent of the Dirac equation be for such a particle? Klein Gordon with m = 0? 76.67.79.118 (talk) 05:33, 9 July 2009 (UTC)

Goldstone bosons? JMiall₰ 08:14, 8 July 2009 (UTC)

Black or white aircraft paint?

I have a question that is (sorta-kinda) related to the question "Black or white parasol" in the science reference desk archives. This has to do with the paint job on the Lockheed SR-71 vs. that on the Concorde. You see, the SR-71 is painted a flat black (that's why they call it the Blackbird), while the Concorde is painted a glossy white. I was just wondering, which is a better choice for dissipating the heat generated by air friction and such during supersonic flight? Thanks, and clear skies to y'all! 76.21.37.87 (talk) 06:03, 8 July 2009 (UTC)

I'm not sure about the heat-reflective differences, but my understanding is that the reason the Blackbird is painted black is to help it hide from Radar. At least that's what I heard on some tv show. According to this (http://answers.yahoo.com/question/index?qid=20080604155845AA2TCgt) Yahoo answers the colour white is used to help facilitate ground-checks (though to be honest there's no more detail on how white iteslf helps do this) ny156uk (talk) 07:22, 8 July 2009 (UTC)

There could be a simple explanation. At [1] it says: White colors are much easier to cover with final topcoats. That is, it's easier to paint a logo or some pattern on the aircraft if you do it on a white background. When it comes to military crafts, the stealth aircraft article notes that F-22 was designed to be less visible to the naked eye. I guess dark colours play a part in that. EverGreg (talk) 07:49, 8 July 2009 (UTC)

The SR-71's black paint was selected primarily for its radar absorption properties. Stories about the thermal effects of the paint may have been injected as intentional misinformation to draw attention away from the "stealth" radar characteristics. It's worth noting that most of the useful stealthy characteristics come from the shape of the airframe, the engines, and the (minimal use of detectable) onboard electronics - so even the radar dissipating paint is itself sort of a red herring. Nimur (talk) 14:03, 8 July 2009 (UTC)

A physicist once told me that a steam radiator painted black would emit heat more efficiently than one painted white or silver. The SR-71 gets very hot from friction with the air at extreme speed. Would the black paint allow the heat to be radiated out better than a silver or white finish? Edison (talk) 15:35, 8 July 2009 (UTC)

Yes, in general darker colors have higher emissivity and better approximate a black body spectrum when heated, allowing them to dissipate energy by radiation more rapidly. Dragons flight (talk) 16:42, 8 July 2009 (UTC)

The curator at RAF Cosford told me that the BAC_TSR-2 was painted Anti-flash_white to protect the crew from A Bomb heat. I'm not convinced paint would protect you from a nuclear explosion. --TrogWoolley (talk) 21:54, 8 July 2009 (UTC)

All the V bombers were painted white for the same reason. MilborneOne (talk) 22:20, 8 July 2009 (UTC)

Yeah, I think paint would provide about as much protection as a school desk. Red Act (talk) 10:33, 9 July 2009 (UTC)

Thanks, Edison and Dragonsflight, you really answered my question from a physics point of view (BTW, my physics textbook also confirms that black paint radiates heat better). Now just one final point, it says in The Lore of Flight that the Concorde's white paint "reduces the temperature of certain areas [of the plane's airframe] by more than 10 degrees Centigrade", is that book just wrong about it, or are there some other heating effects (in the case of the Concorde but not the Blackbird) that are better countered by white paint? Thanks, and clear skies! 76.21.37.87 (talk) 09:26, 9 July 2009 (UTC)

Torque multiplication in a torque converter

How does it actually happen ? I fail to accept the explanation according to which the redirected oil flow (done by the stator) entering the impeller would do the trick, because it would only relieve the load on the engine and not transfer more force to the transmission.

My own guess is that there must be some kind of reaction force acting on the turbine in a similar manner as in a fire hose when the hose is opened at a close proximity to a solid wall.

Hope that someone with a scientific approach could shed some light on this phenomenon. —Preceding unsigned comment added by 193.210.65.69 (talk) 09:50, 8 July 2009 (UTC)

See Torque converter for more on this and it and the article has a link to howstuffworks. An interesting sort of related topic is torque amplifiers which I've made a couple of, they are used in power steering for instance. Dmcq (talk) 10:10, 8 July 2009 (UTC)

To quote the howstuffworks article: Modern torque converters can multiply the torque of the engine by two to three times. This effect only happens when the engine is turning much faster than the transmission. —Preceding unsigned comment added by EverGreg (talk • contribs) 10:14, 8 July 2009 (UTC)

Does fluid coupling make sense - they transmit torque, but do not multiply the torque, a very simple torque converter is just a fluid coupling with the output stage modified - see Fluid_coupling#Developments - if you don't understand fluid couplings then torque converters will be a mystery.83.100.250.79 (talk) 15:34, 8 July 2009 (UTC)

Remember that a fluid coupling is a torus - there are two types of fluid flow

• Going around the torus (ie like a wheel)
• Going around the circular segments of the torus (ie going around the circular cross sections)

It's the first that transfers the torque in a fluid coupling).

In a simple torque converter the stator redirects the second flow (using angled blades) so that some of its motion is converted to the first type of flow. (The turbine blades can also be angled, but it's unnecessary to imagine this for a simple explanation)

OF COURSE there is a reaction of the liquid flow on the output stage - this is how all fluid couplings and torque converters work fundamentally. ie if you point a fire hose at a shovel the shovel will be forced back by the water.

Definately read about simple fluid couplings first, before moving onto torque converters.83.100.250.79 (talk) 19:53, 8 July 2009 (UTC)

Does humidity affect hair growth?

I live in dry southern california, it's practically desert. A few times, I've traveled to other countries with much more humidity than where I normally live and notice that my hair (as well as my other family members) has grown faster during the time I've spent in this country. I don't know if I'm just imagining things or if humidity really does affect the speed of hair growth. On a related note, after removing a cast after a broken bone has healed will reveal that the hair on the skin below has grown considerably longer. Can this also be related to the dampness of the skin under the cast? -- penubag  (talk) 10:21, 8 July 2009 (UTC)

This is a fun thing to notice! :-) Hair actually expands in moist conditions and contract in dry ones. I've seen 3% being cited as a figure. If your hair is 30cm long, that should make for a difference in almost 1cm. This has been the basis for some hygrometers, which measure the humidity in air. EverGreg (talk) 10:36, 8 July 2009 (UTC)

Hmm, that is really interesting, perhaps that's what happens when I travel! But it doesn't answer my second question as to why hair grows long and dark under a cast.-- penubag  (talk) 11:02, 8 July 2009 (UTC)

No it dosn't. Though I suspect that if it seems dark, that's because it's in stronger contrast to the skin, which is paler after being covered in a cast. That it looks longer may be an optical illusion from the increased contrast. The hair on a stubbled chin is more prominent if it's black for instance. EverGreg (talk) 11:10, 8 July 2009 (UTC)

Nope, I guess you've never worn a cast (lucky you). It grows substantially longer while under the cast thus darkening as most longer pieces of hair do. -- penubag  (talk) 11:24, 8 July 2009 (UTC)

I suspect the difference is not in growths, but in life time. The cast protects the hair, so it will not fall out or break of as fast as on the unprotected skin. So you will have more and longer hairs, although none grows faster. --Stephan Schulz (talk) 14:21, 8 July 2009 (UTC)

The darker color might be due to it not being exposed to the bleaching effects of the sun. Grey hair has recently been identified as being caused by hydrogen peroxide accumulating in the hair. I don't know if it requires light to bleach hair, but that may also happen. 71.236.26.74 (talk) 15:27, 8 July 2009 (UTC)

Sunlight can certainly lighten hair. When a small boy I went (from the UK) to live in the much sunnier Far East for a few years; my normally dark blond/light brown hair turned very light blond for that period, but re-darkened on returning to Blighty. 87.81.230.195 (talk) 20:18, 8 July 2009 (UTC)

Glycerine + Ca(OH)2 ?

As I know, glycerine is hygroscopic and can absorb some quantity of water. What is the theoretical range of pH of this mixture? —Preceding unsigned comment added by Renaldas Kanarskas (talk • contribs) 12:42, 8 July 2009 (UTC)

I find it difficult to understand what you mean. Do you want to know what happens if you mix Calciumhydroxide with Glycerine (as the Title suggests) or what happenes if you mix it with Water (as the Text suggests). To find out about the pH of the resulting Mixture you simply need the pKs-Value/ pKa-Value of the Substance in question. In your case I just found the one of ethylene glycol, which already is 14.2 so considering the chemical relation between the two substances I would guess there is no big change in pH of the water whatsoever as glycerine should not be that easy to deprotonate. And of you mix it with a base you would either find that nothing happened, or you might create an Adduct depending on base strength. --91.6.6.157 (talk) 16:55, 8 July 2009 (UTC)

If I mix pure anydrous glycerine and CaOH2, I will not get any H+ and OH- ions because of anhydrous mixture. Glycerine absorb some water, I want to calculate pKa/pKb of this solution. Renaldas Kanarskas (talk) 22:45, 13 July 2009 (UTC)

Particles that are their own antiparticles and vice versa

How does this work? Neutral pions for example. Would two of them annihilate eachother when they get too close together? -- Aeluwas (talk) 12:43, 8 July 2009 (UTC)

It appears that it IS its own antiparticle, and "self-anihilates" all on its own. The quark structure of the pi-0 particle is listed in the article, which would also seem to indicate that it is clearly its own anti-particle. As with all aspects of quantum physics, try to suspend basic logic and reason when understanding how the system works. There are two possibilities here; either neutral pions do not exist, or your own understanding of the matter/antimatter interaction is flawed. Perhaps there is something in the pi-0 structure which makes it metastable; that is it probably doesn't exist for long, but it hangs around just long enough to prove that it exists. --Jayron32.talk.contribs 12:49, 8 July 2009 (UTC)

Things are simpler than Jayron32 presents them. A neutral pion consists of one quark and one anti-quark. It is therefore a composite of matter and antimatter and can annihilate itself. To dig deeper, the first thing to grasp onto here is the conservation laws. For instance the Charge conservation or more to the point, Baryon number conservation. The baryon number is the number of quarks minus the number of antiquarks divided by 3, so it's zero for the pion. Zero means it can evolve into something with zero quarks without breaking baryon number conservation. For the neutral pion the sum of the electric charge of the quarks sum to zero, so it's also ok to transform into something with no charge. (In fact, it couldn't be its own antiparticle if it had a nonzero charge, because particles and antiparticles have oppsite charges) In total, this means that the pion is allowed to transform into pure energy, or two photons to be precise:

π0

→

2 γ

It can however also transform into an electron and a positron since these too consists of no quarks and their electric charges sum to zero. Another particle which is its own antiparticle is the Z0 boson. Not surprisingly, this also has the ability to turn into photons, or pure energy:

Z

→

3 γ

EverGreg (talk) 13:27, 8 July 2009 (UTC)

To be super-precise, an antiparticle has the opposite charge of its corresponding particle. When you have zero charge, you can therefore be your own antiparticle :-) EverGreg (talk) 13:31, 8 July 2009 (UTC)

To be even more precise, a particle can only be its own antiparticle if all of its quantum numbers, including charge, are zero. A neutron is not its own antiparticle because its baryon number is not zero; a neutrino is not its own antiparticle because its lepton number is not zero. Gandalf61 (talk) 15:16, 8 July 2009 (UTC)

Gandalf, it is actually not yet known for a fact whether neutrinos are their own anti-particle or not. Lepton number conservation is not writen on stone. See majorana neutrinos. Dauto (talk) 18:33, 8 July 2009 (UTC)

Thanks guys, that clarifies it a bit. :) Especially "It is therefore a composite of matter and antimatter and can annihilate itself.".

I'm still confused about the whole pion as a strong force carrier, though. Particle physics is a very weird field. Are those pions there all the time (and add to the mass?!), or are they virtual, or what? :) -- Aeluwas (talk) 15:13, 8 July 2009 (UTC)

It seems as if the article about virtual particle semi-answers that question... not that I can say that I understand that it works. ;) -- Aeluwas (talk) 15:15, 8 July 2009 (UTC)

That is actually a confusing topic! Nobel prize winner Yukawa thought that the strong force was transmitted via pions. It is actually transmitted via gluons, but gluons can turn into quark-antiquark pairs, which is what pions are. These pions can in turn back into gluons. These constitute the sea quarks. So it's not completely wrong to say that the pion is involved. Yukawa's pion model has also been retained in nuclear physics as an approximaiton because it has been mathematically difficult to work with gluons alone, or so I've heard. EverGreg (talk) 18:31, 8 July 2009 (UTC)

EverGreg, There is nothing wrong with saying that pions transmit the strong force between the protons and neutrons inside a nucleus the same way that there is nothing wrong with saying that the nucleus is made of protons and neutrons. In fact, whenever dealing with sacales larger than the size of the nucleons, due to color confinement, the strong force is constrained to being transmitted by color singlets (white, if you will) which cannot be satisfyed by single gluons. The lightest color siglet particles are the pions and that's why they are indeed the most important component of the interaction between nucleons. Dauto (talk) 22:15, 9 July 2009 (UTC)

Good point! EverGreg (talk) 07:46, 10 July 2009 (UTC)

plasma

Can plasma movement in a theoretical pipe that plasma could not destroy be accurately modeled using fluid dynamics? 65.121.141.34 (talk) 16:08, 8 July 2009 (UTC)

Absolutely. Plasma is a fluid and as such obeys the Navier-Stokes equations. Readro (talk) 16:10, 8 July 2009 (UTC)

Because a plasma is an electrically conducting fluid, it is subject to electromagnetic forces, so you specifically need magnetohydrodynamics, a sub-field of fluid dynamics. Gandalf61 (talk) 16:28, 8 July 2009 (UTC)

Price of agricultural products

is there a direct correlation between price of agricultural product and growing time of its tree/plant? What are the most expensive agricultural products?--Quest09 (talk) 17:50, 8 July 2009 (UTC)

Saffron is one of the most expensive agricultural products—it's the most expensive spice by weight. I wonder if there are any pharmaceuticals that are derived from plants in tiny, expensive quantities? -- Coneslayer (talk) 17:56, 8 July 2009 (UTC)

Marijuana is a rather expensive agricultural product, and it is very fast growing. I think that the fact of it being illegal is the primary impact on its high price. I don't know how long it takes to grow the plants for cocaine. 65.121.141.34 (talk) 18:11, 8 July 2009 (UTC)

Were marijuana not illegal in many countries I have no doubt it would be much more expensive than tobacco. -RunningOnBrains^{(talk page)} 04:36, 9 July 2009 (UTC)

One would naively expect that the slower the plant grows, or the longer it takes to reach maturity, the more expensive would be its fruit (or, generally, any product obtained from it). That is true in some cases (walnuts, for example), but not in general. Prices are set by supply and demand, and the rate of the plant growth is just one of many factors. Some other factors that play a role are: 1. Desirability of the product (compare good Burgundy wine to cheap local one); 2. Legality of the product (see above); 3. Yield (roses are rather fast growing, but rose oil is very expensive nevertheless); 4. Ease of cultivation (e.g. truffles and brazil nuts). And there are more factors, of course. --Dr Dima (talk) 19:10, 8 July 2009 (UTC)

Perishability is a big one. Raspberries grow like weeds in my part of the world, yet they cost about US$16/lb for moldy ones at the grocer. --Sean 23:25, 8 July 2009 (UTC)

Some essential oils are amazingly expensive. This site claims that 7 tonnes of lemon balm are needed to produce 1 kilogramme of Melissa essential oil. [2] This site sells 1 kilogramme of Melissa essential oil for £1,800! [3] Some of the absolutes are even more expensive: 1kg of lotus (plant) absolute costs £5,900!--TammyMoet (talk) 19:26, 8 July 2009 (UTC)

The caveat in this analysis is that many of the incredibly expensive (per pure unit) things are used in only minute quantities (50 g leaves for melissa-based therapy at £1,800/7 tonne oil equivalent?), so the cost-per-enduser-product isn't so bad. Same pattern holds for API for pharmaceuticals...manufacturing price-per-truckload of the active ingredient might look huge but at only a few mg per dose the dose cost is reasonable. DMacks (talk) 21:07, 8 July 2009 (UTC)

Truffle (fungi)s can sell for a fortune. According to the article the record for a white-truffle was £165,000 for one that weighed 1.5kg. 22:37, 8 July 2009 (UTC)

banana plants take a long time to grow and only bear fruit once and then die off. They are a third world country product, though and economic pressures keep the price low. Some rain forest timber takes decades to grow but it doesn't fetch a fair price because it's not a "standard" species like oak or redwood. So world economy plays a role in pricing. 71.236.26.74 (talk) 04:50, 9 July 2009 (UTC)

"Some rain forest timber takes decades to grow but it doesn't fetch a fair price because it's not a "standard" species..." -- And what do you define as a "fair" price?

76.21.37.87 (talk) 10:20, 9 July 2009 (UTC)

Better than what it's fetching now at least. It is generally valued at less than "standard hardwoods" because consumers are not familiar with the names, etc. If you want to start a discussion on there not really being a "fair" price for cutting down a tree from a rainforest I don't think this is the place (but I happen to agree). 71.236.26.74 (talk) 14:40, 9 July 2009 (UTC)

The amount of time that a certain crop is in the field would be a factor in its price because of the opportunity cost of said crop taking up the space when another one, possibly faster growing, could be planted instead. —Preceding unsigned comment added by Frogmaster3950 (talk • contribs) 15:37, 10 July 2009 (UTC)

anchors and tides

If you have a boat and drop an anchor, and the tide goes up a lot, like 20+', will the anchor sink the boat if the anchor line was pretty taut at low tide? 65.121.141.34 (talk) 18:54, 8 July 2009 (UTC)

Only if the anchor weighed so much that it pulled the top of the ship's hull below the waterline - and that won't be the case, because the ship wouldn't ever be able to lift and carry its own anchor. Anchors don't rely on their mass (mostly), but on hooks or plates to catch the seabed; the weight of a heavy anchor is there only to help it bite into the seabed better. 87.113.26.43 (talk) 19:02, 8 July 2009 (UTC)

Well, it's possible that the anchor could get wedged under something really heavy and get stuck. However, even then, the anchor line/chain is likely to break before the boat could go under. As a practical matter, this is never an issue. Even with an all-chain anchor, good boating practice is to lay out enough chain to give a scope of about 7:1 -- translated, for every one foot of depth, you should have seven feet of anchor chain in the water. In adverse conditions, even more should be laid out. Consequently, you've always got far more chain in the water than the tide could impact. — Lomn 19:29, 8 July 2009 (UTC)

For interesting consequences of a (fictional) failure to do this, read We Didn't Mean to Go to Sea by Arthur Ransome. 87.81.230.195 (talk) 20:10, 8 July 2009 (UTC)

I've seen the opposite of that happen though - someone tied their boat to a jetty and the tide went out - initially lifting the boat out of the water - then ripping the fixtures that the ropes were tied to off of the deck - then finally allowing the boat to float away. SteveBaker (talk) 20:25, 8 July 2009 (UTC)

If an anchor chain is pulled to a vertical position by a rising tide, further rise of the water will pull the anchor free. In case any reader is a land lubber and does not know how anchors work, an anchor has a crossbar at the top, or in the case of a patent anchor it has flukes which are hinged at the bottom. Immediately after the anchor is dropped, the ship drifts a bit due to current or wind. The crossbar causes one of the flukes to be at an angle to the bottom. The drift causes the fluke to dig into the bottom (unless the bottom is rocky). Further drift causes the fluke to dig deeper until the ship is brought to a standstill. Obviously, the ship does not have to drift far for this to happen. In the case of a patent anchor, both flukes initially lie flat on the bottom. As the ship drifts, the weight of the flukes causes them to dig into the bottom. With either type of anchor, if the chain becomes vertical, further pull on the chain will lever the anchor out of the bottom (unless a fluke is hooked under a rock, as another poster pointed out.) The bottom is relatively soft – it had to be for a fluke to dig in. So the anchor can be levered out of the bottom. When pulled vertically, I don't think the chain is likely to break – it held the ship against drifting so it is not badly flawed.
The Wikipedia article for "anchor" is very poor. Also, the anchor shown in the illustrative photo seems to be without the essential crossbar.
GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 01:04, 9 July 2009 (UTC)

The captain of this boat might not mind as long as it comes back up. [4] :-)71.236.26.74 (talk) 06:20, 9 July 2009 (UTC)

I don't think the captain even dropped the anchor. He should have done that before he got to the bridge. - GlowWorm. —Preceding unsigned comment added by 98.17.35.216 (talk) 03:58, 10 July 2009 (UTC)

Or maybe the anchor didn't have a crossbar. - GlowWorm.

On a practical front, sailors are taught to use a length of anchor rode (the technical word for the chains and ropes) between five and seven times the depth of the water, AND to take account of tide changes in the calculation. Most anchors will drag if the rode is much shorter than this. DJ Clayworth (talk) 18:23, 10 July 2009 (UTC)

B vitamins

NZ is currently planning to begin mandatory folic acid (vitamin B9) fortification of most bread. This has lead to a lot of debate and one of the issues which people have been saying on forums is that if you increase consumption of one B vitamin you need to increase them all or you risk deficiencies in the other B vitamins. This seemed strange to me and reviewing further I can't find any evidence of this being true. From what I can tell, the only currently known risk is between folic acid and vitamin B12. Specifically since the effects of these two are connected, taking extra folic acid may mask some of the symptoms of vitamin B12 deficiency (but it doesn't treat all the problems) so that it's not so obvious the person is suffering from it (it doesn't require you increase your vitamin B12 intake if it's sufficient). The evidence for this being a problem in the US and Canada who also have fortification however appears limited. There is also some more recent suggestion that a high folic acid intake and a low B12 may be bad and excess folic acid consumption "worsens the effects of B12 deficiency and in fact may affect the absorption of B12" (although I suspect this is talking about very high levels that your rather unlikely to get from fortified bread anyway). In particular, there's little evidence if you have a healthy/sufficient B12 intake, taking extra B9 suddenly requires you to increase B12 intake or any other of the B vitamins. Is there something I've missed or am I right that the claims about needing to increase all B vitamins are unsupported? Nil Einne (talk) 21:24, 8 July 2009 (UTC)

I have nothing to add beyond the B vitamins article, which I assume you've read, and which does mention that too-high doses of folic acid can mask a vitamin B12 deficiency. Tempshill (talk) 22:18, 8 July 2009 (UTC)

I guess one could counteract that by eating marmite on each slice of B9-fortified bread, since it is high in B12. Gwinva (talk) 22:53, 8 July 2009 (UTC)

Yes that and the Vitamin B article (as well as a quick Google) neither of which provide any real support for the notion other then what I mentioned. I normally would have dismissed the comments as 'ill-informed' (the place I read them isn't known for the high standard of debate [5]) but decided to check since more then one person made the claim. I presume they're confused by the B9-B12 issues as well as perhaps the general advice it's not wise to take excess of any vitamin and the general belief that improving one's diet and better food is better then supplements and fortification. Nil Einne (talk) 01:01, 9 July 2009 (UTC)

Ctenophores as human food source

It's frequently been suggested that we could adopt jellyfish as a food source once fish stocks are depleted, but could we do the same with ctenophores? Are they common and nutritious enough to make this idea viable? 69.224.113.202 (talk) 23:18, 8 July 2009 (UTC)

The main reason people eat meat rather than textured vegetable protein is palatability and "ick factor". I can hardly see either jellyfish or ctenophores overcoming either of those obstacles. The latter appear to be mostly water, anyway. --Sean 23:31, 8 July 2009 (UTC)

I've eaten jellyfish in Chinese restaurants -- I confess that I found it icky though. Looie496 (talk) 01:01, 9 July 2009 (UTC)

Jellyfish do contain nourishment. They are one of the food items of the ocean sunfish. Sadly, some of the sunfish are killed by swallowing one of those thin plastic bags, thinking it to be a jellyfish. Like other human castoff material, those bags even find their way into the sea. - GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 01:33, 9 July 2009 (UTC)

Relatedness of species / Last common ancestor

Hi all,

I have a bit of confusion about species. I recently learned that if two species had a more recent common ancestor than either of them to a third species, then those two species are considered more closely related to each other than either is to the third species.

A       B   C
|       |   |
|       -----
|         |
-----------
     |

So B and C are "more closely related" than either is to A.

But what if A and B have barely evolved at all since their respective splits? Say the common ancestor at the bottom splits 100 million years ago and the resulting "A" branch doesn't change ever after (kind of like a crocodile). Soon after (95 m.y.a), the right lineage splits, and the resulting "B" branch doesn't change ever there after. The "C" branch, however, changes tons and tons, and all sorts of other species branch off of that last branch, and C is very, very different from its last common ancestor with B.

In this case, A and B are virtually identical -- they evolved from a LCA in just 5 million years apart and never changed. C is really, really different, though, and has millions of new genes. In this case, wouldn't A and B really be more closely related, even though B and C had the more recent common ancestor? —Preceding unsigned comment added by 76.118.181.97 (talk) 23:27, 8 July 2009 (UTC)

I believe you will find the answer in the definition of "more closely related". The assertion is correct if you mean more closely in time, and incorrect if you mean more closely in common genes. Avoiding this kind of discrepancy is why scientists talk like a bunch of nerds. --Sean 23:35, 8 July 2009 (UTC)

Both ways of describing how closely related species are are useful and so both are used. It's very common so see statements about what percentage of genes two species share (even that varies depending on your exact definitions). --Tango (talk) 00:53, 9 July 2009 (UTC)

The use of the term "closely related" is used pretty much exactly like it is in your family tree; just because your second cousin look a lot like you doesn't make him more closely related to you than your sister. You may also find the article on convergent evolution to be germane; it is often the case that even totally unrelated organisms can look similar due to being exposed to similar environmental pressures. Matt Deres (talk) 01:42, 9 July 2009 (UTC)

There are almost certainly genes that B and C share that A doesn't have...that makes them (genetically) more closely related than A and B. SteveBaker (talk) 02:38, 9 July 2009 (UTC)

The diagram you gave (as described) was only the qualitative branching. You can make it more quantitative to illustrate the amount of evolutionary change ("...and then C evolves much further while A and B did not change much or diverge very far"):

        C
        |
        |
        |
        |
        |
        |
    B   |
    |   |
A   -----
|     |
-------
   |

and now it's more clear that while B and A are more diverged from each other than B and C are, C has evolved further from A than B has. See our Phylogenetic tree article for several different types of representations (with actual diagrams vs our quick'n'dirty ASCII art:) DMacks (talk) 07:35, 9 July 2009 (UTC)

July 9

Rubbish/Garbage Island

Would it be feasible to create a new island at somewhere like the Dogger bank (which I understand is a large sand bank off the coast of Britain that you can walk on at low tide) merely by dumping the nation's garbage/rubbish there for a few years? If needed, the rubbish could be contained by an earth or sand wall around it. Such an island would be usefull to put things on like wind farms, nuclear power stations, oil refineries, chemical plants, and prisons. I expect it could take a decade or two for the rubbish to stabilise enough to build on, unless you used deep-pile foundations. 78.147.135.194 (talk) 00:09, 9 July 2009 (UTC)

The major problem is erosion which could compromise the integrity of the artificial island so maintenance would be expensive since garbage is not exactly as tough as granite. There's also the problem of the garbage contaminating the sea.--Lenticel ^(talk) 00:55, 9 July 2009 (UTC)

It would be feasible to create an island that way but it probably wouldn't be permitted. Garbage in water tends to, um, exude aspects of its essence, so to speak. Looie496 (talk) 00:56, 9 July 2009 (UTC)

Much of modern Boston's land area is fill, including demolished building rubble and post-consumer waste. Nimur (talk) 01:32, 9 July 2009 (UTC)

Landfill is a major method of constructing new land over former waterways. However, garbage (rather, post-consumer waste) has many properties that make it unsuitable for construction of buildings - most notably, it is too squishy for safe construction of building foundations. A lot of engineering has to go into the landfill design to make sure that the ground is solid enough to use. Also, there are potential aesthetic (smell) and health issues, depending on the type of garbage used to build it. However, in some cases, garbage has been used as a fill constituent, properly mixed with other construction materials. Boston and some parts of the United Arab Emirates are notable examples of this. In fact, most of the Back Bay is artificial land; the fill is largely imported from elsewhere in the state, but was mostly dry ground (not garbage). Here is a thorough history from Boston College. Nimur (talk) 01:32, 9 July 2009 (UTC)

Here's our article on the Palm Islands, in Dubai. The fill material is mostly quarried rock and sand; I can not find any indication that post-consumer waste was used anywhere.

Also see: Artificial island and List of artificial islands. Nimur (talk) 01:45, 9 July 2009 (UTC)

"Would it be feasible to create a new island... merely by dumping the nation's garbage/rubbish there for a few years?" -- Now why in the world would anyone want to do that? There are other much better options for garbage disposal (reclamation, trash-to-steam incineration, etc., etc.), and if you want to build an artificial island, then gravel would work one hell of a lot better. 76.21.37.87 (talk) 06:28, 9 July 2009 (UTC)

A good example of what you'r looking for is Pulau Semakau, the scenic landfill of Singapore. Even referred to as The island paradise built on a garbage dump [6]. The trick appears to be using incinerated trash. EverGreg (talk) 08:54, 9 July 2009 (UTC)

Grant Park (Chicago) was extended by waste from the Chicago Fire and elsewhere. It really depends on what kind of rubbish you have available. Brick and stone will work better than banana peels. Rmhermen (talk) 18:46, 9 July 2009 (UTC)

What's now the waterfront of San Francisco is built partly on the hulks of abandoned ships; the Embarcadero extension of the N Judah line to Pac Bell Park SBC Park AT&T Park passes through one, and another was partly exposed when a building at Battery and Clay Streets (now four blocks from water) was torn down in 2001. —Tamfang (talk) 18:00, 21 July 2009 (UTC)

What type of tick is this? Is it even a tick?

A friend and I walked through some brush in Nova Scotia yesterday and emerged with many of these on our pants and shoes. We got them off quickly and didn't appear to have been bitten or anything. What is it? Thanks, Kinou (talk) 00:15, 9 July 2009 (UTC)

Sure looks like a tick (see pics in tick article). Don't know what kind. But get in the shower as soon as you can, and check yourself very carefully ALL OVER (scalp, nether regions etc.) for any ticks that may have stuck to you, or any bite marks. Ticks can spread some pretty nasty diseases. 208.70.31.206 (talk) 00:40, 9 July 2009 (UTC)

If you search for images of a wood tick, you'll find a bunch that look just like that. Brown dog tick also looks similar—but I can't decide, and I'm not an expert. Alfonse Stompanato (talk) 00:44, 9 July 2009 (UTC)

Thanks for the responses :) Kinou (talk) 06:18, 15 July 2009 (UTC)

Railroad train wheels

After reading most of the references on trains I have nor found the answer to this question. "What keeps a train on the track around curves"?. Cars do it by virtue of a differential, but train axels are solid so both wheels travel at the same speed. I know the answer but I wonder who invented the cone shaped wheel? What are the limitation of speed around curves? I would appreciate all serious answers. Thanks, wsc. —Preceding unsigned comment added by 98.149.228.69 (talk) 00:33, 9 July 2009 (UTC)

I see some detailed math related to conical wheels way back in Byrne, Oliver (1 March 1862). "The elevation of the exterior rail on railroad curves" (PDF). The Civil engineer and architect's journal. 25: 71–72. There actually are differentials for railroad wheels available now, for example see US patent 7316436, Kummings, John, "Differential wheel mounting for railroad car", issued 2008-01-08  and its cited precedents. DMacks (talk) 01:29, 9 July 2009 (UTC)

If I can digress a bit, the top of the rail is somewhat rounded, even on straight runs. Together with the cone shaped wheels, does that help overcome lurching of the carriage? - GlowWorm.

