:(ec) Conventional wisdom says that it emits light because it is hot - [[white hot]] in fact (in the same way a [[Incandescent light bulb]] emits light because it is hot).[[Special:Contributions/83.100.183.63|83.100.183.63]] ([[User talk:83.100.183.63|talk]]) 22:37, 2 June 2010 (UTC)
:(ec) Conventional wisdom says that it emits light because it is hot - [[white hot]] in fact (in the same way a [[Incandescent light bulb]] emits light because it is hot).[[Special:Contributions/83.100.183.63|83.100.183.63]] ([[User talk:83.100.183.63|talk]]) 22:37, 2 June 2010 (UTC)
::[[Thermal Radiation]], essentially. Anything with a temperature above absolute zero "glows". That is, it releases electromagnetic radiation at a variety of wavelengths dependent on how hot it is. Humans glow mostly in the [[Infrared]] range. The sun glows across a wide range of wavelengths, including [[Visible light]]. [[User:Buddy431|Buddy431]] ([[User talk:Buddy431|talk]]) 22:36, 2 June 2010 (UTC)
::[[Thermal Radiation]], essentially. Anything with a temperature above absolute zero "glows". That is, it releases electromagnetic radiation at a variety of wavelengths dependent on how hot it is. Humans glow mostly in the [[Infrared]] range. The sun glows across a wide range of wavelengths, including [[Visible light]]. [[User:Buddy431|Buddy431]] ([[User talk:Buddy431|talk]]) 22:36, 2 June 2010 (UTC)
==Contents of Organic Pesticide==
I just used an organic pesticide that contains the potassium salt of various fatty acids as its main ingredient. Will this actually kill/repel/do something to insect pests or did I just waste my money on some oily, salty water?[[Special:Contributions/24.88.87.41|24.88.87.41]] ([[User talk:24.88.87.41|talk]]) 22:41, 2 June 2010 (UTC)
Revision as of 22:41, 2 June 2010
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
In one of Roger Penrose's lectures (video here: http://www.youtube.com/watch?v=f477FnTe1M0 , part in question at 1:12), Penrose talks about some studies done on birdsongs. The studies supposedly had humans give an aesthetic rating the songs of male birds that were then followed in order to determine their reproductive success, and whether it had any statistical correlation with the humans' ratings.
If you know the height of a satellite above the Earth (h) and you also know the velocity with which the satellite rotates around the Earth (v) what calculation do you perform to determine the offset of the clock aboard the satellite due to the combined effects of special and general relativity?--Wikinv (talk) 02:26, 28 May 2010 (UTC)[reply]
I don't think there are any general relativity effects. The satellite is in free fall, so it's experiencing no acceleration (force). All you have is velocity, and of course that only has meaning in comparison to something, presumably the earth. The interesting part is that the earth is experiencing general relativity effects due to it's gravitational field, not the satellite. Ariel. (talk) 03:21, 28 May 2010 (UTC)[reply]
The offset I'm talking about is relative to a clock on the surface of the Earth, meaning that the effect of general relativity on board the satellite will be less than that on the surface of the Earth, so I think it will still have an effect. How do you do it for special relativity then?--Wikinv (talk) 03:36, 28 May 2010 (UTC)[reply]
Watch this video [1]. What I want to know is what calculation the presenter uses to arrive at his conclusion for the offset of the clock aboard the satellite.--Wikinv (talk) 04:32, 28 May 2010 (UTC)[reply]
How about this ? 04:40, 28 May 2010 (UTC)
That's special relativity only, which could still be useful. How would you use that formula to determine the offset of the clock aboard the satellite relative to the clock on the surface of the Earth given the velocity with which the satellite travels around the Earth?--Wikinv (talk) 04:43, 28 May 2010 (UTC)[reply]
Perhaps with a tick counter and identical clocks being synchronized (started) at some (identical) point in time and the counters then compared at some time in the future. 71.100.8.229 (talk) 05:14, 28 May 2010 (UTC)[reply]
(ec)So according to the video the clock will speed up by 45µs per day due to the difference in gravitational potential. Plugging values into the above formula you get:
=-0.00004565 s/day. At 3.87 km/s slow down by 7µs per day:
There's also a lot more going on, the relative velocities are constantly changing, the orbits are not spherical, etc. so there is also a periodic adjustment throughout the orbit, works out to between +70 and -70 nanoseconds.—eric05:28, 28 May 2010 (UTC)[reply]
You can get a decent approximation using the Schwarzschild metric, which is (using h instead of the usual r). If the orbit is circular (or approximately so) then , which leaves , or
.
That's the clock rate compared to a "stationary clock at infinity". To get the ratio between two clocks at finite heights, you compute clock1/clock2 = (clock1/clock∞) / (clock2/clock∞), or
where s is the satellite and r is the receiver. With factors of G and c put in, that's
.
This is equivalent to the formula from Seeber if you take (but even for a "stationary" ground receiver, is really nonzero because of the rotation of the Earth). This formula gives the average time discrepancy of the satellite and ground clocks over a long period of time. At any given moment, the ratio of the ground clock rate to the received signal from the satellite will be somewhat larger or smaller than this average, because of redshift/blueshift. -- BenRG (talk) 05:54, 28 May 2010 (UTC)[reply]
Look at the article Gravitational time dilation. That's the name of the effect you're asking about. From that page:
Circular orbits
In the Schwarzschild metric, free-falling objects can be in circular orbits if the orbital radius is larger than . The formula for a clock at rest is given above; for a clock in a circular orbit, the formula is instead
This is a consequence of the equivalence principle of general relativity (not special relativity). One related fact is that a monochromatic source of radiation will be observed with a lower frequency (longer wavelength, relative to the source) if the receiver is at a higher altitude (gravitational potential) and will be observed with a higher frequency if the receiver is at a lower altitude, due to the photons' losing (gaining) energy overcoming (having work done on by) the gravitational potential (gravitational redshift)Inasilentway (talk) 22:06, 1 June 2010 (UTC)[reply]
dam people
Paraphrasing Ronald Regan as having "...seen one tree, you've seen them all." where would be the best places to dam up the Grand Canyon and how much energy from fossil fuel would be replaced? 71.100.8.229 (talk) 02:31, 28 May 2010 (UTC)[reply]
Oooh! I know - they could call it the "Hoover Dam"...Oh...wait, did someone already use that name? Anyway, it produces 2080 MegaWatts. If I have my math right (and someone should check!) - that's equivalent to about 80,000 barrels of oil per hour. SteveBaker (talk) 04:03, 28 May 2010 (UTC)[reply]
Yeah but that is just one site where a large reservoir might be located. Take another look at the expanse of the Grand Canyon and you will see that if you are able to sacrifice the senic wonder in line with Regan's philosophy that you might be able to build another dam or 100. 71.100.8.229 (talk) 04:10, 28 May 2010 (UTC)[reply]
Lake Mead, which lies above Hoover Dam at the base of the Grand Canyon, has a water level of 1200 feet and a drop of about 500 feet. Lake Powell, at the other end of the Grand Canyon, has a base level of about 3100 feet. So that gives about 1900 feet of altitude to work with, meaning potentially around four times the output of Hoover Dam could be generated, assuming you dammed the entire Grand Canyon. Looie496 (talk) 04:28, 28 May 2010 (UTC)[reply]
Assuming there is enough water to work with. The Colorado River already doesn't reach the Gulf of California anymore; it hasn't for decades. Lake Mead's and Lake Powell's levels have dropped in recent years, there has been some serious speculation that their levels may drop below usable levels in the not-to-distant future. Additional dams are a veritable impossibility. There are similar problems on most western rivers; we've literally almost run out of usable dam sites in western North America; its why hydroelectric isn't seriously discussed anymore as a viable alternate energy source; there's no where else to put dams. --Jayron3204:38, 28 May 2010 (UTC)[reply]
Indeed - there is more talk these days of removing old dams than of building new ones. The issues of the region behind the dam silting up - and the river in front of it moving too slowly to sustain native wildlife have really put dams out of favor. You can buy a lot of windmills for the price of a major new dam! SteveBaker (talk) 02:56, 30 May 2010 (UTC)[reply]
How do Astronauts performing spacewalks deal with an itch?
Suppose the Astronaut has an itch at the tip of his/her nose and just began a 6 hr spacewalk, how would they handle that situation? I can't imagine them being able to slip their arm up through their spacesuit just to scratch an annoying itch. Thanks!Drummerdavid (talk) 03:58, 28 May 2010 (UTC)[reply]
I believe there is a little gizmo that sticks out into the helmet that the astronaut can turn his head around to in order to scratch against. It's put there for just such a reason - there is also a tube for sucking a little water or juice and some kind of an energy bar stick to chew on. SteveBaker (talk) 04:06, 28 May 2010 (UTC)[reply]
"The problem is the crossover?" What's that mean? --Anonymous, 16:55 UTC, May 28, 2010.
detergent
There are detergents specifically designed to remove oil and grease (hydrocarbons) from eating and cooking utensils by one end of the molecule attaching to the oil and the other to the water. Is there a detergent that will attach one end specifically to water and the other end to just soot or pure carbon? 71.100.8.229 (talk) 04:59, 28 May 2010 (UTC)[reply]
Not that I know of -- but detergents that remove oil and grease should in principle work pretty well to remove soot or coal dust. FWiW 67.170.215.166 (talk) 07:06, 28 May 2010 (UTC)[reply]
Incidentally, you don't need special detergents to do what's described by the OP. That's how regular old soap works (for non polar grease) Nil Einne (talk) 07:40, 28 May 2010 (UTC)[reply]
You mean you do not classify soaps and Surfactants as detergents? In any case I'm looking for a "detergent" where one end binds only with or specifically with carbon or carbon monoxide or carbon dioxide but with a hydrocarbon and it might not be known specifically as a "detergent". 71.100.8.229 (talk) 10:02, 28 May 2010 (UTC)[reply]
You said "There are detergents specifically designed to remove oil". Soap isn't 'specifically designed'. It's something that can occur naturally and people have been making before anyone had any understanding of the chemistry involved. (In addition, our article does say a distinction is sometimes made between soap and other surfactants as detergents, but that wasn't my point.) Nil Einne (talk) 12:50, 28 May 2010 (UTC)[reply]
Soap is made from fat and sodium hydroxide with sodium at one end of the molecule and hydroxide at the other same as many synthetic detergents. I recall a "detergent" with different ions at the end which had a greater affinity for various oils while the other end had a greater affinity for water. My memory is failing so maybe I'm just confused. 71.100.8.229 (talk) 03:53, 29 May 2010 (UTC)[reply]
Your description isn't quite right - I've put images of the chemical structures in - so you can see the difference between what you remember.77.86.47.199 (talk) 09:33, 29 May 2010 (UTC)[reply]
Okay I see. It was the sodium ion that was replaced with a hydroxide ion with the hydrocarbon chain remaining the same. Is ther a hydrocarbon chain then that will attach to soot or pure carbon specifically, assuming the sodium or hydroxide end is the one with affinity for water? 71.100.8.229 (talk) 03:17, 30 May 2010 (UTC)[reply]
(It's not hydroxide - in the diagrams it's carboxylate or sulphonate an organic sulphate)
Since like dissolves like a surfactant with a napthalene or anthracene at the end of the non-polar part might be a good choice for graphite based soot. Other soots are considerably oxidised, and contain many OH and C=O bonds - for a substance encouraging the suspension of soot particles you might consider a strong sugar solution - such as golden syrup.77.86.47.199 (talk) 14:42, 28 May 2010 (UTC)[reply]
Orbital stability
How would one go about showing that an inverse-sqaure force produces stable orbits (or how to check whether a given central force produces the like)? I tried googling, but most of the sites I was linked to dealt with mathematics that was beyond me (eigenvalues and so on). Are there simpler, calculus-based or, better yet, qualitative methods of answering such questions? 173.179.59.66 (talk) 05:37, 28 May 2010 (UTC)[reply]
Stability means decay of small perturbations. A small perturbation of a Kepler orbit will not decay, but will not grow either (to put this in the simplest terms, in the 1/r potential, gently nudging an orbiting body moves it from one closed orbit into a slightly different closed orbit). Therefore, it may be argued that a closed orbit of the two-body system with 1/r interaction potential exhibits a marginal stability. Actually, this is a far more general property of a broad class of so-called conservative systems (we don't have an article, but reading Conservative vector field may help anyway). Such systems don't normally have stable limit cycles; instead, depending on the initial conditions and the type of interaction, the behavior may be ergodic, or the system may be in a closed orbit, or the system may collapse into a singular state (see e.g. Coulomb collapse). --Dr Dima (talk) 07:22, 28 May 2010 (UTC)[reply]
Turns out we don't have an article on Coulomb collapse (for some reason I thought we did). I guess I'll have to explain briefly what it is. Imagine a classical 3-body (or N-body, N > 2) system with 1/r pairwise interaction where at least some of the interactions are attractive. (Classical -- neither quantum-mechanical nor relativistic -- gas of electrons and ions interacting pairwise via Coulomb potential is an example, hence the name; or imagine a cluster of gravitationally interacting stars and planets). When an electron gets close to an ion, it has higher-than-average kinetic energy; that's because the vicinity of an ion is a deep potential well for an electron. Electrons with higher-than-average kinetic energy tend to lose energy in collisions with other electrons. The more energy our classical electron loses, the deeper it falls into the potential well around an ion. The deeper it falls, the higher its kinetic energy becomes. (Remember that, on average, in a Kepler orbit the kinetic energy is minus one half of the potential energy; see Virial Theorem). In a classical system this will go ad infinitum, with r going to zero and the potential energy of the electron-ion pair going to minus infinity. This is known as the Coulomb collapse. Quantum-mechanical phenomena stabilize atomic orbitals against Coulomb collapse. Finite size and internal pressure of the star prevents gravitational systems from going into collapse. When this fails and the gravitational system does collapse, a black hole is formed (however, the energy released is still finite). --Dr Dima (talk) 07:53, 28 May 2010 (UTC)[reply]
Spoke and Hub
Are there any two commercial airports that would require a minimum of 5 flights to get from one to the other? Please note I mean standard commercial flights, nothing chartered or private. TheFutureAwaits (talk) 08:39, 28 May 2010 (UTC)[reply]
I wouldn't like to try it as Glasgow to Auckland is the best part of 32hrs, with 1.5hr stop-overs at each airport, I'd imagine Wellington and Christchurch are the same. CS Miller (talk) 11:47, 28 May 2010 (UTC)[reply]
As a general guide, I'd look for itineraries of the form
remote location → regional airline hub → major intercontinental hub → (new continent, change of airline) major intercontinental hub → regional hub → remote location
Bonus steps can be added if the intercontinental hubs are far enough apart that you need a fuel stop between them (as in London to Sydney). Good luck on your painfully long journey! TenOfAllTrades(talk) 13:58, 28 May 2010 (UTC)[reply]
I found one that would need ten, since it looks like Greenland does not like to use hubs. It is seasonal, but regularly scheduled while in season and would consist of
The inter-airport structure is analyzed in some detail in Guimera et al 2005. Basically, it fits a Small-world network model, which displays the popular Six Degrees of Kevin Bacon phenomenon. In most such networks, however, the usual "degree of separation" is significantly less than six. From Guimera, 56% of all pairs of cities are within 4 flights of each other, and the vast majority are within 5.
"The farthest cities in the network are RAF Mount Pleasant in the Falkland Islands and Wasu, Papua New Guinea: To get from one city to the other, one needs to take 15 different flights. From Mount Pleasant, one can fly to Punta Arenas, Chile, and from there fly to some hubs in Latin America. At the other end of the path, from Wasu one needs to fly to Port Moresby (Papua New Guinea), which requires a unique sequence of eight flights. In the center of the path, between Punta Arenas and Port Moresby, six different flights are needed. In contrast to what happens the ends of the path, in the central region of the path there are hundreds of different flight combinations, all of them connecting Punta Arenas and Port Moresby in six steps." - from Guimera et al 2005. SamuelRiv (talk) 04:44, 29 May 2010 (UTC)[reply]
As you see on the top of the reference desk page, it says that you can search for your applicable term in the search box on Wikipedia. If not try a Google search. Then, if you do not get your answers clearly you may ask. This is to prevent excess cluttering of the reference desk with basic questions that could be answered simply by a search.--Chemicalinterest (talk) 10:56, 28 May 2010 (UTC)[reply]
Can I have another simple meaning for the underlined phrase told by Einstein:
The precise formulation of the time-space laws was the work of Maxwell. Imagine his feelings when the differential equations he had formulated proved to him that electromagnetic fields spread in the form of polarised waves, and at the speed of light! To few men in the world has such an experience been vouchsafed . . so bold was the leap that his genius forced upon the conceptions of his fellow-workers
What he is saying is, "his idea was such a brilliant and unexpected one, that the fact that Maxwell was a genius was obvious to every other scientist once they heard of the idea." Does that clarify it? That is not a exact "translation" of what Einstein is saying, but should help you parse exactly what he's trying to indicate, I hope? --Mr.98 (talk) 14:47, 28 May 2010 (UTC)[reply]
Actually I don't think that's what it's saying at all - more like "His ideas were so advanced nobody understood them for years..."77.86.47.199 (talk) 14:57, 28 May 2010 (UTC)[reply]
You can read the full article here [3] p.489 left column (Einstein was quite a good writer)
There's some missing text where you have dots ".." - if you add that it makes more sense. I can't (work out how to) copy paste that article here - so you'll have to read the link.77.86.47.199 (talk) 14:48, 28 May 2010 (UTC)[reply]
I'll just type it in
"Meanwhile it took physicists some decades to grasp the full significance of Maxwell's discovery, so bold was the leap that his genius forced upon the conceptions of his fellow-workers" Science, May 24 1940, A. Einstein, article
That makes more sense with the rest of the sentence does it not?77.86.47.199 (talk) 14:51, 28 May 2010 (UTC)
Bold leap - is metaphorical, his ideas were completely different to what was understood (to be true) before
forced upon the conceptions - challenged what they thought was true (conception/conceive can mean what you think is true, as well as pregnancy. See the wiktionary entry, meaning 2)
Someone told me that Charles Darwin corresponded with Karl Marx, and that he had copies of Das Kapital and The Communist Manifesto. Is this true? --J4\/4 <talk> 15:56, 28 May 2010 (UTC)[reply]
As a learned man, he may have had those books. I see no mention of an association in the Charles Darwin article. Keep in mind that some people make an effort to discredit Darwin for their own reasons.. they apparently think that attacking the man himself somehow renders modern scientific findings invalid. See also Creation–evolution controversy. Friday(talk)16:10, 28 May 2010 (UTC)[reply]
There is no evidence that Darwin corresponded with Marx. Apparently Darwin sent a letter to someone else asking not to be mentioned in a book's dedication, and for some time it was thought this letter was to Marx when in fact it was not. See here and here and here for details. As for books, Darwin did indeed own Das Kapital, as Marx himself sent Darwin a copy. That copy now resides at Down House. Hope this helps. --Sean16:21, 28 May 2010 (UTC)[reply]
I'm not sure how your question relates to the section title you gave it - but back then, being well-read and having a rounded education stood for a lot - and reading ideas by people you don't agree with is one excellent way to get that kind of education. As the son of a wealthy doctor and financier, he would certainly have owned a large and diverse library - such was the mark of a well-to-do intellectual man of the mid-1800's. So we don't know that Darwin necessarily agreed with Marx - and even if they corresponded, that would not be considered unusual between intellectuals of the day when there was more of a spirit of open debate than we're (sadly) seeing these days. Darwin lived for 73 years - it would be exceedingly strange if the only thing he did in his entire life was to formulate the ideas behind evolution!
However, one thing is for 100% certain and that is that no effort to claim that Darwin was a pinko commie or a flaming gay or a religious fanatic (all of which I've seen claimed here by various religious nuts, young-earth creationist crazies and intelligent-design fanatics over the past year or so) will make the slightest difference to the scientific principle of evolution. The anti-evolution nutcases like to refer to believers in evolution as "Darwinists" in the hope that by pulling down the "Father of Evolution" they can end the belief in the scientific principle. Sadly, while that might have worked in the first few years after publication of "On the Origin of Species", we're way beyond that now. Science is an evidence-based practice - the people involved in finding that evidence don't matter beyond some small historical curiosity. The evidence for evolution is utterly overwhelming and only the most close-minded or ill-educated individuals could possibly be blind to that fact.
So maybe Darwin was a pinko, god-fearing, gay, child-molesting, lying, cheating, occultist (did I miss any?)...but that doesn't change the scientific fact that species change over time in reaction to their environment and on the basis of well-established genetic principles. We have tons of solid proof of that that are completely independent of Darwin. For what it's worth, I don't think Darwin was any of those things - he was a "gentleman naturalist" - a quiet contemplative man who didn't hold strong views about much beyond what he discovered. But that really doesn't matter a damn except to historians.
This screed and Chemicalinterest's response are off-topic and inappropriate. Opie asked a simple question about an interesting factoid in Darwin historiography (the case of the misfiled letter) and doesn't deserve this kind of knee jerk response. --Sean20:34, 28 May 2010 (UTC)[reply]
Solid proof? I do not stand for attacking people who believe in evolution (calling them names), but I do not hesitate to attack the philosophy. Anyone who attacks people (Darwin) while missing the subject (evolution) is like trying to kill a bear by shooting its leg: It weakens it, but it makes it much madder and more defensive. --Chemicalinterest (talk) 18:47, 28 May 2010 (UTC)[reply]
Marx did read Darwin, and wrote to Engels that "Darwin’s work is most important and suits my purpose in that it provides a basis in natural science for the historical class struggle."[4] Which is historically pretty interesting.