The reason I think that will help overcome lurching is that the side of the carriage in the direction of lurch will rise slightly, opposing the lurch. The cone shaped wheel will then ride on a slightly different track on the rail top, hence the rounding. This effect would also help oppose the centrifugal "force" on a curve, like a banked auto race-track. These effects may seem slight, but the wheel rim is actually tapered quiite a bit. - GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 02:56, 9 July 2009 (UTC)

P.S. When one side of the carriage rises, the other side falls. These actions thereby reinforce each other. - GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 03:16, 9 July 2009 (UTC)

P.P.S. The train wheels slide sideways on the rails to bring these effects about. That's no problem. We've all heard a locomotive spinning its wheels when starting to move.- GlowWorm. —Preceding unsigned comment added by 98.21.111.233 (talk) 03:41, 9 July 2009 (UTC)

The article about tapered wheels I cited above has information about side-to-side tilt and curved-track issues. DMacks (talk) 06:41, 9 July 2009 (UTC)

Tilting train and High speed tilting train (unfortunately only a stub} may help. 71.236.26.74 (talk) 06:08, 9 July 2009 (UTC)

The Wikipedia article Wheelset says a bit about conical wheels. But I think it is incomplete and poorly written.. Also, it says "Most wheels have a conical shape of about 1 in 20.", which is unclear. - GlowWorm. —Preceding unsigned comment added by 98.17.35.216 (talk) 04:47, 10 July 2009 (UTC)

It means that the conical surface deviates from the angle it would have if it was cylindrical by about 2.86° (I'm sure that's excessive precision) -- because the tangent of that angle is 1/20. In Britain the style "1 in n" is very commonly used to express the inclination of a gradient on a road or railway, so if one of those is rising at 2.86° above the horizontal, that's a "1 in 20 grade". (In North America we would instead convert the tangent to a percentage and call it a 5% grade.) --Anonymous, 05:13 UTC, July 10, 2009.

The problem I have with a cone angle of "1 in 20" is whether it applies to the angle between the two sides of the cone, or whether it applies to the angle between one side and the axis of the cone. - GlowWorm. —Preceding unsigned comment added by 98.17.35.216 (talk) 05:38, 10 July 2009 (UTC)

There's a reasonable discussion in an Institute of Civil Engineers publication on google, Cost-effective maintenance of railway track which tends to corroborate much of this discussion. As to cone angle, if this definition is correct then 98.17's objection does not apply. I should like to know the maths by which 1 in 20 comes to be 2.86°, GlowWorm, if you'd be so kind. --Tagishsimon (talk) 10:43, 10 July 2009 (UTC)

• I said above: the tangent of 2.86° is 1/20. --Anon, 05:43 UTC, July 11, 2009.

Tagishsimon's reference shows another useful function of conical wheels. It is the reduction of "hunting". Figure 3 shows it clearly and simply. - GlowWorm. —Preceding unsigned comment added by 98.17.47.39 (talk) 22:22, 10 July 2009 (UTC)

Not quite - hunting is caused by the conical wheelsets, the article Hunting oscillation begins to explain.83.100.250.79 (talk) 15:29, 12 July 2009 (UTC)

I thought hunting was caused by hillbillies like myself wanting some red meat... :-D 76.21.37.87 (talk) 09:28, 14 July 2009 (UTC)

They have a flange around their inner edge to ensure they don't come off the track. 78.151.124.180 (talk) 23:34, 11 July 2009 (UTC)

Can you legally have hypodermic needles in rochester new york without a perscription?

Can you legally havehypodermic needles in rochester new york without a perscription? —Preceding unsigned comment added by 74.65.3.30 (talk) 01:18, 9 July 2009 (UTC)

Wikipedia cannot give legal advice. Nor can we give medical advice. While we can point you to encyclopedia articles and outside sources which can help inform you, this question is specifically requesting an interpretation of law, which nobody on Wikipedia should be giving. Nimur (talk) 01:35, 9 July 2009 (UTC)

Our article presents several examples of hypodermic uses that are intended for "non-specialists", which suggests that they are commonly used without a medical prescription. Nimur (talk) 01:38, 9 July 2009 (UTC)

No it doesn't!! It says nothing of the sort! It lists a bunch of medical conditions that would require people to inject themselves...but with a prescription syringe - then it says that recreational drug users use them (illegally) - and only in the next section does it point out that the syringe MINUS THE NEEDLE is used in various industrial applications. Certainly the syringe part is useful without the hypodermic part - and the odds are good that those are perfectly legal. But the article doesn't give a single legal, non-prescription use for hypodermic needles - which is what our OP actually cares about. SteveBaker (talk) 02:14, 9 July 2009 (UTC)

well apparently they are illigal in ny state but can i buy them for ear peircing? thats what i need them for —Preceding unsigned comment added by 74.65.3.30 (talk) 02:12, 9 July 2009 (UTC)

Needles, like hypodermic needles? Those may be regulated, but they are not what is necessary for ear pearcing. Why not just head to the piercing kiosk at your local mall. For the cost of a $10.00 set of cheap starter studs, they'll pierce your ears for free! --Jayron32.talk.contribs 02:33, 9 July 2009 (UTC)

(Please don't start new threads on the same topic - I've moved it back together again) SteveBaker (talk) 03:05, 9 July 2009 (UTC)

You can buy a complete ear piercing kit (no illegal hypodermics involved) here for $70. You can buy proper (sterile) ear piercing needles here for about $1.50...they seem very similar to hypodermic needles - but they don't have the fitting to attach to a syringe. I suppose that's what makes them legal...but who knows? SteveBaker (talk) 03:13, 9 July 2009 (UTC)

I’m not an expert on piercing, and it’s hard to tell for sure from the picture, but my guess is that piercing needles aren’t hollow. There’d be no need for them to be hollow, since no fluid needs to go through them. So piercing needles would be useless to a drug addict, and there’d be no need to make them a legally controlled device. Red Act (talk) 03:24, 9 July 2009 (UTC)

Years ago someone stole a bunch of analytical-HPLC syringes from a lab where I worked. For those playing along at home, that means the syringes hold a few tens of microliters and the needles are blunt. We figured it'd be easy for the cops to find the druggie who was not high and had a line of bruises instead of needle-tracks up his arm. DMacks (talk) 03:35, 9 July 2009 (UTC)

I don't know what's in kits sold to the general public, but Body piercing#Contemporary piercing procedures says hollow needles are used. My WP:OR is "may as well go with a cheap, widely available, sterile existing item" rather than something less common or more special-purpose (i.e., more expensive). DMacks (talk) 03:32, 9 July 2009 (UTC)

If they actually are illegal then what do they pack into ink jet cartridge refill kits sold in that state? The one's I've bought so far all contained a hypodermic needle. I doubt they are sterile, though. (Not a known transmission path for computer viruses :-) 71.236.26.74 (talk) 04:28, 9 July 2009 (UTC)

<giggle> - Hordaland (talk) 11:54, 9 July 2009 (UTC)

Latex vs polyisoprene condoms

A company recently released polyisoprene condoms to the market. Reading that entry says it's natural rubber. How does it compare with latex condoms as far as allergies, strength, and protection? --70.167.58.6 (talk) 01:41, 9 July 2009 (UTC)

Probably the same as latex on all three counts (after all, latex and natural rubber are both isomers of polyisoprene). 76.21.37.87 (talk) 06:38, 9 July 2009 (UTC)

So it's just a marketing gimmick? --70.167.58.6 (talk) 01:22, 11 July 2009 (UTC)

Yeah, they just try to come up with all kinds of fancy words for everyday materials to trick customers into thinking that it's something really high-tech (e.g. "anionic detergents" or "alkali-metal salts of trans-fatty-acids" -- any guesses as to what this stuff could be? (Hint: both of these terms describe pretty much the same material.)) 76.21.37.87 (talk) 05:10, 11 July 2009 (UTC)

Purification of fish oil

Does anyone know how fish oil is purified? I've seen a fish oil product which says on its bottle that it is purified by molecular distillation. Is the distillate purified fish oil or is it volatile impurities? What is the effectiveness of the process? Is it able to remove many broad classes of impurities/contaminants, or is it only effective against very specific ones? What level of purity can be expected from fish oil purified by that process? —Preceding unsigned comment added by 98.114.146.41 (talk) 03:01, 9 July 2009 (UTC)

Distillation separates the components out by boiling point - therefor it is up to the maufacturer as to which Fraction (chemistry) (s) they put into the final product. In general you should read about distillation to find out about potential limitations of this method.83.100.250.79 (talk) 15:36, 12 July 2009 (UTC)

In general distillation can remove many impurities - but if there are impurities with similar boiling point to the product it will be less effective.83.100.250.79 (talk) 15:37, 12 July 2009 (UTC)

oscillators and frequency.

How are oscillators and frequency related to each other?Is constant frequency a compulsion for generating oscillations?please help!! —Preceding unsigned comment added by 210.212.103.10 (talk) 07:20, 9 July 2009 (UTC)

Frequency is a measure of the rate of oscillation. DMacks (talk) 07:27, 9 July 2009 (UTC)

An Oscillator is something which oscillates, that is, goes back and forth. So when something goes back and forth, each round is called an Oscillation. Now it takes some time to complete each oscillation. This is called Time Period of the oscillation. Now, the inverse of this, that is, 1/t, is called the frequency of oscillation. This need or need not remain constant with time; it is an inherent characteristic of something which oscillates. For more information, please read the relevant articles. Rkr1991 (talk) 08:27, 9 July 2009 (UTC)

Calculating time to full battery recharge

I need a little help calculating how long it would take to charge the battery pack of an electric vehicle with the following parameters:

The vehicle has six 12-volt flooded electrolyte batteries, and an on-board 72-volt DC charger that plugs into a standard 110-volt AC 15-amp outlet.

The manufacturer of this particularly odious Neighborhood electric vehicle (they're all a little odious) doesn't mention the time to full charge in its published specs- a rather telling omission, I think.

I posted this over at the Math desk as well. Thanks Wolfgangus (talk) 08:36, 9 July 2009 (UTC)

Do you know what is the batteries' storage capacity in amp-hours? If you do, then it's a rather easy calculation (for me, at least), but if not, then the calculation becomes absolutely impossible. 76.21.37.87 (talk) 09:06, 9 July 2009 (UTC)

I noticed that the on-line calculators I found (before posting this here) were asking for that information, and since I didn't have it, I couldn't use those calculators. But above, I provide all the information that's offered at the company's website. So you're saying that it's impossible to know without the storage capacity in amp-hours. OK, got it. Thanks for the info. Wolfgangus (talk) 09:15, 9 July 2009 (UTC)

Another consideration is that while the charger uses a 15A 110V hookup, that will not likely lead you to the actual charge current of the device (22A if the device is almost 100% efficient, which it likely isn't even close). Knowing the sustained charging current is critical to know how fast those amp-hours will be replenished.--Jmeden2000 (talk) 19:58, 9 July 2009 (UTC)

And the other problem (with at least some sorts of battery) is that they can overheat if you charge them at full speed - so you may have to charge them in briefer pulses to keep them from self-destructing. SteveBaker (talk) 04:37, 11 July 2009 (UTC)

Can lightning strike an airplane?

I copied this question from the Newcomer's desk: — QuantumEleven 09:19, 9 July 2009 (UTC)

Is it technically possible for lightning to strike an airplane?

Icanhasaccount (talk) 05:59, 9 July 2009 (UTC) Icanhasaccount

Of course it's possible, and had actually happened numerous times (surprisingly, the planes involved usually sustain little if any damage from the lightning strike). 76.21.37.87 (talk) 09:29, 9 July 2009 (UTC)

A simple Google will find a lot of reliable sources discussion this [7]. A frequently made claim is that statistically aeroplanes will be hit by lightning an average of twice a year. You can probably also find a lot of discussion when looking in to the recent Air France crash. Nil Einne (talk) 10:22, 9 July 2009 (UTC)

There is a brief discussion at Air safety#Lightning. 88.114.222.252 (talk) 10:50, 9 July 2009 (UTC)

And do the passangers notice anything?Quest09 (talk) 10:52, 9 July 2009 (UTC)

They may hear a loud noise and the lights may flicker - but, as aircraft fuselages are Faraday cages, they won't feel any direct effects. — QuantumEleven 13:14, 9 July 2009 (UTC)

That, as the man said in Men in Black (film), was on Jeopardy! last night"! The current champion, Alyssa McRae, was once in a plane that was hit by lightning, and she talked about it on the show... which, conveniently, I taped. She said: "You look out the window and see a bright flash, and it feels like the plane has hit something, and you just prepare to meet your maker. And it keeps going, apparently. I don't know if that's what always happens, but for me that's how it happened." --Anonymous, 20:08 UTC, July 9, 2009.

My knowledge of the issue is that most aircraft are protected/relatively good at withstanding a cloud-to-ground lightning strike. Issues come from different types of lightning such as ground-to-cloud which strike the underside of the plane, and sheet lightning. Some planes aren't quite as well adapted to these types, and it can cause issues. Regards, --—Cyclonenim | Chat  16:17, 9 July 2009 (UTC)

I dispute that; Cyclonenim, you're going to have to cite a source on that claim. Tempshill (talk) 18:24, 9 July 2009 (UTC)

Sorry, I looked back at the lightning article where I first heard it and it is positive lightning, not ground-to-cloud which causes the issues. The second paragraph which states its danger to most aircraft is cited. See Lightning#Positive lightning. Does that help? Regards, --—Cyclonenim | Chat  22:05, 9 July 2009 (UTC)

I've actually been in an aircraft that was struck by lightning. It's a lot less dramatic than you might think. My father used to fly for the flying doctor service in Kenya - which is based in Nairobi (hmm - we don't seem to have an article on the East-African flying doctors) - and on one occasion I went out with him (I was just a kid at the time - maybe 12 years old) and we got caught in a nasty storm. The meteorology services in Kenya left something to be desired in the mid 1960's - so we didn't know it was in our way until it was too late. We couldn't get above it because Nairobi is already something like 7,000 feet above sea level and the poor little Cessna doesn't have enough altitude ceiling to get much higher than that - and the plane was somewhat overloaded with land-rover parts that were going out to some back-of-beyond medical center. My recollection was of an extremely bright flash - followed by some complete confusion as the cockpit instruments went nuts and our eyes gradually adapted to normal light levels - but after not very long, everything settled down and enough of the old mechanical instruments worked to get us back to Nairobi without problems. The plane was a high-wing nose-wheel Cessna...a Cessna 172 probably. There was a scorch mark on top and bottom of the wing - maybe an inch or so across and the bulk of the energy seemed to have flowed through a 'stringer' in the wing - melting one of the rivets that held it in place. The damage was fixed in a matter of hours and the plane was back in service on the following day. (The way that outfit worked - it would probably have been flying again the next day WITHOUT the damage being fixed!) SteveBaker (talk) 15:34, 10 July 2009 (UTC)

Preparing for war

How well prepared are modern Western democracies? Do governments care about provisions of food, energy, and medicines?

--Quest09 (talk) 10:47, 9 July 2009 (UTC)

It varies, country to country, but I expect most are prepared for reasonable wars or warlike scenarios. Independent of warlike scenarios, governments are always concerned with the supply of food, energy, and medicine. After all, the disruption of such supplies has been a casus belli in the past. The US' 1940 oil embargo on Japan springs to mind as one such. — Lomn 12:35, 9 July 2009 (UTC)

Several western democracies are involved in wars at the moment (eg. Iraq, Afganistan, although they are often euphemistically called "conflicts"), but I assume you mean wars where fighting takes place nearer to home. Most countries have some kind of contingency plans, but I don't know if there would be anything particularly specific. You generally get some warning of wars. Prior to World War II and during the Cold War there were all kind of preparations going on. At the moment there is no reason to expect any major wars, so there is no need for much preparation. There are all kinds of preparations for major terrorist attacks, though, since those are far more likely. --Tango (talk) 16:39, 9 July 2009 (UTC)

Yes, governments care a great deal about provisions of food, energy, and medicines. See Strategic National Stockpile, Strategic Petroleum Reserve, and Defense National Stockpile Center for relevant references. It doesn't look like there's much detail in the articles about different countries, but I would hope that most well-governed nations have established some form of strategic reserve. --- Medical geneticist (talk) 17:30, 9 July 2009 (UTC)

Few countries have military-quality petroleum reserves. The United States has one of the largest, but it is for mostly economic reasons. No country has more than, IFRC, 60 days' worth of petroleum. Even if regular citizens were cut off, that is simply not enough to sustain modern military operations. See the IEA for more on that point.

If every country went to war with every other, only the oil-producing nations would still have airplanes flying and tanks rolling and ships sailing after about a year. Andyo2000 (talk) 19:07, 9 July 2009 (UTC)

Assuming they retained the infrastructure to continue to produce their oil perhaps, but such infrastructure is a high priority target, and it would not be likely to escape unscathed. Googlemeister (talk) 19:10, 9 July 2009 (UTC)

...as has twice been demonstrated in recent history. With modern aerial warfare, these longer term considerations of running out of 'stuff' don't apply when a powerful nation attacks a weaker one. It's usually all over in a matter of days to weeks. SteveBaker (talk) 14:58, 10 July 2009 (UTC)

Well, the large-scale fighting is over within days or weeks, getting full control of the newly occupied territory can take far longer. The initial invasion of Iraq, for example, took about 20 days, but the conflict still isn't over. --Tango (talk) 16:46, 10 July 2009 (UTC)

True, but under that definition, the Nazis never controlled France. Googlemeister (talk) 18:28, 10 July 2009 (UTC)

In any case, as far as petroleum supplies are concerned, it is the initial large-scale fighting that depends critically upon those; the guerilla warfare that (often) follows afterward is mostly infantry warfare that uses lots of ammunition and food supplies but relatively little fuel. FWiW

76.21.37.87 (talk) 05:19, 11 July 2009 (UTC)

Dark skin vs. fair skin

What of both is the evolutionary adaptation?--Quest09 (talk) 10:54, 9 July 2009 (UTC)

This answers why dark skin is both an advantage and a disadvantage. Vimescarrot (talk) 11:13, 9 July 2009 (UTC)

I believe the question is asking which is the original color and which is an adaptation. It depends entirely on who you want to listen to. Nobody was around when the first humans were walking around so nobody knows for sure. Of course, that assumes there was a single group known as the first humans. There may have been been many groups of so-called humans that, over time, intermixed. -- kainaw™ 21:56, 9 July 2009 (UTC)

Oh. I never thought of that. I thought he was asking what evolutionary advantage each colour inferred, and what pressure there was on it to change. Vimescarrot (talk) 22:04, 9 July 2009 (UTC)

The mainstream model of human origins is the Out-of-Africa model. And mean skin color within a population adapts to UV radiation levels from the sun quite rapidly (500-1000 years) on human evolutionary time scales. So if the mainstream model of human origins is correct, homo sapiens presumably originally had dark skin, due to the advantage of dark skin in Africa, where there is a lot of UV radiation, and light skin arose fairly rapidly among those populations that migrated to parts of the world further from the equator, where lighter skin is an advantage. Red Act (talk) 00:47, 10 July 2009 (UTC)

That is not quite as much a given as it may seem. If the humans that made it out of Africa were still very hairy, their skin underneath might well have been light (like e.g. Chimpanzee) The dark skin might then have developed in Africa as an adaptation later. Not saying that is what happened, just saying it's just as likely. (BTW Polar bears have dark skin.)71.236.26.74 (talk) 10:14, 10 July 2009 (UTC)

If the humans that left Africa remained very hairy, that hypothesis would involve widely dispersed populations all evolving from being very hairy to having little hair. It makes more sense to assume that the evolutionary loss of hair occurred while all or at least most humans were in reasonably close genetic contact. Otherwise, it seems likely that there would be some humans in some isolated parts of the world that retained the thick, chimp-like hair. Red Act (talk) 11:05, 10 July 2009 (UTC)

SeeRobin Williams. Googlemeister (talk) 13:17, 10 July 2009 (UTC)

The Ainus of northern Japan are very hairy.76.21.37.87 (talk) 05:24, 11 July 2009 (UTC)

The plural "ainu" used as a collective noun is acceptable.83.100.250.79 (talk) 15:42, 12 July 2009 (UTC)

Then, we have to make assumptions about how the non-hairy humans got to Africa to start the "out-of-Africa" process. What if they were originally from South America, became ocean creatures, lost much of their hair (as the ocean mammals tend to do), and popped out of the Ocean in Africa? Then, they could have been rather gray at first and turned black. The problem is identifying the first "human". -- kainaw™ 11:11, 10 July 2009 (UTC)

According to the Recent African origin of modern humans article, “According to both genetic and fossil evidence, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 100,000 years ago ... The recent single origin of modern humans in East Africa is currently the near consensus position held within the scientific community.” I’m just going with the scientific consensus about human origins. Red Act (talk) 11:25, 10 July 2009 (UTC)

I'm not challenging that, however your comment above would rule out any further development of "anatomically modern humans" after the out of Africa movement. The fact there are no pockets of all hairy populations is not conclusive proof. Parallel development is not unheard of in humans [8]. There are people with Hypertrichosis, but that condition is poorly understood. I don't think the exact conditions for humans to have less hair is not yet conclusively known. (There are indications for genetic causes, but environmental factors are also being considered [9].) If the genetic or environmental condition that caused less hairiness were encountered equally by all human populations in their development, there is no need for it to have occurred before the split. "May have happened" is not equal to "must have happened" even if the latter fits nicely with one's assumptions. 71.236.26.74 (talk) 12:26, 10 July 2009 (UTC)

Dude, did you even glance at the second reference in your post ([10])? It’s about root hair, a feature of a plant’s roots, and has nothing whatsoever to do with when, where or why our ancient ancestors lost most of their body hair. Red Act (talk) 14:01, 10 July 2009 (UTC)

Oops, late night and too little time to dig up references, sorry. 71.236.26.74 (talk) 14:55, 13 July 2009 (UTC)

Homo sapiens has nothing to do with it. Homo lost its body hair long before that, before 1 million years ago. The "ocean creature" scenario is in fact a respectable theory, known as the aquatic ape hypothesis --dab (𒁳) 13:39, 10 July 2009 (UTC)

That is a point I was intending to make... If you say "homo sapien", you have a rather precise point of evolutionary development. If you say "human", it is very fuzzy. At what point along evolution do you consider the animal to be a "human"? Then, there is the issue that none of the skin of those pre-homo-sapien creatures is around to take a gander at. So, we can only consider other mammals that have had almost no adaptation since pre-human times, such as the hedgehog. A common hedgehog's skin is greyish-pink, but the Algerian hedgehog is almost black. Again, we have to work out which came first, the pink hedgehog or the black hedgehog. So, I don't see any means of answering this question with the knowledge available today. -- kainaw™ 14:09, 10 July 2009 (UTC)

Note that my exact original statement above was “…homo sapiens presumably originally had dark skin…”. “Homo sapiens” and “originally” pins the time I was talking about down to about 200,000 years ago, at which point, according to the most widely accepted theory, all our ancestors had little hair, and were living in Africa. However, the original question is completely vague about what evolutionary time scale is to be considered.

Hedgehog skin is a rather meaningless comparison, since hedgehogs are covered in spines. The environmental factor that appears to determine human skin color in a population is how much exposure the skin gets to UV. Human skin doesn’t have the UV protection afforded by spines. Red Act (talk) 14:39, 10 July 2009 (UTC)

The questioner did not ask about "homo sapiens". The questioner asked about "skin color". An answer limited only to homo sapiens is barely a partial answer. Which came first, light skin or dark skin? -- kainaw™ 20:49, 10 July 2009 (UTC)

That is true. The question exactly as asked isn’t really answerable. Red Act (talk) 23:32, 10 July 2009 (UTC)

In most animals, dark skin is a result of chromatophores; usually neural crest derived melanophores or melanocytes invading the epidermal or dermal layers after they have already formed. Without this process the skin is functional, but light (consider, for example, albinos). Light skin therefore precedes dark skin in ontogeny; if one considers the most parsimonious method of how skin tone evolved, it is most likely that light skin will have preceded dark skin evolutionarily too. Of course, this will all have happened long before humans arrived on the scene. Rockpocket 00:17, 11 July 2009 (UTC)

NH4CL

when ammonium chloride sublimes, it forms nitric acid and hydroclhoric acid. i wanted to ask if this reaction is physical or chemical. cos, this reaction is reversible (in wiki, it's written - "Ammonium chloride sublimes readily but this process involves dissociation into ammonia and hydrochloric acid followed by reforming of the compound." but i know perfectly well that this reaction is also chemical, as it involves chemical changes, and not simple physical changes. please help me! (PHYSICAL OR CHEMICAL?????) thanx!!!!!!! —Preceding unsigned comment added by 122.50.134.64 (talk) 13:10, 9 July 2009 (UTC)

When ammonium chloride sublimes, it does NOT form nitric acid and hydrochloric acid. It forms ammonia and hydrochloric acid. Also, it should be noted that all chemical changes are also physical changes; it is impossible for a chemcial reaction to happen which does also not change some physical property of the materials. When one says "physical change" they are implying only a physical change; that is one in which the shape, size, or state of matter of a substance is changed without making a change to the composition of the substance. So the answer here is that this is clearly a chemical change, since the change results in different chemicals being formed after the change than before. Physical changes would involve such simple things as smashing the ammonium chloride into little bits or dissolving it in water. --Jayron32.talk.contribs 13:15, 9 July 2009 (UTC)

Isn't the whole division of changes into physical and chemical somewhat artificial?

We say melting is a physical, not chemical, change, but you are changing the bonding situation going from solid to liquid.

Ben (talk) 19:47, 9 July 2009 (UTC)

It is artificial, but it is something that is common in beginner-level chemistry textbooks. I honestly can't remember the definitions now, but it was simplified to three or four points. —Akrabbim^talk 20:01, 9 July 2009 (UTC)

Like many parts of introductory high-school level classes, a big part of the curriculum is about organizing your thinking rather than just presenting actual facts. The idea behind recognizing "chemical" processes vs. "physical" processes is in the first about learning to categorize things. Secondarily, it is about recognizing what a "chemical" is, and what it means for a chemical reaction to occur. It is not readily apparent to most people that a process like melting is not a chemical process (but it was "ice" before and "water" after? Isn't that two different things??? (Ans: no...) ) or that dissolving salt in water is not a chemical process (but, like, the salt dissappears!) Recognizing what sorts of things can be counted as chemical reactions and which are not requires some training... Which is what this activity is also about. Usually in the first week of high school chemistry, besides learning this, one also learns basic classification schemes of matter, so that one can recognize the difference between, say, a pure substance and a mixture of substances, or between a heterogeneous mixture and a solution. --Jayron32.talk.contribs 20:21, 9 July 2009 (UTC)

Indeed. But you can learn how to categorise things without resorting to concepts that are not really important to real scientists.

I guess you could say chemical changes involve breaking and forming chemical bonds. But there are many processes that are traditionally considered physical which do in fact involve bond fission and formation. For example, water boiling. Intermolecular hydrogen bonds are broken as the liquid turns into gas. It all seems a bit pointless to me.

I imagine it would be perfectly possible to avoid classifying things as physical or chemical changes and just talk about what's actually going on at the molecular scale. Dissolving is one of those processes that falls on the border between chemical and physical: Na⁺···Cl⁻ ionic bonds are broken and ion-water interactions form, energy changes hands (enthalpy change of solution is +3.9 kJ/mol), you can write a chemical equation for the process {NaCl(s) + aq → Na⁺(aq) + Cl⁻(aq)}, and the product (NaCl solution) has very different properties from the starting materials (NaCl(s) and water).

Ben (talk) 21:45, 9 July 2009 (UTC)

It's a bit late at night, so my interpretation is a bit fuzzy, but from what the last two posts above me have said, it seems they're discussing lies to children - which is a good and necessary thing. The link might be useful to either of them, or to anyone interested in what they were saying. Vimescarrot (talk) 22:02, 9 July 2009 (UTC)

Its not really lies; its more of a bridging heuristic. Its not that, several weeks later, we don't teach more details about these things. Its more of a learning to crawl before you walk thing. Yes, some kids can walk right away, but many need the extra help crawling first. They can all get there, but just as you wouldn't teach someone to read Shakespeare before you read Dr. Seuss, generally we teach the simplified stuff first. --Jayron32.talk.contribs 01:25, 10 July 2009 (UTC)

Plasma weapons

We see plasma weapons in movies and games all the time. I didnt understand what plasma was until I played Halo. The plasma pistol and rifle in the game are powered by batteries and when I fired it on a wall it would show a sort of melting of the wall. I suppose the batteries heat up the plasma. What really is plasma and can such weapons be really made? —Preceding unsigned comment added by 116.71.49.65 (talk) 16:17, 9 July 2009 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see plasma weapon. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. --Shantavira|^{feed me} 16:28, 9 July 2009 (UTC)

Weapons in science fiction stories (including games) tend to be based more about looking and sounding good, than any sound scientific principles, so don't expect to see a Type-25 Directed Energy Rifle to look anything like it does in the game, if it's remotely possible to make a weapon on the same principles. Vimescarrot (talk) 18:55, 9 July 2009 (UTC)

In almost every case they grossly underestimate the amount of power needed to make such things do what they do in the game. Sure, you could probably make something that sat on the back of a large truck...with another two large trucks full of batteries to power it...but something you could lug around like a machinegun is really not reasonable. The stored energy for any weapon has to come from somewhere - and there are few sources of energy more 'dense' (in terms of power-to-weight ratio) than explosives. This is the main reason why we don't see people using laser pistols and rail guns out on real battlefields. Game designers (and I'm a games programmer - not a designer) don't care to be limited by the bounds of what is realistic - and that's a good thing in many ways because breaking the shackles of reality is what makes most games fun. SteveBaker (talk) 04:34, 11 July 2009 (UTC)

"Sure, you could probably make something that sat on the back of a large truck...with another two large trucks full of batteries to power it..." -- I think they actually made a plasma cannon that would just barely fit inside a jumbo jet (the plasma generating equipment and the batteries, plus all the fire-control computers and whatnot, took up most of the fuselage). So that would give you some idea of how big a plasma cannon would be in real life.76.21.37.87 (talk) 05:32, 11 July 2009 (UTC)

So perhaps a plasma cannon is a viable weapon for a nuclear powered battleship, but not so much for an individual solider. Googlemeister (talk) 16:39, 13 July 2009 (UTC)

My point exactly. 76.21.37.87 (talk) 00:43, 14 July 2009 (UTC)

On the other hand, would a plasma cannon fitted on a warship be any more useful in battle than the conventional stuff that you usually find on there already - the main guns, large gattling guns, missiles, etc.? --Kurt Shaped Box (talk) 00:53, 14 July 2009 (UTC)

It could be useful for shooting down nuclear missiles... 76.21.37.87 (talk) 01:16, 14 July 2009 (UTC)

Barton's pendulums

Was Barton's Pendulums invented by Arthur W. Barton or his father Edwin H. Barton and does the original experiment apparatus still exist today. Thank you. Clover345 (talk) 16:38, 9 July 2009 (UTC)

The source linked from the article says it was E.H. Barton. 71.236.26.74 (talk) 16:48, 9 July 2009 (UTC)

The apparatus being a very simple one, but not very manoeuvrable, it was almost certainly dismantled soon after the experiment.--Shantavira|^{feed me} 07:25, 10 July 2009 (UTC)

Freeview (UK) - software updates?