As for Darwin's correspondence, it has been meticulously categorized as part of the Darwin Correspondence Project, which is still a work-in-progress. Darwin did correspond with Marx in 1873, thanking him for sending him a copy of Das Kapital, and expressing that he wished he understood more of "the deep & important subject of political Economy."[5] The full digitized version of the letter appears in the link above. It does not appear they had an extensive correspondence and it appears that they would have corresponded long after Darwin came up with the ideas and even execution of The Origin of Species. Which is understandable—Darwin certainly had an interest in political philosophy (Malthus was a major inspiration), but he wasn't much of a heavy reader of such things. After 1869 he was a major British intellectual figure, so it's no surprise that Marx read him and perhaps vice versa (though I doubt it). As for any implications on his own politics, Darwin was many things, but a Communist he was not. He was rather conservative by most political standards of his day—he read the British equivalent of Fox News as his regular newspaper (for details on this, see R. Colp, Jr., "Charles Darwin: Slavery and the American Civil War," Harvard Library Bulletin 26 (1978), 471-489), which occasionally led him to rather retrograde opinions (he was extremely anti-North for most of the Civil War, even though he was a passionate abolitionist). --Mr.98 (talk) 00:08, 29 May 2010 (UTC)[reply]
Training your body to not be lactose intolerant
Someone I know said they were diagnosed as a child to be lactose intolerant, but then as an adult they are no longer lactose intolerant. Then a friend of hers said that she trained her body into not being lactose intolerant anymore by gradually introducing milk products into her body over a long period of time. Is this possible? Is what her friend saying true? ScienceApe (talk) 15:58, 28 May 2010 (UTC)[reply]
There are a few papers that point toward such a thing, but a more important point is that numerous studies show that the majority of people who think they are lactose-intolerant aren't really, except in a psychological sense. (In many people who think they are lactose intolerant, milk with the lactose removed produces the same symptoms as whole milk.) Looie496 (talk) 16:28, 28 May 2010 (UTC)[reply]
Syrup
1 Hi. More of a cooking question than science but here goes .. Does corn syrup taste different from golden syrup (I know what golden syrup tastes like, but haven't seen corn syrup in the UK. I would be comparing the light corn syrups with golden syrup. Also what does 'karo' taste like.
2 Does anyone have enough expertise to say what flavour chemicals are present in these syrups, if any. I guess it's lower concentrations of whatevers in molasses/treacle that makes golden syrup golden.. ? ? 77.86.47.199 (talk) 17:10, 28 May 2010 (UTC)[reply]
there doesn't seem to be an answer to any of my questions there (apart from the possibility of a salt trace in there - depending on method) - obviously I don't know what if any taste differences there are between glucose, fructose and sucrose - I thought there was something else in there beyond sugar, in low concentrations that gives it a different taste to say - pure glucose?77.86.47.199 (talk) 17:21, 28 May 2010 (UTC)[reply]
I'd be somewhat surprised if anyone here can give you a definitive answer on the relative taste of golden syrup and corn syrup, but you never know. As a practical matter, though, no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor. It's a cheap sweetening agent — you put it in rather than on things, and the things you put it in should have enough of their own flavor to overwhelm any from the syrup. --Trovatore (talk) 18:44, 28 May 2010 (UTC)[reply]
"no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor" - so you have never poured Karo over your pancakes then. Especially dark Karo on cornmeal cakes, mmm. 75.41.110.200 (talk) 19:22, 28 May 2010 (UTC)[reply]
I would have said that golden syrup has a pretty distinctive taste, while corn syrup, especially light, non-vanilla flavored corn syrup, is relatively tasteless. Just my non-scientific opinion, though. Buddy431 (talk) 21:19, 28 May 2010 (UTC)[reply]
Its ironic that Marx, of all people, should marry into the aristocracy. None of his descendants appear to have survived into the present time. How did Marx support himself and his family while writing Capital? 92.15.30.36 (talk) 20:24, 28 May 2010 (UTC)[reply]
a. Use the humanties desk, and b. Read Karl Marx as the answer to your question is in that article: "Marx's major source of income was from the support of Friedrich Engels, who was drawing a steadily increasing income from the family business in Manchester." 77.86.47.199 (talk) 20:55, 28 May 2010 (UTC)[reply]
(ec) Blue cheese. "Probiotic" is a marketing term rather than a scientific one, so it isn't particularly well defined (or defined at all, really). You can decide for yourself whether the bacteria in blue cheese count as probiotic or not. --Tango (talk) 19:17, 28 May 2010 (UTC)[reply]
A tiny bit, maybe. The yeast is supposed to be removed before bottling, for bottled beer, or it being put in a barrel, for lager. Real ale is put in the barrel with yeast still in it, but you are supposed to leave barrels to settle after tapping them before serving, so there shouldn't be any yeast in the actual served beer. --Tango (talk) 22:34, 28 May 2010 (UTC)[reply]
Not true... even after allowing the beer to clear, there is still a small amount of yeast in suspension, even in very bright beer. Exactly how much depends on the yeast's flocculance character (I'm a 10th level beer nerd). – ClockworkSoul22:37, 28 May 2010 (UTC)[reply]
Like I said, you may (ok, will) get a tiny bit. It's an insignificant amount, though (both in terms of digestive health and continued fermentation). --Tango (talk) 00:38, 29 May 2010 (UTC)[reply]
I concur. Some British and many Belgian bottled beers (for example) contain a very noticeable quantity of yeast in order to cause a secondary fermentation in the bottle; one may either pour carefully to leave this at the bottom of the bottle, or deliberately mix it into the beer, according to taste: although much of this yeast may have died (especially if the bottle is well matured) enough usually remains alive to enable re-cultivation.
Cask beer (as opposed to filtered keg beer) typically contains an even higher proportion of live yeast than bottled beer, and although finings are added to make this flocculate and settle out, much remains invisibly in suspension (and knowlegeable drinkers don't object to a degree of cloudiness due purely to yeast). Having worked at scores of beer festivals, I have often observed glasses of visually clear beer, left undrunk overnight, having by morning a couple of millimetres' thickness of settled out yeast at the bottom. 87.81.230.195 (talk) 02:36, 29 May 2010 (UTC)[reply]
I am looking for an author ( possibly an anthropologist, maybe a professor from the Seattle area ( Pacific Northwest )) who wrote a book called " Second Genesis " theorizing about brain growth in early hominid during the drying of the Mediterranean Sea following the closing of the Gibraltar Strait.
Men were separated in " Terrariums " ( his word ) created by the rivers flowing into the Mediterranean as the sea receded lower into its basin, depositing more salt at the bottom.This book is probably 30 or 40 years old and dated the time of the discovery of a Nile Canyon now submerged, which proved the drying and high salt content of the Mediterranean.
Daniel —Preceding unsigned comment added by 96.50.111.4 (talk) 19:00, 28 May 2010 (UTC)[reply]
Sounds like Genesis Revisited: A Revolutionary New Solution to the Mystery of Man's Origins (1979), by Glenn G. Strickland (apparently an engineer rather than an anthropologist). Description here—scroll down to the post by "Morphane". Deor (talk) 19:51, 28 May 2010 (UTC)[reply]
Unpleasant materials
I have an aversion to some textiles (don't know exactly which ones), that give me the creeps. When I touch them long enough (especially directly with bare hands), I experience very creepy feelings and the hands nearly sweat. Particularly, I had a jacket that nearly tormented me. Maybe someone has the same. Why is that? 213.154.25.253 (talk) 19:18, 28 May 2010 (UTC)[reply]
Could it be what it's made of - do you have the labels - a lot of people don't like polyester, also fleeces/corduroy/others feel unpleasent to some since the ends of the fibre point up (like tiny brushes). Or maybe the jacket was rubbery , some people done like that - even a small percentage of lycra to make the material more stretchy can impart a rubbery feel. 77.86.47.199 (talk) 19:30, 28 May 2010 (UTC)[reply]
How odd. Do these same people dislike the feel of other furry things, such as kittens? Are you implying that the ends of the fibers stab into delicate skin and cause pain, or what? 81.131.68.87 (talk) 19:50, 28 May 2010 (UTC)[reply]
I've experienced a similar reaction - so, no, you're not alone. It's hard to describe. Artificial fabrics that cling to my fingers kind of creep me out. Cheaply made fake fur, for example, always seems to have too much friction and the oils from your hand sometimes make weird squeaking noises when you wipe them on it. Yuck. Matt Deres (talk) 00:12, 29 May 2010 (UTC)[reply]
I'm stroking a teddy bear right now (presumably polyester fur) in an effort to work out what you mean, and I really don't get it. Sure, it doesn't feel quite like real fur, and it has slightly more friction, and I guess it makes a bit more rustling noise (it doesn't squeak!) ... so all in all it feels slightly different from real fur. So why is that disturbing? Is it an uncanny valley effect? That relies on our inbuilt instincts for identifying humans, though, and it's not like we have an instinctive affinity for the feel of real fur - or maybe you guys do? 81.131.23.148 (talk) 04:17, 29 May 2010 (UTC)[reply]
I'm designing an experiment to measure the effect of a treatment on the composition of substance. Of course I want do replications, but the right or most sensible way to go about this is less obvious that it might seem.
I could:
Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample once
Apply the treatment to one sample of the substance, and then measure the composition of the treated sample five times
Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample five times
Repeating the treatment is much more 'expensive' that repeating the composition measurement. Although I want to be thorough, I need to make efficient use of my resources. Can you help me understand how I should be thinking about these different alternatives? If you can point me to somewhere that I could read about this issue, that would help. I've searched, but I must be using the wrong terminology because I haven't found much.
ike9898 (talk) 19:48, 28 May 2010 (UTC)[reply]
If you don't do the 5x5 experiment you won't know anything about one of the two possible errors.
Experiment 2 gives you some indication of the error of measuring the composition. You can't really say much about the experimental error in treatment of the substance until you measure this.
If you are certain within yourself that one of the two errors is likely to be small (eg you think the treatment process is reliable and consistent, or you think the measurement of the composition is so reliable that you only need to do one measurement) then you could do experiment 1 or 2. but you have no statistical knowledge about the error at all.
Straight answer: What I'd suggest is do experiment 2 once (maybe with more than 5 measurements) - so you have an idea of the statistical error in the measurement - this should then give you enough information to know how many times you need to do the measurent for future samples to get a reliable answer:77.86.47.199 (talk) 20:47, 28 May 2010 (UTC)[reply]
Process 1 is valid, and process 3 probably won't be much better. Process 2 is not valid unless you are sure that all samples are the same. The crucial point is that when you calculate a mean and standard error, the samples that go into the calculation have to be completely independent of each other, and they have to be chosen randomly from the distribution. That means if you apply process 3, you would have to calculate the mean separately for each of your 5 samples, and then use the calculated means as input to a 5-sample check. But in any case you're putting the cart before the horse: you need to have a well-defined hypothesis to test in order to properly design an experiment, and you didn't state what your hypothesis is. Looie496 (talk) 20:49, 28 May 2010 (UTC)[reply]
OP here. Well, I'm not sure what my hypothesis is, but let me explain what I am trying to do, which is slightly more complex than what I described. There's not just one treatment; the treatment is a continuous independent variable, and I intend to perform experiments with treatment variable set at 5 different values. I want to produce is a figure that shows the composition at the various settings for the treatment. I think I'd also like to be able to fit a curve to the results. ike9898 (talk) 21:29, 28 May 2010 (UTC)[reply]
Suggest following my straight answer above - do 5 (or 10) measurements with one sample - this gets you an error bar for that measurement. For the others if you don't have time(/don't want) to do repeat experiments you can use the same error bar (probably best to scale as a percentage error) for the other measurements (assuming you do only one measurement per sample) - if plotting this as a graph you should clearly state and distinguish the proper and extrapolated error bars (eg solid for measured error, dotted for extrapolated) - though there is no substitute for actual measurements, and some people may take issue with extrapolated error bars...
As for curve fitting - It helps if you have a hypothetical equation first (ie a hypothesis) - do you have one, otherwise you could guess the curve - (see also Curve fitting) - though the problem here is that logarthymic/quadratic/exponential curves can look much like a straight line if the range of points is small. Not sure how much info you need on curve fitting. A quick look at this [9] suggests it's a good introduction though searching for "curve fitting" turns up many results of use - often the URLS that end with .ac. are useful since they are from universities.77.86.47.199 (talk) 22:11, 28 May 2010 (UTC)[reply]
"Dichroic liquids" / dyes
Has anyone ever seen a phenomenon like this before? It is quite remarkable imo. Does anyone have any ideas as to what might be causing it? Perhaps it is a colloid with suspended particles being of different color than the solvent they are suspended in; whereby transmitted light is absorbed by the solvent at selective wavelengths but absorbed at all wavelengths by the dispersed solid particles, which also simultaneously scatter light at selective wavelengths (green).
Thank you very much that is fascinating - this article [10] suggests that methanol / chloroform mixtures, though miscible can show localised regions where hydrophobic and hydrophilic ends of molecules agglomerate - ie like micelles (I would assume that dyes contain both hydrophilic and hydrophobic parts) - could a micelle like structure explain the optical properties?
I also think it may be some sort of colloid or emulsion - the green colour looks 'diffuse' as if it is particulate, whereas the purple color is clear. I'm not sure if it is coincidence that the green colour is the complement of the purple colour or not (ie green+purple=white)
Also towards the end of the video he says that the transmitted light (ie the light going through the liquid and out the bottom) is still purple - so that suggests no chemical change and that the green light is backscattered. Also when pouring the liquid it looks like thin films and the edges of the liquid look purple - suggesting that the green colour is cause by a bulk volume of liquid - again suggesting a colloid or emulsion or similar.77.86.47.199 (talk) 21:11, 28 May 2010 (UTC)[reply]
I think is a combination of reflectance and absorption. If you have a material that absorbs and reflects green light it would explain this. When the liquid is shallow, you see the green reflection. Little light is absorbed because there isn't much liquid (so it's mainly white with a tinge of magenta). However the human eye is much more sensitive to green, so the small amount of green light that is reflected is noticeable. When the liquid is deep a lot of green light is absorbed, leaving behind the magenta light. This mixes with a small amount of green that is reflected, but there is enough magenta, that that is what you see. On top of that the reflection is directional - so the green is reflected away from you. If you have a youtube account, link to this page in the video comments. Ariel. (talk) 23:36, 28 May 2010 (UTC)[reply]
I posted a comment on his blog, except I'm not sure comments are working. My suggestion is reabsorption by the competing molecules - the blue light reflected off the methanol is absorbed by the red chloroform and re-emitted as green (because the red dye is a reflection of white light - depending on the black body model, it'll look somewhat greener when a bluer-color light is shone). The converse occurence also happens, such that the net result is green. This occurs with magnitude not seen in other solutions I think because both chloroform and methanol are linear-polar, where ethanol is bent. Thus I think the chloroform and methanol align in the mixture and thus re-absorb each other's light much more effectively. But I do physics, not chemistry. SamuelRiv (talk) 04:25, 29 May 2010 (UTC)[reply]
2 gallons
i drink 1 gallon water a day. sometimes i drink 2 gallon water a day. when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this common occurrence. —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:56, 28 May 2010 (UTC)[reply]
Drinking too much water can be very dangerous - people have died from doing that. Check out our article on Water intoxication. Daily intake recommendations for water depend on how much you exercise and how much body weight you have. Most web sites say that a typical person should drink eight 8oz drinks per day - that's just a half of a US gallon - others say 1.2 liters - or a third of a gallon per day. But this depends on body weight and exertion levels...you might well need more if you do heavy work. Drinking about one liter per hour is considered to be most a healthy person should consume because that's the fastest a pair of healthy kidneys can process the stuff into the bladder. 2 gallons is 7.5 liters - so if someone were to drink that much over (let's say) an 8 hour period - then they would be pushing the limits and entering into life-threatening territory. Those are the facts.
However, we're not allowed to offer medical advice here - so if you are concerned, you should consult a doctor.
BTW, the 8 cups a day thing has no scientific basis at all. Someone just made it up. The only recommendation is to drink when you are thirsty. Drinking more than that just makes you more likely to get dehydrated (since your kidneys are accustomed to a lot of water, and if you don't constantly drink you will get dehydrated, since the kidneys are still excreting water at the usual pace). It takes a little while for the kidneys to get used to a new water level. See Drinking water#Requirements. Ariel. (talk) 23:31, 28 May 2010 (UTC)[reply]
Let's cut out the alarmist health crap. A healthy human can easily handle two gallons (~8 Liters) of water a day (source: [11]) (Note, though, that there are a number of diseases/disorders/etc. that can hinder the body's ability to process water. Echoing Steve, if you're concerned, see a doctor). Buddy431 (talk) 00:40, 29 May 2010 (UTC)[reply]
Well, using Steve's own number we find that that 2 gallons is fine. I don't know why Steve is using 8 hours as the length of a day... As long as you drink the 2 gallons spread out over the whole day and there are no exceptional circumstances (that's the bit we can't cover here and you need to see a doctor for), you should be fine (in the short term, at least - I have heard from reliable sources that there is a possibility that people drinking too much water "wear out" their kidneys over years. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
Thirst is a very bad way to determine when to drink. If you are thirsty, you should definitely drink, but that isn't enough. A lot of people aren't good at noticing thirst, so they would only be drinking when they are already approaching dehydration. The colour of your urine is a better measure - it should be pretty much clear. If it is green/yellow, you need to drink more. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
It's not "alarmist health crap". If you drink two gallons of water as fast as you possibly can - it could easily kill you. If you drink two gallons over 7 hours then you'll be consuming it at a higher rate than a healthy pair of adult kidneys can handle it - and it's likely that the resulting dilution of your blood will make you feel very strange - kinda like being intoxicated. If you drink that much over 24 hours, you should be perfectly OK. However, how do any of us respondents know whether the OP has healthy kidneys or unusually low body mass - or is a child? Are these "US Gallons" - because if not, then the risks are even higher than I estimated. Over how much time is the OP consuming this amount? We don't know any of those things - and because this is a potentially fatal situation, we MUST err on the side of caution. Two US gallons per day is an awful lot...and it's most certainly in the range where side-effects are possible. Since our OP explicitly expresses noticable symptoms from drinking that much - we have to consider the strong possibility of water intoxication. That's a potentially fatal condition, so we must not dismiss the possibility out of hand - and Buddy431 is taking an exceedingly irresponsible action by doing so. This is a situation where bad advice given on the ref desk could literally kill our questioner! Caution is therefore strongly advised here. Since we're most certainly not allowed to diagnose a medical condition, we should explain the facts in general terms and advise our OP to discuss this with a doctor - which is precisely what I did. SteveBaker (talk) 18:22, 29 May 2010 (UTC)[reply]
Let me echo the anon. If one is drinking whenever one gets thristy, and hence staying comfortable, then what physiological benefit is there to drinking more than that? Obviously, the color of urine can indicate how much water was excreted with the urine, but is the person who drinks more and has light urine actually measurably healthier than the person with darker urine by any other objective measure? Dragons flight (talk) 09:00, 29 May 2010 (UTC)[reply]
"If [mild to moderate] dehydration is chronic (ongoing) it can affect kidney function and may lead to the development of kidney stones. It can also cause:
From your link, "Mild to moderate dehydration: The first sign of dehydration is thirst." So again, if one consistently satisfies ones thirst, what evidence is there that drinking more beyond that matters? Dragons flight (talk) 19:38, 29 May 2010 (UTC)[reply]
The problem is that a lot of people don't notice thirst (or mistake it for hunger). That's why the standard advice for checking you are drinking enough is to check the colour of your urine. If you follow the "Diagnosis" link at the top of that page you'll see it talks a lot about urine and doesn't mention thirst once. --Tango (talk) 20:45, 29 May 2010 (UTC)[reply]
I certainly don't welcome kidney stones. I notice though the diagnosis page says if "it is unusually dark in colour, you are probably dehydrated." Which is vague, of course, but it doesn't say "it should be almost clear" or "it shouldn't be yellow". I appeal to the fact that everybody knows urine is greenish yellow. 81.131.66.87 (talk) 00:54, 30 May 2010 (UTC)[reply]
Mine isn't. Mine is almost clear. The reason a lot of people "know" urine is greenish yellow is because a lot of people don't drink enough. --Tango (talk) 22:10, 30 May 2010 (UTC)[reply]
i live in a very hot place thats why i drink 1 gallon a day. my question is when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this possible.
I believe people who take a lot of multivitamins tend to end up with strange colour pee from all the vitamins being excreted. Perhaps when your pee is more dilute since the strange colours aren't so noticeable this is making you think there's something wrong. In addition see placebo. Nil Einne (talk) 00:35, 29 May 2010 (UTC)[reply]
It isn't vitamins you feel, it is salt. As a former desert resident myself, I know that it's quite difficult to keep your electrolytes in balance when you consume that much fluid. Drinking even a part of it as Gatorade or another sports drink reduces the problem quite a bit. Even something like ice tea causes less of that feeling than drinking straight water. When I did midsummer bike rides in Tucson, I would regularly down a gallon or more of unsweetened unchilled ice tea afterward, and it worked pretty well for me. Looie496 (talk) 00:38, 29 May 2010 (UTC)[reply]
Multivitamins don't really do anything (unless you have a vitamin deficiency, which you won't have as long as you aren't pregnant and have a good diet), so you won't really be able to tell the difference. It is all in your head. (Yes, there have been studies that show a benefit to multivitamins beyond placebo. There have also been studies showing a benefit to homoeopathy beyond placebo. You need to look at more than one study to draw a conclusion.) --Tango (talk) 00:43, 29 May 2010 (UTC)[reply]
Let's be honest though. There are plenty of people, even in the West, who don't eat a terribly balanced diet and could benefit from a multivitamin. We shouldn't be making any assumptions about Tom's eating habits, health, or nutrient situation. That's exactly what our medical advice guidelines are for; we haven't examined Tom, and we don't know his his history. It's irresponsible to recommend either taking or not taking a multivitamin. Buddy431 (talk) 00:50, 29 May 2010 (UTC)[reply]
it is not placebo. i dont eat vegetables or fruit. so if i dont take a vitamin i feel it. i also think "placebo" is a scam by lying psychiatrists —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:51, 29 May 2010 (UTC)[reply]
In that case, it is almost certainly more important that you start eating fruit and vegetables than that you change your water consumption. A multivitamin is not a good substitute (it is better than nothing, but far far worse than a good diet - it doesn't contain any fibre for one thing). Placebos are definitely real - they are used in an enormous amount of medical research (and some treatment) that has nothing to do with psychiatry and a lot of people would have noticed if the effect didn't exist. --Tango (talk) 01:00, 29 May 2010 (UTC)[reply]
Actually, it is you who have derailed the question, because here on the Reference Desk, other editors generally never just let a comment like that pass, whether you like Anti-psychiatry or not. You weren't actually being told that your feeling had anything to do with the placebo effect. So, on your placebo comment, our placebo article makes it clear that there is definitely a placebo effect. The article also mentions at least one study that concluded that placebos had no clinically important effect, though these studies have been controversial. Comet Tuttle (talk) 02:36, 29 May 2010 (UTC)[reply]
If you could find multivitamins with relatively little taste and placebo pills that look (and taste) the same [13] you could test this yourself. (The great difficulty here would be getting multivitamin pills and placebo pills that taste and look the same.) Get a friend to toss a coin, and decide whether to put the real pills or placebo into a container. Then either leave them for you or hand them over without saying anything or exchanging looks. Try these for a few days. If you can genuinely 'feel' the difference, you should have no problem working out if these are the genuine pills or the placebos. Don't talk to your friend about this. When you've done, ask your friend for another batch (using the same or a similar container), tossing a coin or whatever to choose whether to give you the real pills or the placebos, and again without talking in any way about the brief or current batch. Again decide whethere they are the genuine multivitamin pills or placebos. Repeat 6 more times.
After these 8 repetitions, ask your friend for list of when the container had placebos and when they had genuine multivitamin pills. (8 repetitions isn't really enough but hey I'll be generous.) If in all 8 repetitions you correctly identified when you had real pills or placebos (which should be no problem if you can feel the difference) then people would be more willing to accept perhaps you really can feel it when you don't take your multivitamins (although I'd be more inclined to believe the pills didn't actually taste and look exactly the same) and you can be more confident in your believe that you really can feel the difference.
Note that the placebo effect has been observed in many cases outside of the medical field. E.g. people who are convinced they can hear the difference between various types of speaker wires.
Er, placebos are an important and well-established part of scientific medicine. (Mostly in regards to double-blind drug research.) They're not really connected with psychiatry. Even if every psychiatrist in the world suddenly admitted they were making their entire field up and were nothing more than a pack of liars the fact of placebos would be unchanged because our knowledge of placebos doesn't come from psychiatrists, it comes from medical researchers. APL (talk) 06:44, 29 May 2010 (UTC)[reply]
Getting back to the original question, vitamins A, D, E and K are fat soluble. It is difficult to see how they could be 'flushed out' through the kidneys. This implies that the feeling you are getting is not related exactly to the 'lack' or otherwise of vitamins. Caesar's Daddy (talk) 07:08, 29 May 2010 (UTC)[reply]
And also back to the original question, I have kidney problems and have to drink a certain amount each day and no more. If that happens, my electrolyte balance is thrown out, and I feel quite sickly. I guess that's what's happening to you: you've drunk more than your body needs, and the balance of your constitution has been shaken. So in a sense you're right, but it's not the vitamins you're feeling the loss of. (Apologies if this constitutes medical advice, if it is can someone more experienced that I am delete it.) --TammyMoet (talk) 07:54, 29 May 2010 (UTC)[reply]
That would only be the case if the OP also has kidney problems (healthy kidneys should be able to deal with the extra water, as long as it isn't drunk over too short a period of time). So, if you are right, it is very important that the OP go and talk to a doctor. --Tango (talk) 16:20, 29 May 2010 (UTC)[reply]
All water soluble vitamins will be excreted, the level generally dependent on how much you consume. However interesting enough the level of vitmain B12 excretion may be dependent on urine output [14]Nil Einne (talk) 19:01, 29 May 2010 (UTC)[reply]
This is getting dangerously close to our no medical advice guideline so feel free to remove it if you feel it necessary but if you are able to feel it when you don't take your multi vitamins, it's more likely to be a general 'poor'/'unwell' feeling then anything specific therefore in line with some of the above answers, I wonder if you're getting to the level where you're taking too much water with 2 gallons which in itself may lead to such a feeling and may also negativelly affect the ability of your body to excrete other stuff like vitamins (i.e. you may have too high a level), which could also lead to such a feeling. So anyway, yeah I agree with people above you may want to see a doctor. Nil Einne (talk) 18:12, 30 May 2010 (UTC)[reply]
May 29
Sun Distance
How much closer would the sun have to be before we'd all die? I will also accept the scenario where we have to stay inside specially built igloo houses, for fear of death in the outside world.74.104.107.137 (talk) 02:24, 29 May 2010 (UTC)[reply]
If we're considering "specially built igloo houses" (ie technologically sophisticated living quarters) then we could survive much closer to the sun. We could imagine solar-powered refrigeration units keeping us cool - perhaps in some underground situation. With such technology, we could live much closer to the sun than halfway. Also, consider some place like Mercury: The sunny side gets up to about 500C and would be utterly unlivable - even with high tech habitation. But the 'dark side' is at -170C - which is way too cold. Someplace between those two extremes, there ought to be a place on the boundary between the sunlit and dark sides of the planet where there would be perpetual twilight and we could live - albeit with some fancy technology. Since Mercury is the closest body to the sun, that is the limit. Of course if we're talking about stars in general - then I'm sure there are other stars with planets even closer in than Mercury that could sustain sufficiently high-tech humans. Another problem with living close to a star would be radiation - but again, if you have an entire planet between you and the star, you'll be reasonably well protected. SteveBaker (talk) 17:59, 29 May 2010 (UTC)[reply]
Mercury doesn't have twilight. You need an atmosphere for that. Twilight is defined as the time between sunset and it getting dark (for a given definition of dark, which depends on what you are doing). If there is no atmosphere, then it will get completely dark as soon as the sun sets (well, a mountain just on the other side of the terminator might reflect some light, I suppose, but it's unlikely to be enough to be considered twilight). A habitable ring near the terminator of a tidally locked planet (you seem to be assuming a tidally locked planet) is a feature of sci-fi and could happen, but it requires an atmosphere to moderate the temperature gradients. --Tango (talk) 20:54, 29 May 2010 (UTC)[reply]
That's true. But without an atmosphere, you're obviously not going to be wandering around on the surface without a lot of technology. Assuming you're living in a well-engineered habitat, the important thing is that you're able to control the temperature cheaply and easily. If you live close to the terminator - you could run pipes with water or some other liquid flowing through them out onto the sunny side and the dark side of a small hill - and by controlling the flow rates get water at any desired temperature. The other nice thing about a tidally locked planet is that you can erect solar panels that are at the perfect angle to collect sunlight without having to make them turn to face the sun - and you don't need backup batteries because there is never any cloud cover and it's never nighttime. With a perpetual/limitless 600 degC temperature differential, you could also use steam engines to generate power. With ample electricity and no problems with heating or refrigeration, it's actually not such a terrible place to set up home. But if you are close to the terminator, any object with even a modest albedo that's sticking up into the sunlight would provide ample illumination into the areas in shadow. But given the level of radiation coming from the sun and a planet with no magnetic field to deflect it - you're not going to be going out onto the surface anywhere near the terminator! SteveBaker (talk) 23:45, 29 May 2010 (UTC)[reply]
One problem with a tidally locked planet that has an atmosphere, though, is that the temperature gradient would create hurricane-force winds that would blow you away before you could say "convection". Looks like Tango completely forgot about that :-) 67.170.215.166 (talk) 02:53, 30 May 2010 (UTC)[reply]
On second thoughts, you don't need an atmosphere to moderate the temperatures - the ground will do that. You just have a build your settlement underground. The surface will have a sudden 600 degree temperature jump, but the temperature a few metres underground will be gradual. I'm starting to like your idea! A venue for Wikimania 2100, perhaps? --Tango (talk) 23:56, 29 May 2010 (UTC)[reply]
=((((R^2)*σ*(Te^4)*(1-A))/(4*ε*(d±(d*e))^2))^0.25)-273.15
So I can get a global annual average temperature for a planet,
If I assume a global average albedo and a global average emissivity
Albedo
εmissivity
0.20
0.25
0.30
0.35
0.40
0.45
0.80
5°C
1°C
-4°C
-9°C
-14°C
-20°C
0.75
10°C
5°C
0.7°C
-4°C
-10°C
-15°C
0.70
15°C
10°C
5°C
0.3°C
-5°C
-10°C
0.65
20°C
16°C
11°C
5°C
-0.1°C
-6°C
0.60
26°C
21°C
16°C
11°C
5°C
0.5°C
0.55
33°C
28°C
23°C
17°C
11°C
5.4°C
Ignoring the perspective that single value Albedo and Emissivity are very
simplistic, since "Global Annual Average Temperature" is also but it exists:
A) at what levels of irradiance (max/min) does this become moot?
B) what combinations of Albedo & Emissivity are unrealistic or possible??
Thanks, 24.78.167.139 (talk) 06:35, 29 May 2010 (UTC)[reply]
Have you had a look at Atmosphere of Venus. Venus reflects two thirds of the light and yet its surface temperature is higher than that of Mercury. Even so there is a zone high up in its atmosphere which just might be okay for microbes. Dmcq (talk) 09:03, 29 May 2010 (UTC)[reply]
I came upon this chart in a search and realized this illustrates well the idea that there are a lot of possibilities but some are unrealistic. - 24.78.167.139 (talk) 17:36, 30 May 2010 (UTC)[reply]
So the button cell I have must be a silver oxide or manganese dioxide cell with a tiny bit of mercury added to it. I was wondering if I could open it up and dissolve the mercury(II) oxide. But there isn't enough. --Chemicalinterest (talk) 16:26, 29 May 2010 (UTC)[reply]
If I might intercept the question - aren't those flashing LED shoes that kids used to wear back in the early 1990s using a liquid Hg amalgam to complete the circuit? Are those banned too? SamuelRiv (talk) 17:10, 29 May 2010 (UTC)[reply]
For my understanding the chemistry of mercury is interesting, but to use mercury cells as a source for experiments is not very good. Working with mercury is unpleasant and I would only do it in a lab with a fume hood. The chemistry of manganese and vanadium is similar interesting and both metals are by far less toxic!--Stone (talk) 22:04, 29 May 2010 (UTC)[reply]
How about zinc - excluding the absense of a +1 oxidation state much of the chemistry is 'similar' to mercury, it's not particularly toxic, and readily available. Yes I know zinc is boring - but it's not what you've got it's what you do with it...83.100.138.38 (talk) 14:15, 30 May 2010 (UTC)[reply]
I have an old mercury dial thermostat, if you really need some mercury..... Not sure it's safe to mail it though. Maybe offer to replace thermostats for people for free? But please do be careful. Ariel. (talk) 02:34, 30 May 2010 (UTC)[reply]
It's illegal to send mercury (or anything that contains mercury) by mail -- the reason is because mercury dissolves aluminum (including Boeings and Airbuses, and DC-3's too) -- so if the stuff leaks out, it could cause a nasty crash. Clear skies to you 67.170.215.166 (talk) 02:58, 30 May 2010 (UTC)[reply]
No I didn't ask for Hg metal, asked for HgO or mercury(II) compounds. Forget about Hg; NH2Cl and Cl2 are enough toxicity, not to mention Cr6+. --Chemicalinterest (talk) 19:43, 30 May 2010 (UTC)[reply]
I should explain some more! The famous fictional vampire is said to have been very loosely based on (and named after) the exceedingly nasty Vlad III the Impaler - who was arguably a much nastier person than the fictional Dracula. The name "Count Dracula" is attributed to this guy - because: "His Romanian surname Dracula (also spelled "Draculea", "Drakulya"), by which Vlad was referred to in several documents, means "Son of the dragon" and points to his father, Vlad Dracul, who received that moniker from his subjects because he had joined the Order of the Dragon. Dracul, from the Latin word Draco, meaning "dragon", is derived from the Greek word Δράκων (Dracon), though in modern Romanian it means "devil".". He was a Prince of Wallachia - not a "Count".
Of course, we must never forget that bloodsuckers still lurk among us. Like legends of yore, they will rise again. But seriously, the Vampire article is terrific, and the Vampire lifestyle briefly discusses and links to this unique teen subculture, though without a "Dracula"-like leadership. SamuelRiv (talk) 18:16, 29 May 2010 (UTC)[reply]
By the way, he has not much to do with Transylvania, which was then part of the Kingdom of Hungary. He was the ruler of Wallachia (a country roughly corresponding to today's Southern Romania), maybe the name "Transylvania" sounded more spooky to Bram Stoker and chose that instead. --131.188.3.20 (talk) 21:36, 29 May 2010 (UTC)[reply]
Notice that Transylvania is a real place, though, even if Vlad is from just South of there. (The word means "across the woods", and Vlad was just across the woods from there.) Also note that vampire bats are real, and really do suck blood from the living, although humans are only rarely their target, and they are in the Americas, not anywhere near Romania. StuRat (talk) 01:38, 30 May 2010 (UTC)[reply]
I don't think the WHO or UNICEF manufacture them directly. Rather, they publish standards, and encourage individual nations to produce and distribute the solutions ([17]). I don't know where you are, so I can't really help hook you up with free packets (if free packets are even available in your area). Here's the WHO's recipe, if you wanted, you could make your own: [18]. Otherwise, there appear to be a number of commercial sellers online if you're not able to get free packets. For more information on oral rehydration in general, see our article Oral rehydration therapy. If you gave us more information on where you are, and what you need it for, we can probably help you better. Buddy431 (talk) 20:32, 29 May 2010 (UTC)[reply]
If you are in a disaster area, then aid agencies or the national authorities drop free ORS from planes and helicopters and set up distribution centres where you can queue for the stuff. If you aren't in a disaster area, then you might be able to get it free from health clinics, etc., but you probably have to buy it or make it yourself. --Tango (talk) 21:00, 29 May 2010 (UTC)[reply]
im in the usa can i get it?
Echoing Tango, I'd check any local health clinics. It seems doubtful to me that you'd be able to get it free in the US, but I don't really know. You can also probably buy some at a local drug store (though it may be marketed specifically for infants, i.e. Pedialyte). Sports drinks, such as Gatorade, are pretty good for this sort of thing as well (you won't get it free, but the prices aren't outrageous). You can also make a pretty good substitute with just sugar and salt (13 g sugar, 3 g salt per liter of water, as per the WHO composition) (though having the potassium and citrate are of course preferable). The question is, what's it for? If you or your kid has diarrhea, you may want to talk to a doctor or other medical professional anyway. They may be able to suggest the best solution. Buddy431 (talk) 22:40, 29 May 2010 (UTC)[reply]
I would be very surprised if you can't buy it in US drug stores. You certainly can in the UK (I think there are different versions for adults and children). --Tango (talk) 23:32, 29 May 2010 (UTC)[reply]
Yes and it tastes revolting! I'd much prefer to get a glass of diluted Ribena, add a pinch of salt, and drink it in one! --TammyMoet (talk) 07:30, 30 May 2010 (UTC)[reply]
If it tastes revolting, you don't need it. When you are dehydrated you lose the ability to taste salt and suddenly ORS starts to taste nice! I don't think there is enough sugar in Ribena for that recipe to match the WHO recipe - you need to add some extra sugar too. Otherwise, I can't see a problem with adding flavouring like Ribena to ORS. --Tango (talk) 15:01, 30 May 2010 (UTC)[reply]
Does that mean you've gone into local health clinics and local drug stores as suggested above, and asked? Did they not offer suggestions of where you might be able to get it? It also occured to me from the above posts that you may want to try some sort of travel/adventure/outdoor oriented store (a bit like Kathmandu (company) here in NZ). I presume if you've looked all over the USA you've already looked in places like Walmart. Nil Einne (talk) 09:11, 31 May 2010 (UTC)[reply]
I hope you can help me as I have had no luck in finding the answer to this question. If someone is addicted to & using crystal meth almost daily, can the meth get stored in fat cells, then later be released into the system when increased physical activity burns off fat? My son has been through rehab & swears he isn't useing and his moods & attitudes would seem to back up his words, however, he recently started work with a landscaping company & it is very hard work. Suddenly his weekly UA tests are reading positive & he is steadfastly denying that he is useing again. Thanks for any possible help71.34.135.9 (talk) 20:41, 29 May 2010 (UTC)[reply]
This happens with THC from cannabis and various other hallucinogens, so it wouldn't surprise me. Can't find a specific citation though. Regards, --—Cyclonenim | Chat 21:13, 29 May 2010 (UTC)[reply]
Gosh, best of luck to you and your son. I hope you can find a doctor to defend this concept, because coming off of something like that is so utterly important and it would be terrible if he lost his job and perhaps sink into a vulnerable state (especially since construction is great work). SamuelRiv (talk) 18:43, 30 May 2010 (UTC)[reply]
Salty Q
It's good to eat salt tablets when in the desert yet bad to drink saltwater when in a lifeboat. Why the diff ? StuRat (talk) 21:49, 29 May 2010 (UTC)[reply]
Precisely. Seawater is just too salty. You can drink it as a source of salt, but only if you drink enough fresh water with it (or, preferably, dilute it with fresh water). Likewise, you shouldn't eat salt tablets in the desert unless you have plenty of water with them. --Tango (talk) 23:14, 29 May 2010 (UTC)[reply]
Dude, you mixed ammonia and bleach? That's like the one thing that everyone's told not to do with cleaning chemicals. Our Ammonia article says that Chloramines can be formed. Our Bleach article also has some of the reactions possible, including the possibility of making Hydrazine. I hope you're being careful. Buddy431 (talk) 02:02, 30 May 2010 (UTC)[reply]
I absolutely agree with Buddy (and others). Did you really have to mix these together yourself to see what happens? There is plenty of stuff on the internet telling you what will happen. After reading a bunch of your questions and answering them (under an IP address, I have since signed up with an actual user ID) I should warn you that all of these exotic reactions and metals (chromium, lead, mercury) can be very dangerous. If you are doing this at home, what sort of apparatus do you have for these experiments? What do you do for waste disposal? My apologies if you are already doing this in a safe environment.
Don't get me wrong, I think that it is great that you want to learn about chemistry, and experiments can be a great way to understand something, but be careful! I'd recommend asking your science teachers, but I seem to remember from a previous post that your chemistry teacher is a dolt - don't ask him/her. Maybe someone else in the department can help you get some background material on your proposed experiments, or even let you use some equipment at school. I am a chemist myself, so I think that it is absolutely awesome whenever students are interested in chemistry, but there is a lot more to it than pretty colours, funny reactions and party tricks. To answer your original question, Buddy is right, chloramine will be produced and this may or may not be the gas observed. It could be chloramine, or it could be ammonia evaporating if the reaction is exothermic.Pmdove (talk) 03:04, 30 May 2010 (UTC)[reply]
I totally agree, but the bleach/hypochlorite reaction is almost universally presented totally wrongly in all internet discussions - the reaction is actually used to treat water, and is nothing like the hazard presented someplaces online. Nevertheless Chloramine is produced in considerable quantities.. Be Safe. 83.100.138.38 (talk) 14:12, 30 May 2010 (UTC)[reply]
Actually chloramine is likely to remain in solution, and the gas is likely to be nitrogen. Both NHCl2 and NCl3 are not stable in alkaline solutions and will not be present in the very basic NH3 / NaOCl mixture to any significant extent (except as intermediates) (They are formed in acid solutions) (also MSDS reports present a worse case scenario - not what will typically happen). This thesis gives some of the background [19] intro upto p.10 (the internet is full of worst case 'mis-information' that does not apply in strogly alkaline solutions.) All the reactions are exothermic, so de-gasing of NH3 is also a possibility as stated above.
Nevertheless the reaction is still not advisable due to Chloroamine produced, and the heat produced (which could be considerable with concentrated NH3 and bleach).83.100.138.38 (talk) 14:02, 30 May 2010 (UTC)[reply]
see also [20] The reaction is used in water treatment - and called "Breakpoint chlorination" Breakpoint chlorination involves the use of chlorine (in the form of gas or sodium hypochlorite solution) to chemically oxidize ammonia and convert it to nitrogen gas.p.2 (14th page adobe reader count)83.100.138.38 (talk) 14:07, 30 May 2010 (UTC)[reply]
See this article for a technical explanation of complications. Check down about 5 or 6 blue headings until you come to "Complications". Bielle (talk) 03:05, 30 May 2010 (UTC)[reply]
An Anonymous editor (149.135.96.120) asked at the New contributors' help page; "What are possible birth defects to a baby that can be caused by the mother being morbidly obese while pregnant? Thank you" ;"Could you please inform me of what birth defects can arise?" -- wiooiw (talk) 02:57, 30 May 2010 (UTC)[reply]
From the abstract of “Maternal obesity and morbid obesity: the risk for birth defects in the offspring” found here comes:
Maternal prepregnancy morbid obesity was associated with neural tube defects OR 4.08 (95% CI 1.87-7.75), cardiac defects OR 1.49 (95% CI 1.24-1.80), and orofacial clefts OR 1.90 (95% CI 1.27-2.86). Maternal obesity (BMI > or = 30) significantly increased the risk of hydrocephaly, anal atresia, hypospadias, cystic kidney, pes equinovarus, omphalocele, and diaphragmatic hernia. CONCLUSION: The risk for a morbidly obese pregnant woman to have an infant with a congenital birth defect is small, but for society the association is important in the light of the ongoing obesity epidemic.