Does Freeview transmit software updates for TVs? I know it sounds unlikely, but I swear my TV (which has an integrated freeview receiver) announced a couple of days ago that a software update was available & did I want to install it. So. Unlikely as it sounds, does Freeview transmit software updates for TVs? --Tagishsimon (talk) 22:06, 9 July 2009 (UTC)

You'll have better odds of getting an answer at the Computing Reference Desk. Looie496 (talk) 22:53, 9 July 2009 (UTC)

Good point. I'd forgotten we had such a thing. Question now removed. --Tagishsimon (talk) 22:57, 9 July 2009 (UTC)

Milky Way colliding with another galaxy

From a human on earth perspective, what would it be like to witness a galaxy colliding with ours? --Reticuli88 (talk) 22:40, 9 July 2009 (UTC)

Well, for one thing, on human time scales, the collision of the galaxies wouldn’t be an event to observe, so much as a very long process, of which only a small portion would be visible within one lifetime. The milky way galaxy has a diameter of 100,000 light-years, and the colliding galaxy would be approaching at sub-light speeds, so the collision process would take perhaps a million years. Red Act (talk) 23:19, 9 July 2009 (UTC)

For one thing, the band of light which is the Milky Way would appear much different, depending on the other galaxy's angle of approach. Red Act is right, though, in saying that we probably wouldn't see much of anything in terms of dynamic movement or astronomical events; the likelihood of even one star colliding with another during this process is minimal. Perhaps the supermassive black hole at the galaxy's center would be a bit more active due to an increase in infalling matter, but that would only be of interest to astronomers. -RunningOnBrains^{(talk page)} 23:27, 9 July 2009 (UTC)

Many earthlings don't see the Milky Way much anyway. Algebraist 23:34, 9 July 2009 (UTC)

I remember reading somewhere that when M31 and the Milky Way collide, out of the ~250 billion stars in both galaxies combined, no more than five actual stellar collisions are expected to occur. That's like 2 * 10^-9 percent of the stars. J.delanoy^gabs_adds 23:51, 9 July 2009 (UTC)

This is correct. When galaxies collide, essentially none of the stars actually run into each other. But the gas does, causing a massive starburst, which means lots of bright blue stars and spectacular emission nebulae. Plus a whole load of supernovae going off. Of course, the time scale for this sort of thing is on the tens of millions of years. On a rather smaller scale, the Large Magellanic Cloud is currently running into the Milky Way, only one galaxy (the MW) is much more massive than the other (the LMC). If you go to the southern hemisphere, you can easily see the LMC with the naked eye from a dark site - it's much bigger than the full moon and looks like a detached bit of the Milky Way. And you can see the SMC too. Modest Genius ^talk 03:06, 10 July 2009 (UTC)

That's amazing considering that, from photos of galaxies, they look so dense. thanks.--Reticuli88 (talk) 16:19, 10 July 2009 (UTC)

They look dense because the instrument taking the photo doesn't have the resolving power to show just how small stars are compared to galaxies. For that matter, your screen doesn't have pixels small enough for that either. Algebraist 16:21, 10 July 2009 (UTC)

Bear in mind that the ratio between the distance to the nearest star to the diameter of the sun is about 30 million to one. there's a lot of empty space. Modest Genius ^talk 23:08, 10 July 2009 (UTC)

July 10

SAT identification

Yesterday (July 8) at around 11:17 local time I saw two satellites, separated by about a degree, pass by Cassiopeia. They were initially both of magnitude 2-3, but dimmed as they climbed higher into the sky. Does anyone know what these satellites are, and why they have nearly the same orbit? I live in Toronto. Before you suggest one of the them was the ISS and the other was a spacecraft trying to dock with it, that can't be it because I saw the ISS pass by several minutes later. Interestingly, a search on Heavens Above turned up nothing. --Bowlhover (talk) 00:11, 10 July 2009 (UTC)

It seems likely one of them was Cosmos 1602, it went through Cassiopeia at about that time [11]. I don't have any ideas about the other. anonymous6494 16:29, 10 July 2009 (UTC)

Amytriptyline

Is this the kind of drug for which users develop a tolerance, requiring higher doses to achieve the desired effect? If so, does the fatal dose also increase as tolerance goes up?

This is not a request for medical advice, this is part of my research in writing a work of fiction based on the life of Nick Drake, who died from an overdose of this drug. -GTBacchus^(talk) 01:22, 10 July 2009 (UTC)

In short, yes. In this study, tolerance to the effects of amitriptyline built up differentially over measures of sedation, psychomotor function and memory. See also [12]. - Nunh-huh 02:50, 10 July 2009 (UTC)

The word "tolerance" may be a bit misleading when it comes to antidepressants. A great deal of research shows that it usually takes a couple of weeks before the mood-altering effect kicks in; however other effects such as sleep alterations kick in immediately. This is often taken to mean that some sort of tolerance-like effect in the brain plays an essential role in the function of the drug. It's generally not the case, as I understand it, that people taking antidepressants need to take steadily increasing doses to get a constant result. Looie496 (talk) 03:16, 10 July 2009 (UTC)

Thank you both. That's very helpful. -GTBacchus^(talk) 03:19, 10 July 2009 (UTC)

OR Speaking as a long-term amitriptyline user, it's not the case that I have had to increase the dosage over the years to get the same effect, so no tolerance has been developed. However, I'm now trying to stop taking it and am having to slowly decrease the dose to nothing: so far it's taken 3 months and I'm on course to be off it in another month's time. This is because of the physical side-effects of stopping taking the drug, which include the possibility of heart arrhythmia (or so I understand). You could say I'm addicted to it, under some definitions of addiction. --TammyMoet (talk) 08:51, 10 July 2009 (UTC)(Edit) The only tolerance I had to build up was tolerance of the effects of the drug, in other words, adjusting to the change in sleep patterns the drug brought.--TammyMoet (talk) 08:53, 10 July 2009 (UTC)

Coriolis force

Suppose a mass m is moving radially from the centre of a moving carousel. There has to be a tangential force in order to keep it moving in a straight line, and my question is what is this force. One way I would do it is to find the angular momentum, differentiate it to find torque, and divide by r to get the force. This gives me 2mw*v_rad. Doing something similar with momentum though, I get half that value (p=mwr, F = dp/dt = mw*v_rad). What did I do wrong? —Preceding unsigned comment added by 70.82.247.24 (talk) 03:23, 10 July 2009 (UTC)

Momentum and velocity are both vectors. So

${\boldsymbol {p}}=m{\boldsymbol {v}}=m(v_{r}{\boldsymbol {e}}_{r}+r\omega {\boldsymbol {e}}_{\theta })$

where $v_{r}{\boldsymbol {e}}_{r}$ is the particle's radial velocity and $r\omega {\boldsymbol {e}}_{\theta }$ is its tangential velocity. So

${\boldsymbol {F}}={\dot {\boldsymbol {p}}}=m{\dot {\boldsymbol {v}}}=m(v_{r}{\dot {\boldsymbol {e}}}_{r}+v_{r}\omega {\boldsymbol {e}}_{\theta }+r\omega {\dot {\boldsymbol {e}}}_{\theta })$

where I have assumed that v_r and ω are constant. Now

${\dot {\boldsymbol {e}}}_{r}=\omega {\boldsymbol {e}}_{\theta }$

${\dot {\boldsymbol {e}}}_{\theta }=-\omega {\boldsymbol {e}}_{r}$

so

${\boldsymbol {F}}=m(v_{r}\omega {\boldsymbol {e}}_{\theta }+v_{r}\omega {\boldsymbol {e}}_{\theta }-r{\omega }^{2}{\boldsymbol {e}}_{r})=2mv_{r}\omega {\boldsymbol {e}}_{\theta }-mr{\omega }^{2}{\boldsymbol {e}}_{r}$

The first term is the Coriolis force; the second term is the centripetal force. Gandalf61 (talk) 11:54, 10 July 2009 (UTC)

dino to bird query

This page http://creation.com/bird-breathing-anatomy-breaks-dino-to-bird-dogma challenges the dino evolving into birds theory. I am wondering about the accuracy of the science behind the author's arguements. Please: no creationism vs. evolution debates. —Preceding unsigned comment added by 216.154.22.92 (talk) 04:09, 10 July 2009 (UTC)

It's the same tired arguement that has been going around for years and years. The basic principle is that of "intermediate forms". In order to say that Animal X evolved into Animal Y, there needs to be a "smooth transition" between the two; new structures or forms don't just spring out of no where, the change gradually over time. That's a cornerstone of evolution. So, the creationist side of the debate (which is what creation.com is all about, n'est ce pas?) finds some evolutionary gap in the fossil record, and hammers it home as PROOF that evolution does not happen. First it was the flagellum in single-celled organisms, then it was the eye, now it appears they have latched on to bird lungs. The deal is, finding a SINGLE example which has not yet been adequately explained does not in any way invalidate the entire system.

Look at it this way: Imagine a brick road, with billions of bricks, stretching from Los Angeles to New York. Now, imagine that there are some bricks missing. Like, once every ten or twenty miles, there's a missing brick. Now, imagine saying "I cannot get from LA to New York because there's a brick on this road that is missing. It is impossible to drive that long distance given that the road is not complete." That is exactly what this guy is saying. There are literally millions of pieces of evidence, which DO neatly connect the extinct forms to modern forms via evolution. The deal is, that sometimes there's a bit, like these bird lungs, which has not been discovered yet, or adequately explained yet. Just like the flagellum before it, someone will eventually come along to connect the dots. --Jayron32.talk.contribs 04:19, 10 July 2009 (UTC)

Ignoring the creationist aspect, all reputable paleontologists believe that birds evolved from some type of reptile, but there is a small minority, including the ones interviewed for that program, who think that the reptiles in question were not dinosaurs. Most paleontologists feel that the dinosaur origin is supported beyond reasonable doubt by the existing evidence. Looie496 (talk) 04:43, 10 July 2009 (UTC)

Possibly a better analogy: In the Sahara a dune shifts, revealing a piece of Roman road. Over time more such pieces are revealed, near the line between Carthage and, let's say, Old Ghana. Scoffers object to the inference that there was a continuous road .... But the analogy is flawed, in that road-building is teleological (so we know that continuous roads between inhabited places are more likely than random patches of road) and evolution isn't. —Tamfang (talk) 17:42, 21 July 2009 (UTC)

It you're going to ask a question based on an overtly creationist website report - on a reference desk that's dedicated to giving proper, scientific answers - you cannot reasonably demand that no creationism-versus-evolution discussion will be required. As Jayron32 so eloquently points out - the absence of one tiny step in the path doesn't destroy the argument that birds evolved from dinosaurs. Absences are only to be expected in a science where we mostly rely on chance findings of bazillion year old animals that were frozen in carbonite or something - mostly out in the middle of a few hundred miles of rocky desert in outer mongolia. For there to be a solid consensus that birds did NOT in fact evolve from dinosaurs, there would have to be a piece of contradictory proof that they evolved from something else. Efforts to use these small gaps to somehow "prove" that evolution isn't true are simply not going to convince the vast majority of people in the world. Frankly, the more interesting questions are:

• Did birds evolve directly from Dinosaurs? If so, which family?
• Did birds and dinosaurs evolve independently from a common ancestor? If so, which ancestor?
• Did dinosaurs evolve from birds? (This is a radical viewpoint that is probably pretty much disproved now - but was around when it was first speculated that birds are descended from dinosaurs...the theories were called "Birds are dinosaurs" and "Dinosaurs are birds" - and proponents of the latter liked to use the initial letters to indicate that Birds Are Dinosaurs is a "BAD theory").

"None of the above" does not seem to be a viable theory.

SteveBaker (talk) 14:49, 10 July 2009 (UTC)

These god in the gaps clowns are shooting themselves in the foot when they claim that a missing link disproves evolution, because every time scientists find one, they have to retreat to an even narrower intellectual precipice. --Sean 13:52, 13 July 2009 (UTC)

Every time you find a Missing Link, you create two gaps where there had been only one! —Tamfang (talk) 17:30, 21 July 2009 (UTC)

cauterize instead of suture

can you cauterize instead of suture —Preceding unsigned comment added by 74.65.3.30 (talk) 05:54, 10 July 2009 (UTC)

If you're really tough, and I mean Rambo tough, sure you can, but don't take that as medical advice. Just advice from someone who's been places and seen things (or been at home and seen some bad movies). See cauterization. Incidentally, these two consecutive questions, coming from the same poster and taken together, paint a very frightening picture. See a doctor, they won't judge you.--Rallette (talk) 06:56, 10 July 2009 (UTC)

Since silver nitrate is a cauterizing agent, and was historically used to treat gonorrhea, I’m thinking the connection between the two questions is that the poster’s been doing some reading about silver nitrate, not that the poster is contemplating doing surgery on himself. Red Act (talk) 07:20, 10 July 2009 (UTC)

Damn, and I was so enjoying imagining him treating his ear gonnorrhea by cauterizing it. ~ mazca ^talk 08:04, 10 July 2009 (UTC)

It really depends on the context. One of the big differences between cauterization and suturing is what ultimately happens to the patient's SKIN. A cauterized wound will form scar tissue, which shrinks and tightens around the area. If this is a large area, it will likely be extremely uncomfortable and may even require a graft. Cauterization is generally prefered for smaller jobs. Suturing, on the other hand, brings existing regions of skin together, so the resulting scar tissue is much less. Of course, there needs to be skin available for this to even be an option. There are other factors involved, this is just one consideration. It really depends what the injury is you're talking about. --Shaggorama (talk) 14:23, 10 July 2009 (UTC)

the clap

how did they treat the clap before antibiotics —Preceding unsigned comment added by 74.65.3.30 (talk) 05:58, 10 July 2009 (UTC)

Historically, silver nitrate was used, and according to some, mercury. See Gonorrhea#Historically. Red Act (talk) 06:19, 10 July 2009 (UTC)

I thought that mercury (in the form of calomel) was used to treat syphilis, not gonorrhea... 76.21.37.87 (talk) 09:00, 10 July 2009 (UTC)

Besides syphilis and gonorrhea, mercury was used to treat ailments as diverse as depression, tuberculosis, toothaches, and constipation.[13] There were essentially no legal restrictions on claims of medical effectiveness back then, so a lot of drugs were touted as curing practically everything. Red Act (talk) 09:37, 10 July 2009 (UTC)

"A night in the arms of Venus leads to a lifetime with Mercury." Matt Deres (talk) 17:25, 11 July 2009 (UTC)

Ear infection

how did they treat Ear infection before antibiotics —Preceding unsigned comment added by 74.65.3.30 (talk) 07:16, 10 July 2009 (UTC)

Are you aware of our "search" function, over on the left there? You could type things like ear infection and click Go, and you'll get a whole article on it. I did so just now, and found that in the page regarding middle ear infections, it sounds like they had to wait until it got severe and then performed a myringotomy. Tempshill (talk) 07:21, 10 July 2009 (UTC)

Uh, yeah, silver nitrate is an antiseptic, so they presumably sometimes used it to treat otitis externa, too. Red Act (talk) 07:33, 10 July 2009 (UTC)

Just in case you’ve been reading some stuff about the medical wonders of silver, note that while all sorts of claims are being made about the use of colloidal silver as an alternative medical treatment, there are no evidence-based medical uses for ingested colloidal silver. Furthermore, excessive consumption of colloidal silver can make your skin turn bluish-gray, and may hamper the effectiveness of some drugs which actually do work, such as tetracycline. Red Act (talk) 08:09, 10 July 2009 (UTC)

There are various folk remedies for earache, one of which involves baking an onion until soft, then removing the core and inserting it into the affected ear. The heat will disperse the gunge, while onions are known to have antiseptic properties. --TammyMoet (talk) 08:46, 10 July 2009 (UTC)

I've recently read that the outcome for ear infections with or without antibiotics treatment does not differ significantly. You can treat them with anti-inflammatory drugs, like Aspirin, and there are any number of folk remedies involving onions and potatoes. --Stephan Schulz (talk) 09:08, 10 July 2009 (UTC)

In recent years there have been a number of studies showing that "watchful waiting" is a reasonable course of action in uncomplicated acute otitis media in a healthy child. See this [14] for an example. There are many others. Of course, there are rare complications in which the ear infection proceeds to cause mastoiditis or meningitis. So, one needs to weigh the costs and benefits of the treatment. It is argued that since most cases of acute otitis media will resolve on their own (that's what the immune system is for, after all) and since antibiotic therapy is associated with increased antibiotic resistance among the organisms we are trying to treat, we should not immediately give antibiotics every time a child gets an ear infection. Even without immediate antibiotic therapy, the child needs to be re-evaluated within 48 hours or so to make sure that the infection isn't getting worse. Of course, the management decision is a very complicated equation -- how sick is the child? how old is the child? how reliable are the parents? how good will be the follow-up? These are questions the doctor should be asking every time he/she decides whether or not to prescribe antibiotics. And as always, the question continues to be debated. But this is certainly not "dubious". --- Medical geneticist (talk) 11:52, 10 July 2009 (UTC)

Thanks for the ref. I put in the templates as a mild joke and a reminder that stuff someone recalled from somewhere is not always the best source - even if someone is me ;-) --Stephan Schulz (talk) 12:17, 10 July 2009 (UTC)

Onion juice dripped into the ear is still used for persistent ear infections. It works as an Anti-inflammatory the compound identified was Quercetin. Onion contains thiosulphinate (no page?!) that works as an antibacterial and antifungal agent [15]. Thyme has Antiseptic properties. So, no they didn't have to wait, some herbal remedies actually are effective without employing products of the pharmaceutical industry (who are quite good at extracting some substances and selling their products at a price several orders of magnitude higher than the origin).71.236.26.74 (talk) 09:57, 10 July 2009 (UTC)

I assume you are looking for thiosulfate. --Jayron32.talk.contribs 12:28, 10 July 2009 (UTC)

Thought so at first, but there seems to be some difference. Maybe you could check this [16] and see what it's about.71.236.26.74 (talk) 15:11, 10 July 2009 (UTC)

This page shows the structures for both thiosulfate and thiosulfinate. Note that thiosulfate is a specific compound, and the thiosulfinates are a whole class of compounds. Red Act (talk) 15:33, 10 July 2009 (UTC)

Taking this question with the preceding one, wonder if someone's been having unprotected aural sex? DMacks (talk) 16:43, 10 July 2009 (UTC)

Pardon? 87.81.230.195 (talk) 22:28, 10 July 2009 (UTC)

The clap + ear infection = what HAVE you been putting in your EAR? --Jayron32.talk.contribs 22:39, 10 July 2009 (UTC)

Brain Freeze

Hello, my name is corey. I had a question about your definition of a Brain freeze. Now, while i admit your explaination is correct, i also wondered this- would not the "Brain Freeze" in fact be your brain overheating? Because i read an article in a magazine some years back that stated your heart and body forces too much blood to your head which in fact causes it to overheat. The explaination you have refers to the pain suffered from your constricting arteries in the roof of your mouth, but it confuses me. If i wrap something around my arm tightly for ten to twenty seconds, the veins and arteries swell. When i remove it, there is very little pain that comes. If the pain associated with brain freeze comes with shrinking blood vessels why is there no pain when they are swollen? Also, during a brain freeze, one can place theyre hands on the sides of thier neck to relieve the pain- how could this be if the pain is directly stemming from the roof of your mouth?

Sorry, i guess i kinda asked several questions there.

Basically my question i was wondering about is this-

During a brain freeze, does your body push more blood to the area to compensate, thereby causing brain overheating, or is the pain only caused by your blood vessels regrowing to normal size? —Preceding unsigned comment added by 75.164.152.179 (talk) 08:32, 10 July 2009 (UTC)

In no way am I an expert, but while you wait for a better response, here is my best attempt at answering the question:

There are 2 main theories on the origin of pain, one theory holds that the pain is simply caused by the rapid dilation of the blood vessels of the palate and pain is transferred to the brain via the trigeminal nerve. While the other theory states that the body overreacts to this cold stimulus and pushes more blood to the brain trying to heat it. This alters the follow of the blood in the brain and causes this familiar brief headache. Personally, I am more inclined to believe the latter theory.

Cheers!

Λuα ^{(Operibus anteire)} 10:49, 10 July 2009 (UTC)

I thought blood vessels contracted in the cold, so wouldn't it be rapid contraction, not rapid dilation of blood vessels? Regards, --—Cyclonenim | Chat  18:03, 10 July 2009 (UTC)

True, but the pain is not usually attributed to vasoconstriction, but to the rapid dilation that follows.

Actually, this question is quite interesting and one which can be to a certain point investigated at home. If the first theory is right, then keeping the cold substance in contact with the roof of the mouth shouldn't cause a brain freeze. On the other hand, if a brain freeze is experienced with the cold substance still in contact, then the second theory is right. In either case, the cold material used should not be allowed to reach body temperature or the results will be invalid.

This is in no way encouraging anyone to try this at home. Don't sue me should permanent damage happen.

Do not try this at home...No, really, don't!

Cheers!

Λuα ^{(Operibus anteire)} 20:01, 10 July 2009 (UTC)

Tried it with an ice lolly, got brain freeze whilst still in contact with the ice. Regards, --—Cyclonenim | Chat  20:29, 10 July 2009 (UTC)

You know, im inclined to believe both theories. Ive tested both, and they both seem to have substance. I still don't quite understand it- if both instances are right, do we include both theories in our definition of "Brain Freeze" here on wiki, or do we just shrug off my suggestion that i first posted as merely a possible theory and not a literal possibility? sorry- i'm too inquisitive for my own good :p

For those wondering, i just registered here a few days ago, and im the one who posted this question in the first place. —Preceding unsigned comment added by Blaze113 (talk • contribs) 09:07, 11 July 2009 (UTC)

Unfortunately it constitutes original research if we just stick it in an article here. We need to find a reliable source before we can put it in. Regards, --—Cyclonenim | Chat  09:46, 11 July 2009 (UTC)

Ah, very true. Forgot that little bit there... oh well. I'll keep hunting and researching, see what others have to say about it. If anyone gets more info, please, feel free to place it in here. —Preceding unsigned comment added by Blaze113 (talk • contribs) 09:55, 11 July 2009 (UTC)

Both mechanisms could be at work, but until someone proves it conclusively, we will never know.

Not that big of a deal though.

Cheers!

Λuα ^{(Operibus anteire)} 13:07, 11 July 2009 (UTC)

Zigzag pattern on railway tracks

I was in Newcastle railway station this weekend. Sitting waiting for my train to leave, I noticed the tracks on the adjacent line showed an unusual zigzag pattern. I took a photo (it's rather poor mobile-phone quality) which is here. Can anyone explain what these patterns are?

My thoughts are:

1. it's an artifact of manufacturing, but the tracks really don't look new
2. it's an artifact of some rail-surface reconditioning machine, but why would it leave this pattern
3. it's been added to enhance friction (to help trains brake), but why this pattern?
4. it's caused by the action of train wheels - but it seems much too regular and well defined, and this is a terminal platform where trains are moving slowly and braking very gently

Because I noticed it only once I'd sat in my train, I don't know if other tracks have this pattern, or if this pattern is visible for more than the 20ft or so section I could see. I can't see anything relevant in the rail tracks or the like. 87.113.26.43 (talk) 11:30, 10 July 2009 (UTC)

I should note, incidentally, that I don't think the pattern is sinusoidal, I really think it is triangle wave with rounded corners. A sinusoidal form might suggest some kind of cleaning or reconditioning machine which moves a helical element down the track, but this doesn't look to be the case for this track. 87.113.26.43 (talk) 11:35, 10 July 2009 (UTC)

The irregularity of the marking pattern suggests that it has been applied manually. My first guess is that it was drawn by a maintenance worker to identify rail(s) due for replacement or realignment. My second guess is that it marks a stopping point for train drivers to see. Cuddlyable3 (talk) 11:59, 10 July 2009 (UTC)

I was going to say that I thought it was too regular to be manually applied (at a large scale); at a smaller scale I'd say it had been applied by an angle grinder or some machine with similar function, which makes for a rather rough line. Clever though it is, I don't think your "stopping point" theory is correct - for terminal lines the buffers should be sufficient for that, and for through lines (which this isn't) there are signs which mean "if you're a six car train, stop here". 87.113.26.43 (talk) 12:08, 10 July 2009 (UTC)

Speaking of stopping, might this be a pattern that facilitates stopping the train if the rails are covered in ice or snow? I seem to recall that last winter British Rail had some stopped services because of ice and snow.71.236.26.74 (talk) 12:35, 10 July 2009 (UTC)

This section is well inside the canopy of the station, at least 100m from anywhere snow could land. Ice could form, but only from condensation (so not much). It's my understanding that snow-and-ice affects british railways mostly due to points getting frozen. 87.113.26.43 (talk) 12:43, 10 July 2009 (UTC)

Is that actually etched into the track? In the photo, it looks like chalk markings. They mark tracks to be repaired with chalk here (U.S.). My son loves railroads and we got to walk along the tracks recently when the local railroad was being marked for repairs. -- kainaw™ 12:49, 10 July 2009 (UTC)

To me that looks deliberately applied for some reason. I can't think of any reason. Maybe the local kids having input to their surroundings? It also might be a reflection of the overhead structure, having no material presence on the tracks at all. Bus stop (talk) 12:51, 10 July 2009 (UTC)

It's a rubbish photo: yes, it's definitely etched into the track somehow (I'd say with some kind of grinding tool or wire brush deivce), but only to a very shallow degree (maybe "polished" would be more accurate than "etched"), which is why I don't think it'd be of much help for traction. If it was marking, as you and Cuddlyable3 have suggested, it seems unlikely they'd go to such trouble (surely a chalk mark on the side of the rail would do), and surely track is replaced by removing and replacing a whole length, rather than just a bad section. of a given length. I'm confident it does have some utilitarian purpose, as Network Rail certainly aren't given to fripperies like decorative rail etching. 87.113.26.43 (talk) 12:58, 10 July 2009 (UTC)

It might be put in at the factory as a wear marker - either to indicate that the rails have worn out or that they've been broken (?) in (more likely, given the shallowness of the markings). --Stephan Schulz (talk) 13:08, 10 July 2009 (UTC)

My mistake -- it really does exist. (Enlarge photo to see it better.) I also found this picture which might shed some light on it. This could also possibly explain how those marks got there. Bus stop (talk) 13:11, 10 July 2009 (UTC)

Thanks, I'm very impressed that you found such a clear photo. Note that the track in Bus stop's photo is a through-platform, carrying intercity traffic, rather than a terminal backwater platform. 87.113.26.43 (talk) 13:45, 10 July 2009 (UTC)

Could it serve a similiar purpose as a rumble strip? Livewireo (talk) 14:08, 10 July 2009 (UTC)

They're rumble strip welds, used improve electrical contact between rail and wheel (for track management, not power). See [17] Paragraph 17. Bazza (talk) 14:34, 10 July 2009 (UTC)

Fantastic, well done and thanks a lot; the photos in that report look exactly like those in the station. This is just the kind of thing that there should be a wikipedia article about; but I can't seem to find any further information under that name (perhaps they're also called something else). 87.113.26.43 (talk) 15:29, 10 July 2009 (UTC)

It is done by grinding, it is done intentionally [18] and the book one can not access here [19] says that it's done to avoid exchanging rails which have a rolling contact surface that is still o.k. 71.236.26.74 (talk) 15:06, 10 July 2009 (UTC)

No - the marks in the OP's photo are not done by grinding. They have been welded on, as I explained above. Bazza (talk) 15:23, 10 July 2009 (UTC)

Your post came in while I was digging up references and my ISP offers "high speed" by cashing pages and only reloading once in a blue moon. The wikipedia software then sorted the timeline correctly, but made it look as though I was contradicting you. No such intent, your source looks like that's what OP encountered. 71.236.26.74 (talk) 15:04, 13 July 2009 (UTC)

Wow -- that is it. It is used on stretches of track that do not receive sufficient or fast enough traffic to keep the surfaces clean of oxidation or other detritus. This is to increase electrical conductivity between the wheels and the track, and this in turn is to enable detection of the train in its "berth" in the station. Bus stop (talk) 15:33, 10 July 2009 (UTC)

This is mentioned at Track_circuit#Railhead_contamination, if someone can supply a picture that would no doubt be a good addition.83.100.250.79 (talk) 15:56, 12 July 2009 (UTC)

distance between plants

From a guide I got that to plant carrots you need a distance between 25 and 30 cm. What would happen if the distance is greater than 30 cm? I suppose that a shorter distance means that the planst will compete with each other, but what speaks against the other case?--Quest09 (talk) 15:47, 10 July 2009 (UTC)

If you plant your carrots further apart than necessary, than you get less carrots than you could be getting. I expect (but do not know) that that's all there is to it. Algebraist 15:50, 10 July 2009 (UTC)

Plant distances given are a minimum. If you want to plant your carrots 500' apart, it will not bother the carrots, but will make for a lot more time spent walking between your carrot plants then a shorter distance. Googlemeister (talk) 15:56, 10 July 2009 (UTC)

It is assumed that maximum carrot per unit of growing soil is the aim of all farmers. Bus stop (talk) 16:04, 10 July 2009 (UTC)

I assume you are talking about the spacing between rows of carrots. The spacing between plants is only a couple of inches (few centimeters). Rmhermen (talk) 01:57, 11 July 2009 (UTC)

Why is the temporal bone classified as irregular?

Hi everyone I noticed that most of the bones that encase the human brain such as the parietal, frontal and occiptal bones are all classified as flat bones whereas the temporal bone is not. I've had a look at the article on the temporal bone but it doesn't say why it is classified as an irregular bone whist the other bones that make up the skull are flat bones. Can anyone offer me an explanation or point me in the direction of some info? Cheers RichYPE (talk) 16:26, 10 July 2009 (UTC)

Have you read irregular bone? It gives a definition of what is required for a bone to be classed as irregular. Regards, --—Cyclonenim | Chat  17:14, 10 July 2009 (UTC)

Smoking tea or coffee

Would smoking tea or coffee get the caffeine from these products into your bloodstream efficiently enough to be comparable to drinking it? I would think that it would be a quicker way, but I am not sure if the caffeine actually makes it through the burning process or converts into something else. —Preceding unsigned comment added by Frogmaster3950 (talk • contribs) 16:27, 10 July 2009 (UTC)

Coffee grounds do not burn readily, so you would have to mix them with large quantities of additives. Tobacco is usually soaked in a little butane to help it light; these additives are major contributors to the "unhealthy side effects". The amount of extra additive needed to burn coffee grounds would probably result in an extremely unhealthy concoction. As far as smoking tea, it can be done, but it is generally not regarded as a pleasant aroma (and this is considering that it is compared to smoked tobacco....) Nimur (talk) 16:48, 10 July 2009 (UTC)

I have actually smoked coffee in a water bong without having any problems with getting it to ignite. My question mainly concerns how readily the caffeine gets from the coffee or tea being burned into your bloodstream.(I have found the smell of both tea and coffee smoke to be no more offensive than tobacco).

You might want to reconsider - haven't you heard of Coffee Worker's Lung? Nimur (talk) 17:05, 10 July 2009 (UTC)

I'm not certain of this, but I was under the assumption that if you inefficiently combust organic material (such as by smoking it), it can release carcinogens, producing a cancer risk. For example, burnt toast has some carcinogens. So whether of not it works/is as effective etc, I suspect this danger would mean it would be a less widespread method than simply drinking it. Regards, --—Cyclonenim | Chat  17:12, 10 July 2009 (UTC)

I am fully aware that inhaling smoke from burning organic material can be carcinogenic. I am not too worried about that because I don't plan on making any kind of habit of smoking either tea or coffee as i enjoy their taste and would just assume to drink them. I am just wondering if anyone knows how readily caffeine is absorbed by inhalation of smoke. —Preceding unsigned comment added by Frogmaster3950 (talk • contribs) 17:30, 10 July 2009 (UTC)

"Smoking Tea", as in the line from Mama Kin, "Sleeping late and smoking tea" is a euphemism for what the kids call "the reefer". See Urban dictionary which has some reference to the use of "tea" to mean "marijuana". this google search makes it clear that smoking actual tea will not get you high at all; except in the case of cutting off oxygen supply. --Jayron32.talk.contribs 18:10, 10 July 2009 (UTC)

I once emptied a Lipton's tea bag and rolled the contents into a cigarette. One puff was enough to explain why tea cigarettes aren't being sold. It was nauseating. B00P (talk) 06:03, 11 July 2009 (UTC)

The only way tea is worth smoking is in a closed pan over just enough heat to keep it smouldering. Slices of salmon or chicken placed over them will cook in the smoke in 15 minutes or so, developing a beautiful golden colour and smokey flavour. The tea leaves should then be discarded. - KoolerStill (talk) 12:05, 12 July 2009 (UTC)

According to Solzhenitsyn's The Gulag Archipelago, inmates in the Soviet forced-labor camps used to smoke tea, not so much to get high, as to cause self-inflicted heart and lung damage so they wouldn't have to work (the idea behind the labor camps was to literally make the poor devils work till they drop dead). FWiW 76.21.37.87 (talk) 02:27, 13 July 2009 (UTC)

Evolution of the anus

Serious question, it seems like the human body has changed a lot since our very early (similar to lungfish) ancestors. The human mouth has specialized teeth, limbs have complex hands and fingers, etc. Why does it seem like the human anus has barely changed at all. Are there any major differences between the human anus and other animals? Has the human anus evolved any particular adaptations over evolutionary history? TheFutureAwaits (talk) 18:02, 10 July 2009 (UTC)

it's one function hasn't changed at all over the many years, so why would it need to evolve? —Preceding unsigned comment added by 82.43.91.128 (talk) 18:23, 10 July 2009 (UTC)

Sure it has, the type of matter that passes through it has changed many times over the eons. Not to mention moving from an aquatic to land based environment. TheFutureAwaits (talk) 18:30, 10 July 2009 (UTC)

Unlike a lot of other higher animals we have evolved voluntary anal sphincter control which, as it turns out, is pretty useful.--Frogmaster3950 (talk) 19:17, 10 July 2009 (UTC)

Citation? TheFutureAwaits (talk) 19:28, 10 July 2009 (UTC)

A lot of other animals don't even have an anus. They have a cloaca, or similar. I think it is only placental mammals that have an anus like we do. --Tango (talk) 19:36, 10 July 2009 (UTC)

As far as differences go, off the top of my head I can't think of any other animal that has to wipe. Dogs, cats, fish, rabbits, etc, even other primates just pinch it off. No or minimal cleanup is needed after the deed is done. Dismas|^(talk) 05:28, 11 July 2009 (UTC)

I imagine that's related to the fact that, whether due to bipedalism or sexual selection or both or something else, human anuses are more 'hidden' between the gluteal muscles (buttocks) than other animals'. Our inconvenient cleanup needs are likely a result of this. Maelin (Talk | Contribs) 05:53, 11 July 2009 (UTC)

No offense guys, but so far all this seems to be is a bunch of commentary. Can no one provide any useful information? TheFutureAwaits (talk) 11:22, 11 July 2009 (UTC)

Honestly, I think the anus has been more or less an anus since well before humans were humans. I doubt the human anus is significantly different from that of any other mammal. It's just a sphincter, and its requirements have been more or less constant throughout mammalian development, hence there have been no significant selection pressures to change it. In fact the only thing I can think of is that humans have developed the need to practise hygiene due to the buttocks being in the way, but the anus itself is, I would expect, largely the same as it's been since early mammalian evolution. Maelin (Talk | Contribs) 11:50, 11 July 2009 (UTC)

Slight correction: When you say "mammal" you actually mean placental mammal. Marsupials and monotremes have different arrangements. --Tango (talk) 16:36, 11 July 2009 (UTC)

Yes indeed, my mistake. Thanks for the clarification :) Maelin (Talk | Contribs) 04:06, 12 July 2009 (UTC)

Dirty Question

No, not THAT kind of dirty, maybe kinda gross would be the better way to describe it.

Without getting unnecessarily graphic, we all know what happens when we corn.

Goes in, comes out, looks exactly the same. Little if any decomposition seems to have taken place.

How, then do our bodies derive any significant form of nutrition from it? 70.25.46.99 (talk) 22:24, 10 July 2009 (UTC)

The exocarp is the part of the corn that you poop out. Its the same bit that gets stuck in your teeth when you eat popcorn. The stuff inside of the kernel, which contains all of the starches and sugars and protein and fats, is easily digestible. That's what you get nutrition out of. --Jayron32.talk.contribs 22:36, 10 July 2009 (UTC)

Thanks Jayron! Finally an end to all those sleepless nights of wondering! :-) —Preceding unsigned comment added by 70.25.46.99 (talk) 22:50, 10 July 2009 (UTC)

Drafting

In cycling, when one biker uses the draft of another to reduce their energy expenditure, does the biker in front expend more energy "pulling" the biker behind? --71.191.104.213 (talk) 22:43, 10 July 2009 (UTC)

Almost certainly not significantly, otherwise there would be no net advantage to being in the peloton. What happens is that the group as a whole is more aerodynamic than a single rider. --Stephan Schulz (talk) 23:11, 10 July 2009 (UTC)

How about just a pair of bikers? Does the one pull the other, or does the one in the rear simply take advantage of an aerodynamic effect that is already occuring behind the first rider? --71.191.104.213 (talk) 23:22, 10 July 2009 (UTC)

It's certainly the case in car racing that when two cars get up really close, they both benefit. The amount of drag on a car is a function of (amongst other things) it's cross-sectional area. When two cars 'tailgate' each other - it's almost like the two of them are glued together into one car that's twice as long. The total cross-sectional area (and hence the drag) is the same for the two cars as it is for just one of them. When a car experiences drag, it's doing two things - firstly it's pushing the air out of the way at the front - but it's also pulling a drop in pressure at the back - and that takes energy too. In the case of our two car convoy - the one in front is paying the price of pushing the air out of the way - but the one behind is paying to pull the air back in behind it. Which of those is the most costly is hard to guess - it probably depends on all sorts of subtle details of the shape of the cars/bikes/whatever. But certainly it ought to be easier for the guy in front as well as as the guy at the back...it's only a matter of how 'fairly' the overall energy savings are split. SteveBaker (talk) 00:09, 11 July 2009 (UTC)

Some species of migratory birds fly m a V formation during migration. Does this produce a moving mass of air that assists all of them? (A single bird leaves turbulence behind that simply goes to waste.) Occasionally a straight line of birds is seen, lined in the direction of flight. Is the V formation more aerodynamically efficient than a straight line? A straight line formation is easier to take up than a V formation, so maybe it is an intermediate formation for intermediate-duration flights. I think I remember reading that from time to time the lead bird in a V formation gives its place to another bird. Is that because the lead bird has the most exhausting job, without other birds ahead of it to assist its flight? Is the 2-dimensional V more efficient aerodynamically than some sort of 3-dimensional formation? Or is it just easier to stay in formation in 2 dimensions? For a short flight, geese take up a disordered 3-dimensional formation - it is not worth the time and trouble to get into a line or line or V formation. Some non-migratory species also fly in disordered 3-dimensional swarms for short flights. Would it be more efficient for a group of cyclists to move in a V formation rather than as a disordered group? (They are necessarily restricted to 2 dimensions.) Some fish also move in disordered 3-dimensional swarms. I think that is partly to confuse predators, especially considering the sudden turns some swarms make. But probably, also, the moving mass of water created by a swarm of fish assists all of them - albeit there is turbulence within the mass of water. - GloWorm

The V formation is indeed highly efficient, but for different reasons. If you look carefully, you will see that in addition to the position, the birds also synchronize their wing beats. This allows the use of the vortices generated by one bird to be used by the next bird. See [20] or [21]. --Stephan Schulz (talk) 16:34, 11 July 2009 (UTC)

That's interesting about synchronized wing beats. But wouldn;t a straight line formation be better for that? It seems that a V formation gives each bird the advantage of only one of its leaders wings. A straight line formation would give the follower the advantage of both the leader's wings. - GlowWorm. —Preceding unsigned comment added by 98.21.109.135 (talk) 16:53, 11 July 2009 (UTC)

The bird situation isn't the same as the 'drafting' situation with cars & bikes - it's about making it easier to generate lift - not to minimise drag. Isn't it the case that (seen from behind) a bird's left wing generates a clockwise vortex and the right wing an anticlockwise one. The bird behind it needs a clockwise vortex under it's right wing and an anticlockwise one under the left...so if they flew in a straight line, there would be no benefit. However if one bird positions it's right wing behind the left wing of the lead bird - and another puts it's left wing behind the lead bird's right - then they both get half of the benefit. This would lead naturally to the V formations we see. Alternatively - (but less likely), it might simply be that each bird desires to see where it's going...I don't think that's it though...I'm going with the clockwise/anticlockwise thing. SteveBaker (talk) 17:52, 11 July 2009 (UTC)

Totally anecdotal: When I've seen geese, etc., in a line, the line has been a "half V"—that is, they aren't flying exactly in the direction of the line, but as though the line were one side of a V with the other side missing. I've also seen formations in which there was only one or two birds behind the leader on one side and many more on the other side. I don't think I've ever seen a formation such as GloWorm describes: "a straight line of birds … lined in the direction of flight." Deor (talk) 02:23, 12 July 2009 (UTC)

Dirty Question II

I know this might come off as a joke, and it sorta...kinda is.

Yet at the same time I'm asking it with genuine curiousity, because I've never been able to get a direct answer for it.

To get into Medical School, you've gotta pretty much work your ass off (pun to be intended).

In most countries you usually have to earn a separate Bachelor's degree before even being eligible.

After four years, if you happen to have exceptional grades, and if you manage to score exceptionally well on your MCAT (or similar Standardized Test depending on Jurisdiction) you might actually have a chance to be accepted into a decent Medical School.

After several more years of working your ass off (see above), you finally earn your MD (Unless you flunk out or quit), allowing you to practice as a GP.

Sorry for the long intro, but here's the question: After all those years of hard work, once earning an MD, some, for reasons I cannot comprehend, opt to further extend their grueling studies, and forego several years of a GPs salary in order to pursue a specialty in proctology. (pun finally arrived at).

My question couldn't be simpler.

Why?

Is it a matter of supply and demand? Do proctologists earn far higher incomes than GPs as a reward for having to dedicate the rest of their lives to further humanity's understanding of the human anus?

Sorry again if this comes off as a joke, but I'm genuinely perplexed by this.

Any proctologists in the house?

Oh there you are! All the way back in the rear! (Sorry couldn't help it. But still, serious question). 70.25.46.99 (talk) 22:46, 10 July 2009 (UTC)

My wife reports that, after utilizing the services of a proctologist for less than an hour, upon seeing the bill, it is quite clear what advantages that particular speciality offers the doctor. She does report, however, that the services were worth every dollar... --Jayron32.talk.contribs 22:55, 10 July 2009 (UTC)

Why not? On seeing every crevice of human anatomy in its naked glory, day in day out for 10 years, the anus, vagina and penis lose their 'eewwww- gross novelty value pretty quickly. A digital investigation of an anus is no more inherently "gross" than a digital investigation of a mouth. Yet no-one asks why would anyone choose to become a dentist.

Moreover, a huge number of people die from colorectal cancer each year, so the job satisfaction is hardly restricted to "understanding the human anus". Its about saving lives. Rockpocket 00:34, 11 July 2009 (UTC)

I completely understand how the grossness would wear off "after ten years", thing is, the OP was talking about Med School Grads, not ten year vets.

WRT job satisfaction, how is saving the lives of colorectal cancer patients more personally rewarding than saving the lives of lung cancer patients?

I'm not quite sure what Rockpocket means to say when s/he uses the term "inherently gross". Alls I know is that it's the anus that releases what I would consider some "inherently" foul smelling matter, not the mouth.

If I were the newbie still not quite immune to the "gross" factor, I'd go for the lungs.

I'm with Jayron here, unless someone comes up with an even more sensible answer. Rockpocket's first response is based on a misreading of the question, and the second is logically flawed. 76.67.137.220 (talk) 01:52, 11 July 2009 (UTC)

The exact time isn't particularly relavent. Even after a couple of years of exposure, one gets immune to it. By the time you are in a position to specialize, you have seen all the shit you could imagine, and a fair bit more. You respond to my comment about inherent distaste with a subjective response: Yes, you consider it gross. Just because you do, doesn't mean everyone else does. That, if anything, is a logical flaw. Finally, rather than dismiss an answer on whether you consider is sensible or not, you could actually check whether it is accurate. Proctologists earn a decent salary, but (in the USA in 2008) it only comes in 17th in the list of best paid specialities, behind a lot more - what you would likely consider - less gross jobs. Go figure. Rockpocket 03:11, 11 July 2009 (UTC)

I'm not sure what you mean by "GP". In the UK a General practitioner is roughly equivalent to a consultant, it's a senior job that comes after years of experience as a doctor. --Tango (talk) 02:49, 11 July 2009 (UTC)

Ah, after looking it up I see the phrase is used differently in the US. Our article is rather difficult to understand, though... --Tango (talk) 02:58, 11 July 2009 (UTC)

I once asked my urologist why he chose that particular speciality. He said that he had considered a few specialties before deciding. The reason he chose urology was due to the fact that the other doctors that he spoke to who were in the field already seemed like people that he would get along with best. There was something about the cardiac guys having a god complex from what I recall... It's been about four or five years... Dismas|^(talk) 05:16, 11 July 2009 (UTC)

Yes, you consider it gross. Just because you do, doesn't mean everyone else does.

Agreed! Perhaps I'm the only person on the planet who finds that shit stinks.

Who knows? Perhaps the rest of the world actually savours the aroma of human feces! 76.67.137.220 (talk) 08:12, 11 July 2009 (UTC)

"Finally, rather than dismiss an answer on whether you consider is sensible or not, you could actually check whether it is accurate. Proctologists earn a decent salary, but (in the USA in 2008) it only comes in 17th in the list of best paid specialities, behind a lot more - what you would likely consider - less gross jobs. Go figure."

Precisely!

Go figure!

How does that help the OP in any way other than to repeat the question?

Go figure!

Q: Go, Wikipedia people, please figure out why certain Med students decide to go into proctology because it just plain doesn't make sense to me.

A: Go Figure!

Q: Why do certain brilliant med students decide to specialize in the the shit hole?

A: Go figure!

Aren't we here to actually try to ANSWER questions? 76.67.137.220 (talk) 09:03, 11 July 2009 (UTC)

Please do not edit my comments. If you have something to contribute, do so under your own signature. Thank you. Rockpocket 19:05, 11 July 2009 (UTC)

The OP asked about Med School Grads. Your first post spoke of 10 year vets and was therefore wrong and potentially misleading. Please remove it. Thank you. 76.67.137.220 (talk) 08:07, 12 July 2009 (UTC)

Let's try. Possibly partly because of the yuk factor, or certainly a lack of glamour factor, fewer doctors choose proctology, therefore there is less competition for patients, therefore possibly higher income. There is also the social life consideration, shared with opthalmology, dermatology, cosmetic surgery, dentistry etc., that some specialities are unlikely to involve emergencies, so make a comfortable settled life possible. Cardiology, neurosurgery, orphopaedics etc. can involve unexpected call-outs and extremely long hours. Some of these necessarily involve large staffs and many assistants, therefore working at or out of a hospital. Others can be conducted as private practice from own rooms, with minimal or no surgical theatre space or gazillion dollar equipment required. So proctology allows a good living with minimal set-up costs for private practice, and "normal" working hours without emergency calls; an added bonus is the lower likelihood of being approached for free medical advice at social functions than a dermatologist or plastic surgeon might face. - KoolerStill (talk) 16:07, 11 July 2009 (UTC)

I know a few people who specialize in a certain field because of some prior tragedy related to it. If one has a family history of a certain type of cancer, one might choose a life goal to treat it in some way. DMacks (talk) 19:56, 11 July 2009 (UTC)

A compelling advantage of proctology over specialties like nephrology, neurology, and cardiology is that you can actually see the item in question during a routine examination. --Sean 14:04, 13 July 2009 (UTC)

Horse

What is "tying up": [22][23]?174.3.103.39 (talk) 23:06, 10 July 2009 (UTC)

"Tying up" is a kind of muscle spasm - aparrently it's caused by overwork and chronic tension in the muscles. Basically some form of lactic acid problem. SteveBaker (talk) 23:57, 10 July 2009 (UTC)

Is it the same as human cramp ?83.100.250.79 (talk) 15:59, 12 July 2009 (UTC)

I'm not an expert - but it looks like the causes and symptoms are kinda similar - although a 'cramp' usually means that the muscle refuses to function where 'tying up' refers to a spasm. It's hard to imagine how changing a horses' diet would affect that...but that's what appears to be being said here. SteveBaker (talk) 11:54, 13 July 2009 (UTC)

Our article lists a number of deficiencies (salt, calcium, potassium) that can cause cramps. --Sean 14:07, 13 July 2009 (UTC)

July 11

Washboard effect on gravel roads

Can anyone explain to me the cause of "washboarding" on gravel roads? Thanks WSC —Preceding unsigned comment added by 98.149.228.69 (talk) 00:25, 11 July 2009 (UTC)

Have you read Washboarding? It seems to explain it pretty well. Regards, --—Cyclonenim | Chat  00:47, 11 July 2009 (UTC)

Huh? It doesn't explain the cause, just talks about whether or not it's related to the vehicles' suspensions. --Anonymous, 05:41 UTC, July 11, 2009.

"when vehicles move above a critical speed, that depends on the properties of the vehicles and the road surface. If all the vehicles move below their critical speed the road will remain flat, but if they move faster, ripples will slowly grow and move in the direction of the vehicles." Regards, --—Cyclonenim | Chat  09:44, 11 July 2009 (UTC)

Exactly. It just describes what happens, not why. --Anon, 10:01 UTC, July 11.

Quote from the German wikipedia "A depression in the road causes intense ground contact (?) between the wheel of the vehicle and the road surface. When moving out of the depression the wheel moves upward like on a ramp and briefly jumps to cause a new depression." Bei dem Herausfahren aus der Vertiefung bewegt sich das Rad wie auf einer Rampe nach oben, um nach einem kurzen Sprung eine weitere Bodenvertiefung vorzubereiten.71.236.26.74 (talk) 11:19, 11 July 2009 (UTC)

Vehicle suspensions are harmonic oscillators. Each vehicle tends to resonate with the depressions and bumps left by previous vehicles. The effect over time is erosion in the road of ripples corresponding to the average resonant frequency of vehicles. Cuddlyable3 (talk) 22:55, 11 July 2009 (UTC)

Although the article does not say this, I am firmly of the opinion that a light rain -- enough water to partly fill the holes -- is the primary "exacerbater" of the condition once it starts for other reasons. Water gathers in the "valleys" and softens the dirt; the next vehicle along splashes the mud mixture out, usually to the sides, making the valleys even deeper. --DaHorsesMouth (talk) 22:19, 12 July 2009 (UTC)

Your assertion is not backed by scientific studies, or the fact that washboard conditions occur even in the driest deserts. See these articles. -RunningOnBrains^{(talk page)} 22:38, 12 July 2009 (UTC)

Fire

Could someone expain this passage from the fire article?

Apart from a controversial gap in the Late Devonian, charcoal is present ever since.

I don't understand what gap is being referred to. And the source for that statement is a bit over my head. Thanks, Dismas|^(talk) 03:23, 11 July 2009 (UTC)

It's fairly simple. We can tell in what time periods wildfire occurred by looking for charcoal in the fossil record. The record shows that wildfires first occurred in the Late Silurian and have occurred ever since, with the (apparently controversial, though a glance at the source doesn't indicate what the controversy is) exception of a period in the Late Devonian (the source says middle to early late) in which there is no charcoal in the fossil record, so presumably no wildfire, so presumably low atmospheric oxygen. Algebraist 03:36, 11 July 2009 (UTC)

I should have been more clear. What is this supposed controversy centered on? What is disputed? Dismas|^(talk) 03:42, 11 July 2009 (UTC)

That is not entirely clear. The controversy is about the lack of charcoal in the Late Devonian, but whether the dispute is over whether this lack exists at all or over some more subtle point I can't tell. Algebraist 03:46, 11 July 2009 (UTC)

Absence of evidence is not evidence of absence. --TammyMoet (talk) 08:50, 11 July 2009 (UTC)

If you have looked for evidence and found none, then that is evidence of absence... Absence of evidence is only nonevidence of absence if the evidence is absent because you haven't actually looked for it. Maelin (Talk | Contribs) 11:39, 12 July 2009 (UTC)

Not logical Maelin. The other possibility is that your method of search is fallible. In real science, this is often the most likely possibility. alteripse (talk) 19:09, 12 July 2009 (UTC)

Or in photo-reconnaissance... 76.21.37.87 (talk) 02:30, 13 July 2009 (UTC)

It certainly is logical. If the hypothesis predicts that you make a particular observation, and you in fact make a contrary observation, that is evidence that your hypothesis is false. When I open my pantry and I look for the bread and I conclude, "I cannot see any bread in the pantry", that is good evidence that there is no bread in the pantry. Contrast this with simply not opening the pantry at all and then saying "I cannot see any bread in the pantry". Absence of evidence is evidence of absence, provided you have looked for the evidence and found it to be lacking. Maelin (Talk | Contribs) 05:40, 13 July 2009 (UTC)

If you're looking for something and you can't see it, it might just mean that it's really well-hidden. Conversely, if you're looking much too hard for evidence of something in particular, you might see it whether it's there or not (happens sometimes in forensics, or in foreign intelligence operations, sometimes in science too, as seen in the case of global warming)...

76.21.37.87 (talk) 00:53, 14 July 2009 (UTC)

Fire particles

I remember reading something a couple years ago about an old theory (1500 - 1600s perhaps?) that fire was the release of particles from a substance. And when, for instance, a piece of wood was burned, these particles were no longer present in what remained. What is the name of the particle? Does this ring a bell with anyone? I thought I read it here but I don't know if I'm mis-remembering since Google searches for things like Fire Particles hasn't turned up anything familiar. Dismas|^(talk) 03:45, 11 July 2009 (UTC)

Phlogiston. Algebraist 03:47, 11 July 2009 (UTC)

That's them! Thanks! Dismas|^(talk) 03:56, 11 July 2009 (UTC)

The neat thing about the phlogiston idea was that the particles had negative mass - so when you light a fire with (say) some wood, the phogiston from the flames enters the wood and reduces it's mass - thereby reducing it to ashes. Similarly, when you boil water - the water level drops. When you sweat - the water evaporates, taking with it some of the phlogiston which is why you feel cooler. It's quite a clever idea given the very limited experimental evidence of the time...but it requires some complicated logic to explain the fact that heating mercury (which produces mercuric oxide) produces something that's actually heavier than what you started with - despite all of the phlogiston you poured into it. SteveBaker (talk) 04:21, 11 July 2009 (UTC)

No, phlogiston is present in flammable materials and leaves them when they burn. That's why you end up having to assign it negative mass when you discover (for example) that burning metals gives you more mass than you started with. I'm pretty sure no-one thought it came in particles, either. It was more a fluid of some sort. Algebraist 04:25, 11 July 2009 (UTC)

Our article mentions it has no mass. So why should negative mass be assigned, or why would mass increase when phlogiston leaves an object ? Rkr1991 (talk) 08:52, 11 July 2009 (UTC)

Well, I think Algebraist just answered both of those...It has negative mass because when it leaves an object, the object becomes heavier (burning substances which become heavier after a reaction are thus explained this way). The real reason an object becomes heavier after a reaction is because it has more mass (obviously not true for all reactions); but they didn't know that at the time. Vimescarrot (talk) 09:12, 11 July 2009 (UTC)

You don't get it. The article says it has zero mass, not negative. That is the main theory. When contradicted, some scientists suggested that it may have negative mass so that it may explain things like the burning of Magnesium. Yet, it would not work. The way Algebraist puts it, it sounds as if the main theory itself suggested that Phlogiston has negative mass. But according to the article, that was just a view of some of its later proponents. Rkr1991 (talk) 13:05, 11 July 2009 (UTC)

At the time the theory was created, most things that were burned contained Hydrogen and Carbon, and those were the parts that were oxidized into H20 and CO2, i.e. into invisible and odorless gases that vanished. Thus, if you burned wood, or tallow, or lamp oil, or paper, the visible remains (the ashes) are indeed lighter than the original substance - and what you lost was the hypothetical Phlogiston. This is not true for substances that create only solid ashes, like several metals. To apply the Phlogiston theory to e.g. magnesium, you need to postulate a negative weight (and thus, I assume, different kinds of Phlogiston). --Stephan Schulz (talk) 12:55, 11 July 2009 (UTC)

Wasn't the whole phlogiston theory disproved three centuries ago? 76.21.37.87 (talk) 09:27, 11 July 2009 (UTC)

Two and a half. The linked article has a detailed history of it. Our whole discussion here is about the theory as it was and its correctness as far as they knew at the time. It's actually still a viable discussion topic as an example of how science makes testable hypotheses and changes or discards theories as new evidence becomes available. DMacks (talk) 09:38, 11 July 2009 (UTC)

What about photons? 93.132.152.73 (talk) 09:49, 11 July 2009 (UTC)

What about them? Algebraist 12:26, 11 July 2009 (UTC)

Airplane glory shadow

One million square kilometres of sea ice from this area could disappear by September, including the Beaufort sea and areas farther northwest.

Hi. As I was in an airplane travelling over what was presumably north of the Beaufort Sea, I saw a glory over the sea ice. The sea ice was riveted with cracks and melt ponds, and perhaps the whole section will melt by September (about 1 million km² of it; by the way are there any predictions for minimum Arctic sea ice extent for this year?). However, that's not the point. Now, presumably in the centre of the glory should be the plane's shadow. However, that's not quite what I saw.

Now, I didn't take a picture, but it was approximately midnight local time, but there was sunlight. It was the Arctic midnight sun. I was travelling approximately west, and the sun was near the front-right area of the plane. I was looking from the left side of the plane, and the glory was slightly behind the direction facing from the left (therefore, the Sun was to the northwest and the glory to the southeast). However, the shadow of the plane was a strange shape. It started in the centre of the glory, but then extended back almost parallel to the plane, very slightly pointing away from it. There were no wings visible in this shadow; it was faint and was basically a thin line that extended farther back on the ice than I could see. Was this the shadow of the plane, and if so, how did it form such a shape? The sun was presumably very low on the horizon (15 degrees according to Yoursky); the glory was probably only visible for about 10 minutes, while Arctic daylight on the aircraft lasted seven hours (we kept just prior to midnight local time during the whole trip).

Now, here's an aside. How does one identify the difference between cloud iridescence and irisation? Is it the type of cloud, the dominant colours, the pattern of the colours, how far away it is from the Sun, the season, etc? Thanks. ~AH1^(TCU) 08:01, 11 July 2009 (UTC)

About the strange shape of the shadow: since the sun was at the plane's one o'clock to two o'clock and very low on the horizon (as is always the case with midnight sun), the shadow projected onto the glory was identical in shape to the plane's view from that angle, so it's only natural that the wings would not be visible (the right wing was very likely being projected onto the fuselage and the left wing obscured by it). I'm not really sure why it was stretched out "farther back than you could see"; it could have had something to do with the curvature of the plane's window, or it could have been something else. 76.21.37.87 (talk) 08:28, 11 July 2009 (UTC)

As for your second question, I'm not really sure, but the Wikipedia articles say that cloud iridescence is usually caused by light refraction/scattering by water droplets/ice crystals/smog particles (similar to a rainbow/glory/halo), while irisation is a less common phenomenon caused by diffraction and mostly seen in stratospheric nacreous clouds. However, it appears to me that there's also some overlap between these two terms, so it wouldn't surprise me if I found out that they are interchangeable. FWiW 76.21.37.87 (talk) 09:09, 11 July 2009 (UTC)

The shadow of your own head (or the shadow of the part of the plane where your head is situated) will be precisely at the center of the glory...which it sounds like it was. The other parts of the plane's shadow could be anywhere...the extreme distortion of the shadow comes about because the sun was so low in the sky - and that causes very distorted shadows. SteveBaker (talk) 17:27, 11 July 2009 (UTC)

can i say so

what kind of cooling arrangments do american steel manufacturers use? They tag a high steel price.I suspect some kind of air+water mixture type cooling.Kindly let me know.

sam —Preceding unsigned comment added by Sameerdubey.sbp (talk • contribs) 09:22, 11 July 2009 (UTC)

I'm not a steelmaker, but I think they quench the steel in water to give it extra strength and hardness. FWiW 76.21.37.87 (talk) 09:30, 11 July 2009 (UTC)

the process varies depending on what the steel will be used for. Generally, in the case of Canned food or sheet metal, a process called Cold Rolling Is used, in which case they deform the metal by passing it through a roller that has a temperature lower than its recrystalization process allows. Then again, another process known as Quenching Has been used which increases the durability and strength of the metal.

http://en.wikipedia.org/wiki/Cold_rolling -Heres a link to cold-rolling

http://en.wikipedia.org/wiki/Quenching - heres a link to Quenching

Hope this helps. --Blaze113 (talk) 10:14, 11 July 2009 (UTC)

I don't think cold rolling is actually a cooling process

For continuous production of steel water is sprayed onto the steel.

For batch production water, oil or even mercury can be used to cool the steel by plunging it into the liquid.83.100.250.79 (talk) 16:09, 12 July 2009 (UTC)

They don't use mercury because the vapors generated would be highly toxic. They do, however, use water, oil (which stinks like you wouldn't believe, but is not very harmful), and sometimes silicone-based liquids for quenching of steel. FWiW 76.21.37.87 (talk) 02:35, 13 July 2009 (UTC)

Yes I should have said no-one uses mercury for a a long time - though it has been used in the past, as has even molten lead.83.100.250.79 (talk) 16:44, 13 July 2009 (UTC)

Orbital Capture of Moons

Can someone explain to me how a large moon could just be flying through space and suddenly captured by a planet? (fyi, I know most moons aren't formed this way) This doesn't make sense to me as whenever spacecraft want to enter into orbit of a distant body they need to burn off excess energy at the periapsis to circularize the orbit. Spacecraft can also utilize atmospheric drag, assuming the planet has one, and I suppose the moon could skim through the atmosphere but it seems the odds of the resulting orbit being stable would be very low. So how does a planet without an atmosphere capture a moon? TheFutureAwaits (talk) 11:21, 11 July 2009 (UTC)

• Atmospheric drag is not a possible mechanism for capture. The effect of "burning off energy at the periapsis" is to convert an open, hyperbolic orbit into a closed, elliptical one, or if the orbit is already elliptical, to lower the apoapsis. (In a two-body situation, once you have an elliptical orbit, it always continues to pass through the point where a force was last applied, i.e. the atmosphere.) Atmospheric drag could "capture" an object into collision with the ground, but not into an orbit above the atmosphere. --Anonymous, 20:29 UTC, July 11, 2009.