An "OR" is an odds ratio. A "CI" is the confidence interval. Simply put, there is about a 4-fold (range from 1.87 to 7.75) increased chance for an obese woman to have a baby with a neural tube defect. The "odds ratio" can be multiplied with the baseline odds of having a baby with a neural tube defect to calculate an actual risk, which is usually still quite small for the individual (as noted above), but when considering millions of births the increased risks amount to an important public health problem. --- Medical geneticist (talk) 11:46, 30 May 2010 (UTC)[reply]
One additional risk is that obese women often don't seem to notice they are pregnant as soon and those around them may not notice all all. They might just normally have an irregular period and figure that's what's happening, since the "baby bump" isn't as apparent. This could lead to consuming alcohol, smoking, or taking drugs which should be avoided during pregnancy. In extreme cases (probably with some denial tossed in), obese women may not even know they are pregnant until they give birth. StuRat (talk) 03:36, 30 May 2010 (UTC)[reply]
I'm not sure that's true. Having a bump is a relatively late symptom; the woman is more likely to be concerned with no period and morning sickness, which come before the bump. By your logic we'd have loads of women not knowing they were pregnant until the bump came, and that comes later than the missed period or morning sickness. Regards, --—Cyclonenim | Chat 19:17, 30 May 2010 (UTC)[reply]
It's not common - but just Google for "gave birth didn't know pregnant" and you'll find that it's not exactly unknown either! SteveBaker (talk) 02:13, 31 May 2010 (UTC)[reply]
Obesity can be associated with all sorts of endocrine dysfunction, such as polycystic ovarian syndrome, so the woman may be having such irregular menstrual periods that she really doesn't notice missing her period. The morning sickness, who knows... it's so variable between women that it isn't really a reliable clue about pregnancy. Anyway, SteveBaker is right, this is not unheard of. There's even a Discovery channel television series about it. --- Medical geneticist (talk) 03:15, 31 May 2010 (UTC)[reply]
Females of Saturniidae moths will start laying unfertilized eggs a few days after eclosion if they cannot find a mate by then (note that the imago stage of Saturniidae has a typical lifespan of only about a week). Nothing will hatch from unfertilized eggs, though, since (as StuRat said already) Saturniidae are incapable of parthenogenesis. --Dr Dima (talk) 06:12, 30 May 2010 (UTC)[reply]
Drew Brees Sports Science
I had some questions about what I thought was some spurious science in a video I saw today, http://www.youtube.com/watch?v=tVoqA-LKGb4. To begin with, the whole football player/archer comparison is quite silly in my opinion, but the questions I had concern the physics at the end. First off, while my physics may be a little rusty, the term "gyroscopic torque" seems like a load of bull to me. Then they talk about gravity inducing a torque, but isn't the only torque on the ball caused by aerodynamic influences and the like? They also mention that the ball wobbles at an "ideal" rate of three wobbles per five spins. But isn't the rate of precession for a small angle of wobble always fixed? And can anyone give a reason why a small wobble would be better (as opposed to no wobble)? And while I'm at it, what causes the ball to dip with its nose always pointing to where it's headed? I might have asked this question a while back, and the answer involved the Magnus effect, but how does this make the dip so perfect? Thanks. 173.179.59.66 (talk) 03:58, 30 May 2010 (UTC)[reply]
First of all, Olympic archers shoot from 70 meters - this guy was throwing from 20 yards - so let's keep that all in perspective for that video (though still impressive). They did confuse the torque a little bit: The ball is a gyroscope, as you probably know, and therefore exerts resistance to anything trying to change its axis of rotation. The force of gravity is trying to do just that, so a "gyroscopic torque" is exerted to preserve the ball's direction (I wouldn't use that term - they were just using it to sound all-sciencey). As for the wind going around the ball, there is a airfoil effect for sure and that probably acts in concert to counter gravity. At the end of the day, the "equations" are best worked out by the feedback in distance and grace that the athlete feels.
I'm not familiar with the Magnus effect until reading the article, after which I remember us playing around with that in grad school when we were discussing table tennis with the Chinese students (and we derived most of it ourselves). So when a football spins on the axis on which it's thrown, it should curve a bit like a sliced golf ball, which is definitely not desirable. My guess is what the previous people told you is that the precession (wobble) is a way to counteract that slice effect. It would make sense to me, sorta, without doing the math. Sports physics is very interesting, but I really hate trajectories. SamuelRiv (talk) 19:13, 30 May 2010 (UTC)[reply]
Sorry, you're of course absolutely correct - gravity is not important in this case. The air flow causes the torque (it blows the nose upward because of the shape of the ball) but the ball stays in the same direction by a gyroscopic effect. The "gyroscopic torque" is about the "odd" axis of the ball going through the fat middle.
The reason, again, this is all necessary is because the ball is an airfoil, so it's generating lift by its upward pitch (the nose is higher than the tail, like a climbing airplane). But the air going by is trying to destabilize it, and since the ball doesn't have any of the fins or wings of an actual airplane, it has to spin to remain stable. Thanks for pointing out the error though - gravity exerts no torque on this system. SamuelRiv (talk) 05:47, 1 June 2010 (UTC)[reply]
One purpose of having attic vents is to vent the smoke out of the attic in case of a house fire -- or else the flammable pyrolysis gases would build up in the attic and form an explosive mixture with the air, which could cause a dangerous smoke explosion or flashover as soon as the firefighters open a door or window in the attic (not to mention that it could choke someone up if not properly vented). 67.170.215.166 (talk) 05:29, 30 May 2010 (UTC)[reply]
Warm, moist air which permeates up from the house in winter can cause condensation within the cold, uninsulated, attic space. This condensation then encourages the growth of fungi and moulds which may be harmful to the wooden structure of the roof. In extreme cases moisture may drip back onto the ceiling and cause watermarks. Ventilating the attic/roof space keeps the space dry. Caesar's Daddy (talk) 07:42, 30 May 2010 (UTC)[reply]
Here in Texas, the heat that builds up in the attic space is enough to dramatically increase your air conditioning costs in the summer even when the attic floor is well insulated. Venting the attic (and even using a fan to get airflow through there) is a huge help. SteveBaker (talk) 15:29, 30 May 2010 (UTC)[reply]
The chief purpose of attic ventilation is to remove moisture that escapes from the interior of the house through poorly-sealed penetrations in the ceiling membrane that can be found in even a well-constructed house. Once it reaches the attic, it will condense on cool surfaces like the roof sheathing. There is no practical reason to keep an unoccupied attic warm in winter - the insulation above the ceiling is supposed to be of sufficient thickness and provided with a vapor barrier. If moisture builds up, it will compromise the insulation's effectiveness, grow mildew and rot the structure. I've never seen any reference to smoke ventilation - the small scale of typical vents would have no practical effect on even a small fire. In warm climates or in summer, roof ventilation will help keep the attic a few degrees cooler, although the effect in most cases is marginal unless you've installed a fan or are using light-colored roofing. Insulation deals with a warm-cold transition better than a cool-hot gradient (it gets heat-saturated), so any cooling of the attic, however slight, will help the air conditioning system.
Even if the attic is occupied, in most cases it is wise to have a ventilated airspace between the insulation and the roof sheathing. Exceptions would be found in a well-installed sprayed insulation installation, or in construction using structural insulated panels, which won't transmit water vapor. Acroterion(talk)15:48, 30 May 2010 (UTC)[reply]
container ship
If the crew of a container super ship spotted a person floating on a raft in the middle of the Pacific would they be obligated to stop and pick the person up? 71.100.8.229 (talk) 05:19, 30 May 2010 (UTC)[reply]
Now what the hell is so offensive about me saying that I would probably stop to help, except in certain cases? I bet it's a lot more that what most of you would have done if you saw someone in a lifeboat! 67.170.215.166 (talk) 05:28, 1 June 2010 (UTC)[reply]
Primer on sailing the high seas. Super container ships, run at speeds of -teens up to approx. 20 knots. While this is not technically fast on land (1 kt is ~1,852 km/h), it causes their braking distance to amount to around a kilometer (give or take) on sea. So in the simplest case it would take them a while to stop/turn/whatever. An immediate stop is not possible.
Such a ship, however, in a situation just like the one described by the OP, is obliged by maritime law to help directly (i. e. by lifebuoy or whatever, time permitting) or indirectly (i. e. by sending out a distress call or informing vessels nearby that a person is in distress) anybody who may be out on sea in distress. Apart from strictly legal requirements, seamen are often plain helpful to each other in what goes just a little bit beyond simple human readiness to help. Father's a sailor, that's how I know. HTH. --Ouro (blah blah) 05:52, 30 May 2010 (UTC)[reply]
Ouro is correct about the distance required to stop or turn a large vessel such as a container ship. To reverse direction and return to a point previously passed, such as when rescuing a man overboard, requires careful maneuvering and navigating. See Man overboard rescue turn. Dolphin(t)11:00, 30 May 2010 (UTC)[reply]
Surely they'd have a lifeboat or some kind of zodiac inflatable that they could use to pick up the survivor without the need to stop the container ship? SteveBaker (talk) 15:26, 30 May 2010 (UTC)[reply]
Imagining the situation you described, I am seeing a lost sailor trying to reach the released lifeboat and the mother ship disappearing behind the horizon ;) I suppose they could release a lifeboat on the spot, but should at least stop and wait for the guy to reach the ship in order for the rescue to be complete, provided the floating person had enough stamina left to reach the vessel in the first place, seeing as they could have been lost at sea for days without proper food... I guess it depends on the exact situation, i. e. if the person is spotted ahead (like, if the vessel had not passed by them yet, and on seagoing ships lookout is usually maintained via radar and binoculars during watch so as to notice everything, because a radar will probably not pick out a person floating in the water), then the ship could react more quickly by stopping and could probably be able to come to a full stop somewhere around where the person is. A person spotted far off would require much more manoeuvering. If you're worried about delaying the ship that's delivering important cargo, do not - afaicr, delayed ship arrivals aren't all that extraordinary, especially on longer routes. --Ouro (blah blah) 15:53, 30 May 2010 (UTC)[reply]
Freefall lifeboat
Usually there aren't traditional lifeboats, or a semi-rigid inflatable in a state of instant readiness. Lifeboats on bulk carriers and tankers, which are prone to sudden, catastrophic failure, and some container ships, are usually freefall-style, and aren't suitable for going out and picking somebody up. Acroterion(talk)15:58, 30 May 2010 (UTC)[reply]
Good photo. However, there are usually others as well, though, which pop out on contact with water and can be recovered, and as such ships usually have at least a small crane or something to hoist things like i. e. crates on board, it is not impossible. I have work and I'm sitting here. --Ouro (blah blah) 16:07, 30 May 2010 (UTC)[reply]
They sit inside all the time, Robin, always ready, because nobody ever knows when they will be needed to take action. --Ouro (blah blah) 11:11, 31 May 2010 (UTC)[reply]
I believe any ship that can't stop quickly enough to deal with a MOB (either someone from their own ship falling over the side, or someone else they just happen to pass close to) is required by international law to carry a powered boat suitable for such rescues. It wouldn't take too long for that smaller boat to catch back up with the larger ship, assuming the larger ship started slowing down straight away. (In fact, WP:WHAAOE: MOB boat - it's very short and doesn't mention legal requirements, though.) --Tango (talk) 16:27, 30 May 2010 (UTC)[reply]
Meditation and sleep
Can you sleep less if you meditate? The guy who told me this, also told me you can levitate through meditation, so I am not quite sure I should believe him on this point. On the other hand, it sounds plausible that you might need less sleep if you have less stress along the day. -Mr.K.(talk)12:47, 30 May 2010 (UTC)[reply]
Regarding levitation, I read that the monks in Tibet and elsewhere sit cross-legged in their cells, and with a lot of practise they can jump into the air while maintaining that posture, leading to stories and photos of levitation. 92.15.12.12 (talk) 13:42, 30 May 2010 (UTC)[reply]
That's a really funny image; somehow I doubt that it would look like levitation, as opposed to a bizarre form of hopping. Anyway, concerning the question, it would make sense, and there are claims by proponents that that happens, but I couldn't spot much in the scientific literature to support it. A more common report is that meditation increases sleep in some people by reducing stress-related insomnia. Looie496 (talk) 14:37, 30 May 2010 (UTC)[reply]
Meditation might temporarily make you less tired even given the lack of sleep, but I wouldn't count on it over longer periods as sleep deprivation sets in. Stress can contribute to either insomnia or hypersomnia. Techniques like yoga and taichi may lower your stress, but again any reduced need for sleep is probably only temporary. ~AH1(TCU)18:11, 30 May 2010 (UTC)[reply]
Ecological implications of eradicating malaria-carrying mosquitoes
What would be the ecological implications of eradicating Anopheles mosquitoes, particularly Anopheles gambiae, which are responsible for transmitting malaria? I don't mean from the huge decrease in human mortality, with the population pressures that would be likely to result, but in terms of the effect on whatever else (apart from malaria itself) which relies on these mosquitoes for its life. DuncanHill (talk) 16:40, 30 May 2010 (UTC)[reply]
Any mosquito (larval stage, specifically) tends to be an important food source for water borne organisms. Indeed, some organisms subsist entirely on mosquito larvae. Then again, the average area in Africa that permits mosquito habitation tends to support more than one species, so the annihilation of one species may not be that big a problem in the long run (and better yet, the malaria bearing mosquitos form only a very small subset of the total set of mosquito species). There's aren't that many scientists studying total (but species specific) erradication. I looked at the most recent good paper on this, but they didn't really mention environmental impact [22]. An earlier paper from another group considered population replacement with a non-malaria-bearing, but otherwise identical species, to avoid the environmental issues [23] (unfortunately, they only got it to work in fruit flies, which as you may be aware, is not exactly a major source of malaria). Someguy1221 (talk) 09:26, 2 June 2010 (UTC)[reply]
Setting up a fishtank
I had many a fishtank when I was a kid and now as an adult, I just bought a 20 gallon for my family to enjoy. As a kid, I completely ignored pH, ammonia/nitrogen and everything else that relates to "water management" and everything always went great -- I did, however, worry about chlorine and made it a rule to use 1-day-old tap water when adding/exchanging. So my question is now that I'm starting again, was it dumb luck that things worked out or is it really not such an issue assuming one has a good filter and does exchange water about once every 2 months (and to give you an idea of the hardiness/sensitivity of the fish that I will include in my tank, it will most likely consist of danios, gouramis and catfish).
And then as a follow up, the fishtank article has a bunch of photos -- about halfway down is one of a sad looking tank while the upper most photo in the article displays a beautifully decorated tank. Would I only be able to get all those plants in there and keep them alive if I take care of the pH, salinity, ammonia, etc. or what? DRosenbach(Talk | Contribs)17:46, 30 May 2010 (UTC)[reply]
You'd need to watch the nitrate and ammonia levels in the tank, as those are the biggest killers of aquarium fish. Cleaning the feces from the tank by vacuuming the substrate regularly should do the trick. ~AH1(TCU)18:02, 30 May 2010 (UTC)[reply]
With the caveat that I know absolutely nothing about tropical fish, my experience in the areas that I do know something about is that most of the advice you read on any given topic is aimed at getting you to spend money on stuff. Looie496 (talk) 23:40, 30 May 2010 (UTC)[reply]
That question is a whole book in itself ..
firstly what sort of filter did you use/are you planning to use
secondly you might be lucky with plants (I wasn't)
thirdly for having a successful planted aquarium the conditions and set up can change considerably compared to conditions for a successful non-planted equation
fourthly - no it doesn't need to be an exercise in water testing and chemistry , (but it can be if you want)
fiftly - one big factor that must be considered is the requirement for CO2 for plant growth - luckily fish breath out CO2 - unluckily strong filtration can de-gas the water of CO2
sixthly - your fish might eat the plants... especially if the plants are soft leaved and the fish are omnivores - one of the more successful experiences I had was with carnivorous and heavy eating catfish and soft leaved plants - the fish made the fertiliser, and the plants grew in it...
seventhly - some plants are easy, others are hard to grow - just like fish.
I'd like to recommend a book - in fact most I've seen contain about the same info - in general the tricky bit is growing both fish and plants in the same aquarium.94.72.235.30 (talk) 23:42, 30 May 2010 (UTC)[reply]
I used to run 2 tanks and am now running one - a Rio 300 (about 3x larger than yours). When we initially set up our first tank (about the size you're talking about) I knew nothing about the chemistry of tanks and my initial fish (mostly guppies) pretty much all died fairly quickly. I then learnt about the chemistry, and it became clear that the probably died of ammonia poisoning. The best way to avoid this is to start with few fish and add them slowly, so the bacteria in the tank can grow to accommodate the larger ammonia load. You need 2 types of bacteria - ones that convert the ammonia to nitrite, and others that convert nitrite to nitrate. You don't need to add them - they grow of their own accord. I would recommend testing for ammonia in a new tank if you do nothing else. If it gets too high, change some of the water. You can use tap water but you must use a additive to remove the chlorine. You should also count on making regular water changes in order to keep the nitrates down - I change about 4 to 5 gallons of water each week and would recommend you do the same. --Phil Holmes (talk) 11:31, 31 May 2010 (UTC)[reply]
Controlled burns on oil and hurricanes
Hi. Let's say that a medium-sized hurricane was threatening the Gulf Coast, and was heading directly for the Deepwater Horizon oil spill. If controlled burns were set over a large portion of the oil, what if any effect would that have on the hurricane? Would the extra heat fuel the hurricane, or would it cause the storm to expand and unravel, or expand to have a dangerous storm surge, or disrupt its eyewall, or cause it to change direction, or would the surge of the storm cause the oil to pool underneath the eye, or would it cause upwelling that cooled the oil, or would it create more shear and tornadoes, or would the storm plow the fires into the coast? Thanks. ~AH1(TCU)18:00, 30 May 2010 (UTC)[reply]
There is no way to really predict what would happen. Weather is chaotic by nature, so the hurricane would react differently for different sizes, shapes, orientations, temperatures, durations and positions of fires. We know large fires can create storms; there was a large vortex—called a tornado by some—caused by an oil tank fire in California in 1926 that killed two people after traveling almost a mile away from the fire. Pyrocumulus are a well-documented phenomenon whereby clouds and even thunderstorms can be created by large fires. However, I feel it would be impossible to predict the effects, and they would probably not be good. Hurricanes are basically a giant heat engine; adding more heat just isn't a good idea. Not to mention that, with the amount of rain and waves generated by the average hurricane, it seems likely that the fire would just go out.-RunningOnBrains(talk)20:22, 30 May 2010 (UTC)[reply]
On top of which modelling the burning oil is hellish tricky. Rough waves mean the oil forms a moussy emulsion with sea water: when we tried (twenty years ago) replicating the mousse to try to burn it we found the characteristics were incredibly sensitive to how well mixed the emulsion was, as well as the exact crude characteristics including how long it had been on the surface losing volatiles. We even looked at floating wicks in it etc but it is not going to be burning well in a storm, not so much because of the rain but from the breaking waves. The only good news is that oil is basically biodegradable; in a decade all traces will have gone eaten by bugs and the sensitive nature sites will be mainly back and happy. Of course some Corals and some oil companies might not survive the "obvious" solution of time. --BozMotalk21:14, 30 May 2010 (UTC)[reply]
Hurricanes are FAR bigger than that (than tornadoes or pyrocumulus). The heat from fire would have no measurable affect at all. The change in the water/air interface might have an affect, but I don't think it'll be big. The energy released in a hurricane is on the scale of hundreds of nuclear bombs. Ariel. (talk) 21:44, 30 May 2010 (UTC)[reply]
Would the huge fire generating a pyrocumulus storm be likely to cause rotation and gradually become a tropical depression (and then tropical storm, followed by hurricane)? Falconusptc23:41, 30 May 2010 (UTC)[reply]
Unlikely. Ariel is correct in that it would be very unlikely to have any effect at all; pyrocumulus storms are on the order of a few kilometers. Hurricane formation depends more on large-scale features than storm-scale features. I was just playing devil's advocate in saying that if you managed to make a fire big enough to affect a hurricane, it might only serve to strengthen the storm. Careful using that "nuclear bomb" analogy though...nuclear bombs are near-instantaneous events, while hurricanes can last weeks.-RunningOnBrains(talk)00:59, 31 May 2010 (UTC)[reply]
new LED lightbulbs
I've heard that a new generation of LED light bulbs are coming out soon. Will they come on quickly (the main problem with compact flourescent bulbs is the time it takes them to get bright.) Bubba73(You talkin' to me?), 21:07, 30 May 2010 (UTC)[reply]
It depends what you mean by 'new generation of LED light bulbs'. LED are continually improving, and light bulbs for existing fixtures already exist. In other words, there are what could be called new generations of LED light bulbs probably every year. One of the biggests problems is probably cost particularly for bright lights. There should be some decent replacements for 60W incandescent lightbulbs coming out at the end of this year or early next year (some decent ones may already exist), these were demonstrated at the recent Light Fair in the US. [24][25] Expect them still to cost quite a bit though. Sorry misread the question, see the next answer. Nil Einne (talk) 21:33, 30 May 2010 (UTC)[reply]
LED lightbulbs are already here - I have three of them in my home and I'm typing by the light from one of them right now! They don't need any time to 'warm up' like CFL's do. They use less electricity than any other type of light - are longer-lived than any other kind - and they are actually made of clusters of LED's so when they do fail, they tend to do so one LED at a time - so they rarely just go black like a failed incandescent or CFL. However, they are still hideously expensive - and unless you want one as a gimmick or you are a fanatical tree-hugger, you should probably wait for the prices to drop. They aren't close to being cost-effective yet. Mine are cool because you can adjust the color to any RGB value, remotely from your PC...I like a slightly yellowish light - but...hold on...there...now the light is blue-ish...and now pink! LED Xmas tree lights were in most stores last Christmas - and specialized lighting for swimming pools and hot-tubs have been using LED's for at least 10 years (my 10 year old hot-tub has LED lighting). SteveBaker (talk) 02:09, 31 May 2010 (UTC)[reply]
Like CFls, LEDs can come in a variety of colour warmths - like CFLs the common type seems to be warm white ie 3500K rather than daylight 6500K+ , but you can get daylight type too.94.72.235.30 (talk) 14:01, 31 May 2010 (UTC)[reply]
(EC with both above) I originally thought you asked 'are the next gen LEDs coming out soon' but then realised I was mistaken. Glad that it was still of interest. I've been following this area recently, more from a torch/flashlight angle but I've of course read or thought of things related to LEDs that may be of interest even from a lightbulb perspective.