Collison with an existing satellite or transfer of energy in a three-body gravitational interaction between the incoming body, the planet and an existing satellite are other possibile mechanisms. For further information see Irregular moon#Origin, Ananke group and Triton (moon)#Capture. Gandalf61 (talk) 11:50, 11 July 2009 (UTC)

Yes, that's it. The involvement of a third body is required. --Anon, 20:29 UTC, July 11.

I am no physicist, but I assume the energy is needed by a spacecraft if it wants to get into a circular orbit. Without that, it, or a potential moon, would get into an elliptical orbit. I believe that over time (very much time), that would get 'flattened' more and more until finally it approaches a circular orbit, but I'm not sure why that is. DirkvdM (talk) 13:20, 11 July 2009 (UTC)

Well, the conservation of momentum laws apply. If the planet were somehow nailed down and unable to move - it would indeed be impossible for a moon or a spacecraft to get 'captured' into a stable orbit. But planets are not nailed down - so conservation of momentum allows for the COMBINED momentum of planet and moon/spacecraft to be conserved because each of them cannot be considered as a "closed system". To envisage this, consider the planet and the moon as being roughly equal in size - it's not much of a stretch to imagine them both winding up orbitting about a point midway between them - and together moving off from the planet's starting point at about half the speed of the incoming moon. SteveBaker (talk) 17:02, 11 July 2009 (UTC)

• This does not seem to help with "envisaging" the point that there needs to be a third body involved somehow. --Anon, 20:29 UTC, July 11.

If there were only the planet and the moon then you are absolutely right, you can't be captured without a rocket burn. With a many body problem, however, it is far less simple. You can get all kinds of complex interactions that can result in capture. Once you've got a periodic orbit tidal forces can circularise it. --Tango (talk) 17:40, 11 July 2009 (UTC)

Yes, that's it. --Anon, 20:29 UTC, July 11.

Aren't Mars' moons supposed to be captured asteroids? If so, there was no third body involved when the first of the two moons was captured. --Roentgenium111 (talk) 13:42, 13 July 2009 (UTC)

Apart from everything else in the solar system, you mean? Algebraist 13:46, 13 July 2009 (UTC)

See Deimos (moon)#Origin for various theories. Some theories invole other bodies which were ejected from Mars orbit by the encounter. Other theories involve non-asteroid origins. Gandalf61 (talk) 13:59, 13 July 2009 (UTC)

H and O in H2O

I was wondering, say the bond between H and O in H2O could be broken safe and economicaly, how much of each would a liter of Water contain. Using it as a fuel, would it be necassary to carry many, heavy lites of water, making it useless as a fuel for say a plane ?41.15.144.2 (talk) 11:45, 11 July 2009 (UTC)

The molecular weight of water is 18, hence a liter of water contains 1000/18=55.55 mol of water. This means it contains 55.55 mol of H2 and half that of O2, or, in other words, about 1300 l of H2 and 650 l of O2 at normal conditions. Unfortunately, you cannot carry this around for fuel in the compact form of water, since the energy you get from burning it is exactly the same you need to split it in the first place, and you will have losses either way. --Stephan Schulz (talk) 11:58, 11 July 2009 (UTC)

If you use it as fuel, of course you don't carry it in the form of water, but as hydrogen (the oxygen you get from the air, so you don't have to carry that). In a car, the large volume is a problem, so it has to be compressed, but for a plane the fact that hydrogen is light can be a huge advantage. Airships sometimes use hydrogen for lift. But as you say, you can also use that hydrogen for propulsion, so you get two for one. Of course, as you burn hydrogen, you lose lift, so you'll need more hydrogen-power to keep the plane in the air. But still. I wouldn't be surprised if this idea has already been worked out in more detail, but I have never heard of it. Hydrogen economy appears to mention planes just once, in the intro, so no help there. DirkvdM (talk) 13:04, 11 July 2009 (UTC)

Burning the lifting gas would require ballast to be released, reducing the range of the airship. Conversely, burning gasoline or similar fuels, as in most airships, causes the vehicle to get lighter during the cource of each flight and requires some of the lifting gas to be released, which also reduces the range (and adds to the cost). In the airship Graf Zeppelin they avoided both problems by burning a gaseous fuel that was about the same density as air: Blau gas. (They carried some gasoline as well, to burn in case they wanted to lighten the airship gradually.) I presume the reason other airships did not adopt this was that the volume occupied by the Blau gas was inconveniently large. --Anonymous, 20:42 UTC, July 11, 2009.

Oh, there is a Hydrogen airplane article. To my surprise, this doesn't mention the lift advantage and says the hydrogen should be pressurised. Of course, a sufficient amount of uncompressed hydrogen would make the airplane rather big, which would not be good for the aerodynamics. DirkvdM (talk) 13:13, 11 July 2009 (UTC)

To be VERY clear - (as Stephan points out) - the laws of thermodynamics require that it takes more energy to pull the water apart into H2 and O2 than you can possibly get back from recombining them. So you cannot use water as a "fuel"...that a flat out guaranteed: "NO!" Some people suggest that using electricity to split the water and then burning the gasses conveys some advantage - but that too cannot be more efficient over (say) just using the electricity to drive electric motors. Moreover, since the result of burning hydrogen with oxygen is just water again - you could capture the exhaust from such a vehicle and put it back into the water tank. That makes water the "working fluid" - and not the "fuel". However, thermodynamics is a harsh mistress and there is no possible way to make an energy "profit" while doing that.

So "water as a fuel" is quite utterly "busted". Sadly, there are a lot of people out there (like these evil bastards and these nut-jobs and these scam artists and these conmen...and many, many more) who'd very much like to take your money by selling you things like that...but please don't believe a word they say! They are all liars, cheats and con-men - the laws of thermodynamics say so.

SteveBaker (talk) 16:48, 11 July 2009 (UTC)

I see you took a class in the Christopher Hitchens school of polite expression ;-). --Stephan Schulz (talk) 17:30, 11 July 2009 (UTC)

To note some possible caveats to Steve's rant, though, there's a possible rationale to using water (well, the hydrogen component, as noted above) as fuel. If you've got a clean plentiful source of grid electricity, then you may not care about the thermodynamic losses of cracking water on an industrial scale. That hydrogen supply could then serve as a clean car fuel that's easily refilled -- while it's less efficient than an electric car, it doesn't suffer the range limitations. Note that this is different from the scams noted above, though -- it relies on a clean power source that we don't yet have at the scale required. "Clean" is included because we could do this now with coal plants, but the greenhouse emissions make it a non-starter. Fix that, though, and the rest becomes pretty simple to implement. — Lomn 17:47, 11 July 2009 (UTC)

Steve is exactly right. There is no scenario under which the water can be used as a fuel^§; any attempt to produce excess energy from breaking and reconstituting the hydrogen-oxygen bond would constitute a perpetual motion machine, whose existence is ruled out by the laws of thermodynamics and is not simply a matter of developing an advanced enough technology.

The scenario Lomn outlines is that of using hydrogen as a fuel, which of course is completely reasonable. The fact that water may be used as the source for hydrogen, doesn't make it a fuel though - at least, if we are using that word in the conventional sense; note that conmen often assign non-standard meanings to scientific terms in order to hoodwink lay customers/investors (see Stanley Meyer's water fuel cell for one such scientific and financial scam; ).

§: Here, I am specifically referring to dissociating water into hydrogen and oxygen, and then burning the released hydrogen to produce energy. Of course, falling water can be used to generate electricity, and water is used in a steam engines, but in neither of those cases do we refer to it as the fuel. In addition, there are several exothermic reactions involving water that can in principle be used to run a generator; in such cases water could validly be called a fuel, but I don't think there are any such reactions that are of any practical importance for energy generation. Abecedare (talk) 18:28, 11 July 2009 (UTC)

Sure - you can make hydrogen from water (at some cost in electricity or whatever) and use THAT as a fuel. But it's (a) not an efficient process and (b) not using water as fuel. Water is the 'ashes' you get left over after burning hydrogen..it has no energy left to release - the only way to get energy out of water - is to put more energy into it first. Once you do that (eg by boiling it in a steam engine - or splitting it into H2 and O2 in an electrolysis cell) - you can take back some of the energy you put in...but you don't get it all back. That doesn't make steam engines or hydrogen manufacturing plants useless - using energy in a more convenient form is valuable. Hydrogen powered cars make a certain amount of sense. If we somehow manage to build enough windmills or get fusion reactors working - they'll be the way forward. But we have to be very VERY clear that we aren't getting energy FROM water - we're putting energy INTO water. Which is the complete opposite of what these evil conmen are claiming. SteveBaker (talk) 18:30, 11 July 2009 (UTC)

Sadly, about a year ago, Reuters got sucked into doing a story on Genepax, who had supposedly developed a water-fueled car.[24] You’d figure a big news service like Reuters would have science editors who would know better. Red Act (talk) 20:03, 11 July 2009 (UTC)

Sad to see Reuters fall into the trap. Such scientific illiteracy is usually restricted to local TV news reports, which always seem to include the claim that the military (or NASA) is studying the technology. Abecedare (talk) 20:30, 11 July 2009 (UTC)

Well, what do you expect from Reuters? They're just reporters, how scientifically literate could they be, anyway? You want scientific literacy, go with Scientific American or with Popular Mechanics.

76.21.37.87 (talk) 01:06, 12 July 2009 (UTC)

Whilst on the subject of water as fuel - there have been attempts to inject water into combustion engines along with the fuel - reason being that the water is vaporised when the fuel combusts - converting heat to 'pressure' (as steam) - note that the water is not a fuel in this case. The high heat capacity and enthaply of vaporisation of water would seem to be disadvantages here...

The reason to do it is to increase the energy efficiency of a combustion energy by adding a 'filler' that can convert heat to pressure (usable as work) by the engine.

I'm not sure if it has ever been proven to actuall increase efficiency..83.100.250.79 (talk) 16:17, 12 July 2009 (UTC)

Combined dynamo and starter motor

An electric motor can operate as a generator and vice versa. Why then do automobiles have separate dynamo and starter motor? Combining them saves many mechanical parts such as solenoid, starter gear, and pulley wheel. The current is much higher during the brief time a starter operates than in the dynamo that runs continuously, so they probably need separate windings. The Isetta article says BMW used such a combined unit in their Isetta 250 microcar. Cuddlyable3 (talk) 22:29, 11 July 2009 (UTC)

Possible reasons that occur to me:

1. If the separate starter motor fails, you can still bump-start the car in order to drive it home/to the garage/whatever (as has happened to me); if the two are a combined unit, then such a failure might make the car undrivable.
2. The reliability of a (presumably more complicated) combined unit might be appreciably less than that of two simpler separate units.
3. A combined unit is likely to be more expensive than either of the two separate units, so in the long run, repair/replacement costs would likely be higher.
4. A combined unit is presumably smaller and lighter overall than two separate units, and its use in the tiny Isetta 250 microcar was presumably to save space and weight; in a normally sized car the space and weight saving would probably be insignificant, so would not outweigh the disadvantages. 87.81.230.195 (talk) 23:41, 11 July 2009 (UTC)

The starter motor is more powerful than the alternator. "Cranking" a car consumes electrical energy faster than an alternator stores it. One rotary device could doubtless be designed to serve both roles. A rotary electrical device powerful enough to crank the engine might be inefficient when spun continuously as an alternator to provide steady state power. It is certainly something to look into. I seem to recall that General Motors was looking into using one motor/generator for this purpose, shutting down the internal combustion engine when the car stopped at a red light, then restarting it when you wanted to go, with a drive belt connecting the gas engine and the motor/generator. Edison (talk) 03:51, 12 July 2009 (UTC)

Parallel hybrid cars also uses single device as starter motor and alternator. -Yyy (talk) 06:27, 12 July 2009 (UTC)

I would say that the requirements for a high torque electric motor and a low load electrical generator are probably incompatible. However, it is possible that a combined device could be designed. But, as a previous poster says, the decision to go for separate devices is probably to do with economics and reliability. —Preceding unsigned comment added by 79.75.92.24 (talk) 21:18, 12 July 2009 (UTC)

A single rotar device can have multiple windings: one for steady low level generation and one for short term high current. Some motors have starter windings as well as run windings. Some utility generatos over 100 years ago had both DC and AC generation windings, could generate AC at two frequencies at the same time, or could transform one frequency to another, DC to AC, etc. Edison (talk) 19:34, 14 July 2009 (UTC)

Swine flu versus ordinary flue

How does the mortality rate, duration, and severity, of being ill from Swine flue compare with that of being ill from ordinary flue, without any drug treatments in either case? In the UK people with swine flu are given Tamiflu, so its difficult to gain an idea of what its like untreated. I understand that in the US, most people are not being given Tamiflue. I understand that most people start getting better after two or three days - previously I would have called such a short illness a cold rather than flue. I thought flue was suppossed to last more like a fortnight (which translates as two weeks in American English). Thanks. 78.151.124.180 (talk) 23:49, 11 July 2009 (UTC)

It's not actually much different to ordinary seasonal flu: as our article notes. However, it is considered by some to be "unstable" and therefore more likely to mutate. There are some reports that it is a devleoping resistant to anti-virals (such as Tamiflu). This could, perhaps, bring some debate regarding the routine administration of Tamiflu to all sufferers, rather than restricting it to severe/problematic situations. Gwinva (talk) 00:03, 12 July 2009 (UTC)

And just to be clear, flus (influenzas) and colds are not distinguished by their duration: they have different viral agents, as the articles make clear. Indeed, our cold article states that the cold typically lasts 7-10 days (up to three weeks!). Matt Deres (talk) 01:42, 12 July 2009 (UTC)

To give you an idea of how swine flue is viewed in the states: A few weeks back when swine flu was all over the news, the local government for my state (Vermont) was telling people who thought that they may have swine flu to stay at home. They recommended only the elderly, very young, and those with compromised immune systems to actually go see a doctor. Otherwise healthy people were asked to just stay at home and treat themselves as though they had any other cold or flu. Dismas|^(talk) 04:28, 12 July 2009 (UTC)

July 12

What are these structures?

Can anybody please tell me what these circular structures are? Thanks ItchyHoover (talk) 00:56, 12 July 2009 (UTC)

If you use the Google 'street view' camera - it's obvious that they are Gas holders. Large cylindrical tanks which rise within a circular frame when filled with gas - and whose weight pressing down on that gas ensures that there is sufficient pressure to push it through the local pipework to people's homes and businesses. SteveBaker (talk) 01:14, 12 July 2009 (UTC)

The photo at right is an almost identical Gas holder from West Ham. SteveBaker (talk) 01:40, 12 July 2009 (UTC)

Life span of the Voyager Golden Record

In the Article on the Voyager Golden Record there is a bit in the Appearances in fiction section that reads:

• "In the speculative nonfiction series Life After People it is said that, after a million years of travel in interstellar space, the Voyager probes will be so heavily damaged from micro meteor impacts that the disks will become unreadable."

Because there is no mention of this beyond the fiction section i wanted to know if there was any truth to that statement.--SelfQ (talk) 01:25, 12 July 2009 (UTC)

The probes are so far from the sun now (well outside the Kuiper belt) that the amount of debris is almost zero - the odds are extremely good that these records will last for well over a million years. SteveBaker (talk) 01:54, 12 July 2009 (UTC)

On a related note, how are the disks packaged? It seems to me that the most likely scenario for an alien civilization to get the disks is if the Voyager actually collides with an inhabited planet (therefore, a planet with a breathable atmosphere), with all the consequences that this entails. And you can't very well read a bunch of disks if they've burned up during reentry, can you? 76.21.37.87 (talk) 03:19, 12 July 2009 (UTC)

The discs are packaged in a protective cover, shown here. Micrometeorites would have to penetrate this cover to damage the actual recording medium. Nimur (talk) 03:38, 12 July 2009 (UTC)

It could enter the atmosphere of some alien planet and be burned up. The last meteor to enter the Earth's atmosphere might have been a space probe from some wonderful planet, complete with examples of their music, poetry, and science, that would have enriched our lives. But another scenario is that 100,000 years from now, Voyager is detected by radar and telescopes of another world, and a robot space tug takes it to their scientists for analysis. They play the record, look at the pictures and marvel that there were once such people as us, though we be tribal killer apes who may destroy our race. See also the Star Trek Next Generation episode wherein Picard is the particular target of such a probe from a vanished race and is forever changed as a result. See The Inner Light (Star Trek: The Next Generation) (took some searching to find it). Edison (talk) 03:40, 12 July 2009 (UTC)

Not within the next million years. Neither Voyager probe is aimed towards any particular star - and the odds of just happening to fly close enough to one are astronomically small. There is no possible way they could enter the atmosphere of a planet within that short an amount of time. Also, the Voyager probes will run out of power in about 15 years from now - beyond that, they would pretty much be indistinguishable from a rock as far as alien telescope users would be concerned...but since the closest they're coming to a star in the next 100,000 years is 1.6 lightyears - it's really not likely (and probably outright impossible) for an alien telescope to spot them by chance. The universe is a VERY big place and these are incredibly TINY probes. They'll most likely still be heading off in a more or less straight line without noticable deterioration for a few billion years...they'll probably outlast us, and our planet. SteveBaker (talk) 04:02, 12 July 2009 (UTC)

A more advanced civilization might note its approach. It might cross the path of one of their spaceships. By the way. did you read the article about the Startrek episode, which had the topic of a civilization ending out a probe so someone somewhere would remember them? Edison (talk) 04:52, 12 July 2009 (UTC)

I find it interesting that SteveBaker pretty much rules out the likelyhood of an alien civilization finding either Voyager probe. I never realized that you were that well versed in future alien technologies.  ;-) Dismas|^(talk) 05:32, 12 July 2009 (UTC)

You don't have to understand their technologies - you only have to consider the fundamental limitations imposed by the laws of physics and statistics. If you take Dragons Flight's number (below) of 1-10 billion years to get within 60 astronomical units of another star - then consider the likelyhood of detecting something about 2 meters across and weighing 750kg at a distance of 60AU when it's in a totally unexpected (indeed random) position and moving in a random direction. At that kind of distance, the amount of light it would reflect will be truly negligable - it's nuclear power plant will have long ago run down - so it certainly won't be emitting radiation or heat or light or radiowaves of it's own. At 700kg you aren't likely to be able to detect any gravitational disturbance due to it's mass. What conceivable technology could spot it? The extreme limits of our ability to observe objects out that far is to detect Kuiper belt objects down to maybe 100km in diameter! Voyager (at around 2m in diameter) is going to be more than two billion times dimmer! The probability of an alien detector being hit by even one photon reflected by Voyager is quite negligable - so the detector would have to be tracking it for a long time, accumulating these occasional stray photons from it - but since it's coming from a random direction and at a random speed - the probability of the alien detector happening to track it by pure chance is essentially zero. Even if they did happen to pick up some tiny amount of reflected light from it - aside from it's somewhat unusual metallic composition - it's going to be utterly indistinguishable from any other tiny Kuiper-belt type of object - of which there are trillions and trillions to choose from. Why would they bother to investigate this one? Everything says that this craft would be quite impossible to detect with any halfway credible probability. If a similar alien craft entered our solar system - and even if it came close enough to graze our atmosphere - we'd never notice it. If it actually entered out atmosphere - it would burn up before we could tell what it was. There is literally no way for us to detect an alien craft that size. SteveBaker (talk) 15:06, 12 July 2009 (UTC)

A random object travelling through space ought to intersect a star system (within 60 AU) about once every 1-10 billion years. Incidentally, that number suggests the sun may have had a relatively close approach by some other star at some point in its 4.5 Gyr lifespan. It will take Voyager a long time to find another star merely by chance. Dragons flight (talk) 10:34, 12 July 2009 (UTC)

On the other hand, destruction of the disks might not be such a bad thing for us. Consider the inevitable consequences that have occurred on earth every time a culture encounters a vastly more advanced culture, and perhaps the person who characterized that Voyager message as the "single most reckless act in the history of our species" has a point... alteripse (talk) 19:04, 12 July 2009 (UTC)

When we get near-lightspeed spacecraft, we should probably think about going to retrieve it. Googlemeister (talk) 16:35, 13 July 2009 (UTC)

Assuming we would have the faintest clue about where to look for it, which we won't... 76.21.37.87 (talk) 00:58, 14 July 2009 (UTC)

Assuming that the records weren't lost in the meantime, we'd be able to extrapolate its flightpath wouldn't we? Objects travelling in space tend to continue on in a straight line unless influenced by a large gravitational field (which we'd be able to allow for in the calculations), don't they? I think that it's far more likely that Voyager will end up on display in the National Air and Space Museum than in the hands of an alien race... --Kurt Shaped Box (talk) 01:11, 14 July 2009 (UTC)

True, but this assumes that we'd know all the grav fields that the Voyager will encounter along the way, which we don't! 76.21.37.87 (talk) 01:37, 14 July 2009 (UTC)

And besides, if there's two or more grav fields acting on the Voyager at the same time, what we got now is a three-body problem, which is much harder to solve (impossible in some cases). 76.21.37.87 (talk) 01:40, 14 July 2009 (UTC)

And yet another difficulty with extrapolating the flight path: Even for the grav fields that we do know about for certain, in many cases it's almost impossible to obtain an absolutely exact value for their strength, so what we got instead are approximate values with a certain margin of error. Likewise, the Voyager's flight path (therefore its position and direction / velocity) is only known with a certain margin of error (let's say a couple hundred miles for position, a few minutes of arc for direction, and a couple km/s for airspeed). Over time, these errors in flight path will build up (especially since the Voyager's exact flight path influences how close it passes to a given grav field and therefore how much it's deflected), so after a century or two, the uncertainty in the Voyager's position will be so big that we'd have to search a HUGE area! Keeping all this in mind, the search for the Voyager will be MUCH harder even than looking for a tiny airstrip on a tiny desert island in the middle of the South Pacific, especially since islands usually remain in the same place at all times. 76.21.37.87 (talk) 08:01, 14 July 2009 (UTC)

She did not have radar though. We could. On earth, an AEGIS radar can see a small aircraft at 300+ miles, but it is limited by the curvature of the earth. Googlemeister (talk) 19:21, 14 July 2009 (UTC)

So basically, it would be impossible as well for a Message in a bottle to be [read by someone eventually]? If someone wanted a space probe to be found, they could (if their technology were advanced enough) install a very long duration stored energy source and a transponder which would respond to radio signals with a detectable emission, or a beacon which would start operating when it got within plausible detection range of a target starsystem. Edison (talk) 19:24, 14 July 2009 (UTC)

Pain

Congenital insensitivity to pain suggests that the sensation of pain can essentially be isolated from other sensations (with the exceptions of temperature). Does this have any analgesic applications? Is their any method of pain management (obviously one dealing with intense chronic pain) that attempts to "sear" the nerves responsible for pain?

Alfonse Stompanato (talk) 04:00, 12 July 2009 (UTC)

Well, there are many methods that temporarily block the nerves responsible for pain: some of the ones that you're likely to be familiar with are painkiller shots to numb your jaw before a dental procedure such as a dental filling or (if you got really bad teeth) a root canal; or (if you're a woman who's had kids), an epidural block to reduce the pain of childbirth. As for permanently "searing" or deactivating the nerves responsible for pain, I haven't the foggiest. 76.21.37.87 (talk) 04:23, 12 July 2009 (UTC)

Well, there's radio frequency nerve ablation that's been used for chronic pain, but the problem is that nociceptive nerve fibers coexist with those of other perceptions - they don't exist in isolation - so you can lose sensation as well as the pain. - Nunh-huh 04:38, 12 July 2009 (UTC)

About time dilation

Sorry to ask frequently asked things. But I have two. The first is: I know if two observers start from the same inertial frame, accelerating and decelerating alike in opossite direction, experience the same time of inertial motion, and comes back to where they started, time dilation for both is the same (because everything is symmetrical). But while both are in inertial motion, each observe the other's time delay, and to compensate for that, the time for each (not the other) must delay during acceleration.(I don't think gravitaional time dilation quickens the other's time.) But the other's time does not delay the same amount? If it delays, special relativistic time dilation is not compensated. The second is: In the same situation, but changing only the duration of inertial motion for both, total special relativistic time dilation increases. What compensates for the adittional special relativistic time dilation? Gravitational time dilation has "vertical" distance h in the formula to calculate the gravitational time dilation. I'm not sure, but acceleration at differently distant point (even if the acceleraion is the same) causes different time dilation? And that equals the difference of special relativistic time dilations? Like sushi (talk) 04:38, 12 July 2009 (UTC)

You seem confused. There is no need to include gravitational effects in any of your examples since there is no gravity present. Acceleration is equivalent to a gravitational field only locally which is not the case here since there are two observers with an arbitrarily long space-like distance between them in your examples. When your observer accelerates it jumps from one reference frame into a different reference frame with a different set of simultaneaties. It is even possible that a distant event that was considered already past before the accelaration becomes a future distant event after the accelaration. No gravitational doppler shift (a better term than time dilation) can do that. Dauto (talk) 05:11, 12 July 2009 (UTC)

"Acceleration is equivalent to a gravitational field only locally" and we are dealing with "observers with an arbitrarily long space-like distance"? But if the motion of both are symmetrical,they would return to the point they started, and at the time they have just returned to the point they started and to the same reference frame, the traces of both are fully in the light cone of both. So everything is not "spacelike" at the time?

Like sushi (talk) 06:18, 12 July 2009 (UTC)

You are saying that the other is out of the light cone when the acceleration takes place? That is impossible (at least for an observer to see, because the skirt of light cone expands faster than the speed "the other" is observed to recede).

Like sushi (talk) 06:48, 12 July 2009 (UTC)

Or you are saying that the observer can not see the other's acceleration?

Like sushi (talk) 06:52, 12 July 2009 (UTC)

I forgot to write this, I am assuming that the two observers start from the same point.

Like sushi (talk) 07:25, 12 July 2009 (UTC)

I think what you're saying is this: if two people travel in a perfectly symmetrical way then when they meet again the elapsed time must have been the same for both (by symmetry). But that's inconsistent with each one seeing the other's clock run slower. The answer is that they don't see the other's clock run slower, they see it run sometimes slower and sometimes faster, with the average speed over the whole trip being the same as their own. The observed speed of the clock is determined by the Doppler shift factor, ${\sqrt {\tfrac {1+v/c}{1-v/c}}}$, not by the time dilation factor, ${\tfrac {1}{\sqrt {1-(v/c)^{2}}}}$. The latter is rarely relevant in physically meaningful situations. -- BenRG (talk) 08:59, 12 July 2009 (UTC)

Thank you. The formula you wrote is a variant of one in Velocity-addition formula#Doppler Shift##Relativistic Doppler Shift? I haven't known that. The observers do not always see time to delay. Thank you again!

Like sushi (talk) 10:18, 12 July 2009 (UTC)

Well, I have thought about it, and using the formula ${\sqrt {\tfrac {1+v/c}{1-v/c}}}$, there is still time dilation observed in the case each recedes and approaches with the same speed, because observed time dilations are reciprocal to each other, adding them does not (at least always) result in no dilation.

Like sushi (talk) 10:42, 12 July 2009 (UTC)

No, this is not time dilation, time dilation and time hastening (should I say?) both occur and total time in this case is hastened.

Like sushi (talk) 11:32, 12 July 2009 (UTC)

This isn't usually called time dilation (or time hastening). The effect actually called time dilation is something more abstract involving distributed networks of synchronized clocks. The total time (i.e. number of ticks) is not hastened, it's identical for both travelers (both in reality and "as observed" by each one). It's complicated to work this out explicitly. For one thing, the Doppler shift formula depends on the velocity of the emitter when the light is emitted relative to the velocity of the receiver when the light is received. Since those times are different for light going in the opposite direction, there's no simple relationship between the Doppler shifts seen by the two travelers.

Look at relativistic Doppler shift for the formula. The one I gave, ${\sqrt {\tfrac {1+v/c}{1-v/c}}}$, is only for motion in a straight line. For the general case it's more complicated. -- BenRG (talk) 11:29, 13 July 2009 (UTC)

Thak you. I don't know if I understand it, but I am taking it this way. Ignoring acceleration, the trace of both observers are a rhombus, and thinking about "the velocity of the emitter when the light is emitted relative to the velocity of the receiver when the light is received", the time during which one observes the other receding is full one way, but because there is time during which one observes the other to move in the same direction, the time during which one observes the other approaching is less than full one way. While receding, the other's time is observed to run slower, and while approaching, the other's time is observed to run faster, but because "the time during which the other's time run slower" is more than "the time during which the other's time run slower", both multipied is the same?

Like sushi (talk) 02:13, 14 July 2009 (UTC)

I tried calculation.

When the distance at which both swicth from receding to approaching is l, the time observed to pass during recesion and aproach seem to be both

${\frac {l}{2v}}{\sqrt {\frac {c-v}{c+v}}}$

and the time during which one observe the other to recede and approach added seems to be

${\frac {l}{v}}{\sqrt {\frac {1}{1+{\frac {v}{c}}}}}$

${\frac {former*2}{latter}}$ = ${\sqrt {1-{\frac {v^{2}}{c^{2}}}}}$

Am I doing wrong?

Like sushi (talk) 04:42, 14 July 2009 (UTC)

Dumb sheep

What is Natalie Angier talking about 44 minutes into this 1995 Charlie Rose interview when she apparently states that the encephalaization quotient for sheep is the "highest of any mammal"? http://video.google.com/videoplay?docid=946792731875962671&ei=QKVZStmnCIPslQeU3sWoDg&q=natalie+angier&hl=en There is NO WAYYY we didn't know the EQ of sheep in the mid 90's, which, so far as I can see is nowhere near the largest of any mammal. So what is she talking about? —Preceding unsigned comment added by 67.240.160.115 (talk) 09:29, 12 July 2009 (UTC)

Well there is a lot of bullshit out there. However, I listened from 41:00 to 47:00 and she didn't come anywhere close to mentioning sheep or encephalization quotient.--Shantavira|^{feed me} 10:59, 12 July 2009 (UTC)

Oops sorry here's the right link: http://video.google.com/videoplay?docid=-8169749641559849989&ei=PbZaSumdLaXqrAL4za3JDw&q=natalie+angier&hl=en&emb=1 ......anyone? —Preceding unsigned comment added by 67.240.160.115 (talk) 04:30, 13 July 2009 (UTC)

Well, she also says that without dung beetles "we wouldn't have a planet", so I'd take her pronouncements with a grain of salt. Anyway, page 243 of Macphail, E. "Brain and Intelligence in Vertebrates". Clarendon Press, 1982 lists the following EQs:

Man           7.44
Dolphin       5.31
Chimpanzee    2.49
Rhesus-Monkey 2.09
Elephant      1.87
Whale         1.76
Dog           1.17
Cat           1.00
Horse         0.86
Sheep         0.81
Mouse         0.50
Rat           0.40
Rabbit        0.40

I looked in the book she was hawking and saw the sheep EQ assertion, but there wasn't any citation for it, or even a notes section. --Sean 15:05, 13 July 2009 (UTC)

It's of note, in that list, that the sheep certainly is the dumbest of the large mammals listed. (Obviously "large" is somewhat subjective but mouse/rat/rabbit aren't large by any definition.) That being said, being just slightly "dumber" than a horse ain't too bad. Not like being as dumb as a rabbit, which even in causal acquaintances are pretty dumb. --98.217.14.211 (talk) 20:51, 13 July 2009 (UTC)

Trading agro products

Is there a Board of Trading where all agro products are traded? So far, I only found the more important like coffee, rice and such stuff. --Quest09 (talk) 11:08, 12 July 2009 (UTC)

OR Some (most?) vegetables don't get traded by boards of trading because they are grown on contract. I.e. depending on company rules/contract terms, a company like Green Giant will give the farmer the seeds, the fertilizer and if required pesticides (or issue rules for "organic" produce) and will come pick up the harvest with their trucks right from the field. They'll process and package the produce in their facilities and deliver to their distributors. Smaller non-contract producers will sometimes make contracts directly with local supermarkets. Restaurants and small markets pick up produce at local Farmer's markets sometimes.71.236.26.74 (talk) 20:48, 12 July 2009 (UTC)

Check out List of traded commodities which has a list of commodities and the location where they are traded.--SPhilbrickT 23:00, 12 July 2009 (UTC)

This is list is clearly incomplete. Frozen orange is not there, frozen butter is not there. The question still remains: are there other products like dried garlic, apple juice or the two in the last sentence so uncommon that no trading board would trade them? I understand that lettuce, strawberries or even tuna can not be easily traded by a board, but many other precisely defined product should be traded in a trading board. Just compare it with the small caps that are traded at stock markets. How small must a market be to be excluded from a trading board? --Quest09 (talk) 10:19, 13 July 2009 (UTC)

Plse. feel free to expand the article with well sourced material. Your question wasn't really a Science question to begin with and you might have had more luck on the Humanities desk. (There's some discussion on creating a business desk because "humanities" don't really come to mind there.) I don't really see a necessity for things to be traded by a board. FWIW the following links might help Onion Futures Act, [25], [26], [27], [28] probably not a good article reference, but for information check out commodities trading sites e.g. [29] -- 71.236.26.74 (talk) 17:10, 13 July 2009 (UTC)

I can't really comment on the reasons, but I think organized market trading is more of the exception than the rule for ag products. Feedstuffs, for example, seem to be bought and sold through individual contracts, even through they are fairly standard and traded in large quantities. (I'm not 100% sure about this. I know it is the case for animal byproducts, but not as sure about others). ike9898 (talk) 19:23, 13 July 2009 (UTC)

Why do men and women exist? (evolutionary biology)

This might seem like a simple question, but I still can't figure out the answer. Evolution of sexual reproduction gives some plausible reasons for the development of sexual reproduction, in the sense of reproduction requiring more than one individual. But why are we and many other species not hermaphrodites (like Earthworms and plants)? After all, this seems like an advantage to me: a hermaphrodite can reproduce both as a male and as a female, thus increasing its reproduction chances. --filip (talk) 11:21, 12 July 2009 (UTC)

An earthworm has been around for a long time. It hasn't evolved much. This is one of the reasons for it. Having two sexes increases the chances for evolution and diversity. Rkr1991 (talk) 11:33, 12 July 2009 (UTC)

Expanding a little on Rkr1991, some creatures (eg aphids) will even reproduce by parthenogenesis at times when food is plentiful, making an immediate supply of identical creatures to consume the food. Later they will reproduce sexually to increase their diversity. Hermaphrodites will turn into female to take advantage of good conditions, as one male is enough to impregnate many females. This type of arrangement is suitable where quantity of population is needed for species survival. I all these cases the young are produced and left to their own devices.

In higher animals, much of survival depends on the (few) young being well cared for and educated, over long periods of time. This makes a variably large number of females a disadvantage, over a fixed smaller number having the permanently female characteristics needed for the nurturing of the young. In other words, we don't come in two sexes to be able to conceive more young, but to be able to nurture to maturity the few young that we do conceive. - KoolerStill (talk) 12:19, 12 July 2009 (UTC)

The benefit of not being hermaphrodites is that there are adaptations in the two sexes that make child rearing more efficient. For example, if we were hermaphrodites, we'd all have to have all of the baby-making apparatus - mammaries, womb, fallopian tubes, extra-large hips, monthly periods, etc. Since human children cannot be abandoned to fend for themselves at birth (as is the case with the offspring of hermaphroditic species) - it takes a minimum of two individuals to care for the child - one to stay home and look after it - the other to hunt the mammoth for supper. The one who is hunting the mammoth is more a more efficient hunter because he doesn't have to carry around all of that baby-rearing stuff. Of course, in reality - the split came a very long time ago when some hermaphroditic ancestor of all non-hermaphroditic animals evolved to have two different sexual morphologies - we would really have to ask the question as to why the change was most beneficial for THAT creature - which is tricky because it's unlikely that we know precisely when that happened and why. SteveBaker (talk) 14:31, 12 July 2009 (UTC)

Steve, that explanation applies to very few species, so clearly is not the explanation. It also smacks of 'Man, the mighty hunter' anthropology, which surely was discredited years ago because it doesn't really make sense? 86.140.144.220 (talk) 18:28, 12 July 2009 (UTC)

Agreed. Steves explanation, especially the part about having a womb and boobs making someone a less efficient hunter is a pile of steaming bs.

bs or not (ok bs) - 2 sexual organisms tend to be(are) higher up the food chain - thus a grain of truth

There is some sort of link here - 83.100.250.79 (talk) 21:35, 12 July 2009 (UTC)

The latest explanation, for which there is some recent experimental evidence involving sexy & unsexy snails (actually sexually and asexually reproducing) is that the main benefit of sexual reproduction is parasite protection because a greater genetic variety of individuals is generated with each generation. Far more individual variation is provided by recombination of chromosomes than by single codon mutations. alteripse (talk) 18:58, 12 July 2009 (UTC)

That explains the point of sexual reproduction, which the OP already said he understands, but I don't see how it relates to the actual question: what's the point of some snails (or humans) having only male reproductive organs and some having only female reproductive organs? —JAO • T • C 19:33, 12 July 2009 (UTC)

You are correct, I misunderstood the question. I suspect it has to do with the expense of maintaining parallel or bipotential reproductive systems not being worth it. There are a few vertebrates, like the wrasse that have capability to change sex if environmental circumstances make it advantageous. alteripse (talk) 20:17, 12 July 2009 (UTC)

Men and women exist because the far more primitive organism(s) from which we evolved found pressures to reproduce sexually. It was advantageous for some earlier link in the chain of life forms that led to us to reproduce sexually. It doesn't make sense to ask why we didn't switch back to asexual reproduction. (I realize the OP didn't ask this question.) The possibilities of the configurations both physical and behavioral of life-forms is bewildering. Why don't we have antennae? Why don't we possess the ability for echolocation? Bus stop (talk) 20:44, 12 July 2009 (UTC)

The primary function of sexual reproduction is to generate new combinations of alleles of the genes of two organisms. In hermaphroditically generated offspring, all the genes come from the same animal, so you don't get novel combinations. Looie496 (talk) 21:56, 12 July 2009 (UTC)

No. Hermaphrodites, even those that are technically able to, avoid copulating with themselves, so generally the genes will still come from two different animals. Again, this question was specifically not about sexual vs. asexual reproduction. —JAO • T • C 11:57, 13 July 2009 (UTC)

Because it takes a long time to rear the young, there is no point having 99% of the population being able to turn female and HAVE young all at once. They will then have to remain female for the ages it takes to rear the young, including the ability to feed them, which is a substantially bigger change than just changing the reproductive organs short-term. Food supply for the large number of young (and supporting mothers) would become a big problem, with very few food providers not engaged in rearing offspring. All the hermaphrodites just produce some eggs and go their merry way as whatever sex they then turn into. Having the majority of the population do this in good times increases the numbers, and therefore their survival chances as a species while lowering the chances as individuals -- which you can't afford with young that have years of work invested in their nurturing. Higher animals go for quality rather than quantity. - KoolerStill (talk) 18:33, 13 July 2009 (UTC)

But many, many, many animals that do not rear their young have roughly 50/50 male/female ratios, without being hermaphrodites. Again, you are offering (some)higher-animal-specific explanations for something that evolved much earlier, and neglect the species (for example, some garden birds) in which both parents share the child-rearing and feeding, and... it just really doesn't answer the question. It's just the usual 60's explanation of why contemporary gender roles were natural and part of our basic nature. It assumes that the usual situation in 'primitive' cultures and higher animals is for the male to provide most of the food for the children and female. 86.140.144.220 (talk) 21:50, 13 July 2009 (UTC)

Why not hermaphrodism instead of gonochorism? Both strategies can work, but in many instances hermaphrodism is subject to specialization by individuals, leading to gonochorism. Suppose there are many available partners around, and an individual happened to fail to develop the eggs it was carrying but instead used the energy of egg development and nurturing for inseminating others. In many cases it could be much more successful in spreading its genes into the next generation than the typical hermaphroditic individual, who would inseminate fewer times due to the higher resources needed to develop eggs, lay them, and perhaps care for young. In such situations, it would be common for insemination specialists to evolve, and from this the species could easily establish them as a requisite male sex distinct from the egg carrying individuals. -R. S. Shaw (talk) 04:00, 14 July 2009 (UTC)

And keep in mind that this works both ways: the individual that develops the eggs would not have to spend energy for insemination of other individuals, so would be more successful in bringing forth her progeny. FWiW 76.21.37.87 (talk) 08:09, 14 July 2009 (UTC)

Plz help me quickly(some science related questions)

1>Which Filter is used for passing ONLY HIGH frequency a: LADDER B. crystal

2>If water is heated from 0degree to 10 degree effect on volume a: increase steadily b: remain same c: decrease steadily

3>if we dig EARTH FROM North to South pole and a stone is dropped in it then efffect on its velocity a :increase continously b: First increase and become Zero in center c. It Will Start Oscillate

4>Radiation pattern of loop antenna a: cardioid b. semicircular c. circle d. none

5>plural of "DIBIYA"IN HINDI  ?

6>RADDISH is a a: modified root b: bulb c; stem —Preceding unsigned comment added by Swapnendu (talk • contribs) 11:36, 12 July 2009 (UTC)

Pardon me if I am mistaken, but this looks like homework. The Reference Desk does not do your homework. You can try reading the relevant articles or consult your textbooks. If you still have doubts in understanding any particular concept, we would be happy to help. Cheers. Rkr1991 (talk) 12:01, 12 July 2009 (UTC)

I also thought "homework" but I wonder what sort of class would ask questions that diverse. Anyway, coincidentally if there was a hole from north pole to south, or any other line through the centre of the Earth, and all air was evacuated from the hole, it would take 42 minutes to traverse the passage (42, of course, being the meaning of life, the universe and everything). Anyway, velocity of a falling object is due to acceleration due to gravity. At the start of the drop the stone would have the whole world ahead of it - the whole world has quite a bit of gravity. By half way, it'd have half the world ahead and half behind - so would be pulled equally in both directions. As it approached the other end of the tunnel, it would have more and more of the world behind it, pulling it back. Repeat. --203.129.49.222 (talk) 12:10, 12 July 2009 (UTC)

oh and...

1. A high pass filter passes high frequencies. <- If it's homework, check your text book. Radio filters can be made with crystals, but also look a little like a ladder.

2. Hotter gasses or liquids have greater volume. Water is a liquid.

4. See loop antenna

5. Sorry, try the language ref desk.

6. See Raddish, root, bulb and stem

--203.129.49.222 (talk) 12:15, 12 July 2009 (UTC)

Actually for number 2, the volume would increase, then decrease. Water reaches its maximum density at 4°C, which is why water expands when frozen. Chaosandwalls (talk) 13:49, 12 July 2009 (UTC)

This does sound an awful lot like homework - but much nicer answer to Q3 (which is a very complicated question unless there are a LOT of caveats) is that the air pressure in the hole increases the deeper you go - and quite a long time before you reach the center of the earth, the pressure would be sufficiently high to liquify the air - hence your rock will fall for a very long time (because it'll reach terminal velocity quite quickly) then make a very, very distant "splash" sound and then slowly sink to the center of the earth. If there is a vacuum throughout your tunnel then 203's answer above is good enough. For 203's benefit, the reason the hole has to go from North pole to South pole is because coriolis forces on the rock would cause it to hit the sides of the tunnel on the way down if it were drilled in any other direction...so it's NOT true that just any old hole would do! SteveBaker (talk) 14:21, 12 July 2009 (UTC)

I believe 42 is the answer to a couple of other interesting questions as well, which I vaguely seem to remember. I think it is half the time period of an infinitely ling pendulum, and something to do with waves which I can't remember.. And Steve, don't forget that these are just ideal imaginary textbook problems, so we should approach it without thinking too broadly...Rkr1991 (talk) 15:18, 12 July 2009 (UTC)

Perhaps you are thinking of the angle of the bow waves formed by a ship - irrespective of shape or speed through the water - which is 42 degrees. SteveBaker (talk) 16:13, 12 July 2009 (UTC)

If you have a source for that, you may want to add it to 42 (number). Deor (talk) 16:16, 12 July 2009 (UTC)

also number of faces on a football Truncated rhombic triacontahedron - thus football is not the meaning of life...83.100.250.79 (talk) 19:50, 12 July 2009 (UTC)

General all-over soreness and tenderness when ill

I appear to be coming down with some nasty virus, and it has me curious. Nearly every time I get sick, I always get a very unpleasant feeling of general weakness, tenderness and soreness all over my body. It makes me want to curl up in bed and not move. Every tactile sensation, particularly unexpected ones, has a note of unpleasantness that it doesn't normally have. What is the cause of this general "unwellness" symptom? Note: I don't want a diagnosis, that's what I'll go to the doctor for. I'm just curious about the actual mechanism behind the symptom. Maelin (Talk | Contribs) 11:46, 12 July 2009 (UTC)

I have the idea that it comes from interferons and other cytokines. Exactly how they do it I have no idea. I seem to recall that this is considered to be adaptive because it keeps you from running off after mammoths while you're sick. --Trovatore (talk) 11:55, 12 July 2009 (UTC)

Our most relevant articles seem to be Malaise and Sickness behavior, which may lead you to more information. Trovatore's response appears to be borne out by Hyperalgesia#Causes. Deor (talk) 14:37, 12 July 2009 (UTC)

Malaise is my favorite symptom ever; it sounds like some sort of jungle fever. If you call up your boss and tell him your doctor says you have malaise, I can bet that boss is going to let you stay home. :-D -RunningOnBrains^{(talk page)} 22:45, 12 July 2009 (UTC)

What mechanisms trigger vasodilation?

I've been researching a minor affliction I suffer from which I think is cholinergic pruritus (but note that this is not a request for medical advice!). Assuming it is that, is the following an accurate description?:

I get too hot (or embarassed etc.) > ... > ... > Histamine is released as a vasodilator > This also makes C fibers fire which causes the itch sensation (H1 antagonists such as Loratadine are very effective preventatives.)

So, firstly, is that right? Secondly, what happens in the dotted sections? How does thermoregulation work? What detects elevated temperature, what releases histamine (mast cells?) and how are signals sent between the two? Thirdly, what is it that makes me different from most people? Is it how much histamine is released, or how sensitive the nerves are to it, or something else?

My curiosity yearns for further insight so thank you very much for any information you can give on these mechanisms. ASmartKid (talk) 14:14, 12 July 2009 (UTC)

[From Terry0051] May I suggest some preliminaries -- like first taking a step back and having another look. Look at as many alternative explanations as you can find. It might not be the complicated thing you suspect. Common things happen most commonly. Skin is a temperamental and individual tissue/organ. For an otherwise healthy young person, traditional homespun measures to get you comfortable can often be all that is needed. Try various simple and safe measures. Beware of pharmaceutical (over)use. If still uncomfortable, get yourself along to a physician. Good luck. Terry0051 (talk) 21:07, 12 July 2009 (UTC)

Thanks for your concern but I'd love some info on the mechanisms, regardless of what I have. ASmartKid (talk) 16:33, 13 July 2009 (UTC)

Don't know, but the following articles might help Thermoregulation, Human homeostasis (stub), Homeostasis, Vasodilation. 71.236.26.74 (talk) 17:24, 13 July 2009 (UTC)

Abdominal muscles

I have a feeling this question may well be rejected as medical advice but if it is, it was still worth trying. I'm currently working on my abs in hope of getting a sixpack and, after looking around online, the bicycle crunch seems to be the exercise of choice. Now I've been doing this for a while and have noticed it's getting easier and am looking for a way to make it more challenging, in the hope of causing more muscle development. Is there any suggested way of altering it? I've tried making my elbows meet my leg closer to the hip, rather than meeting at the knee as suggested, and this has definitely been tougher. I'm open to any suggested or even suggestions of different exercises to try. Thanks 92.2.120.88 (talk) 15:19, 12 July 2009 (UTC)

According to the crunch article, “the difficulty of the crunch can be increased by lying on a declined bench and/or holding a weight on the chest or behind the head.” Red Act (talk) 16:11, 12 July 2009 (UTC)

Or attaching weights to your legs. Anyway, you'll only get a six pack if your fat is low enough.--Quest09 (talk) 18:57, 12 July 2009 (UTC)

Who needs a six-pack when you can have a whole keg... ;)--Jayron32.talk.say no to drama 04:56, 13 July 2009 (UTC)

I'd imagine it's unlikely that the average person which achieve a six-pack merely through abdominal crunches. As mentioned above, you need to have sufficiently little fat for it to show. I got lucky in that I'm pretty skinny anyway, so exercises tend to work and I got one pretty easy (and as an unexpected byproduct of exercise). I recommend you just keep trying like you are, and if it doesn't work, combine it with another form of exercise which is more efficient at burning away fat (for example, running). As for altering it, or making it harder, the best way is to have weight added as suggested above. Remember though that the key point is reducing the fat levels around your stomach area sufficiently for a six-pack to show as it's pretty easy for fat to cover up the strongest of muscles. Regards, --—Cyclonenim | Chat  19:34, 12 July 2009 (UTC)

Video... thing to I.D

Not for the squeamish. Link. Online guesses include slime mould and tubifex worms. Neither seems quite right. To me, there's something wrong with the supposed scale in the vid; given the size of the supposed tunnel, you'd have to guess the large one here is about a foot high or thereabouts, but the water doesn't look right to me. Water doesn't miniaturize properly and the way this water behaves makes me think there's some trickery involved, like the tunnel is more like six inches high instead of six feet. Gross, anyway. Matt Deres (talk) 16:28, 12 July 2009 (UTC)

I agree it's probably a 6" sewer - with one of those remote cameras 'they' have (ie they = CIA hopefully.. help) 83.100.250.79 (talk) 17:19, 12 July 2009 (UTC)

Apparently 6"CP = 6 inch clay pipe. (or concrete or cement )

also see http://www.cassiopaea.org/forum/index.php?action=printpage;topic=12820.0 83.100.250.79 (talk) 17:28, 12 July 2009 (UTC)

or http://www.news14.com/content/local_news/triangle/611427/raleigh--sewer-creature--surprises-city-officials/Default.aspx 83.100.250.79 (talk) 17:31, 12 July 2009 (UTC)

http://www.villageoffruitport.com/bryozoan.htm 83.100.250.79 (talk) 17:34, 12 July 2009 (UTC)

Actually, it looks very much like a slime mold. I would be surprised if it were not one. There are hundreds of varieties of slime mould. This one seems likely to be a Dictyostelid or something similar. --Jayron32.talk.say no to drama 17:50, 12 July 2009 (UTC)

I'm not disagreeing - but the thing is red - can a slime mold be red? also the things move quickly and appear to be 1" long - I wonder if there's a mixture of different things in there? 83.100.250.79 (talk) 21:09, 12 July 2009 (UTC)

See also this discussion from a few days ago. 62.78.198.48 (talk) 18:04, 12 July 2009 (UTC)

offtopic someone should tell the Church_of_the_Flying_Spaghetti_Monster - if they didn't already know... mmh I wonder [30] 83.100.250.79 (talk) 19:07, 12 July 2009 (UTC)

Cartanium?

Watching Top Gear, they mentioned a new Zonda car which is made of something like Cartanium or some other made up name, a combination of carbon fiber and titanium. The first mention of titanium and carbon makes me think of titanium carbide, which if my memory serves me correctly, is brittle and thus a big reason we don't extract titanium through the blast furnace. Anyone heard about this cartanium or similar name, and why it's so different to titanium carbide? Regards, --—Cyclonenim | Chat  19:26, 12 July 2009 (UTC)

titanium carbide could like any other brittle material be made in to fibes eg glass fibres, basalt fibres

Cartanium i suspect is a joke - ie car-tanium eg indestruc-tanium [31] , category:fictional materials etc.83.100.250.79 (talk) 19:38, 12 July 2009 (UTC)

Just a mention at Pagani Zonda#Zonda Cinque. I haven't found any clear description on the Web, but that's not surprising; I suppose Pagani wants to keep the details secret. Deor (talk) 20:01, 12 July 2009 (UTC)

I've no idea what exactly they do, though I wouldn't be suprised if it were something like this [32], though it could equally as likely be something else involving titanium and carbon... (I'd imagine that the price of a relatively new material would be just as effective as preventing copying as secrecy - I doubt they were trying to cut costs on the design :) 83.100.250.79 (talk) 20:52, 12 July 2009 (UTC)

If it is TiC coated then the aim is to protect the fibre, - it seems that other strong metals are not as good see [33] 83.100.250.79 (talk) 20:57, 12 July 2009 (UTC)

It would be easier to guess if it was known what part of the car was being made - other options exist - such as titanium metal with carbon, or titanium carbide fibre reinforcement, and carbon fibre with titanium carbide inside it eg [34] mentions brake discs. 83.100.250.79 (talk) 21:03, 12 July 2009 (UTC)

If anyone is curious, the actual term used was "carbotanium". --Mark PEA (talk) 11:46, 13 July 2009 (UTC)

Ahh that's the one, thanks! Regards, --—Cyclonenim | Chat  14:34, 13 July 2009 (UTC)

Primate Relatedness

I know that the apes are the closest relatives to humans, with the Chimpanzee/Bonobo being the closest to humans out of the apes. I also know that Old World Monkeys are then the next closest in relatedness to humans after the apes, but which living species of Old World Monkey is closest in relatedness to apes, and thus humans? Hot floppy bread (talk) 21:00, 12 July 2009 (UTC)

Remember that the evolutionary tree spreads (sideways), and is not purely linear - so that the old world monkey closest to apes is not necessarily the closest to humans. (Though it probably will be having said all that)83.100.250.79 (talk) 21:07, 12 July 2009 (UTC)

Indeed that is something I should have taken into consideration. If there are two different species for ape/humans I suppose I'd be interested in what both of them are. I was thinking it may possibly be a species of Macaque seeing as some of them have not much of a tail, although I suppose that it is far more likely a result of paralell evolution between the macaques and apes rather than a direct linear evolution from macaque to ape.

It seems that the prevailing opinion is that the old world monkeys are a monophyletic group, that is, they all derive from a single common ancestor species. This would mean that they are all equidistant from humans in evolutionary terms. Looie496 (talk) 21:39, 12 July 2009 (UTC)

Interesting, thanks. So that obviously explains the relatedness in evolutionary terms, but presumably the genetic relatedness to humans would differ within the old world monkeys, considering the wealth of diversity found within the family? If this is the case, which species would genetically be the closest (if this is even known at all)? Hot floppy bread (talk) 21:53, 12 July 2009 (UTC)

Even if the genes of all were known I think you would be looking at different species sharing and lacking matching dna (with humans) to varying extents (not necessarily the same sets of genes) - possibly with no clear winner. eg which of "1235" and "1245" is closest to "12345". Maybe it would be best to ask in terms of characteristics. 83.100.250.79 (talk) 22:05, 12 July 2009 (UTC)

Looking at characteristics leads to endless disputes with no principle way of resolving them. If you look at genes, and if you buy into the prevailing dogma that average rates of genetic change are constant over time, then the Law of large numbers applies: with thousands of genes to take into account, the differences between various species of monkeys and humans should all be the same to within a few percent. Looie496 (talk) 00:22, 13 July 2009 (UTC)

"The prevailing dogma that average rates of genetic change are constant over time" is neither a dogma, nor an assumption, nor true. It seems to be approximately true for certain types of non-coding DNA among closely related animals with similar generation lengths. --Stephan Schulz (talk) 12:05, 13 July 2009 (UTC)

Gametogenesis in Hermaphrodites (earthworms)

I understand earthworms, nematodes, and several other species reproduce sexually with both sperm and egg production. Since they are hermaphrodites, and they perform both oogenesis and spermatogenesis, I wonder how they split their chromosomes during meiosis. Do they have an X and a Y, or do they have some type of sex determining chromosome?

And how exactly do they form sperm and egg? I know during meiosis in humans, it is supposed to be only sperm or only egg, and the determining chromosome, the Y in males, is what leads to the formation of male sex organs. Do earthworms have specific karyotypes for male or female? XX or XY?

And how are male earthworms made? (A small percentage apparently have only male sex organs).

I ask this because I have learned about the XX and XY chromosomes, but I can't understand the concept of meiosis in hermaphrodites.

Any biologists please help.

--Screwball23 talk 22:11, 12 July 2009 (UTC)

The Sex-determination system article is a good place to start. It addresses some of your questions directly, and provides links for further reading. --Dr Dima (talk) 23:08, 12 July 2009 (UTC)

July 13

Tornado Hypothesis

Hi all,

I would like to open a discussion about a thunderstorm and tornado hypothesis I have developed. Where in Wiki would be the best place to present the theory and data I have compiled as it is to long to be placed here? Thanks

Original research doesn't belong anywhere on Wikipedia. There are lots of places where you can start a blog; that's what you need. Looie496 (talk) 05:53, 13 July 2009 (UTC)

Yeah, see Wikipedia's no original research policy. Blogger is one very popular place to start a blog. It’s what my girlfriend uses for her dog agility blog. The blog article would be a good place to start to find other possible places to host a blog. Red Act (talk) 06:20, 13 July 2009 (UTC)

http://weather.wikia.com might be suitable (I don't know their policies, you'd have to ask there), or you could search for a meteorology discussion board. AlmostReadytoFly (talk) 08:55, 13 July 2009 (UTC)

I'm thinking that [35] looks like an OK forum and on [36] there's even a discussion on tornadoes. These are good places to discuss your hypothesis. As other stated, wikipedia would have been the wrong place :-) EverGreg (talk) 09:30, 13 July 2009 (UTC)

Once your hypothesis is published in reputable, peer-reviewed journals (Nature (Journal) or The Journal of the American Meteorological Society - for example) - and has perhaps been received favorably at some prestigious meteorological conferences - then Wikipedia should probably have an article about it. But until then, it's just some idea some guy had...and if we had articles about every idea any random person had - we wouldn't be an encyclopedia anymore! Our job is to collect facts - and your hypothesis isn't yet a fact - other than "It is a fact that you thought about it"...and that's not a particularly notable fact. Good luck with turning your hypothesis into a theory!

Remember: A good hypothesis explains phenomena for which we currently have no good explanation - and it makes predictions that can be tested experimentally. SteveBaker (talk) 11:42, 13 July 2009 (UTC)

INMARSAT segment

Does anyone know what are network coordination stations (NCS)and Network operations center(NOC)in the ground segment of INMARSAT satellite system? or any other info about segments of INMARSAT..ThanksShraktu (talk) 11:58, 13 July 2009 (UTC)

What do mango pleco's eat?

What do mango pleco's eat?Mangopleco (talk) 14:23, 13 July 2009 (UTC)

This site says it's an aufwuchs eater: "Feeding off the bottom of the aquarium, it gets most of its nutrition from left over food and algae. If there is no algae or left over food present, supplement with high quality flake food, sinking carnivore pellets, freeze-dried bloodworms, and tubifex". --Sean 15:54, 13 July 2009 (UTC)

Possibly avoid too much meat and give veg. —Preceding unsigned comment added by 83.100.250.79 (talk) 16:32, 13 July 2009 (UTC)

Baryancistrus by the way - possibly L47

Wood - ie Bogwood or driftwood is a very good idea - for juveniles it can be essential - not only does the wood provide roughage - but aufwuchs can grow and colonise the driftwood far better than glass/other things in the aquarium.

They might like soft leaved plants like cabomba (they will totally eat it if they do)

Also in the aquarium catfish wafers (ie plec wafers are good)

Also any vegetable - cucumber, spinach etc.

Also algae.

[37]

or just search for "mango plec feeding"83.100.250.79 (talk) 16:31, 13 July 2009 (UTC)

Was this a question about a pet fish? What they eat in the wild is different.83.100.250.79 (talk) 17:44, 13 July 2009 (UTC)

As above, almost all plecs eat aufwuchs (also see periphyton which is pretty much the same thing)

http://www.scielo.br/scielo.php?pid=S1679-62252005000400011&script=sci_arttext Here someone cut open a dead baryancistrus (not the same species) and found - guess what - aufwuchs.

Also see this http://www.planetcatfish.com/shanesworld/shanesworld.php?article_id=382 - it's about plecs in general - some dead ones that people are going to eat (if you are very squeemish) - there are some interesting images

Image 11 - Aufwuchs - if you are wondering what aufwuchs are - they are the tiny things that live on slimy rocks that you find in a river - image 11 is of slimy rocks - they eat the slime, the things that live in the slime, and the green algae that is part of the slime.

In fact they are alot like sheep or cows - that eat grass - constantly grazing (obviously they are smaller)

Last image - very long stomach.