Another interesting this is that Cree (who were mentioned in some of the above links in other areas) are also going to release the XM-L LED in (Northern hemisphere) Autumn of this year [26][27]. This is supposed to be rated to output 750 lumens from a single die emitter (in other words a single continuous LED) which they say is equivalent to a 60W incandescent (although based on our Incandescent light bulb, they probably mean a 60W 220V bulb rather then a 110V one). I suspect the 750 lumens is the maximum of the LED bin at the time of their release, in other words the LED they release might only be rated for something like 675-750 lumens (there is always variance, LEDs are sold as bins and guaranteed to output something in that range at whatever the maximum rated current for the LED) however I still find it an interesting development.
I don't however know whether it will actually be used much in replacement bulbs for incandescent lightbulb types (like the E27), there are already multi-die LEDs (basically they stick 4 or more LEDs on a package and connect them, somewhat similar to some earlier dual core and quad core CPUs) like the Cree MC-E & SSC P7 which are rated for slightly higher output [28] and have been available since early 2008 but don't seem to be used much for this purpose that I could find (of course most manufacturers don't say what LEDs they're using).
It may be because they tend to have poor Colour Rendering Index compared to what people are releasing for other LED light replacements. (Also the maximum output is usually those with the colour temperature of the cool white/bright daylight variety which don't tend to be so popular in the West.) Also these LEDs aren't necessarily the most cost effective from a $/lumens area. Or other factors, I don't really know much about (as said, I don't really know that much about light bulb replacement designs).
BTW, there's also the Luminus SST-50 and SST-90 which are also already available but again don't seem to be used light bulb replacement that I've seen. These use what's called a photonic lattice so can also be called a single die but are somewhat different from more traditional emitters. If you looked at the earlier DealExtreme link you may notice the currently available best bin of the SST-90 outputs when driven with (the maximum rate) 9 A, 2350-2820 lumens! According to our incandescent light bulb article, the minimum is equivalent to a 135W 110V bulb.
But even so, don't expect those sort of outputs to be done in a typical light bulb replacement anytime soon (meaning perhaps within the next year or so). One of the things I didn't mention above is for such high outputs, temperature really starts to become a problem which will not only kill the LED if it gets too hot but reduces effiency too (i.e. light output). (In addition to the heat output from the LED, the driver/regulator of the LED also can output a fair amount of heat since it's unlikely to be close to 100% efficient.) Incandescents and even CFLs can get quite hot, but they can survive such temperatures, LEDs can't. You need good heatsinking and I don't think from what I've read you're likely to be able to provide sufficient heatsinking for something like a E27 to do that (perhaps particularly given the variety of fixtures, including some enclosed, that may be used). Well unless you have some active cooling which is obviously unlikely to be considered suitable for household usage. Of course the fact the heat is a problem means effiency (lumens/watt) is important. See also some discussion [29].
Of course all these are obviously used for general/fixed lighting purposes, flashlights are clearly only a tiny proportion of what they're used for, this mentions a few. Other custom light fixtures (perhaps also fluorescent tube replacements) can obviously better accomodate the heatsinking/cooling requirements then having to design for existing bulb types. [30]
P.S. To avoid confusion, the current draws are at the forward voltage of the LED which is likely to be something in the 3-4 V range.
P.P.S. As a brief mention of cost. For the P7, you can get an LED with some sort of driver suitable for a torch for about US$15 with shipping from China/HK (i.e. this is a retal price). However the optics, heatsinking, driver suitable for main voltage are obviously going to add a fair bit. A cheap P7 based torch which uses rechargable lithium ion batteries is about $30 from China/HK (again with shipping). However these often don't draw and therefore use the maximum rated 2.8A for the P7. I would guess $40+ is likely for a light bulb replacement.
I don't understand your use of "bin." Is it a technical term, or do you just mean "a bin of light bulbs?" Thanks. Edison (talk) 15:11, 31 May 2010 (UTC)[reply]
If you look at [[31]] it looks like LED's are currently about as efficient as CFLs. There is still a lot of room for improvement in terms of luminous efficiency though.94.72.235.30 (talk) 13:45, 31 May 2010 (UTC)[reply]
Lawn Mowers
This is not a medical question, more just looking for confirmation of what seems common sense to me. The other day, my friend informed me that I should stop using my gas powered lawn mower and buy an electric one; he told me that I could get carbon monoxide poisining from using it to cut the grass. Being that I would be using it outside, this sounds rather unlikely to me. So, in short, is there any possible validity to what he is saying? 67.163.183.146 (talk) 21:58, 30 May 2010 (UTC)[reply]
If you cut the grass with a gasoline-powered mower in a small enclosed room with no ventilation, carbon monoxide poisoning is a real hazard. Edison (talk) 22:07, 30 May 2010 (UTC)[reply]
I don't know exactly, but of all of the people that use gasoline lawnmowers responsibly (i.e. not in the living room of their house), I haven't heard of any cases of CO poisoning. Millions of people presumably use them, so if it was a serious risk, I suspect that it would be a very well-known thing. Falconusptc23:43, 30 May 2010 (UTC)[reply]
I have a hard time imagining getting much exposure to CO outdoors, even with a typically fume spitting lawnmower engine; people just don't spend that much time mowing lawns, and outdoors, the risk is greatly diminished. Most of the Google hits relate to not running the mower in a shed or garage, for example. All that being said, lawnmowers (and other gasoline powered yard tools) are notorious for not having very clean or well filtered engines. See, for example, [32], as well as a source from the epa: [33]. So even if it's not a health risk, your mower may be hurting the environment. Buddy431 (talk) 00:43, 31 May 2010 (UTC)[reply]
(edit conflict) Carbon monoxide poisoning is only a hazard in encloses spaces, or in some extreme circumstance that I can't think of right now. It is metabolized quickly, and exposure to oxygen is the antidote, so it has no cumulative effect such as those seen with methyl mercury and other environmental contaminants of concern. Thus there really is no reason I could think of that gas mowers would be dangerous.-RunningOnBrains(talk)00:51, 31 May 2010 (UTC)[reply]
There are lots of reasons to consider getting an electric lawnmower (gas mowers are horribly polluting, noisy, heavy and a pain in the neck to maintain as they get older) - but I agree that if used in a reasonable way, carbon monoxide poisoning isn't one of them. SteveBaker (talk) 02:00, 31 May 2010 (UTC)[reply]
The hows are explained at Time reversibility - for gravity (ie 'newtonian' gravity) the following section applies: "If a deterministic process is time reversible, then the time-reversed process satisfies the same dynamical equations as the original process, AKA reversible dynamics; the equations are invariant or symmetric under a change in the sign of time"
The last sentence above gives the simple way to tell. eg consider motion under gravity as a function of time.
OP here: I would think this means that any time derivative changes sign, and hence a second time derivative preserves sign. So for something like gravity, where d2r/dt2 = (GM/r3)r, nothing changes when time changes sign, so the motion is identical, except the velocity changes sign so the particle will travel in the opposite direction. Is this right? 173.179.59.66 (talk) 02:56, 31 May 2010 (UTC)[reply]
I learned in dental school that nothing reduces the internal production of cholesterol -- 1 mg of the 1.7-1.8mg daily cholesterol necessary for an adult human male is produced by the body as a given. DRosenbach(Talk | Contribs)01:51, 31 May 2010 (UTC)[reply]
Exogenous substances can certainly reduce the internal production of cholesterol. See statin. However, the body will compensate for the decreased cholesterol production and shunt the available cholesterol to the most important functions. According to our bile acid article, "the body produces about 800 mg of cholesterol per day and about half of that is used for bile acid synthesis" so you can bet that bile acid production will still get a significant proportion of the available cholesterol. In addition, about 90% of bile acids are recycled. This is the mechanism of the cholesterol-lowering effect of bile sequestrant drugs. According to bile acid, "since bile acids are made from endogenous cholesterol, the enterohepatic circulation of bile acids may be disrupted to lower cholesterol. Bile acid sequestrants bind bile acids in the gut, preventing reabsorption. In so doing, more endogenous cholesterol is shunted into the production of bile acids, thereby lowering cholesterol levels. The sequestered bile acids are then excreted in the feces." This indicates that bile acid production is pretty important and will likely be maintained in the face of reduced cholesterol synthesis. That being said, it would probably be possible in extreme cases to get such dramatic reduction of cholesterol that bile acid production might eventually be impaired. --- Medical geneticist (talk) 03:05, 31 May 2010 (UTC)[reply]
Deepwater Horizon oil slick - why not burn it off?
Is there any particular reason that bombarding the slick with napalm, or white phosphorus bombs near the point of orign, in order to burn the oil off before it reaches the coast hasn't been considered? Would this actually work? Or would it make an even bigger mess in the long term? --95.148.107.248 (talk) 01:18, 31 May 2010 (UTC)[reply]
They have been burning surface oil almost since day one [34] but the oil is only concentrated enough to burn in certain places...I believe the reason is that it's being released so far below the ocean surface that it diffuses too much to be effectively burned by the time it reaches the surface. Don't take my word for it though, just speculation. -RunningOnBrains(talk)01:27, 31 May 2010 (UTC)[reply]
Why not just stick something like an industrial-strength version of an umbrella or deflated balloon down the pipe to block it, is what I wonder. 92.28.254.179 (talk) 10:33, 31 May 2010 (UTC)[reply]
That won't work because the pressure in the pipe is so spectacularly high. The amount of friction it would require between your gadget and the walls of that smooth pipe would be spectacular (and oil is a pretty good lubricant!). Remember that the oil reserve is under 18,000 feet of solid rock - all of that rock is pressing down on the oil - so it squirts out with an amazing amount of force. Anything you put down that pipe just gets blown back out again. This is also not a small pipe - it is 21" in diameter. The recent (failed) "Top Kill" method was to pump heavier-than-oil drilling "mud" down the pipe to push down on the oil and reduce the pressure - but even that didn't work. SteveBaker (talk) 15:04, 31 May 2010 (UTC)[reply]
I'd love, actually, to hear from you, Steve, if you'd have any idea what might work. Outlandish as this idea might be. --Ouro (blah blah) 16:03, 31 May 2010 (UTC)[reply]
The only novel thing I've been able to come up with (which is probably completely impractical) would be to take four ships - each with a roll of some kind of fabric thats (let's say) 100' wide by at least 5,000' long and weighted at one end. The four ships would take position in a square formation above the outflow and slowly lower the weighted ends of the fabric into the sea. A heat-sealing device would seal the edges of the fabric together to make a tube some 400' in circumpherence that would then be lowered towards the sea-floor. This would contain the oil within a manageable space that could be pumped out continually until the relief wells finally relieve the pressure in three or four months time. The problem with this idea is that the ocean currents would push very strongly on the tube - so it probably wouldn't work for that reason.
Other oil wells have suffered similar fates in the past - it's instructive to read about the Ixtoc I oil spill - which was in much shallower water - and still took 9 months to finally cap. Due to shallower water and much less oil pressure, that should have been a much simpler task than the Deepwater Horizon spill. I'm not optimistic about the present situation!
The real problem here is that we should never have let such a well be drilled in the first place without adequate means to shut it off and multiple backups for that mechanism. Some problems can't be solved...this may turn out to be one of them. SteveBaker (talk) 13:10, 1 June 2010 (UTC)[reply]
Because the pipe (the riser) is incapable of holding the pressure if the gas were to stop flowing. What can hold that pressure is the BOP, and if I understand correctly what they're trying to do now is lower a second BOP on top of the first (broken one) and close that. TastyCakes (talk) 16:54, 31 May 2010 (UTC)[reply]
That's right, our folks are doing just that, but we're also drilling that relief well in case this doesn't work. (Had to give up the second relief well, something went wrong, I'm not quite sure what.) 67.170.215.166 (talk) 05:36, 1 June 2010 (UTC)[reply]
Probably because the pressure is too high. Consider that it is easy to attach a valve to a fire hydrant with no water in it, and then turn on the water; it would be a lot harder to attach it to the end when it was already gushing out, and this is considerably more difficult than a fire hydrant (both in terms of amount and nature of material going through, and because the thing is on the bottom of the ocean). Anyway, if there was an "easy" answer, don't you think BP would have done it by now? They don't exactly stand to benefit from dragging this out. --Mr.98 (talk) 16:54, 31 May 2010 (UTC)[reply]
Because the pipe would burst. Unless by "pipe" you mean blowout preventer, in which case that is essentially what they're trying to do now. But it's not that simple because huge amounts of fluid are coming out of it at the same time and they don't really know what's wrong with the existing BOP. TastyCakes (talk) 18:07, 31 May 2010 (UTC)[reply]
How much oil is actually down there on the other end of the pipe anyway? If they don't manage to successfully cap the leak, how long would it take before the pressures equalized and the stuff stopped spurting (or all the oil came out and ended up in the sea)? --Kurt Shaped Box (talk) 18:43, 31 May 2010 (UTC)[reply]
BP estimated there were 50 million barrels in the field (it's unclear if they meant recoverable or in place, which would change the number by a factor of about 2), but presumably primary recovery will be only a few percent of that (primary recovery is how long the well produces on its own pressure - when the pressure in the reservoir drops to water pressure at that depth, the well will stop flowing). Hopefully the relief well(s) will fix this before that (very high) limit is approached... As for how long it'll take for the pressure to equalize, its impossible to say because the actual size isn't really known and the rate of the spill isn't really known (somewhere between 10,000 and 100,000 bbl/day from what I've read). But if you could figure that out, you could ball park it by calculating say 4% of the reservoir and then dividing that by the rate per day. Which puts it at between 20 and 200 days by this very rough measure. TastyCakes (talk) 19:12, 31 May 2010 (UTC)[reply]
What about a T shaped pipe - attach one side of the T to the pipe with a valve on the other side fully open. Thus there is no pressure on the pipe. Once the pipe has been attached (jubilee clip ?!) the valve on the side can be closed and the flow diverted through the third pipe forming the T ... 87.102.77.88 (talk) 18:51, 31 May 2010 (UTC)[reply]
Incidentally I came across this yesterday on Nature, "Recently, an explosion on an offshore oil platform in the Gulf of Mexico caused both loss of life and a sizable and ongoing oil spill. We are asking Solvers worldwide to respond quickly with ideas and approaches to react to this very serious environmental threat." [35] As with others, I'm somewhat doubtful that there's anything you can propose that hasn't already been tried and I think the request is more for ways to reduce the negative effects rather then stop the spill but hey if you're sure you have an idea that no one else has thought of no reason you can't submit it Nil Einne (talk) 23:41, 31 May 2010 (UTC)[reply]
Living in an Attic
I live in an attic with dormers and it gets REAAAAAAAALLLY hot in the summer months -- so hot that the largest AC that fits in my living room window is a 12000BTU and it doesn't do nearly a good job of lowering the temp. I think it's because the dormers are the inside surface of the actual roof and the sun bakes my apartment. What can I do to achieve normal room temp in this case? DRosenbach(Talk | Contribs)01:54, 31 May 2010 (UTC)[reply]
Can you replace the blinds on your dormer windows with blackout ones? If you keep them closed during the day you will achieve a reduction in the temperature you achieve, compared to not using them. I confirmed this for myself during the UK hot summer a few years ago, when our south-facing living room became uninhabitable until I discovered this trick. --TammyMoet (talk) 13:21, 31 May 2010 (UTC) You might also like to see if you can get some of these: http://www.reflectiveblinds.com.au/faq.html --TammyMoet (talk) 13:26, 31 May 2010 (UTC)[reply]
I guess it depends on how drastic you want to get. Better insulation would be a good start - but getting it into the right places is tough. Shutting out light from windows might help some - but I'm thinking that the absorption of heat through the roofing material is the big problem. A lighter colored roof tile would help - but again, it's a pretty drastic solution. You could also cut incidental heat gain by looking for a more efficient refrigerator/freezer and making sure that your hot water tank is well insulated. If the temperature inside the attic is higher than outdoors - even for just a part of the day - then simply opening windows and using a decent fan to recirculate air would help - an experiment with a couple of thermometers over a 24 hour period would be pretty revealing. Make sure the filters on your air conditioner are clean - be sure to change/clean them regularly. 14:31, 31 May 2010 (UTC)
If there is space in the attic between your ceiling and the exterior roof, it can get quite hot under full sun.On a sunny 100 F/38C day, a sealed attic space might reach 130F/54C, causing the top floor living space to keep getting hotter all night even as the exterior temperature drops, as heat conducts through the ceiling, which might be of negligible R value unless insulated. If you are just a temporary renter, there is not much you can do. If your family owns the place, then some improvement is possible. If ventilators are placed in the eaves (screened and louvered metal) then cooler outside air can get into the attic. If exhaust vents are placed in the roof or eaves, then the air can get out. Bats of insulation can be placed between the ceiling joists, taking care not to block the ventilation path. A vapor barrier is suggested between the living space and the insulation, to prevent condensation. A power vent fan can be installed in the roof, which comes on when the attic temperature reaches some hot setpoint. Such a fan may have a high temperature shutoff to avoid providing forced draft if a fire occurs. Note that none of this ventilation refers to exhausting air from the living space. Edison (talk) 14:56, 31 May 2010 (UTC)[reply]
Sounds like good suggestions, though with 38 degree C day unvented ceiling would be 70 degrees C. Also, shading the roof with cheap cotton sheets or junk will work well, though messy. Also, put insulation on the inside and cover with cloth. (Polyester insulation is fine to live with if there are no flames). Also good because you can take it with you when you move. Putting a whirlybird vent on top of the roof to increase the ceiling ventilation wont make much difference inside the house, the ceiling temperature will go down maybe from 70 to 55, the room will still be very hot. Feel the ceiling and walls to see where the hottest parts are and then you will know where to concentrate on. Polypipe Wrangler (talk) 13:23, 2 June 2010 (UTC)[reply]
No, not right. It is possible to define comoving coordinates within special relativity. There is nothing fency about a comoving set of coordinates. it is simply a set of coordinates chosen in such a way that it moves along with the general flow of the matter of the universe called Hubble flow (universal expansion). As I said above, any given galaxy is likely to have some random movement (called peculiar velocity) added to the smooth movement given by the Hubble flow. Dauto (talk) 03:04, 2 June 2010 (UTC)[reply]
I know that the formula for gravitational acceleration is . Is this valid to all distances, or is there somehow a distance at which it's rendered invalid? In other words, do 433 Eros and Rigel have any absurdly-tiny effects on me? I've read Newton's law of universal gravitation, but I can't find anything to answer my question. Nyttend (talk) 02:54, 31 May 2010 (UTC)[reply]
I'm well aware, by the way, that we can't measure the effects of Eros' and Rigel's gravities if they do exist as far away as Earth. Nyttend (talk) 02:55, 31 May 2010 (UTC)[reply]
The answer depends somewhat on whom you are asking :) . Professor Mordehai Milgrom of Weizmann Institute has a theory that says it is not valid at all distances, but the "majority opinion" (if there is such a thing in physics) is that it is valid at all distances. --Dr Dima (talk) 03:06, 31 May 2010 (UTC)[reply]
Yes, as far as we can tell the gravity formula is valid for all distance and indeed rigel has a effect on you. But, as you pointed out, those distant forces are too small to be measured directly and we cannot be sure if the inverse square formula is really valid for all distances. Nevertheless we know that an effect exists (even if the formula chages at some distance) because we know that the sun (and other stars) orbit the center of the milkyway under its gravitational atraction. We also know that gravity acts at distances as far as galaxy superclusters or more, otherwise theose superclusters would not exist. Dauto (talk) 03:33, 31 May 2010 (UTC)[reply]
Hmm, interesting; I had no clue about that. Eros shouldn't take that long; it's going to be less than 0.2 astronomical units away in a couple of years. Nyttend (talk) 13:07, 31 May 2010 (UTC)[reply]
There is a quote that goes something like: "If you had an error in measurement of one atom radius in the position of an object many light years distant, it would make it impossible for you to correctly calculate the position of an atom of gas after some number of collisions." (I tried but I just can't find the original quote.) So yes, gravity from distant objects influences events on earth. (The person who said it actually calculated the various numbers, and I really wish I could find the quote again.) 11:22, 31 May 2010 (UTC)
There is no 'classical' cutoff - but it might be that there is some kind of quantum limit. However, because the force drops off as the square of the distance, the gravitational effects of almost everything out there is less than the gravitational field of (say) your pet cat when it's three feet away. At that point, the influences of all of these small (but nearby) things creates a shifting, totally chaotic mess that completely drowns out the influence of distant planets and stars. SteveBaker (talk) 14:20, 31 May 2010 (UTC)[reply]
According to General Relativity, the formula is never more than an approximation in any case -- GR replaces it with a formula that gives the curvature of space-time as a function of mass. Also, as another editor has pointed out, GR predicts that gravitational effects propagate at the speed of light. This implies that beyond a certain distance, the source of gravitational force will have moved to a different location by the time its effects arrive, so the formula will give the wrong result. Looie496 (talk) 15:42, 31 May 2010 (UTC)[reply]
But, since you're generally observing the source through another mechanism that propagates at the speed of light (i.e. light, or at least electromagnetic radiation), you can take that into account fairly easily. Confusing Manifestation(Say hi!) 23:54, 31 May 2010 (UTC)[reply]
Gravitational waves travel at the speed of light in GR, but there's no such lag in gravitational forces. Usually an object's gravitational field moves along with the object as though it was rigidly attached to it, and the gravitational force points toward the object's current location (with respect to any inertial frame, in the weak-field approximation). The gravitational attraction of the Sun doesn't point in the same direction as the Sun appears in the sky, because the latter is subject to aberration (which you can think of as a time-lag effect) while the former isn't. The difference is between waves and forces, not between electromagnetism and gravitation. If the Sun had a net electric charge then its electric field would point in the same/opposite direction as the gravitational field. -- BenRG (talk) 03:33, 1 June 2010 (UTC)[reply]
That's not correct BenRG, the force also travels at the speed of light. If it didn't you could rapidly move an object and measure the force to transmit information (not to mention energy) faster than light. Note that if the object is moving at a constant velocity, the force does too, such that when the force reaches the second body it is pointing at the current location of the object, and is not delayed. But if you suddenly move the object, the change propagates at the speed of light. Ariel. (talk) 10:38, 1 June 2010 (UTC)[reply]
May be I can help clarify what BenRG is saying. He is talking about a situation in which the source of the gravity field, say the sun, is moving at constant speed. In that situation, if ou look at the source you don't see it where it is now because there is, as you said, a delay caused by the finite speed of light (and gravity waves). But if you measure the gravity force (or the electromagnetic force) you will find out that the force points to where it is now. Now, as you said, information cannot travel faster than the speed of light so if the gravity source were to accelerate and change its path, there would be no way you could tell that had happened (assuming there hasn't been enough time for the information to reach you). In that case instead of the force pointing to where the object actually is, the force actualy points to where the object would have been had it not accelerated. It still doesn't point to where you see it. The article Liénard–Wiechert potential ought to have some information about that phenomenom. Dauto (talk) 03:56, 2 June 2010 (UTC)[reply]
Chemical reaction within a thin film of a chemical solution
Hey guys,
My lab project involves research on the next generation of clean energy. I need to deposit a special organic film on a surface and the reaction should happen in a thin chemical solution.