Also in the wild they will eat dead stuff - eg dead fish, or dead animals that have fallen in the water - ie carrion. But most of the time they just graze - they're not fussy eaters.83.100.250.79 (talk) 17:58, 13 July 2009 (UTC)

Note that aufuchs/periphyton contains a lot of small insects and larvae - so there is 'meat' in it - a bit like meat and vegetable stew.83.100.250.79 (talk) 18:00, 13 July 2009 (UTC)

Alcohol and Exertion

Not medical advise. I get exceptionally winded when working out hard for more than 20 minutes. After that, it feels like I can't go on and my lungs are gonna burst. However, one day I went to a bar before hand and had a vodka shot with a friend. 15 minutes later, I went to work out and for some odd reason, I was able to work out beyond 20 minutes and not feel like my lungs were gonna burst. I was sweating, my heartright was up and I did the same exact thing I did everytime I went to the gym. So to test this again, I repeated this the next week. Monday, no vodka shot, same situation, winded after 20 mins. Tuesday, one vodka shot, was not winded. What medically could be happening? I am not looking for medical advise. I am asking those medically inclined how the alcohol could somehow affect the lungs in such a way that it allows for more oxygen, I dunno. --Reticuli88 (talk) 15:17, 13 July 2009 (UTC)

(Wild speculation) could it be that the alcohol relaxes your muscles a little? I'm just guessing, but without my inhaler any amount of sport is liable to make me gasping for a deep breath, yet with my inhaler (a wonder of modern medicine I might add) I can compete with almost all my friends in terms of longevity of energy. Perhaps the alcohol is having a similar impact as my inhaler does (which I think is that it relaxes the ventricles/something in my lungs to make breathing easier). ny156uk (talk) 15:43, 13 July 2009 (UTC)

Alcohol is known to dilate blood vessels (see here and here), increasing blood flow. I'm unaware of any information on the effects of alcohol on the lungs. Disclaimers notwithstanding, you should direct any serious inquiries to a medical professional. — Lomn 15:52, 13 July 2009 (UTC)

Use of performance-enhancing drugs in the Olympic Games, Doping at the Tour de France, and List of doping cases in sport all list alcohol as a performance-enhancing drug (mostly from the lower-tech past). --Sean 16:04, 13 July 2009 (UTC)

While you might be correct, there may be some bias built into your experiment. The scientific controls would seem to be lacking, the exact amount of time you spend lifting vs resting, the quality of how you do the exercises, other things you've done that day, what classifies as "winded" and so on. Just the belief you have formed that alcohol has improved your performance may affect your results. Perhaps while you're trying things, however, you might have a go with caffeine - I've heard it's one of the most effective legal performance enhancing drugs and that many competitive athletes use it before events (I read specifically on runners). TastyCakes (talk) 16:33, 13 July 2009 (UTC)

I agree with this. Scientific studies say that alcohol reduces the ability of muscle cells to use glycogen, their primary fuel. Since alcohol also impairs judgement, it is likely that you're not really working as hard after the drink as without it. I have to say that for me personally, the sedative effect of alcohol is so strong that I would never think of taking a shot before working out, it would make me too lethargic. Looie496 (talk) 17:05, 13 July 2009 (UTC)

Einstein equations for scalar field plus gravitation

My question is: Is it true that static solutions to the Einstein equations for a real scalar field coupled to gravity always have a singularity? I found this statement in several research papers, but without any reference to a paper or book where this is proved (I know that there exist some explicit examples of such solutions with singularities, but I am interested in a more general statement).XYZsquared (talk) 16:19, 13 July 2009 (UTC)

Amount of life on Earth

Is this quantity fairly constant? I guess you can interpret this question in terms of the number of living cells. Whenever any living organism dies it provides food and nutrients to some other organism which then can reproduce. So, barring a global catastrophe, is the amount of life on Earth constant? —Preceding unsigned comment added by 75.52.253.33 (talk) 16:47, 13 July 2009 (UTC)

Probably not. Atmospheric carbon dioxide and oxygen levels have varied quite substantially for the last billion years, and amount of sunlight available for photosynthesis was not exactly constant, either. Besides, different species comprised the bulk of the biomass at different times. So I do not see any solid basis for your hypothesis. Sorry. --Dr Dima (talk) 17:05, 13 July 2009 (UTC)

I'm not aware of any rigorous data on this, but I would say it's surely not constant across all time scales. On a yearly time scale, the amount of land life is quite a bit higher during the northern hemisphere summer than during the northern hemisphere winter. On geological time scales, the total amount of life seems very likely to decrease during heavily glaciated periods, and also following catastrophes that lead to mass extinctions. Looie496 (talk) 17:11, 13 July 2009 (UTC)

Organic matter doesn't always get consumed by another organism. It sometimes gets turned into oil, for example. Limestone contains large amounts of animal produced calcite. There are various other examples of ways organisms get removed from the cycle. --Tango (talk) 17:40, 13 July 2009 (UTC)

The number of living cells on Earth may be constant over a decade, a century or a millennium. That is possible. I don't think there is any reason to believe that the number of living cells in one decade in time is likely to be any different from the number of cells alive in an adjoining decade. The questioner should specify what time frame is intended to be considered. Bus stop (talk) 17:53, 13 July 2009 (UTC)

white paint to fight golabal warming plan?

I read on CNN today the the US secretary of Energy wants to fight global warming by painting roads and the roofs of buildings white. My question is, will the amount of global warming fighting from the reflected sunlight be more then the penalty of producing millions of gallons of white paint? Googlemeister (talk) 18:25, 13 July 2009 (UTC)

I'm not going to calculate this. Where is that sunlight going to be reflected to? the heat will just be hanging around 4 feet above the roadways instead of 4 inches above. Overall I can't see it making any difference. The making of the paint and the labour to apply it would involve substantial costs, not to mention additional accidents from driving on glary and slippery roads. A white roof may reduce INTERNAL temperatures slightly in a building (but not as much as good insulation would). But the air above the roof is much hotter than over a dark roof which absorbs more heat (tho' this will radiate back more heat once the sun is off it). This is fine for keeping the interior of a building cool. Otherwise, this type of scheme just rearranges the deck chairs by a few feet; it won't reduce the total heat in the atmosphere....which is where global warming is happening, not under our wheels. - KoolerStill (talk) 19:01, 13 July 2009 (UTC)

Not quite true. White reflects a lot in the optical wavelengths. The atmosphere is quite transparent in the optical - that's how most of the heat came down from the sun in the first place. So a lot of the reflected light goes back into space. On a global scale this is a very small contribution. However, it reduces heat in cities and buildings, and hence reduces the need for air conditioning - which a) uses energy and hence (with the currently prevalent technology) causes CO2 production and b) adds to the urban heat island effect (there ain't no free lunch from the second law of thermodynamics...), causing cities to heat up, requiring more air conditioning... I don't know how quickly this pays of, but (some) roofs need regular painting anyways, so painting them in a highly reflective color the next time seems like a no-brainer. --Stephan Schulz (talk) 19:12, 13 July 2009 (UTC)

Painting roads a reflective white sounds like a horrible idea for a sunny day. Not to mention it would make it difficult to stay on them or anticipate curves when they are covered in snow. Livewireo (talk) 20:52, 13 July 2009 (UTC)

It sounds like another bullshit solution for a real problem; instead of addressing the problem head on, lets propose an ultimately worthless and probably even harmful solution (see Ethanol fuel, especially Corn ethanol ). The better solution is to instead work on accelerating non-combustion technologies (like solar and wind) or to get the hydrogen economy up and running. The problem with those solutions is not that they are substantially harder to implement, its that there are monied interests on maintaining the old infrastructure, or in coming up with solutions like ethanol fuel which was merely an excuse to make Archer Daniels Midland a shitload of cash. These are all distractions from the real solutions, and the sooner we get on implementing the final solutions, the better we all will be. --Jayron32.talk.say no to drama 21:17, 13 July 2009 (UTC)

Not to mention an irresistible canvas for graffiti artists. Clarityfiend (talk) 22:07, 13 July 2009 (UTC)

Does anyone know whether their "back of the napkin" calculations included the green-house gases emitted in producing that much paint? Also what type of paint were they talking? Whitewash won't stay put, so they'd have to consider something polymer like. They'd have to apply a pretty thick layer because otherwise it's just going to rub off in a hurry. With a thick layer your road will get as slippery as ice or you'll have to add grit. (OR around the corner from where I used to live in Germany a company managed to coat a bike-path in bright red polymer. They had to redo it after the first couple of cyclist's accidents.) Adding grit in turn will erode the rubber of tires like shoe-marks on no-wax floor, again leading to dark tracks. Unless they come up with a formula for white asphalt this sounds like a half-baked idea. Passing a law to have homeowners use white shingles when redoing their roof won't look pretty, will take a while to take effect (average roof life=10-15 years) but is doable. 71.236.26.74 (talk) 22:16, 13 July 2009 (UTC)

Putting the paint on roofs is not a silly idea - there are paints that aren't too harmful to the atmosphere - and it really doesn't matter if the stuff cracks and breaks up because 90% of the surface will probably still be reflective decades later. However, this isn't the thing that's going to save the planet - if it made a 1% improvement - I'd be very surprised indeed. Picking lighter materials for the roof makes more sense - pale grey roof-tile rather than dark brown or black. Waterproofed concrete roofs rather than tar-covered roofs - light-colored stone chips embedded in tar roofs where they can be retro-fitted. Rooftop gardens are probably a yet better idea. But there are two effects going on here. One is that the total albedo of the planet is improved - but that's likely to be a tiny effect. The other is that the interior of the building will be kept cooler - which in hot climates has the potential to dramatically reduce the amount of air-conditioning required. I think that's actually the main reason for doing it - and you don't have to go so far as to have a totally white painted roof to do that. Simply choosing lighter colored materials gets you most of the benefits. Painting roads does seems like a bad idea - but building concrete roads instead of tarmac is probably a reasonable alternative. The only snag is that concrete production uses a hell of a lot of energy and produces a TON of CO2. Of course when we finally realise that we have to stop oil production, there won't be any tarmac around anyway - it's basically just a waste-product of oil refining...so no more oil refining means no more tar. Currently, concrete is the only alternative...which is not so great. SteveBaker (talk) 23:06, 13 July 2009 (UTC)

Our so-called ecological footprint is largely a result of the technology we use and the energyconsumption - a person can do about 100 W of work, yet your average person's energy consumption is around 3000 W (on average, not just working hours). That's our real impact. However, our literal footprint (the amount of surface we occupy on the planet) is not all that great. And most of that is agricultural land. The actual built-up area is just a fraction of the Earth's surface. I can't find any figures, but let's assume that's on average 20 m² per person (eg 200 m² for someone living in a 10 storey building). Let's take a world population of 5 billion. That makes for a total of 100 billion m², which is 100.000 km². Earth's surface is 500 million km². So our houses occupy about 0.2 % of Earth's surface. That's a tiny amount, and even that would require a major effort. There are much better ways to invest our time and money, to put it extremely mildly.

Also, not all roofs are fit for this. In Europe, most roofs have tiles. Not that that would not be doable, but it would be butt-ugly. Especially since white buildings have a tendency not to stay white, so you'd have to do a lot of cleaning. And, as anon points out, this is especially true for roads, where you get the extra disadvantage of drivers being blinded by the light, increasing the already catastrophic deathtoll on roads (about 30 million dead and counting).

Now I don't mind if people think of alternative solutions - that's a good thing. The problem is that silly solutions like these, that can be debunked with a bit of secondary school knowledge, draw attention away from the real solutions like the development of solar cells, because it reduces them to 'just another one of the solutions'. If some politician without a clue has a silly plan that's good. At least he's thinking. What's bad is that he doesn't consult (or ignores) people who do have the brains to implement secondary school knowledge. That a news agency reports this idea makes perfect sense. But they also should have someone with some intelligence on their staff who can at the least ask the right questions, thus effectively debunking the idea.

Now I hope I haven't made any mistakes in my reasoning or calculation, because else I'll get this little rant flying back in my face. :)

Btw, Jayron is right about biofuels. Solar cells are at present already 10 times more efficient than plants can ever be (20% vs 2%). And you can put them wherever you like - on rooftops or in deserts, where they don't compete with food-production. And you don't have to harvest of process anything (which costs energy) - just install them and sit back (well, almost, but certainly in comparison). That said, it might make sense to use the parts of food-crops that are not the food-bit. That won't have a very high energy content, but if you already produce this 'waste', you might as well throw it in the oven of an power plant. The gain may be small, but the same goes for the required effort if you just use what you already have more efficiently. At least, that's just a thought of mine - please debunk where needed. DirkvdM (talk) 11:22, 14 July 2009 (UTC)

Have you ever considered that solutions being offered by a Nobel Laurette and the US government might not actually be debunked by secondary school knowledge? Either because you don't really understand the proposal, or because the implications are different than you imagine? Dragons flight (talk) 11:47, 14 July 2009 (UTC)

A Nobel Laurette perhaps, but you appear to have far more faith in the US government in scientific areas then I do. After all, the lawyers are the ones who are in charge, not the scientists, and the job of a senator is 1 part helping the country and 6 parts looking good to the voters. Googlemeister (talk) 19:08, 14 July 2009 (UTC)

The problem is that DirkvdM is only seeing one side of the benefits here. Whilst he's 100% correct that the amount of light we'd reflect back out into space would be negligable - he's neglecting the important part. A dark-roofed building is going to be hotter inside than a light-roofed one. If it's a LOT hotter - and in a place with a warm climate - that means that you're going to need airconditioning...and the amount of energy consumed by air conditioners is FAR from negligable! Worse still, the airconditioner puts out yet more heat into the outside environment - causing something of a feedback effect. Painting the roof white cuts out a significant chunk of heat - which saves on the airconditioning - which cuts yet out more heat and CO2. So the simplistic 'percentage of the earth's surface' calculation - while true and interesting - doesn't explain why the US government thinks it's a good idea. The true calculation would have to estimate the amount of additional energy expended by airconditioners in black-roofed buildings - and compare that to the total energy consumption of humanity. As I said - I doubt it's as much as 1% - but since it's a fairly cheap fix (and every little helps), new buildings really OUGHT to have lighter colored roofs (not bright white paint...but maybe lighter tiles and white gravel pressed into black tarmac roofs) - and I'd like to see the government moving towards mandating that by law. SteveBaker (talk) 20:35, 14 July 2009 (UTC)

You don't need to mandate any particular building material. Just tax energy enough while subsidizing remedies. Dirk, you seem to believe in the silver bullet. I don't. It will be extremely hard to find one technique that will cut carbon emissions by 50%. But we only need to find 50 that each reduce it by 1% (of the original, otherwise around 70, says the mathematician in me) to have the same gain. --Stephan Schulz (talk) 21:13, 14 July 2009 (UTC)

Optical Contact Bonding

What is optical contact bonding? How does it work? --72.197.202.36 (talk) 20:07, 13 July 2009 (UTC)

Google it, the google books results are particularily useful if you are looking for an explanation.

We do seem to lack an article, if no-one voluteers, of finds one, I might write it.83.100.250.79 (talk) 20:28, 13 July 2009 (UTC)

Optical contact bonding —Preceding unsigned comment added by HappyUR (talk • contribs) 20:44, 13 July 2009 (UTC)

ok stub article exists - Haven't got much time so it's not very good.

Please categorise, expand, and correct. Thanks.HappyUR (talk) 21:20, 13 July 2009 (UTC)

Thanks! --72.197.202.36 (talk) 04:52, 14 July 2009 (UTC)

amateur astronomy questions.

Lets say I buy a 8 inch telescope....

1) Are the images of moon, planets and nebulae impressive?

2) Is imaging the sun impressive?

3) Are we talking laptops and software for best effects?

I suppose the most important question....

4) Even if I get a good telescope and laptop [and a few years of observations] are we really still talking about "fuzzy dots" rather than good solid images? —Preceding unsigned comment added by 89.242.135.49 (talk) 22:21, 13 July 2009 (UTC)

I hope you realize that looking at the sun requires a special sun filter - otherwise, you could blind yourself.--SPhilbrickT 22:25, 13 July 2009 (UTC)

1) yes

2) Sure

3) why not?

4) you can get best images in the world, selling them for $$$$$ and giving names to new comets in case you got good telescope and patience to do the observations. Vitall (talk) 22:40, 13 July 2009 (UTC)

yes...ANY sun imaging would be done with a laptop..NO DIRECT OBSERVATION ... —Preceding unsigned comment added by 89.242.135.49 (talk) 22:34, 13 July 2009 (UTC)

WARNING!!! EXTREME DANGER!!! Do not EVER look at the sun through your telescope. You will quite literally burn out your retina before your eyelid has time to close. There are ways to use a telescope to project an image of the sun - but even then, you have to be really careful because you are not only concentrating the light - but also the heat. If you accidentally leave your telescope with the main lens cap off - and it happens to be pointing to a place where the sun will be in a few hours time - you could come home to a burned out house! You have to be super-careful when using a telescope in daylight.

That said:

1. The moon looks very impressive - it seems somehow more "real" than the naked eye view. Planets - less so. You'll be able to see the rings of Saturn - but it's not going to be a huge, sharp image. Most of the other planets are relatively featureless. Nebulae are soft smudges...this isn't the Hubble we're dealing with!
2. The sun...well, WARNING!!! EXTREME DANGER!!!...remember?! Let's not go there! You can safely get a good image of the sun with a home-made pinhole camera (a sheet of cardboard with a pinhole in it taped across a window works well) to produce a magnification of say 2x to maybe 8x in a darkened room. That lets you see prominances and sunspots - it costs $1 to make and it's SAFE. So just forget all about using an actual telescope to observe the sun...bad, bad, BAD idea! There are ways to do it - but you have to be really careful and do it exactly right...not the sort of thing I'd advise an amateur to attempt when the pinhole camera approach works so amazingly well.
3. The single greatest thing about computer-driven telescopes (those with TWO axis motorized mounts) is that when they are properly set up - you can tell the thing "Find me Jupiter" and it'll obediently take you there. That's a lot easier than messing around with star charts and ephemerus to find the darned thing - and as a beginner, one fuzzy off-white blob looks much like another - if you're trying to get the thing focussed in on Jupiter and you're actually pointing at a star five degrees away...you're in for a frustrating experience. The other thing a motorized mount does for you is to automatically counteract the slow rotation of the earth - which can be really annoying when you're trying to set things up because the star or planet you're looking at keeps moving! The computer can fix that for you - which is especially nice if you want to take long-exposure photographs.
4. A lot of what you see will indeed be dots...or (in the case of most of the planets) slightly enlarged dots. The moon and Saturn are very cool - but if that's all you're going to use it for, you're better off borrowing one for a few nights. When there is a comet just below naked eye visibility, the telescope will bring it into amazing clarity...probably the best thing I ever saw in my 8" reflector was comets. You can also pick up things like the space station...but without a fairly fast computerized mount, it's hard to keep it in view!

One other HUGE thing to think about is how good the "seeing" is where you live. If there is a significant city anywhere within the range of the horizon - or a small town somewhere within a mile or two - or even a street lamp 100 yards from the end of your back yard - then you may have a hard time seeing ANYTHING other than the moon and the brighter comets clearly. This cannot be over-emphasised. If you don't have REALLY dark nights - forget it - don't buy a telescope. I have an 8" reflector - which isn't a great telescope - but it was good enough when I lived out in the wilds of nowhere with a gigantic hill between me and the nearest main road. When we moved to the USA and bought a house just 20 miles from Dallas - there was simply nothing in the sky worth seeing other than the moon. Everywhere else, you just see a dim glow of the city lights reflecting off of the sky...no astronomy is possible under those circumstances.

Another consideration is the weather. You obviously need a lot of clear-sky nights (People from Seattle need not apply!) - but remember that you can't do astronomy indoors. You'll be outside - late at night - for hours (potentially). In cold climates - this is no fun! Serious amateur astronomers soon realise that they need a mini-dome system so they can be at least sheltered from the worst of the weather.

SteveBaker (talk) 22:47, 13 July 2009 (UTC)

Uh, Steve? There are safe full-aperture solar filters for telescopes that are made from materials that block enough of the Sun's light to make it safe for direct observing. That being said, an 8" telescope, even with a filter, might deliver an image bright enough to hurt while looking at it. Large-aperture telescopes are generally not good for observing the moon, either, one reason being that the light will be very bright, and another is that the magnification required to resonably work with such an aperture might make the moon appear too large. How much an 8" telescope costs depends on the type: expect to pay roughly $450 US for a Dobsonian of that size, $1300 for a Newtonian reflector, and $2500 for a Schmidt-Cassegrain. That's without any special equipment such as CCD cameras and the like. An 8" telescope may also be good for imaging deep sky objects. ~AH1^(TCU) 00:27, 14 July 2009 (UTC)

Yes, it IS possible to observe the sun - with care - with the RIGHT equipment and knowledge (and I said that) - but it's really dangerous - and we really shouldn't be recommending it...especially when a pinhole camera and a darkened room works every bit as well. I've heard of people who assumed that the "moon filter" that comes with many larger aperture scopes was a "sun filter" - and lost an eye in the process. On an 8" telescope - even the moon is bright enough to hurt your eyes (that's why most scopes come with a "moon filter"). Most scopes that come with a sun filter are much less than 8" aperture. Remember - the sun filter that works for a cheap 4" scope is letting through four times too much light if mounted on an 8" scope! This is totally not a thing for a novice telescope user to be messing with...losing an eye is just FAR too serious. SteveBaker (talk) 01:30, 14 July 2009 (UTC)

Extra warning: I had a telescope that came with a filter for solar observation at the ocular end (eyepiece). Someone at my astronomy club told me that that is also dangerous because, as Steven pointed out, you are not only concentrating the light, but also the heat. That heat still reaches the ocular, which may burst, as a result of which splinters may come off. If you've got your eye at the ocular, those splinters may end up in your eye. Sun#Observation_and_eye_damage also mentions this. The way to obsserve the Sun is by projection, as Steven mentioned. I believe that's how Galilei also did it - he held a piece of paper behind the telescope, on which he then copied the image. A modern alternative to Galilei's method is to mount a digital camera behind the telescope, connect that to a computer and view the image on your computer screen. And of course take photos. I'm not sure if this will work with a standard camera, but there are setups for this. Of course you still need a filter to avoid damaging the ocular or the camera's ccd (its retina, so to say). But even if that goes wrong, you'll still have your eyesight intact.

To get an idea of how beautiful the images are, you might contact an astronomy club to meet up with them on an observation night. They'll probably let you have a look through their equipment. And then you'll be able to compare and decide what kind of equipment you like best.

Btw, the most beautiful thing I ever saw was the Moon - with the naked eye. That was a few days after new moon, just after sunset, with just a narrow strip lit up by the Sun (waxing crescent). The rest of the Moon was quite visible, and suddenly I saw the Moon for what it is - a huge rock at a huge distance. Until then, I knew that, but that was the first time I saw it. Then it sunk in that that strip of light was a mere reflection of the Sun, which gave me a feel for the immense amount of light it emits. And that's just our little corner of our galaxy, which is just one of billions of galaxies. I never felt so tiny. Mind you, this was not so much what I actually saw, but the realisation of what it was that I saw. The same holds true for the zoomed in versions of whatever you see in the sky with your telescope. For example, Hubble images can be very beautiful in an abstract sense, but when you realise what they really are, they're mindboggling. A lot of beauty comes from knowing what it is that you're seeing. DirkvdM (talk) 09:11, 14 July 2009 (UTC)

The first time I had the opportunity to look at Jupiter through a relatively small refractor (perhaps 3 inches) it was literally breathtaking to see the moons of that planet standing out in clear detail. Years later, with my own similar telescope, and some care, it was possible to see the weather bands around Jupiter as well as its moons, and to see the rings of Saturn. A larger telescope such as the OP discusses, especially with a computer controlled drive, would make it much easier to find and observe planets. A CCD camera should make it possible to create some amazing photos. Edison (talk) 14:23, 14 July 2009 (UTC)

A spring in space

If you had a setup so a ball was put onto a spring and tied back with some force to compress the spring (as in space the ball would be weightless, no?), and then the ball was released would it oscillate forever? What would cause damped motion--no air in space, no friction due to it oscillating up and down without touching anything.

xxx(ball) (compressed)

xxxxxxxx(ball)

xxxxxx (ball)|[plate|

2) If the setup involved placing a plate a distance x from the compressed spring so that x was less then the amplitude of the springs oscillation would it strike the plate and come back (3rd law force of plate on ball), compress the spring and then repeat infintly? I think energy would be transferred to the plate though no?

3) Finally what happens if the plate in question to is replaced with a piezoelectric crystal. Could that serve as a battery? (obviously this is just a hypothetical question)

24.171.145.63 (talk) 23:16, 13 July 2009 (UTC)

1. There is friction within the spring.

2. Energy would be lost when the boll bounces against the plate. It would be transferred to both in the form of heat.

3. Energy would be lost to the piezoelectric crystal in the form of electricity.

Also, tiny amounts of energy will always be lost in the form of gravitational waves, so a perpetual motion machine is totally impossible. — DanielLC 00:07, 14 July 2009 (UTC)

If we're talking about a physical spring, there will be some friction inside the spring itself, so it will lose energy over time. With an ideal spring, or eg. a gravitational field working as one, it's possible for your ball to oscillate forever, at least in an isloated system. For example, a planet orbiting a star can actually be seen as oscillating along two perpeticular axes.

Regarding 2) and 3), as you've already said, when you make the ball strike the plate you transfer the energy, so you'll at best be able to recover the energy you already put in the system by compressing the spring, most of it however would be lost heating the ball and the plate. You're right that this could be used for energy storage, but the efficiency would probably not be very impressive.

85.222.93.28 (talk) —Preceding undated comment added 00:35, 14 July 2009 (UTC).

It won't work forever. As I already said, energy will be lost in the form of gravitational waves. This will be unimaginably slow, but it will happen. 67.182.169.172 (talk) 00:17, 15 July 2009 (UTC)

Sky colors on remoter stars

So If the star is white, then what will be the color of planet's sky, if Terra-like. Would white sun make white or purple sky? I know a blue star make a golden sky, what about a blue-white star will make deep yellow or pale yellow sky. A orange star is said on one site to make turquoise sky while pink star gives green sky.--69.226.33.240 (talk) 23:47, 13 July 2009 (UTC)

I believe the Sun is white. It just looks yellow because the blue light is scattered by the sky, hence the sky looking blue. — DanielLC 00:02, 14 July 2009 (UTC)

Some stars is technically white. Like is Vega was the su, will our sky still look blue, if sun was A STAR?--69.226.33.240 (talk) 00:15, 14 July 2009 (UTC)

Our sun IS white - but when the light enters the atmosphere, the blue light is scattered (that's why the sky is blue). Because our eyes basically see only mixtures of red, green and blue light - when you subtract some blue, you have more red and green than blue. Red and green makes yellow - so from down here at the bottom of the atmosphere, the sun looks a little yellowish.

Sorry, but this is not entirely accurate: white stars are classified as A-class on the spectral scale, while the Sun is G-class (i.e. a yellow star).

76.21.37.87 (talk) 08:15, 14 July 2009 (UTC)

76.22.37.87, I don't think you see the true science world. I've been told, human eyes do a terrible perception shift. Language scientifically, ur sun looks yellow in cmputer screen, white when seen in our blue sky, who knows what you'll see in space. 76 IP, you don't see strange human shifts on earth, when you go to Mars or Moon, then all your color vision cell will go hay tangle.--69.231.5.71 (talk) 21:24, 14 July 2009 (UTC)

76 IP, the source I past past discussion is found on this.--69.231.5.71 (talk) 21:28, 14 July 2009 (UTC)

Sorry i need to fix 76 IP's answers. He just don't know enough. For a gentle reminder, is just to clarify the rules the goal of desk is the answers to be "done right". If answers is not answer right then this destroys purpose of desk. Questioners won't want to go back and try to see what the answers is wrong. Questioners usually wants answers answer right at the "first time". And also we people won't want to bite newcomers. Since 76 IP answer is too simple and to general, it's good ot just fix comments and leave it ther.--69.231.5.71 (talk) 21:42, 14 July 2009 (UTC)

The color of the sky is determined by the nature of raleigh scattering - and the color it scatters depends on the size of the particles in the atmosphere - not the color of the star. So if the earth was orbiting a different star, then there are two possibilities:

• If there is a reasonable amount of blue light being emitted by the star - then the sky will be blue.
• If there is little or no blue light from the star - then the sky will be black and you'll be able to see stars in the daytime sky.

The star itself might look a completely different color however. SteveBaker (talk) 01:23, 14 July 2009 (UTC)

Just to clarify: You can only ever see stars in the daytime if you shield your eyes from the sun or anything lit by the sun. This applies on the hypothetical planet Steve describes in the same way it does on the Moon. --Tango (talk) 02:11, 14 July 2009 (UTC)

I think the OP is referring to white as in the spectral class: OBAFGKM. -- penubag  (talk) 07:48, 14 July 2009 (UTC)

I believe the Sun is considered yellow because that is the area of the spectrum where it radiates the most intensely. However, it could easily be considered white, as it emits strongly throughout the visible spectrum. -RunningOnBrains^{(talk page)} 21:53, 14 July 2009 (UTC)

Is just plot of spectrum Sun counts as yellow. When you actually go in space, you look as a totally different things. Your human eyes is very sensitive. Same situation as Mars. you won't even notice the coral color at all if you actually going to it personally. That's enough.--69.231.5.71 (talk) 22:01, 14 July 2009 (UTC)

July 14

Electonic ab belts/abdominators/whatever they're called...

(I'm sure that WP has an article on these - but I'll be damned if I can find it) So, those battery-powered ab belts that supposedly use electricity to rhythmically contract the muscles of the abdomen (or the muscles of whichever body part you've attached it to) and promote muscle growth without actually having to exercise and turn flabby guy --> ripped guy - quackery or effective way? I suspect that I already know the answer to this (I bought one on a whim years ago and it didn't really do much except make my abs twitch mildly for the couple of hours that the battery lasted - and the couple of hours that the next battery lasted). Is there any real science behind these devices? --Kurt Shaped Box (talk) 01:05, 14 July 2009 (UTC)

Is Electrical muscle stimulation what you're looking for? Intelligentsium 01:24, 14 July 2009 (UTC)

Yeah, pretty much. Thanks. Redirect created there from Ab belt... --Kurt Shaped Box (talk) 01:54, 14 July 2009 (UTC)

I think this is absolute BS, they're just trying to steal your money. You want strong abs, do lots of crunches (and it won't cost you a penny). 76.21.37.87 (talk) 01:30, 14 July 2009 (UTC)

Does anything help unjoin PVC?

I have a custom shaped PVC part for electrolysis. A part inside needs fixing, the only way I can get tools close enough is to remove the PVC pipe that is bonded to it. Does anyone know of anything that helps unbond PVC pipes. It looks like the bonding material is clear light yellow substance. I don't know if it is PVC cement or something else, but it looks bonded. My current method is to slowly cut slits into the PVC pipe and chisel it out.--155.144.40.31 (talk) 01:16, 14 July 2009 (UTC)

Just heat it up with a heatgun and stick a sharp edge into it. The glue will come off quite cleanly that way. --antilived^{T | C | G} 01:27, 14 July 2009 (UTC)

Thanks I heated it up and basically peeled it off.

The stuff I use (which is for plumbers - and is a bright purple color) melts the PVC - the glue itself hardly matters because once it's done it's stuff, the two pieces of PVC have become one piece - and nothing will get it apart. Personally - I'd look for longer/thinner tools to try to fix the problem without too much destruction...but without a lot more information, it's hard to suggest what tools might help. SteveBaker (talk) 01:42, 14 July 2009 (UTC)

The glue does matter, as it fills in the spots where the melted PVC didn't touch. Interesting fact: the primer is not inherently purple, but colored that way so that building inspectors can verify that it was used. --Sean 13:27, 14 July 2009 (UTC)

Possibility of a strabismus drug?

In theory, could a drug be developed that would treat the neurological aspects of strabismus with amblyopia (i.e. allow the brain to properly merge images from both eyes)? NeonMerlin 01:28, 14 July 2009 (UTC)

It seems unlikely, because problems of this sort are generally due to "miswiring" that develops over time, and any treatment requires time and experience to correct the miswiring. It seems entirely possible, though, that a drug that increases the plasticity of neural circuits could make physical therapies more effective. Looie496 (talk) 03:35, 14 July 2009 (UTC)

distance light travels per cycle

How far does light travel in one transition cycle of the magnetic phase and the electrostatic phase? -- Taxa (talk) 02:29, 14 July 2009 (UTC)

This is precisely what the wavelength is. So the answer depends on the wavelength of the light. For visible light, the answer is between about 400 and 700 nanometers. But it could be anything. Some radio waves, for example, are several meters long. —Dominus (talk) 02:51, 14 July 2009 (UTC)

The answer above must be correct, eventhough the question isn't since light doesn't have an alternation between a magnetic phase and a electrostatic phase (For one thing, the word static means "no change" so it wouldn't fit here). Both the electric and the magnetic fields oscillate simultaneously in phase (that is, they reach their maximum amplitude simultaneously). Dauto (talk) 11:50, 14 July 2009 (UTC)

Gaviotas sleeve pump

There is a kind of manual water pump, invented at the "appropriate technology" Columbian town of Gaviotas which they call a "sleeve pump" (Bomba de Camisa). Most of the descriptions of it I can find are taken from Alan Weisman's book Gaviotas, which includes a diagram. A reasonable excerpt describing it, with the diagram can be found here (although a higher resolution version of the diagram can be found at this Google Books version). Also, there is an installation manual (in Spanish, scanned into PowerPoint) here.

I have not been able to make out how the thing works. The diagram shows an outer sleeve being moved, but nothing else. No description of what air or water chamber is pressurized, exhausted, or lifted; just water magically flowing up in the right illustration. Can anyone explain what's supposedly going on? Thanks. -R. S. Shaw (talk) 02:45, 14 July 2009 (UTC)

From what I've read in the text on the preceding few pages, it appears to me that the sleeve is rigidly attached to the perforated casing it encloses, which therefore moves up and down with the sleeve in relation to the immovable piston inside the casing, thus creating the pressure that pumps the water. Looks to me like the diagram is wrong. FWIW 76.21.37.87 (talk) 08:44, 14 July 2009 (UTC)

What is this plant?

This weed grows all over Philadelphia. The leaves vary greatly in size, and sometimes span 30 cm or more. It is usually a low shrub. In the summer, it bears hard spherical fruits about 2cm in diameter. What is it?

Thanks. —Dominus (talk) 02:47, 14 July 2009 (UTC)

Looks like a fig tree to me. Probably s.th. like an Alma or Celeste. The fact that it gets too cold in winter might account for the shrub size. 71.236.26.74 (talk) 03:47, 14 July 2009 (UTC)

I don't think it's a fig. I believe what you have there is Paper Mulberry. Our article doesn't seem to picture the lobate leaf forms of the immature plants, but compare the images here (particularly the bottom one, just above the map). Deor (talk) 16:13, 14 July 2009 (UTC)

Thanks. So far, I like the paper mulberry theory much better than the fig theory. This plant does indeed have a variety of leaf forms, with only the larger leaves being lobate. I will try to open up one of the fruits and see if it looks like a fig. —Dominus (talk) 17:22, 14 July 2009 (UTC)

Now that I've done some more reading and seen some more pictures, I am sure that this is correct. Thank you very much. 17:27, 14 July 2009 (UTC)

Wellness and the Wellness Wheel

I've been thinking of starting an article on the concept of the "Wellness Wheel" as per these temporary online sources:

• http://www.friendly-ware.com/wellness/WellnessWheel.html
• http://www.wright.edu/admin/wellness/wellnesswheel.htm
• http://wellgroundedlifestyle.ca/wellnesswheelc67.php
• http://www.sa.usf.edu/wellness/about/wheel.htm
• http://www.definitionofwellness.com/wellness-wheel.html

but I'm unsure whether it is already covered somewhere else in Wikipedia or if it should be a section in the Health article or Wellness (alternative medicine)? Is the term "wellness" used in this context a separate definition apart from alternative medicine? Is this a notable enough topic to write about? From what I know of the Wellness Wheel concept is that it's used in many drug and alcohol rehab centers as a harm reduction alternative to the 12-step program (see google books) yet I see mention of this nowhere. So I'm unsure if I should start the article going of those web refs or just update Health or Harm reduction or to include this ?new? concept. Better yet, if someone more educated in the field than I could take the lead and start me off with a short stub that would be great. -- œ^™ 03:04, 14 July 2009 (UTC)

When is it too cold for Mosquitos?

My friend and I disagree about whether I'll cause us to have mosquito bites if I leave the window open with lights on inside tonight. Thing is it's quite chilly outside at the moment! My understanding is that under such conditions mosquitos would not be a nuissqnce. So who's right? Do mosquitos not roam on very cold nights? (even if they do yesterday and tomorrow, when it isn't really chilly)? Thanks! —Preceding unsigned comment added by 82.234.207.120 (talk) 03:44, 14 July 2009 (UTC)

minimum temp for mosquito growth is 8-10°C [38] so it needs to be that cold for the mosquitoes to stop developing. Also the insects survive the winter via hibernation or as eggs[39] so they won't bother you in the winter or anywhere where it is less than 8 C.--Lenticel ^(talk) 04:02, 14 July 2009 (UTC)

ah, but I was talking about an exceptionally cold night in otherwise mosquito plagued season... So my question is not about breeding, but whether they will bite me on a cold night (where the previous or next night is a definite yes)... —Preceding unsigned comment added by 82.234.207.120 (talk) 04:23, 14 July 2009 (UTC)

As I said earlier, you have to be at winter temperatures (subzero) for the adults to to hibernate or die after laying their eggs. --Lenticel ^(talk) 04:42, 14 July 2009 (UTC)

I've read somewhere that the temperature below which mosquito activity declines dramatically is around 13°C. ~AH1^(TCU) 09:07, 14 July 2009 (UTC)

thanks - you actually answered my question. And it was below 13degrees. 82.234.207.120 (talk) 15:02, 14 July 2009 (UTC)

HUAUZONTLE - red or green or both ???

researching Huauzontle and trying to ascertain different varieties..

on website "seeds of change" the picture is red and on gourmet sleuth the picture is green so I sent emails to relevant websites questioning this and got following replies..

from seeds of change .. "We have a great picture of it in our catalog on page 50 and it is most definitely red. It is also called Red Aztec Spinach. Chenopodium berlandieri is the species we sell. Maybe there is another one that is not red?" ..

from Gourmet Sleuth I got " I can’t speak for what product Seedsofchange.com is referring to but huazontles are long stemmed greens with tiny flower buds (which we can confuse you further because technically the buds are fruit..) The plant grows long stalks, has serrated leaves and the stalks get tipped with seed bundles. The seed bundles are prepared and eaten like a vegetable. The only huazontles I’ve ever seen are green in color so if they are selling something red.. not sure what that would be. That being said this plant does grow in the U.S. (treated like a weed) but was eaten by Native Americans. Our reference is Diana Kennedy, well known writer and considered one of the best authorities on Mexican food and culinary culture. We have more description in our dictionary (this link is to our new site which is still under development but feel free to check out the info)http://dev1.gourmetsleuth.com/Dictionary/H/Huauzontle-6125.aspx

THEN researched Chenopodium berlandieri and found pictures at Google Image Search which show most green but a couple red however no explanation as to why red or green or if 2 different varieties ... similarly on Wikipedia .. different varieties but no red .... can you please help me ... thanx 124.179.215.251 (talk) 05:21, 14 July 2009 (UTC)

Red leaves in plants are usually caused by the [anthocyanin] content. Some varieties will naturally contain more (cf red cabbage, near-black bell peppers). —Preceding unsigned comment added by KoolerStill (talk • contribs) 10:14, 14 July 2009 (UTC)

I have no idea if this is relevant, but in my garden I have both Red Orache and Fat Hen, both members of the Chenopodium family. If you look at our article on Atriplex you will see that there are plenty of members of this family which are edible. I don't know if this is what you were looking for but it might help.--TammyMoet (talk) 18:50, 14 July 2009 (UTC)

Mercury

How do humans eliminate mercury and it's compounds? It says that fish store mercury faster than they eliminate from their bodies. How does this compare with humans? Are that "natural" chelating agents that can be found in the (human) diet?174.3.103.39 (talk) 08:40, 14 July 2009 (UTC)

As far as I'm aware, humans also store mercury in adipose tissue, and eliminate it very, very slowly (over a period of years). Even worse, there are currently no known natural chelating agents, either in the human diet or anywhere else (not even the "miraculous" Acai berry). There are some synthetic chelators available (such as British Anti-Lewisite) to help the body get rid of mercury; however, they should only be used in case of severe mercury poisoning and then only with a doctor's prescription, because they are themselves somewhat toxic (like many other strong medicines). FWIW 76.21.37.87 (talk) 09:04, 14 July 2009 (UTC)

Judging from the mercury poisoning article, there's no particular elimination of mercury by the human body :-( quoting [40]: Methylmercury is believed to cause toxicity by binding the sulfhydryl groups at the active centers of critical enzymes and structural proteins. This is just my guess but i'm thinking from this, that mercury is expelled when enzymes and protein in the body are destroyed, as they frequently are. The rate of metabolism would seem to be the crucial factor then, but this is just my layman thoughts on it. Brain cells are not renewed the same way that say skin cells are, so mercury in the brain probably stays there :-(( EverGreg (talk) 09:15, 14 July 2009 (UTC)

Lack of hunger

I seem to remember reading something about a lack of hunger, even though a person hasn't eaten for several hours, as a sign of something wrong with them. Does this ring any bells with anyone? Dismas|^(talk) 09:08, 14 July 2009 (UTC)

I'm afraid that lack of hunger is a symptom of a very wide rang of diseases, though I can't recall one that has it as its only symptom. EverGreg (talk) 09:17, 14 July 2009 (UTC)

And, of course, if there was, we wouldn't be allowed to talk about it. --Anon, 11:10 UTC, July 14, 2009.

That is completely incorrect. We can discuss medical information all we like. We cannot attempt to diagnose a person through the Reference Desk if the person claims to have a lack of hunger. -- kainaw™ 11:21, 14 July 2009 (UTC)

The symptom of lack of hunger is called Anorexia (symptom), not to be confused with anorexia nervosa, which is the well-known eating disorder. From the anorexia (symptom) article:

Anorexia (deriving from the Greek "α(ν)-" (a(n)-, a prefix that denotes absence) + "όρεξη (orexe) = appetite) is the decreased sensation of appetite. While the term in non-scientific publications is often used interchangeably with anorexia nervosa, many possible causes exist for a decreased appetite, some of which may be harmless, while others indicate a serious clinical condition, or pose a significant risk.

So it might be something; it might be nothing, but please consult a qualified doctor if you're worried.AlmostReadytoFly (talk) 12:13, 14 July 2009 (UTC)

Hmm, thanks for the link to the symptom of anorexia. And to those who didn't get their "we don't give medical advice" jackboots on, thank you! Dismas|^(talk) 16:43, 14 July 2009 (UTC)

Jenkem

[post removed by user]

You asked this question yesterday, then removed it today, along with an answer. 87.114.25.180 (talk) 13:00, 14 July 2009 (UTC)

[post removed by user]

I didn't decline to participate in helping you, I declined to participate in an experimental test of the hypothesis. I agree that you're asking a different question now. Before you asked whether the idea could be ruled out in principle, and I said I thought not. Now you're asking whether there is evidence, and the answer is that I don't know. It would surprise me if anybody had studied this, but I don't know for sure. Snopes has a lot of information about this, and classifies it as an urban legend. Looie496 (talk) 19:45, 14 July 2009 (UTC)

Remove your own posts if you want, but don't touch others'. If you don't like the replies given you for free by volunteers, feel free to ask your questions elsewhere. 87.114.25.180 (talk) 21:14, 14 July 2009 (UTC)

Oh joy the "it's free so don't complain" line. Sure is an easy excuse for not trying. I've removed MY OWN posts and left everyone elses, as you suggested. Onesevensix 77 (talk) 23:06, 14 July 2009 (UTC)

faster then the speed of light?

I understand that light will travel through a vacuum at something like 3*10^8 m/s, but are the individual photons actually traveling faster since they are not going straight, but are instead traveling as a sine wave? What is the actual speed of the particles then? Googlemeister (talk) 14:42, 14 July 2009 (UTC)

When an electromagnetic wave is depicted as a sine wave, the sine wave represents the magnitude (and possibly the orientation) of the wave's electric field. It does not represent a displacement in space of the photons or anything else. -- Coneslayer (talk) 14:57, 14 July 2009 (UTC)

boy is that the wrong answer. The real answer is that WHATEVER LIGHT DOES WHEN YOU SEE IT AS A SINE WAVE (even if it did move up and down, or in and out, or back and forth, or whatever else) is something ENTIRELY DIFFERENT FROM WHAT IT DOES WHEN YOU SEE IT AS A PARTICLE. Read wave/particle dualty. You simply can't apply particle physics to the waveform of light, and vice versa. Beyond that, what a sine wave WOULD represent to a particle, is irrelevant. 82.234.207.120 (talk) 14:59, 14 July 2009 (UTC)

That's not really a helpful way to think about wave-particle duality. Light doesn't behave like particles travelling in a wavy trajectory. It behaves a bit like a wave travelling in some sort of medium (which made people think there was a luminiferous ether), or a bit like particles travelling in straight lines. AlmostReadytoFly (talk) 15:08, 14 July 2009 (UTC)

It looks like we need Stephen Hawking again. Is Stephen Hawking in the house? Bus stop (talk) 15:15, 14 July 2009 (UTC)

You can imagine light to be an EM wave. The electric and magnetic field vectors are sinusoids perpendicular to each other and the direction of propogation. This wave travels at the speed of light. Or, you can imagine light to be a photon, that is, a particle, moving at the speed of light. Hence, it has properties of both waves and particles. What property it will exhibit depends on the experiment. For example, you can imagine an experiment of Diffraction. Assume the source is such that it emits a single photon. The diffraction pattern is still seen. This means light is released as a particle and diffracts as a wave. However, by the complimentarity principle, it can neber exhibit both particles simultaneously. So, its your choice how you imagine light, but it still travels at the constant speed of light. Rkr1991 (talk) 16:29, 14 July 2009 (UTC)

Obviously the light itself travels at the speed of light, there is no question on that. But the photons that make up the light are going faster or not? They have to exist, if it behaves as both right? Googlemeister (talk) 16:48, 14 July 2009 (UTC)

To make it easier to understand... You are imagining that there are little particles called photons. Your imaginary particles are travelling at whatever speed you like. Realistically, there are no particles. The thing you are calling a particle is a thing that, at times, exhibits behaviour similar to a particle. At other times, it does not. You can consider the fact that it should travel faster than light if it was actually a particle an instance of when it is not behaving like a particle if you like. -- kainaw™ 16:54, 14 July 2009 (UTC)

From my understanding of light, it behaves either as a particle, or as a wave, only based on if it is being observed or not. Thus when it is not being observed, it is both. Thus particles would have to be able to travel faster then the speed of light. Is the logic incorrect, or is my understanding of the quantum nature of light off? Googlemeister (talk) 18:09, 14 July 2009 (UTC)

Photons travel in straight lines, not in sine curves. They travel in straight lines at exactly the velocity of light. Nothing about light travels in a sine curve. When people depict the electric and magnetic fields as being shaped like sine waves, it is a metaphor for a certain mathematical abstraction, which you are taking too literally. People also talk about alternating electric currents as being sinusoidal, but that does not mean the electricity travels through the wires along a sinusoidal path, or that there is anything else taking a wiggly path through space. —Dominus (talk) 18:25, 14 July 2009 (UTC)

Periodicity of ionization energies?

I've been set an exercise which consists of putting in order a series of chemical elements according to their first ionization energy, knowing only their atomic numbers. My textbook says that the first ionization energy increases within each period of the table, but Al has a lower IE than Mg, and S has a lower IE than P, for example. How am I supposed to do the exercise then? Can someone give me a nudge in the right direction? Thank you! --83.34.232.200 (talk) 15:02, 14 July 2009 (UTC)

There are rules-of-thumb as you see, but sometimes there's no way to be sure without looking up the actual values. Our ionization energy article is quite detailed and surprisingly complex--tells you that the actual specifics of IE are well beyond the general picture. There's a nice graph at ionization too, and you can see both the periodic nature and also the exceptions that don't follow the general trends. DMacks (talk) 15:40, 14 July 2009 (UTC)

Yes - read the article and look at the graph(s), as a possible hint - try comparing ionsiation energies diagonally if you want to avoid exceptions, also for all but the most dedicated (anally pedantic) of scientists the difference between Al/Mg is really just a blip (though it is real - not a measurement error)

Look at the bigger picture.83.100.250.79 (talk) 16:06, 14 July 2009 (UTC)

Artists' impressions of planet surfaces

Can anyone please indicate a good web-site with lots of (scientifically based) artists' impressions of views from the surfaces of planets in our Solar System - thanks. --AlexSuricata (talk) 18:51, 14 July 2009 (UTC)

[41] Cuddlyable3 (talk) 22:34, 14 July 2009 (UTC)

Big Bang, how did it happen?

I really have no reason to disbelieve the big bang theory, and cosmic background radiation seems to outright prove it in my eyes. But I don't know how it could have actually happened.

The beginning of the universe, as Steven Hawking seems to explain, was a singluarity, similar in type but not scale to black holes. If there was infinite gravitational pull because it was a huge amount of mass in an infitesimal area, how could it possibly blow up?

I don't see it as likely that black holes, no matter how large they are, would explode, and they have some forces tugging outwards on their centers (the gravity of other black holes for example). The singularity at the beginning of the universe would have have gravity, obviously, holding it together, and that would simply overpower every other force that could exist.

I know an explosion happened, but black holes don't explode, and explosions need something to cause them right? Bah, just reading a discover article about steven hawking and this came back into my mind. Please help me understand. Thanks! —Preceding unsigned comment added by 192.234.122.9 (talk) 19:54, 14 July 2009 (UTC)

All of physics breaks down as you go back towards the original singularity. Therefore, notions of gravity that we understand now did not apply when the big bang occurred. -- kainaw™ 19:58, 14 July 2009 (UTC)

Is gravity a theory or a law? Googlemeister (talk) 20:09, 14 July 2009 (UTC)

Well, Newton's law of universal gravitation is a "law" - but it's modified by things like General relativity - which is a "theory". All that we know about gravity is a mixture of laws and theories. But I hope you are aware that scientists don't use the words "Law" and "Theory" in the sense of "that which must be obeyed" and "theoretical". In science, those words mean something quite different. SteveBaker (talk) 20:17, 14 July 2009 (UTC)

The fact is that we don't know why. We know for sure that it happened - but there is a real problem here. Just as with black holes, when distance goes to zero - many other numbers become infinite. Density is infinite, gravity is infinite, but any distance-related repulsive forces (such as the forces that keep the atoms nicely spread apart - or perhaps any repulsive forces due to dark matter and dark energy) also become infinite. Weirder still - all of space was ALSO compressed into that infinitesimal dot. Worse still, the fundamental particles we know about today probably didn't exist back then. Fundamental laws like the Pauli exclusion principle and the Heisenberg uncertainty principle are violated. So the physics of that first gazillionth of a second are really tough to figure out. We have a pretty good idea of the way things were a few milliseconds after the big bang started...but we don't (yet) have a good handle on the absolute zeroth instant. The physics of the interior of a black hole where some of those weirdnesses ought to be playing out - might (in theory) give us a useful starting point to study that - but the event horizon of black holes forever prevents us from studying them in any useful manner. SteveBaker (talk) 20:17, 14 July 2009 (UTC)

We don't know that it happened, if "it" means "the beginning of time". When you extrapolate the original big bang model backwards you get a singularity about 14 billion years ago, but people stopped taking that seriously when inflationary cosmology caught on, because inflationary models don't have an analogous singularity at a well-defined time in the past. Physicists still talk about the "beginning of the universe" being 14 billion years ago, but they don't really mean it (see Age of the universe#Explanation). In chaotic inflationary models the expansion that we see started as literally a kind of explosion in a pre-existing universe triggered by a certain kind of quantum fluctuation. The background universe in which that happened could have existed forever for all we know. Hawking has a pet idea about the origin of the universe called the no-boundary proposal which he talked about in A Brief History of Time, possibly misleading readers into thinking that it's part of the standard cosmological model. It's not, it's actually pretty fringe. Other physicists take Hawking seriously but they don't necessarily agree with his ideas about cosmology and quantum gravity (and they certainly don't see him as a genius the way the general public seems to). -- BenRG (talk) 22:09, 14 July 2009 (UTC)

And it's worth pointing out that Brief History of Time is, by the standards of cutting-edge theory, getting a bit long in the tooth. --98.217.14.211 (talk) 22:47, 14 July 2009 (UTC)

The general public (I include myself here) considers anybody who can understand this mindbending stuff in anything more than a superficial way to be a genius, for some definition of "genius". --Sean 22:54, 14 July 2009 (UTC)

Alumina ceramic

What is it. in laypersons terms? What does it look like? I read in a book that it is elastic - seems very odd for a ceramic. Is it partly metal, partly silicon, since ceramics are made from clay, and clay I think is mostly silicon? Is it a recent invention? 78.147.131.187 (talk) 20:19, 14 July 2009 (UTC)

They make sharpening stones (whetstone) out of it, amongst other things - it's usually light grey (or white when pure) in colour, and just like unglazed ceramic - except maybe a bit harder than the average. There's no silicon in it.83.100.250.79 (talk) 20:57, 14 July 2009 (UTC)

This image is almost certainly an alumina whetstone - if not it looks identical to one

Alumina ceramic looks like this

See Ceramic for a wider definition of a ceramic which is not confined to "made from clay through heat"83.100.250.79 (talk) 22:19, 14 July 2009 (UTC)

It's not elastic in any real, common world sense. At all. 83.100.250.79 (talk) 22:22, 14 July 2009 (UTC)

See Elastic for the different definitions of the term - they are different.83.100.250.79 (talk) 22:37, 14 July 2009 (UTC)

Backup Heart

After reading a news story about how a girl survived with two hearts I started to wonder if humans could conceivably live with a backup heart their whole lives. Would it be possible to have a circulatory system with two pumps where if one fails the system remains viable? TheFutureAwaits (talk) 20:22, 14 July 2009 (UTC)

In principle, sure. The biological concept is accomplished by the lungs, kidneys, and eyes, among other organs. — Lomn 20:26, 14 July 2009 (UTC)

It seems a bit iffy to me. If the two hearts didn't beat in PERFECT synchronism - and with approximately the same pressures - then high pressure blood from one heart would flow against the tricuspid valve of the other - and those things are only held shut by the pressure - so they'd blow back open...right? I could imagine all manner of Very Bad Things happening. But we probably need a biologist to tell us more about that. Obviously, other heart designs would be possible that could overcome this...but the Mark I human heart doesn't sound like the right machine for the job. SteveBaker (talk) 20:51, 14 July 2009 (UTC)

Thanks Steve, this is exactly what I'm getting at. Say you could redesign the human circulatory system. Would it be possible to design a system which could function despite one or many pumps failing? What would such a system look like? TheFutureAwaits (talk) 21:09, 14 July 2009 (UTC)

Not sure if this is an appropriate analogy, but many invertebrates, such as octopuses, have multiple hearts. -RunningOnBrains^{(talk page)} 21:20, 14 July 2009 (UTC)

We're trying to answer a question with woefully incomplete information. Were there were actually two functioning hearts linked to the same circulation? Was it actually a birth defect in which instead of a four-chamber heart there were two two-chamber hearts serving the two sides of the circulation (pulmonary circulation and systemic circulation)? The "news" is notorious for hyping up some oddity yet not providing real information about what was going on. Can the OP at least link to the news story? --- Medical geneticist (talk) 21:21, 14 July 2009 (UTC)

Here's the story if you're really interested [42]. Please note I'm not really interested in learning more about this case, it was just the inspiration for the question. What I'm really interested in knowing is as follows: TheFutureAwaits (talk) 21:30, 14 July 2009 (UTC)

Say you could redesign the human circulatory system. Would it be possible to design a system which could function despite one or many pumps failing? What would such a system look like? TheFutureAwaits (talk) 21:30, 14 July 2009 (UTC)

It would look like a guy with two or more hearts, each capable of pumping hard enough to support life. They would be connected in parallel and share the same nervous impulse. In the event of failure there would have to be some sort of sphincter or valve preventing back flow round the failed organ. —Preceding unsigned comment added by 83.100.250.79 (talk) 22:43, 14 July 2009 (UTC)

I don't see how they could be in parallel. If the second heart fails then the first one can only pump into the opening of the second, after which everything gets clogged. I suppose there could be some side artery between the first and second heart where blood could go around the second and back into the main artery. Not sure if this could actually work though. TheFutureAwaits (talk) 23:46, 14 July 2009 (UTC)

What are the odds?

I just ate a bag of peanut M&M's...yes, I know...an entire bag is kinda piggy. Anyway - I tore the end off of the bag and dumped out the usual 30 or so randomly colored M&M's into a shallow dish on my desk. I'm working - concentrating on a tough programming problem (rendering shadows cast from a non-uniform point source - if you must know) - and I swear that I am paying zero attention to picking up M&M's...until there are only seven left - when I happen to notice that they are ALL blue. This seems like a rather improbable thing...there are maybe 5 colours - so the odds are something like eighty-thousand to one against this happening by chance. So I'm wondering whether my subconscious doesn't really like blue M&M's and hasn't been telling the conscious "me" all this time? I should probably repeat the experiment a few times...right? SteveBaker (talk) 20:46, 14 July 2009 (UTC)

There could have been an error at the packaging plant and some bags did not get the proper mix of colors. I also recall a couple of contests from years ago where the winning bag was all 1 color. You could have just eaten a $1,000,000 bag of M&Ms. Googlemeister (talk) 20:51, 14 July 2009 (UTC)

No - I'd have noticed immediately when I dumped them out if they were all blue. I was obviously concentrating on the bag when I opened it

Maybe blue ones are heavier? but tell us more about you're non uniform point source - that sounds more interesting - though not that difficult on the surface - a point source always produces sharp shadows no matter what the intensity of the light - sounds like you just need more bits in the shadow map to express the non-shadowed intensity - it's always easier to say rather than do isn't it.83.100.250.79 (talk) 20:53, 14 July 2009 (UTC)

Yes - but it's omnidirectional so I can't do the usual "planar rendering from the point of view of the light source" trick - I've got to mess around with rendering to a cube-map. Anyway - I don't need help with that - I need to know about my brain's hitherto unsuspected aversion to blue food! SteveBaker (talk) 20:56, 14 July 2009 (UTC)

Coincidences do happen. Also, while the odds may be one in 80,000, how many packets of M&M's have you eaten in your life? Enough, I imagine, for the odds of the last seven M&M's in one of those packets being all the same colour being significantly higher. Also, it isn't 80,000:1, it is more like 16,000:1 - you don't want the odds of the last 7 being blue, you want the odds of them all being the same colour. You would have been just as surprised had they been all red. --Tango (talk) 21:24, 14 July 2009 (UTC)

You should play the lottery ;) --Mayfare (talk) 21:58, 14 July 2009 (UTC)

It's a very, very common elementary school science "experiment" to see whether the color distributions in M&Ms and other candies are identical. They are often not, probably due to poor mixing. There is no a prior reason to suspect that the packet actually has even distribution to begin with, which obvious affects the odds-making quite a bit. --98.217.14.211 (talk) 22:29, 14 July 2009 (UTC)

(edit conflict) Yes that's right, I work in a M&M's factory (peanut division), and the blue ones always go in first. Somedays, when the boss isn't looking we don't bother to shake them to mixed the different colours, sometimes people just forget - "did you shake that one", "think so"... (lie)83.100.250.79 (talk) 22:47, 14 July 2009 (UTC)

That might actually be close to the truth. Presumably, the open bags are moved beneath a series of hoppers that each spew forth a set amount of M+Ms of a particular colour... --Kurt Shaped Box (talk) 00:29, 15 July 2009 (UTC)

Color distribution on M&Ms is not even. In the mid-70s Cecil Adams claimed that they were 90% brown and yellow. If the color distribution is still close to that (And I can't say I've noticed.) then your coincidence is even more surprising. APL (talk) 22:46, 14 July 2009 (UTC)

Of course it's dangerous to interpret any given event, but there's quite a bit of experimental work in the psychophysics literature showing that people are generally averse to blue-colored food. In fact there is even evidence that coloring a food blue influences the way people perceive its flavor, for example this paper. Looie496 (talk) 22:48, 14 July 2009 (UTC)

Before concluding that anything miraculous has occurred I want to know more about how one pays zero attention to picking up M&M's but picks them up anyway. Some brain activity must be involved in reaching out to a particular M&M. Were the M&M's in the field of view? What colour was the dish? Were more than one M&M touched at a time? Can the subject taste the difference between any M&M colours while blindfolded (a follow-on experiment) ? Which colour(s) of M&M eaten to excess would cause the subject to feel the most shame about being piggy? A point source cannot be non-uniform. It sounds like you have a ray tracing exercise. Cuddlyable3 (talk) 23:00, 14 July 2009 (UTC)

I would imagine a "non-uniform point source" would be a source which emits different light in different directions, but all from one point. --Tango (talk) 00:06, 15 July 2009 (UTC)

If you told us the number of M&Ms in the bag, and the total number of blue ones, then the probability could be calculated. Its an example of the classic beads in an urn (no replacement) combinatorial problem. I'm trying to remember the formula. But, assuming that the probability is the same as the first 7 m&ms being blue, then the probability would I think be B/M x (B-1)/(M-1) x (B-2)/(M-2) ..... x (B-7)/(M-7). Note that the other n million people who have eaten a bag of M&Ms and whose last seven items were not blue, have not reported it to Wikipedia. 92.27.155.47 (talk) 23:18, 14 July 2009 (UTC)

Assuming he didn't count them in advance you have to assume they are independent with equal chance of each colour (you could assume each bag has equal numbers of each colour, but that doesn't seem to be the case), so it is just 5⁶ (there are 6 M&M's which need to be the same colour as the first one, you don't care what colour the first one it). --Tango (talk) 23:39, 14 July 2009 (UTC)

You might care about the color of the first one. If his final seven M&Ms had all been brown, the most common color, would he have considered it notable? APL (talk) 00:33, 15 July 2009 (UTC)

Solubility of Ionic Compounds

Hello. If ionic compounds are polar and like dissolves like, why are some salts water-insoluble at SATP? Thanks in advance. --Mayfare (talk) 21:51, 14 July 2009 (UTC)

"like dissolves like" is a general observation of a certain trend, not a fact (and definitely only a result not a physical law or the cause of anything). If "whatever holds molecules together and to each other" is stronger than "whatever interactions happen between solute and solvent", the chemical is not very soluble. See solubility for a detailed discussion. DMacks (talk) 22:11, 14 July 2009 (UTC)

The Limit of heat?

I understand that there is a limit to the degree of cold (absolute zero), but is there a limit to how hot things can get? Obviuosly in the moments after the big bang, the temprature would of been huge, but can there be a higher temprature, either naturally (in supernovas etc) or synthetically (in collisions and heating [I read that scientists have heated a substance to 510 million degrees!]). Andy (talk) 23:57, 14 July 2009 (UTC)

There is no theoretical limit to the best of my knowledge. There is a practical limit imposed by the total amount of energy in the observable universe, of course. You may be interested in the concept of negative temperature, which is, in a sense, temperature hotter than infinitely hot. --Tango (talk) 00:04, 15 July 2009 (UTC)

Absolute hot 87.114.25.180 (talk) 00:34, 15 July 2009 (UTC)

Beetle factoid

Something I heard on the radio the other day.

"If you were to randomly arrange all the macroscopic animal life on earth in one long line - then every fifth creature would be a beetle."

Confirm/debunk? --Kurt Shaped Box (talk) 00:23, 15 July 2009 (UTC)

I see what they were getting at but if you were to arrange them in a truly random nature, then there is no telling just where in the line the beetles would fall. I know, I'm picking nits... Dismas|^(talk) 00:28, 15 July 2009 (UTC)