I noticed that with the same chemical concentration, the reaction rate of a thin solution (like 5mm thick) is much slower, ~25%, than that of the bulk reaction. What may be the reason? How can I increase the reaction rate of a thin solution?
Hi, so you've got a reactive film applied to a surface and immerse the surface and film to a depth of 5mm in your solution? And that when you cover it much deeper in solution, it goes a bit faster? I can't think of any obvious causes for that, but some of the other users of the reference desks have much more chemistry-fu than I have. All I can suggest is that you help the products (assuming they're still in solution) move away from the film surface by circulating the solution with a pump or a stirrer. This should reduce the dependence of the reaction upon diffusion rate. Brammers (talk/c) 11:46, 31 May 2010 (UTC)[reply]
Surfaces of liquids (well water anyway) have more structure than the bulk, and a lower diffusion rate - if your liquid was 1mm thick and aqueous this might explain it.
What do you mean by reaction rate: the overall rate or the instantaneous rate? Did the solution contain an excess of reagent? if not the reduced concentration in the liquid might explain a reduced overall rate.94.72.235.30 (talk) 13:28, 31 May 2010 (UTC)[reply]
Simple possibility - if the reaction is exothermic, the surrounding solution may get heated fast enough to slow things down (order of 1000J must be released for this to occur). But this can honestly happen for a number of different reactions. For example, if large bubbles of gas are being released, maybe you're submerging it in too shallow a bath such that the bubbles are taking up too much space for the reagents to mix. In general, try changing depth and surface area but not volume. SamuelRiv (talk) 06:03, 1 June 2010 (UTC)[reply]
It is not entirely clear what you mean by that. A standing electromagnetic wave (say, in a cavity of a resonator) is trapped in space, but "propagates through time" as you put it. A traveling electromagnetic wave in vacuum, on the other hand, will always travel no matter what frame of reference you are in. In other words, if you try to chase a photon in vacuum, you will never succeed. --Dr Dima (talk) 06:30, 31 May 2010 (UTC)[reply]
I mean to be trapped in its point (say on a surface), not occupying any space as in the cavity where I believe it is still propagating but reflecting back and forth. The reason I ask this is to understand how energy is conserved as its power is varying with time and there are times electric and magnetic fields both tend to zero.--Email4mobile (talk) 07:01, 31 May 2010 (UTC)[reply]
I'm generally thinking about energy regardless if it were in a particle or wave form. I formulated a similar question several months ago (see here) and understood that energy is almost quantized in such case provided that transformation period is above Plank time. Here we are studying a wave and I don't know if energy has to be conserved within space-time or can also be conserved at a particular time (i.e.:Is power conservative?). These are some of the problems I still can't imagine beside relativity (I'll post some question about it later). Grateful for your assistance.--Email4mobile (talk) 08:09, 31 May 2010 (UTC)[reply]
I've often tried to think of a particle as a wave which has somehow lost its ability to propagate but then there are all theses silly subatomic particles that get in the way. 71.100.8.229 (talk) 08:55, 1 June 2010 (UTC)[reply]
There are no times that the E and B fields go to zero. An electromagnetic plane wave in vacuum just moves in some direction at the speed c; it doesn't grow or shrink or otherwise change as it propagates. You will detect changes in the E and B fields as the wave passes you, but that's because you're measuring different parts of it at different times. -- BenRG (talk) 09:50, 31 May 2010 (UTC)[reply]
Not sure if this answers your question, but a photon can not exist if it doesn't move. But, you can store the energy and properties of the photon (in an atom), and while stored it doesn't move. (And photons always travel at exactly the speed of light, in matter the photon is constantly being absorbed and re-emitted, this causes it to appear to slow down.) Ariel. (talk) 10:59, 31 May 2010 (UTC)[reply]
Ariel, in matter a photon does indeed travel slower than the speed of light because of the interactions of the electromagnetic field with the matter. The constantly absorbed and re-emitted picture doesn't really happen. Dauto (talk) 13:12, 31 May 2010 (UTC)[reply]
Email4Mobile, we have indeed means of "trapping" light using Negative index metamaterials, which are like if you took a prism (those triangles that you look through and everything gets rainbow-like) and pretty much turned the rainbows inside-out. This kind of technique is useful for simulating black holes and for computer information stuff (internet, your processor, etc). As I've heard it described, the method is to get your light beam into these "prisms" and then run it around in a circle enough times until it eventually slows down to a very manageable crawl. The photons themselves all move at the speed of light, but they are veering every whichway by the material, so they go in a very twisty path.
Incidentally, you may also be interested - one other thing metamaterials are nice for, aside from trapping light, is manipulating sound in such a way that we can create an actual sound-based black hole, or dumb hole. The article needs some work, but Cosmic Variance has a great summary. SamuelRiv (talk) 06:23, 1 June 2010 (UTC)[reply]
computer and manual hospital procedures
MedScape only checks for drug interactions and not for effect interactions. For instance mydriatic medications do not interact with Simvastatin purse but the effects of Phenylephrine, which dilates pupils, and the effects of Simvastatin which reduces Cholesterol are counter-indicated since Simvastatin indicates high cholesterol and restricted blood vessels and Phenylephrine which will dilate pupils and further restrict blood vessels should not be given for this consequential or secondary interaction. My question is do American and British hospital procedures require computer or manual checking for such drug effect secondary interactions I will call implication conflicts here? 71.100.8.229 (talk) 07:07, 31 May 2010 (UTC)[reply]
It was bedtime when I asked the question. I've corrected it to clarify I am speaking of dilating pupils using medication which has the side effect of restricting blood vessels. 71.100.8.229 (talk) 08:44, 1 June 2010 (UTC)[reply]
Things to eat in a prehistoric environment.
Let's say you're zapped millions of years back into the past to a time when the biosphere was much different from the way it is today. The biggest obstacle to survival (right after avoiding being eaten) would be to get something to eat. Obviously, meat would be a safe bet, since you can't really go too wrong with it (except in the rare cases where it's poisonous), but not only is meat difficult to acquire, it's also not something that you could easily live entirely off of.
So what kinds of plants would you be able to eat in prehistoric times? What do we know about the edibility of various extinct plant taxa? Is there a way you can test a plant for edibility?
Obviously, the answer would be different depending on what era of history you were dropped into. So I'll give five options here:
The essential thing the that link forgets is a saucepan (with lid for a smokey fire) so that you can cook vegetables and so on. A spoon would be useful too. 92.15.1.82 (talk) 16:53, 31 May 2010 (UTC)[reply]
Yeah, it's far from certain that you could find anything to eat in those times. Our biology has evolved for the kinds of plants and animals that are around today. We have no clue what missing trace elements there might be - or what poisons might exist in both plants and animals of that time. It's not certain that there would be nothing we could eat - but it's also not certain that there would be anything at all. As I pointed out in that previous discussion (thanks to Nil Einne for digging it out!) you don't have to look far back into the era of the dinosaurs to find that the dominant plant life was ferns. We don't (can't?) eat ferns. There were no grasses - hence no grains - and no flowering plants - hence no fruit. There might have been root plants that we could eat - but it's not like you're going to find recognisable stuff like carrots and potatoes - there would be roots...you'd have to experiment to find which ones were both edible and nutritious - and that's a dangerous thing when anything is potentially poisonous. But this is pure speculation - it's possible that there were things that we could eat and thrive on. But realise that our understanding of the biology of these ancient times derives primarily from fossils. You can't measure the chemical composition of a plant from a rough impression of it in a lump of rock!
Bottom line is: We don't know - but we certainly can't assume that "Obviously, meat would be a safe bet" - who knows what toxins were in their flesh or what crucial trace elements were missing? SteveBaker (talk) 12:46, 31 May 2010 (UTC)[reply]
"...to animals such as mice, rats, horses and cattle when ingested". In humans, the jury is still very much out. The article also says it can cause beriberi if eaten to excess, raw. 86.164.69.239 (talk) 21:29, 31 May 2010 (UTC)[reply]
As it would be unethical to do an experiment where you feed potentially carcinogenic food to people and see if it gives them cancer, then it has not been done. Since it is carcinogenic in four different mammals, its reasonable to generalise (in the abscence of more specific data) that it will be cancinogenic in humans as we are also mammals. 92.24.178.172 (talk) 10:49, 1 June 2010 (UTC)[reply]
I'd be really interested in a modern reliable source saying so, because the article could do with one. Even better if it quantified the risk, so you could compare it to the risk from (for example) eating burnt food. 86.164.69.239 (talk) 14:53, 1 June 2010 (UTC)[reply]
Lately all of my local markets have in fact being trying to sell fiddlehead ferns, which I found quite odd looking. The article picture is an accurate representation of what they look like—a cross between asparagus and dead snakes! :-) --Mr.98 (talk) 15:35, 31 May 2010 (UTC)[reply]
Actually gymnosperms date back even farther, to the Carboniferous period, which is part of the Paleozoic. So it seems likely that there would have been something like pine nuts then, which make excellent food. There have been human groups who used them as their main source of nutrition. Looie496 (talk) 15:35, 31 May 2010 (UTC)[reply]
True, but if humans have only come into their modern form within the last 40,000 years, then there's no telling what minor (or major) changes in composition could have occurred in pine nuts, ferns, and critters in the past 65 million years. Just as a thought though, if the species that diverged before that time are all edible today, wouldn't it be probable that they were edible back then too? Maybe not, as we have evolved with them... Falconusptc15:40, 31 May 2010 (UTC)[reply]
Meat
Just going back to the OP for a minute - do we actually know if 'meat' has changed, in terms of what it is, over the last however many million years? AFAIK (according to those survival manuals I read as a kid), nearly all meat from anything that lives on land is edible (sea may be different - there's some strange things down there), when cooked. Is it likely that meat from back when would be so fundamentally different as to be biologically incompatible with our systems? --Kurt Shaped Box (talk) 18:56, 31 May 2010 (UTC)[reply]
The very fact that all meat is edible now tells us that it must have been edible in the past. The only (likely) way that something can be shared between all animals is if it was a property of their common ancestor (who lived about a billion years ago). That means all animals have been edible for the past billion years. --Tango (talk) 20:23, 31 May 2010 (UTC)[reply]
And it really really helps that we're omnivores (they're very uncommon). We can definitely tell if past vertebrates were omnivores by their teeth, and thus we only find a select few of dinosaurs. So count yourself lucky, and remember your place in the food chain! SamuelRiv (talk) 06:30, 1 June 2010 (UTC)[reply]
Light speed
Lately, I conducted an experiment in my house to verify a different, simple but similar evidence to that of Michelson–Morley experiment. A laser pointer was fixed to a wall, 3 meters high and vertically pointing to the ground such that incident light spotted on a graph paper (1x1 mm grids). Reducing temperature effects to minimum, I have been monitoring the light spot for few months (day and night) from time to time and the maximum offset achieved was less than 1 mm (perhaps due to temperature slight variation and different thermal coefficients). This makes me feel convinced about Michelson–Morley experiment.
If light were assumed moving with respect to ether (or absolute speed in space) it should of course have a maximum offset occurring within 12 hours, ; where x is the maximum shift (expected to occur within only 12 hours), h is the height or vertical distance light has propagated, v is Earth maximum known speed (let's say the same as galaxies'), and c is the light speed in air/vacuum. Given h=3m, v ≥ 220 km/s; thus x should be ≥ 4.4mm which is not verified in my experiment.
Eh? I don't understand how this reproduces Michelson-Morley? You don't describe how you're splitting the optical path...it sounds suspiciously like you're just shining a laser onto the floor and expecting to see the spot move...that's not how Michelson-Morley's experiment works. The changes in the speed of light that you'd see are of the order of a hundredth of a percent. Why would you expect that to produce a movement of the spot on the ground at all? Let alone a measurable one! To do this measurement (as our article points out) you need a beam splitter interferometer. The resulting interference fringes are so small that they can only be seen through a microscope. The error you're seeing is doubtless due to some kind of movement within the apparatus. To do this properly, you need a solid optical bench, a carefully constructed interferometer and a decent light microscope. SteveBaker (talk) 12:30, 31 May 2010 (UTC)[reply]
Sorry to tell it to you, but Steve is correct. In addition to what Steve said, This kind of experiment is so sensitive that the table top is usually placed floating on a tub of Hg to avoid vibrations. Dauto (talk) 13:03, 31 May 2010 (UTC)[reply]
I think he's assuming that as the light travels down toward the floor, the motion of the ether "sweeps" it along, and it moves sideways. Ariel. (talk) 14:36, 31 May 2010 (UTC)[reply]
I'm sorry for not explaining well. I've just uploaded a picture showing the experiment setup. The picture shows a house fixed to the Earth's surface (assume it on the Equator). The house is being observed 4 times a day referred to at states A, B, C, and D respectively. The laser pointer was fixed to the wall using some kind of epoxy and is powered by an external supply and confirmed no vibration all the time I was monitoring. I know I had the problems of beam angle which mad a spot of about 2mm on the ground and the house temperature wasn't that much affecting with time or I should have seen some significant deflect from high to low temperature times.
As you can see the experiment is totally different from Michelson–Morley experiment but the purpose and assumption are typically the same. We are trying to assume ether which will be detected when light passes through it at different angles.
Case A: The light is in the same direction of ether, increasing the relative speed of light but not deflecting from the centre.
Case B: Light is in normal direction to that of ether, so the resultant velocity is a vector of original light speed and relative ether-Earth velocity. This case is observed after about 6 hours of case A shifting incident laser spot from its centre. The expected offset/deflection from the center is .
Case C: After about 12 hours of case A and thus opposing the case by reducing the resultant speed but keeping laser spot at the centre.
Case D: After about 18 hours of case A. This is almost the same in case B but opposite deflection (see the astrisk, * in all cases).The expected offset/defection from the center is .
So the maximum possible offset should be .
As you can see, although it is not possible to predict center and offset from just one case but can be deduced after one complete rotation. I don't know what will go wrong with this experiment. Email4mobile (talk) 14:34, 31 May 2010 (UTC)[reply]
Yes but this is not a problem because we can replace the fixed house with the free rotating house in 3 dimensions (at least I don't have to wait for the 24 hours lol). On the other hand, I think we are also (but not sure) moving with the Milkyway partly in the third dimension but too slow angular velocity. Email4mobile (talk) 15:24, 31 May 2010 (UTC)[reply]
Perhaps you're still not following the explanations by Steve and Dauto. Previous experiments have been conducted so carefully that the margin of error is now smaller than a wavelength of light - that's why they used multipath interferometry. In order to "confirm" that there are no vibrations or other experimental errors, you're going to need to ensure that all of your errors are smaller than the wavelength of light. How are you doing this? For example, do you have confidence that all vibration amplitudes are smaller than a few nanometers? This is unlikely if you have epoxied the laser to the wall. You need a well-balanced optical bench. Before you can even hypothesize about a tiny effect, you need to build confidence that all other experimental errors with greater magnitude than your expected effect have been accounted for. Nimur (talk) 16:16, 31 May 2010 (UTC)[reply]
You're right Nimur. I may not be following because this experiment doesn't involve wavelength interferometry at all. Instead, I've to confirm that all sorts of errors are within 0.5mm at the spot for example; not nanometers. The major problem is the one mentioned by 94.72.235.30m the possibility of ether in the 3rd dimension and this can be done by a free rotating solid tube with the desired length and limited bend/vibrations to 0.0001L (L is the tube length). I might be wrong but feel this way is still easier to perform and if at least were true then it should be another method of verification rather than sticking in one method.Email4mobile (talk) 17:10, 31 May 2010 (UTC)[reply]
Decide what is the smallest deviation of the spot that you could reliably detect. Calculate what speed of ether wind could produce that deviation. Your simple experiment will disprove only that wind speed, which you will find is much faster than could be explained by Earth's movement through ether. Cuddlyable3 (talk) 21:35, 31 May 2010 (UTC)[reply]
I'm afraid that this experiment can never work even in principle because the ether theory doesn't predict the spot movement that you're looking for. Regardless of the motion of the apparatus through the ether, the light that emerges from the laser cavity will remain in line with the cavity. One way to see this is to note that the ether theory is equivalent to special relativity without length contraction or time dilation, and those don't have any effect on your setup. (Length contraction doesn't change the point of intersection of a line through the laser cavity with the floor.) -- BenRG (talk) 21:37, 31 May 2010 (UTC)[reply]
Hi
I want to measure the pressure and velocity of air flowing in a closed duct. What instruments should I use?
If it is a pneumatic conveying lift (the air carries fine solid particles with it), will it be ok to use a manometer and a pitot tube? or will the particles enter the apparatus and spoil the equipment? Are there any other instruments I can use?
Thank you —Preceding unsigned comment added by 122.169.188.160 (talk) 13:56, 31 May 2010 (UTC)[reply]
If you have lots of particles then an Ultrasonic Flowmeter would be perfect. Although I think the pitot tube will be OK (at least at first) because no air flows through it, it just measures pressure difference. But dust may eventually accumulate. If you filtered it, the filter will clog instead, so that doesn't help. You could blow a puff of air through the tube every once in a while to clean it. Ariel. (talk) 14:21, 31 May 2010 (UTC)[reply]
Thanks guys, but I need to measure in a closed duct (I can possibly drill a hole through the duct and insert a tube). In this case I dont think any of the conventional flowmeters as described immediately above will help, right? I dont have a very big budget so the ultrasonic flowmeter etc is out I'm afraid. Any other options? Thanks —Preceding unsigned comment added by 122.169.188.160 (talk) 04:04, 1 June 2010 (UTC)[reply]
Back hole
as a black hole has greater gravity due to distance between particles decreasing, doesn't it seem common sense to assume the possibility that gravity is generated , like electricity from a generator, when the static fields of electrons & protons cross at the speed of light? if e=mc2 then m=e/c2
f=g(m1m2/d2) thus f=g(<EeEp>/<c4d2>)sine theta? —Preceding unsigned comment added by 98.22.137.1 (talk) 16:52, 31 May 2010 (UTC)[reply]
First you've got to deal with the problems of the statement "a black hole has greater gravity". A black hole doesn't have any more gravity than its constituent matter. Were you to take the sun and compress it into a black hole, the planets would continue to orbit just as they do now (because both can be adequately represented as point masses). There's only a difference if you examine the gravitational field from inside the radius of the initial object -- but that's no great physics revelation. As such, no, I don't think there's much common sense in the rest of your theory. — Lomn18:08, 31 May 2010 (UTC)[reply]
Also, you can't mix and match the formulas like that. E=mc² is a formulation from special relativity that relates to the interchangability of mass and energy (which shows that something with lots of energy will have a higher measured mass, and also states that if you could somehow transform mass into energy how much you'd get, but doesn't say how to do that), whereas F=GmM/r² is from Newtonian physics, and the very fact that this formula breaks down when you look at large scales (and these scales are measurable from Earth, including things like gravitational lensing and time dilation on an orbiting satellite) is why we need general relativity in the first place. Under GR, gravity isn't even a force any more - it's a deformation of space that causes straight lines to become curves. Confusing Manifestation(Say hi!) 23:50, 31 May 2010 (UTC)[reply]
4-colour TVs
I keep seeing an advert (with Sulu!) for some kind of 4-colour TV, that says it includes yellow as well as red, green and blue, allowing it to give truer colours. Presumably, this works by allowing the red, green and blue to be different, and thus allows you to accurately represent more of the normal human colour space? But wouldn't that require the image to have been filmed using the same system? Or are the colours in some film/TV encoded in some 'absolute' way that the TV then interprets as best it can? I don't quite see how that would work in this case.
No, that's 3 colours plus black - TV's get black by just turning off the pixel (they could have white as a separate colour, I suppose, but there wouldn't be much point - we print lots of black, we don't have lots of white on TVs). --Tango (talk) 17:11, 31 May 2010 (UTC)[reply]
In technical lingo, adding yellow may alter the gamut that the device can display; see that article for an explanation. Not having seen one yet, I'm not sure whether this is hype or something really useful. Looie496 (talk) 17:14, 31 May 2010 (UTC)[reply]
We do, of course, have an article on this technology: Quattron. It doesn't answer your question, though. It's a good question. I can't find an answer to it after a bit of googling - the official press releases don't touch on it, for example. I guess that at the moment they are just converting RGB colour information to RGBY information, which they may be able to do in a clever enough way to get some improvement, but they are probably hoping that the existence of such TVs will encourage the production of 4-colour video and by being first they will control the standard. --Tango (talk) 17:21, 31 May 2010 (UTC)[reply]
Thanks, that's quite helpful (all of it ^). So, the consensus in that last discussion is that it mostly allows a brighter display, with little benefit to the range of colours? Whereas the article suggests the makers claim it works by using something closer to the opponent process, thus supposedly more closely matching how humans see. If you encoded the same colours using red/green, blue/yellow, black/white as the basis instead of RGB, would that actually make a difference to how you saw it? Would that allow brighter displays? 86.164.69.239 (talk) 17:46, 31 May 2010 (UTC)[reply]
A typical RGB gamut Unfortunately, what Steve was saying in that thread is wrong. More phosphors can enlarge the gamut. Take a look at this image. That horseshoe shape is all the colours the human eye can see. The triangle is all the colours that you can get with a particular set of 3 phosphors. As you can see, it only covers a fairly small portion of the total colourspace. If you move the green phosphor down and to the right a bit (which Sharp's TV does) and introduce a new yellow phosphor then you get a quadrilateral that covers more of the colour space. Doing that won't actually improve the yellows much - we can get perfectly good yellows by mixing red and green, as you can see in the image. What's missing in the image that would be added is the blue-greens. That image shows only a very small range of colours around cyan, this 4-colour TV would have much more. The thing that makes this a gimmick isn't that the TV doesn't do what they say it does, it's that the TV signal doesn't contain the necessary information. --Tango (talk) 19:48, 31 May 2010 (UTC)[reply]
Tango: Why don't you actually look at the chromaticity diagram you just attached. Note how close the yellow on the diagram is to the edge of the envelope - even if what you said was true (it isn't) then the effect of extending the gamut in the yellow direction would be negligable. If they were really able to increase the gamut - why wouldn't they have added a cyan pixel? However, those chromaticity diagrams are very dubious ways to represent what's going on. But the killer fact here is that the transmission system in broadcast TV and the storage system in DVD's, etc are RGB based - without an additional 'Y' component created back in the TV/Film studio, this "fourth color" cannot possibly be doing anything meaningful - except (perhaps) to push the overall brightness up. The limitation in the color gamut of TV's is not the display - it's the cameras, mixers, recorders, transmission systems and decoders - and that's not something that's going to change anytime soon. This gizmo is pure advertising hype - and it should be thoroughly exposed as such. SteveBaker (talk) 12:45, 1 June 2010 (UTC)[reply]
In point of fact, MPEG, DV, H.264 and the like use a YCbCr space, and the YCbCr cube is much larger than the RGB cube that it contains (in part because it's oriented differently). So, in principle, you could expand the gamut by simply relaxing the restrictions on what part of the YCbCr space you're allowed to use in encoded video. That's what xvYCC (mentioned below) appears to do. There's no reason, that I can see, to use more than three components to describe an emissive color, even if the display ultimately uses four or more primaries. The perceptual color space is still three dimensional.
After much searching I finally found an image claiming to actually show the Quattron color primaries, here (also found here). I'm not sure I trust it. -- BenRG (talk) 03:13, 2 June 2010 (UTC)[reply]
They key thing isn't the addition of yellow, it's the moving of green. The addition of yellow is just necessary to fill in the gap left after you move green. We're all agreed that at the moment the signals don't contain any more information than can be seen on conventional TVs, but that could easily change in the future. --Tango (talk) 10:58, 2 June 2010 (UTC)[reply]
Ah, so that takes me back to my first thought: thanks. Is there any way they could extrapolate from the information in a normal or HD TV signal, to improve their colours? Or is it a complete bust? It just seems amazing to me that they could really be building an ad campaign around something they can't possibly deliver. 86.164.69.239 (talk) 21:24, 31 May 2010 (UTC)[reply]
I don't know enough about the TV encoding system to be sure. I expect they could do some clever stuff to extrapolate from the information they have, but I don't know how much improvement they would get out of it. --Tango (talk) 22:43, 31 May 2010 (UTC)[reply]
Without getting into whether or not there is actually sufficient information in any current video signal to extract to take advantage of this I would propose an alternative reason: They are doing it because they can:
It's a LCD - thus it's just an extra square in the mask - not actually much new technology
Getting 3 pixels in a square grid is tricky - but 4 is easy
The absolute brightness may be limited compared to a 3 pixel display - but this isn't an issue since LCDs are quite bright enough alreafy thank you
The actually color effect may be slightly 'kodachrome' - it distinguishes the display in the market, may produce extra 'impact' in a shop, and definately won't actually do sales any harm
It gives them a product to display at CES, and makes great advertising copy, and gives hardware sites something to write about.
Thus everyone wins, despite probably no real net improvement.
This article has some information about Quattron (near the bottom). The author is cynical but clearly knows his stuff. He asks the right question ("could it be that existing consumer HDTVs are unable to reproduce the standard sRGB/Rec.709 colour gamut, so Sharp’s fourth primary colour actually has something useful to do?") and answers it with experimental data. The answer is no: an older Sony LCD with three primaries correctly represents all of the colors in Rec.709. So if the Quattron's colors do look more "vivid", and it's not simply an increase of brightness, then it must be displaying them incorrectly. I wouldn't be surprised if they're deliberately oversaturated. That said, there's nothing wrong with the idea of using a larger set of primaries, as 87.* said above. I think the bit about the color opponent process is meaningless hype; I can't see how it could be anything else. -- BenRG (talk) 00:32, 1 June 2010 (UTC)[reply]
In addition to sRGB, HDTVs often support the xvYCC color space, which has a larger gamut. It's possible that the yellow subpixels would help in the xvYCC color space. Of course, xvYCC is not widely used at this time. -- Coneslayer (talk) 12:27, 1 June 2010 (UTC)[reply]
That is interesting. They might be making these TVs in anticipation of xvYCC becoming more widely supported. I expect their 4-colour TVs can display xvYCC colours better than a conventional TV. --Tango (talk) 15:24, 1 June 2010 (UTC)[reply]
I also doubt they cover the whole xvYCC gamut, but if they cover more of it than conventional TVs then they'll be able to display signals that support xvYCC better than conventional TVs (not that there are many such signals, but there may be more in the future). --Tango (talk) 19:20, 1 June 2010 (UTC)[reply]
Thanks for that, guess I was wrong. Was looking myself but got distracted by discussions of displays with xvYCC (and also was searching for xvYCC). I still wonder whether there's any real advantage though. It seems other xvYCC displays exist [37][38][39], if these already support the full gamut (and in theory there's no reason why they can't, xvYCC is still RGB based after all) then we hit the same issue. Nil Einne (talk) 19:41, 1 June 2010 (UTC)[reply]
Generally, "support" for xvYCC just means that the display accepts the xvYCC signal, and does not imply anything about the actual display gamut. My hunch would be that both 3-color and 4-color displays show less than the full xvYCC gamut, but that the 4-color display might show a larger fraction of the gamut. But unless somebody can dig up real measurements, that's just my hunch. (In a couple of months, I plan to build a new computer with a Radeon 5xxx GPU and connect it via HDMI to my Panasonic G10 plasma... the GPU apparently supports xvYCC, so maybe I can see if there's a visible or measurable difference in display gamut on my set.) -- Coneslayer (talk) 23:43, 1 June 2010 (UTC)[reply]
Why the standard value of "g = 9.8 m/s/s or 32 ft/s/s" is subjective and varies if expressed in unit of time other than second (e.g . m/half-sec/half-sec or m/hr/hr or m/min/min)?
Further falling velocity of object is increases at every fraction of second in given spacetime therefore acceleration is produced at every fraction of second rather than per second therefore I don’t understand why it is assumed by the experimenter that falling velocity of an object is constant vehemently/ specifically for one second duration in given spacetime. Is this is fixed by the nature for falling velocity to be increased constantly only after every second? 68.147.38.24 (talk) 17:50, 31 May 2010 (UTC)khattak#1-420[reply]
(edit conflict)Yes g is a constant, no it has nothing inherently to do with the units of meters or seconds. You can use other units (furlongs/fortnight/fortnight, if you prefer), the math will still work out but your velocity calculated at any given time will be in furlongs/fortnight, rather than the more familiar m/s or ft/s. Similarly, you don't have to calculate the velocity change for complete seconds, if you're accelerating at 20 m/s/s for .5 seconds, your final velocity is 10 m/s. TastyCakes (talk) 18:05, 31 May 2010 (UTC)[reply]
(ec) The standard value of g will be slightly different in different units due to rounding (9.8 m is 32.152231 ft, but it is false precision to keep that many decimal places after converting, so we quote it as 32 ft), but that's all. The acceleration is continuous. If an object starts from rest (stationary) and falls then after a tenth of a second, it will be going 0.98 m/s, after half a second, it will be going at 9.8/2 m/s=4.9 m/s, after a second, it will be going 9.8 m/s, and so on. It is quoted in seconds simply because that is our standard unit of time. --Tango (talk) 18:07, 31 May 2010 (UTC)[reply]
Gravitational acceleration is (close to) a constant and is not subjective. Time passes continuously and the OP needs to learn that the normal expression of acceleration g=9.8 m/s/s does not mean anyone thinks nature increases the speed in jumps of +9.8m/s every second. The OP can express the same acceleration as g=588m/min/min g=588m/min/s or g=35280m/min/min which is are both correct. However it is nonsense to attack the common use of the second as time unit as "contentious, not viable etc." as they are doing at Talk:Standard gravity. Cuddlyable3 (talk) 21:07, 31 May 2010 (UTC)[reply]
To answer the original question, scientists don't assume that the speed changes only once per second. If we only want to calculate the speed after one second, we can just multiply 9.8m/s/s * 1 s and get 9.8 m/s, but if we want to calculate the distance that the object travels, we can't just assume that it is still for one second and only starts moving at the end of the second. Instead, we have a more complicated formula (the equations of motion). These can be described as taking infinitely small fractions of a second into account. We can do this because of calculus, which was first invented by Isaac Newton for exactly this reason. 76.67.73.201 (talk) 05:28, 2 June 2010 (UTC)[reply]
Let's also recall that g is NOT constant: its numerical value on Earth varies with altitude, latitude and longitude, as well as with time, in whatever system of units of measurement it is expressed. The Gravitational constant (also known as 'Big G') is a true constant, but the question refers to the 'small g', which includes all applicable gravitational forces, including due to the Sun and the Moon. The field of science that studies these questions is called Gravimetry. The value 9.81 m/s/s is often quoted in schoolbooks and may be sufficient for most everyday applications but would be wholly inadequate in some fields of scientific research and technological development, such as geophysics (e.g., to predict tides) or space exploitation (e.g., to manage artificial satellites). Michel M Verstraete (talk) 21:42, 2 June 2010 (UTC)[reply]
While I love the antics of my beloved Earthicans, there are often jokes that I don't get. In 'Crimes of the Hot', Linda expresses the idea that turtles will be cooled off by windmills. Morbo responds that WINDMILLS DO NOT WORK THAT WAY!!
My question--while windmills clearly are designed for energy and not cooling things off, wouldn't they also do that? Aren't they sorta like over-sized fans? I'm sorry for my lack of scientific knowledge. Thanks gang!209.6.54.248 (talk) 20:05, 31 May 2010 (UTC)[reply]
They're like fans, except backwards. A fan consumes power to produce wind; a windmill consumes wind to produce power. --Trovatore (talk) 20:17, 31 May 2010 (UTC)[reply]
(ec) A windmill is a fan in reverse. A fan turns electricity into wind, and windmill turns wind into electricity (or some other useful form of energy). A windmill powered fan would be like a solar-powered torch - completely useless. The cooling power of the wind would be greater than the fan, due to inefficiencies. --Tango (talk) 20:20, 31 May 2010 (UTC)[reply]
Ya, but to boil it all down, I think the essence of the joke is that Linda was suggesting that the giant turbine could cool the turtles down, and Morbo was angrily pointing out that she has it backwards and that, although they look like big fans, wind mills don't create wind (they absorb it). TastyCakes (talk) 20:53, 31 May 2010 (UTC)[reply]
Part of the joke is also that Morbo, a huge alien who might eat you up, is pedantically irritated by Linda's weak grasp of physics. This mixture of lurking alien menace and pedestrian vulnerability is the running Morbo gag. 213.122.3.204 (talk) 19:29, 1 June 2010 (UTC)[reply]
hey, OP here--thanks for the clarification, but I'm wondering if you stood in front of a windmill, you're saying that it wouldn't be blowing air at you?209.6.54.248 (talk) 00:39, 1 June 2010 (UTC)[reply]
If you're infront of the windmill and the windwill is between you and where the wind is coming from - then you'll feel less wind (the wind gets slowed down, and as a consequence some goes round the windmill).87.102.77.88 (talk) 01:16, 1 June 2010 (UTC)[reply]
Neither fans nor windmills change temperatures (try sticking a thermometer in front of a fan and turn the fan on and off...the temperature reading won't change). The only reason fans make people feel cool is that they move the thin layer of air that's warmed by our body heat and trapped close to our skin by hair and clothing away - letting us feel the temperature that the air really is. When the air temperature is above body temp, fans actually make you feel hotter. Windmills remove energy from the air - thereby slowing it down - so they'll somewhat reduce the cooling feeling of the wind - but they won't change any temperatures (other than by friction and stuff - but that'll be negligable). I suppose that standing behind a windmill when the air temperature is above body heat would make you feel cooler. SteveBaker (talk) 03:06, 1 June 2010 (UTC)[reply]
Well, no, not quite. At 100% humidity, what you say would be true; the only way the wind cools you is convectively, and above body temperature (actually, above skin temperature, I think) it would actually heat you up.
But if you're not on the East Coast, the more important effect is likely to be evaporative cooling, where the wind strips away the humid air near your skin (made humid by your own sweat), and thereby allows more sweat to evaporate, carrying with it its latent heat of vaporization. This can cool you even when the air is significantly hotter than your core temperature. --Trovatore (talk) 05:06, 1 June 2010 (UTC)[reply]
Windchill is just the perceived drop in temperature when a wind is blowing due to the aforementioned removal of the thin warm air pocket above your skin. --Chemicalinterest (talk) 11:07, 1 June 2010 (UTC)[reply]
This is actually a good point, I'm not sure that ta cold-blooded, dry skinned animal would feel much "cooling" effect from a fan, certainly not on its shell. I'm sure that's not the joke intended by Futurama, though. The joke is simply that Windmills slow the wind down, not speed it up, even though they look like giant fans. Irony. APL (talk) 15:36, 1 June 2010 (UTC)[reply]
June 1
Center of mass question
Suppose two particles, far from any other influence, are orbiting around their center of mass due to gravitation. Then, imagine that a third object is introduced to the system. This third object will obviously will move the center of mass. Will the two objects still move about the center of mass in the same way? If so, is this a general rule about center of masses? 173.179.59.66 (talk) 00:19, 1 June 2010 (UTC)[reply]
It is really complicated. See Three-body problem. With two particles, they will both orbit in ellipses around the centre of mass. With three particles, they can do all sorts of crazy things. --Tango (talk) 00:26, 1 June 2010 (UTC)[reply]
Generally in real systems you'll only have two bodies orbiting as a very-close-to-true two-body system, with the third body orbiting around the two bodies' center of mass from a much-farther distance. However, in our Solar System, small things like comets and other [[Kuiper belt] objects sometimes get disturbed just enough by the larger planets to be ejected into the central solar system, giving us the weird new comets we see on occasion (or the one that crashes into Jupiter). - User:SamuelRiv 1 June 2010
Sure, if the third body is small enough and far away enough not to significantly affect the other two bodies and is far enough away that the other two bodies essentially merge into one body, then you can get an approximate solution by doing the two-body problem twice. It would only be approximate, though. Exact solutions to the 3-body problem are only known for a few very specific (an unlikely to occur in real life) situations. --Tango (talk) 15:41, 1 June 2010 (UTC)[reply]
Tango - in an isolated 3-body system, as in a trinary (I don't use tertiary) star, these systems of a close pair with a far-away orbiter (no matter how massive they are) are the only ones observed. Of course the precise calculation is notoriously unsolvable, and in the case of a many-body solar system, it is utterly a mess with small-bodies being quite unpredictable. SamuelRiv (talk) 16:10, 2 June 2010 (UTC)[reply]
I wasn't aware they were the only ones observed, but it doesn't surprise me - more complicated 3-body systems tend to be unstable, so one of the three stars would probably break away from the other two sooner or later. If the far-away orbiter is sufficiently massive (which I think is unusual) then it will have a significant impact on the way the other two stars orbit each other. --Tango (talk) 16:14, 2 June 2010 (UTC)[reply]
Methanol in water
When something like methanol goes into aqueous solution, the hydrogen on the edges of the methanol form weak polar hydrogen bonds with the negative side of the surrounding water, thus the methanol goes into solution. But, why doesn't the oxygen in the middle of the methanol form some sort of similar bond with the positive, hydrogen side of other water molecules? It seems that if the outside of the methanol has a little bit of a positive charge, the middle might have the reverse. --TheHighFinSpermWhale03:45, 1 June 2010 (UTC)[reply]
I have some of these pads, and one of them seems to recrystallise on its own, very slowly, without any stimulus. Its subsequent heating activity is, of course, impaired. Should I dispose of it, and if so, what is the safest way? Could I, for example, just put it into a rubbish bin? --TammyMoet (talk) 09:04, 1 June 2010 (UTC)[reply]
I hope this doesn't cross the line to legal advice, but as far as I understand, there is nothing toxic or otherwise particularly harmful in them. (Of course, you will make sure to separate the metal for recycling, identify the type of plastic used in the shell and sort it accordingly, water your flowers with the liquid and use the acetate to season some crisps...)--Rallette (talk) 09:58, 1 June 2010 (UTC)[reply]
Sodium acetate is not toxic in normal quantities; react it with acids and you get vinegar. There is probably a scratch in the bag that allows the unstable supersaturated solution to condense as crystals. You can dilute the sodium acetate with water and wash down the drain; shouldn't hurt any more than vinegar. --Chemicalinterest (talk) 11:09, 1 June 2010 (UTC)[reply]
It is a common anecdote that the days seem to move faster as an adult than when you were a teenager and certainly faster than when you were a child. Does this phenomenon continue to accelerate during adulthood? That is to say does someone in their 40s experience time (on average) to be faster than someone in their 20s? TheFutureAwaits (talk) 11:00, 1 June 2010 (UTC)[reply]
I think it has to do with the "busyness" of your days. As a child one doesn't have many responsibilities and cares like adults do, so time seems to move slower for them. Time also seems to move faster when you are more busy. --Chemicalinterest (talk) 11:11, 1 June 2010 (UTC)[reply]
Yes, I'm sure that is a factor, but the effect of time speeding up seems to continue into retirement and even to accelerate, even when days are less busy. Dbfirs13:23, 1 June 2010 (UTC)[reply]
And I'm a complete waster, with absolutely nothing to do all day, and still find that now, in my 30s, the years seem to fly by - unlike when I was, say, seven, and it seemed an eternity until I would be eight. One possibility is that things seem to last longer when they surprise you, and that children are permanently surprised. (It would be funny if it turned out to be physiological, to do with brain chemistry. There are drugs which alter the perception of time, so it's not impossible.) 213.122.61.131 (talk) 20:21, 1 June 2010 (UTC)[reply]
Think of it this way: when you are one day old the next day is one half of your whole life at that point, when you are 20 years that same day is 1/7304th of your whole life at that point. —Preceding unsigned comment added by 165.212.189.187 (talk) 13:26, 1 June 2010 (UTC)[reply]
Simvastatin toxicity
Is sequestered bile acids beyond what the body can tolerate to lower cholesterol levels the mechanism of Simvastatin toxicity in doses above 160mg? 71.100.8.229 (talk) 11:34, 1 June 2010 (UTC)[reply]
I can't seem to find more than the maximum dose as 80mg or the toxic dose as 160mg if that helps. I'm interested in all types of toxicity for Simvastatin from excess dose to interaction with other drugs or interaction of the implied conditions taking Simvastatin represents. For instance, high cholesterol is an indicated condition that suggests that medications which restrict blood vessels such as medications which dilate pupils are toxic in combination with the implications of taking Simvastatin, i.e. high cholesterol. 71.100.8.229 (talk) 13:10, 1 June 2010 (UTC)[reply]
Huge sinkholes in Guatemala
There are reports in the new about a gigantic sinkhole in Guatemala ([40]). A web search turns up stories about another occurrence in 2007 ([41]). How were these sinkholes created? Why do they look almost perfectly cylindrical? Where did the earth that originally occupy the hole go? —Preceding unsigned comment added by 173.49.15.136 (talk) 12:00, 1 June 2010 (UTC)[reply]
It starts with a system of caves, and an underground river. The river falls down a small hole, over time it enlarges the hole, the swirling motion as it does so tends to make the hole round. See Kettle hole, Plunge pool, and Pothole#Other_uses. Like this photo, sometimes they call them "Glory holes". Eventually there was a massive, and deep hole in there, covered by an earth "roof". Probably fed at the side, with a deep drain. The soil was all washed away by the river, as over time the land above falls down into the water. During that massive rain storm, probably the river level went up a lot, and washed even more soil. To the point that it could not support it's own weight, and fell in. If you look closely at the photo you'll see it's full of water at the bottom. Ariel. (talk) 12:37, 1 June 2010 (UTC)[reply]
There might be little or no iridium layer actually at ground zero itself, as the huge explosion caused by the vaporisation of both the meteorite and the rock it struck would have blown all the meteoritic material (which contained the iridium in excess of usual terrestrial concentrations) high into the atmosphere, dispersing it around the globe. Although a small proportion of this material would have resettled at the immediate impact point, that immediate area would have been so heated and/or disturbed by the impact that it would have probably remained in state of turmoil (doubtless there's a technical word for this) long enough to mix up the fallout and prevent the formation of the obvious K-T boundary layer found elsewhere.
In the wider area of the Chicxulub crater, around whose boundaries formed the ring of cenotes/sinkholes that were the clue leading to the feature's discovery, the article's Geology and morphology section states "The K–T boundary inside the feature is depressed between 600 and 1,100 m (2,000–3,600 ft) compared to the normal depth of about 500 m (1,600 ft) depth 5 km (3 mi) away from the impact feature." The original paper from which these data are taken, Hildebrand, Penfield et al 1991 4, might also give the layer's thickness. (87.81.230.195 (talk) 23:34, 1 June 2010 (UTC)[reply]
The responses on the Miscellaneous page seemed to hit the nail on the head. Do you have a particular clarification you'd like? I will just emphasize two points: First, that the consensus seems that crayfish aren't fast in terms of velocity, but rather acceleration (0-60 in 3 seconds, to use a car term). It would be neat if we had a page on the fastest-accelerating animal, because surely none of those listed in Fastest animal would qualify.
Second, the key to this rapid response is a very conductive "wire" that can connect any kind of stimulus to the tail muscles almost instantly. Human reaction time in such a situation is at best 160ms, which for a crayfish would make them easy prey (finding a list of animal reaction times is very difficult, if someone might help). The essential problem is that the "wire" is a neuron, which is not a very good conductor. Mammals get myelin, a fatty insulation, around some neurons to make signals go faster, but arthropods have to instead make their response neuron thicker. At the end of the day, the sequence is that a stimulus from the eyes or wherever travels to the brain and then shoots down this giant neuron into the tail causing this very fast reaction kick. Sorry I can't be more specific. SamuelRiv (talk) 16:39, 2 June 2010 (UTC)[reply]
tendinosis or tendonitis?
Hi all. Are tennis and golfer's elbow examples of conditions caused by tendinosis or tendonitis? The articles on these conditions do not say. Presumably tennis elbow is a tendinosis as there is no inflammation involved and golfer's is a tendonitis because there is histological inflammation? If my presumptions are correct then the link to tennis elbow on the article on tendonitis should perhaps be removed? RichYPE (talk) 13:25, 1 June 2010 (UTC)[reply]
I had heard that tennis elbow was not associated with inflammation, and the wiki article on this seems to say the same thing. 'The condition is also known as lateral epicondylitis ("inflammation of the outside elbow bone"), a misnomer as histologic studies have shown no inflammatory process.' RichYPE (talk) 16:05, 2 June 2010 (UTC)[reply]
The article goes on to say that there is inflammation, so I don't know what to think and will defer to someone with more expertise than myself. --Sean18:23, 2 June 2010 (UTC)[reply]
What's a "Twin Cylinder Reversible Turbine"?
Looking at this 1913 patent, I'm confused: what is it supposed to do? It's obviously some sort of steam turbine; am I correct in guessing that it works inside a steam engine to make the engine more efficient? Nyttend (talk) 15:16, 1 June 2010 (UTC)[reply]
If I understand correctly (and I may not be), it is a steam turbine that can be put into reverse (i.e. it spins the opposite direction). Falconusptc18:11, 1 June 2010 (UTC)[reply]
I wonder if 'cylinder' refers to piston and it is a turbine engine with a piston based gas generator eg Free-piston_engine#Gas_generators , not sure how that would be reversible.
It may not even be an engine - some variation on the fluid coupling seems possible.
Also could reversible mean 'reversing' rather than reversible as in thermodynamics?
(sorry I'm guessing) Is there a better link - all I saw was a very brief abstract - I'm not even sure it is steam from the info I've got. It's US Patent 1064824 - maybe someone else has better resources. 87.102.77.88 (talk) 18:40, 1 June 2010 (UTC)[reply]
It was reversible as in 'can be put in reverse gear'. As far as I can tell it's a stand alone turbine as described.? In fact the patentee describes one of it's advantages as being compact and able to go in the base of a ship - so there probably wasn't any conventional steam engine involved.
Note - the engine seems to rely on gas flow, and there appears to be no expansion (didn't read it all) - this would have been a tremendously inneficient engine - one of the later patents that references this one corrects this flaw. ie this87.102.77.88 (talk) 19:00, 1 June 2010 (UTC)[reply]
No wonder the inventor kept his day job; he was a prominent smalltown physician. I discovered this patent while researching to write an article about his house. Thanks for the input! Nyttend (talk) 21:49, 1 June 2010 (UTC)[reply]
I think the term passive force refers to something like friction or viscous force, which only exist as resistance to motion. Say I apply a pushing force of 500 N to a heavy box, but the friction prevents the box from moving. We know that the friction is equal to 500 N, since the box shows no acceleration. However, if I stop pushing, there won't be a 500 N of friction to cause the box to accelerate towards me. I think it is in that sense that the force is passive. --173.49.15.136 (talk) 12:33, 2 June 2010 (UTC)[reply]
Sima Martel and Sima Humboldt
Is the sunlight reach the bottom of it? And will animals survive if it drop into it? Is there any possibility there's ancient animals or plants live in it? roscoe_x (talk) 18:39, 1 June 2010 (UTC)[reply]
According to our (brief) articles about these holes, (Sima Martel and Sima Humboldt) they are both about 300 meters wide and about 300 meters deep. They aren't narrow holes at all. That means that the sun would only have to be about 45 degrees up above the horizon to light at least a portion of the floor. Google Maps says that they are at about 4 degrees of latitude above the equator - so there will be days in the summer when the sun shines vertically down into the holes, illuminating almost the entire floor of the sink-holes - except that the floor of the holes are slightly wider than the top - so there are probably some small regions that don't get sunlight. However, it's obviously quite light down there most of the time.
Given that, it would be very surprising if there were no plants down there - you'd expect seeds and fruits and nuts to fall down there all the time, so it's quite likely that the floor is mostly covered with the same kind of vegetation as the surface. Animals are a bit more problematic. It's hard to imagine very large animals getting down there and surviving long enough to breed in such a limited space...but anything that can climb a rock wall could make a living there - as could very small animals. With a constant influx of modern life raining down into the holes, it's hard to imagine 'ancient' things living down there. Having said that, many caves have unique life forms (typically, blind, white things) that evolved from animals that fell into the cave system somehow...it's not impossible that such things are in the darker corners. SteveBaker (talk) 00:40, 2 June 2010 (UTC)[reply]
Mafeking Oil - obsolete veterinary preparation
Just watching All Creatures Great and Small, and mention was made of a preparation called "Mafeking Oil". It was being used by a farmer as a muscle rub on a lame cow, and the cow had licked the oil off her leg and developed vesicles in her mouth. Siegfried duly castigated the farmer for using such an out-dated and dangerous treatment, and said that "the only good thing the Germans did in the war was to bomb the factory that makes it". So - it was some sort of embrocation, unavailable after the Second World War, and acidic. Anyone know what it was? I have googled, and found nothing (except another person asking the same question). DuncanHill (talk) 18:58, 1 June 2010 (UTC)[reply]
Hmm. Dippel's Oil is an unpleasant oil once used with livestock, though since it's supposed to repel animals I doubt the cow would have licked it off. I feel like I've heard of Mafeking oil before, too, but then I also find Shatner's bassoon to be plausibly part of the brain, so perhaps what we have here is just an example of James Herriot being a good writer.213.122.61.131 (talk) 21:02, 1 June 2010 (UTC)[reply]
According to a Google Books search, the book All Creatures Great and Small doesn't mention that -- it mentions castor oil, linseed oil, and cod liver oil, but no Mafeking oil. In fact no book of any sort is found that mentions that. Also no mention of mouth vesicles in any of his books. Looie496 (talk) 21:58, 1 June 2010 (UTC)[reply]
Have you considered artistic license? Mafeking being a suitable name for a potent medicine (ie from Siege of Mafeking) - possibly the hypothetical (and possibly imaginary) bottle had a military scene on ala Camp Coffee but with a greater suggestion of physical activity and free from any suggestion of lameness. Maybe simply the words 'mafeking' where enough in themselves. 87.102.77.88 (talk) 23:46, 1 June 2010 (UTC)[reply]
Live bacteria in food
I know I sorta asked this question, but what other foods besides those containing dairy has live bacteria in it? The reason I ask is that I am extremely lactose intolerant and eating yogurt will not be beneficial to me. Nor would drinking beer. Just wondering. Thanks! Reticuli88 (talk) 19:17, 1 June 2010 (UTC)[reply]
Just about any food will have some non-zero number of live bacteria on it unless you just pulled it out of an autoclave. You breathe in a huge number of bacteria a day, and some of those bacteria land on your food. Is there a specific species of bacteria you are looking for in food? Googlemeister (talk) 19:21, 1 June 2010 (UTC)[reply]
Just to state the obvious, remember if you want live bacteria, you can't cook your source or heat it much above 37 degrees celsius. Also based on our yoghurt article, have you looked for lactose free yoghurt? It evidentally exists in the UK Lactofree, seems likely it may exist in the US as well. And it seems soya yoghurt also exists. I presume some of these contain live cultures. Nil Einne (talk) 21:07, 1 June 2010 (UTC)[reply]
It is also possible to buy capsules containing such bacteria in health-food stores. I am neither recommending nor dis-recommending these; just letting you know they exist. --Trovatore (talk) 20:06, 1 June 2010 (UTC)[reply]
I don't believe the health of your gut flora relies on regular consumption of live bacteria, contrary to what the advertisers of Yakult would want you to believe. Vespine (talk) 05:53, 2 June 2010 (UTC)[reply]
And, of course, contrary to what our articles Gut_flora#Alterations_in_balance and probiotics say. That not everyone will benefit from it is pretty clear: that many people in many different circumstances will benefit from it is supported by the evidence. The problem lies in the advertising suggesting that everyone needs it all the time: but then, there are plenty of adverts that talk about specific symptoms being relieved by probiotics. 86.164.69.239 (talk) 19:01, 2 June 2010 (UTC)[reply]
I have no idea what "RTFA" means, but a dihedral makes an airplane more stable, and an anhedral makes it less stable. They sometimes put anhedrals on designs where the plane is too stable (you do need to be able to turn them, after all). The plane I fly (PA28) has a very distinct dihedral, making it very stable, which is what you want if you aren't planning on doing stunts. Falconusptc22:43, 1 June 2010 (UTC)[reply]
I think there's a basic problem with answering your question - more or less under what conditions? for the same width, breadth, weight etc?87.102.77.88 (talk) 22:03, 1 June 2010 (UTC)[reply]
What I'm asking is, if you have have a straight wing and a gull wing of the same length, width, etc., what differences will it make to stability, speed, lift, drag, etc. And what does 'RTFA' mean? --TheHighFinSpermWhale22:14, 1 June 2010 (UTC)[reply]
RTFA means that an answer to your "what does it do to stability" question was to be found by reading the articles linked to in the response above it. --Tagishsimon(talk)22:52, 1 June 2010 (UTC)[reply]
At a basic level lift depends on the angle of attack - no difference as a first approximation.
Drag will depend primarily on the thickness of the wing - here again - no difference as a first approximation for wings of the same thickness.
Speed will be a function of drag - assuming the wings have the same sweep - no difference.
Stability - not sure here - but a gull wing has two angles for anhedral/dihedral , whereas a 'normal' wing has one and you haven't specified what it will be - so I don't think that is answerable yet. Ignoring that aspect for a moment -stability depends on the whole aircraft - ie the other smaller wings etc .. so impossible to say.
Actually if you read the article Gull wing from top to bottom I think you'll get the impression that the main reason for having a gull wing is to solve secondary (non flight) engineering problems (or issues with centre of mass) rather than any intrinsic pluses or minuses flight wise.. 87.102.77.88 (talk) 00:10, 2 June 2010 (UTC)[reply]
The article on the Stuka says The offensive armament was two 7.92 mm (.312 in) MG 17 machine guns fitted in each wing, operated by a mechanical pneumatics system from the pilot's control column. original research but I would not think it would interfere with the bomb load. MilborneOne (talk) 20:26, 1 June 2010 (UTC)[reply]
The plane in that picture has some enormous guns! Are those really MG 17s? Here's a cross section of a Ju87(b) with guns internal to the wing: [43] ... this was normal. 213.122.61.131 (talk) 20:43, 1 June 2010 (UTC)[reply]
If you read the Junkers Ju 87#Ju 87G section, it's immediately clear that your picture shows a variant used for anti-tank warfare on the Eastern Front. Not many were ever produced, I guess. The large guns are evidently 37 mm Flak 18 cannons. The article also says that they were designed to carry one 1000 kg bomb. Buddy431 (talk) 20:50, 1 June 2010 (UTC)[reply]
(ec) The photo caption notes that the gun pods are 37mm cannon, probably for an anti-vehicle/anti-tank role. They appear to be fixed to the hard points that would otherwise mount the 50kg bombs. — Lomn20:51, 1 June 2010 (UTC)[reply]
Dissolved away over many hundreds/thousands of years like other features where the bedrock is limestone. There was probably a limestone cave beneath the sinkhole whose roof collapsed suddenly, the space had already been created. Mikenorton (talk) 22:35, 1 June 2010 (UTC)[reply]
(edit conflict..modified) - for this reason sinkholes are often connected to cave systems and underground rivers Subterranean river
Can decaffeinated coffee still have an effect, whether placebo or directly? I mean, clearly it contains nothing to compete with adenosine so it can't work the same way, and I'm skeptical, but decaffeinated coffee definitely has an effect on my personal sleeping habits. Why would this be? How? Regards, --—Cyclonenim | Chat 00:36, 2 June 2010 (UTC)[reply]
One thing to keep in mind is that decaffeinated coffee may still contain clinically significant amounts of caffeine. I suspect this is especially true for higher-quality blends, where the priority is flavor rather than removing all the caffeine you possibly can, but I don't really know that. --Trovatore (talk) 00:46, 2 June 2010 (UTC)[reply]
I would be quite surprised if there wasn't a placebo effect, but generally that would require the drinker to think they were drinking regular coffee. I'm guessing that isn't the case with you, so it is unlikely to be placebo. It could just be confirmation bias, though. Alternatively, Trovatore may be right and the small amounts of caffeine still in the coffee are having the effect. --Tango (talk) 01:08, 2 June 2010 (UTC)[reply]
Our article on decaffeination makes reference to an "international standard" that 97% of the caffeine must have been removed, and to an "EU standard" that the beans must be 99.9% caffeine-free. On the other hand, one of the references is to this Science Daily article, which implies that decaf may have as much as 20% of the caffeine of regular coffee.
These facts seem somewhat difficult to reconcile. One possibility is that the coffee referred to by ScienceDaily was not compliant with either of these standards. Another is that beans consisting of 0.1% caffeine by weight (how much is in normal beans?) still produce coffee with 20% the caffeine of regular (maybe in part because you need more coffee grounds to get the same concentration of flavor chemicals?). --Trovatore (talk) 01:40, 2 June 2010 (UTC)[reply]
Original research: When I drink a carbonated beverage, I instantly feel a buzz whether or not it has caffeine; I have to think this is some sort of placebo effect my brain is pulling on me (unless it's the carbonation itself). -RunningOnBrains(talk)05:25, 2 June 2010 (UTC)[reply]
Still has caffeine, but maybe similar chemicals (take one or two methyl groups off) also give insomnia. That rooibos tea and chicory root is caffeine free but still has other stimulants. Polypipe Wrangler (talk) 13:40, 2 June 2010 (UTC)[reply]
Why is it that I could stand cold weather or the temperature in Baguio City but shiver when near an air conditioning unit? Do outside weather and air conditioning cools us differently?--Lenticel(talk)02:12, 2 June 2010 (UTC)[reply]
For one thing, the air conditioner is probably blowing the air at you. Moving air will almost always "feel" colder than standing air. (See Wind chill for an extreme example of this). Buddy431 (talk) 02:39, 2 June 2010 (UTC)[reply]
One thought is that usually when you're outside you're not just hanging out, you're doing something even if it's only walking from place to place. Inside you're liking to be sitting in a chair and not exerting yourself. APL (talk) 04:17, 2 June 2010 (UTC)[reply]
Unfortunately, Thermoception is not a very good article, but that may be what you're looking for. We don't typically feel absolute hot and cold, just relative temperatures, so if you put one hand in hot water, another in cold water, and then put both in lukewarm water, the lukewarm water would feel hot to the hand that was in cold water, and vice versa. If you're air conditioning is much cooler. Also, you likely wear warm clothes outside in the cold, but not inside in your air conditioning. Furthermore, forgive a little teasing, but "cold" in Baguio City (record low: 46 °F (7.8 °C)) isn't exactly the same as the "cold" I know (record low: −24 °F (−31 °C)) -RunningOnBrains(talk)05:22, 2 June 2010 (UTC)[reply]
46 °F (7.8 °C)!?? Haha. I still wear shorts and a t-shirt in that kind of weather if there's not too windy! (admittedly, some neighbors think I'm crazy.)
Actually, the air coming out of your air conditioner could literally be colder than that. (Sure, your thermostat is set to something reasonable, but to achieve that it needs to mix some really cold air into your hot home.) APL (talk) 06:12, 2 June 2010 (UTC)[reply]
Air conditioners don't just cool the air, they also dry it, which makes it cool your skin more via evaporation. Since Baguio City, at an altitude of a mile above sea level in the Philippines, must be one of the most humid places on Earth, it can make a big difference. Looie496 (talk) 16:37, 2 June 2010 (UTC)[reply]
"Dirty dozen" fruits and vegetables
CNN.com has an article on fruits and vegetables that contain pesticides even after being washed. The article has a "dirty dozen" list and a "clean 15" list of produce. What is confusing is that while potatoes and lettuce are on the dirty list, sweet potatoes and cabbage are on the clean list. Why? There seems to be no simple rules of thumb that can help you figure out for what produce you should go organic. --173.49.15.136 (talk) 02:40, 2 June 2010 (UTC)[reply]
For sweet potatos, they may be assuming that people aren't going to eat the skin. That's what appears to separaten the clean vs. dirty foods to a large extent: whether people eat the outside layer. I like how they emphasize the number of different types of pesticides in the different types of produce. Wouldn't make more sense to look at the total amounts of pesticides, rather than the variety? Buddy431 (talk) 03:17, 2 June 2010 (UTC)[reply]
Who is applying so many different types of pesticide on the one foodstuff? I find it hard to believe that some foodstuffs contain up to 67 different pesticides. Caesar's Daddy (talk) 07:32, 2 June 2010 (UTC)[reply]
A lot of it's probably contamination from other types of produce grown nearby; a good wind and you've got on your plant whatever your neighbor put on his. Still, 47-67 different pesticides does seem pretty excessive. Is there anyone here with experience in this type of thing who can explain how, and how many, pesticides are typically applied to different types of food? Buddy431 (talk) 16:34, 2 June 2010 (UTC)[reply]
A "single" pesticide, may actually be a combination of multiple chemicals. Like how with roundup the article mentions how roundup itself is pretty safe, but it's extensive list of additives are the problem. It doesn't say how many it has, but if other pesticides are like that, that could easily increase the number. Just a guess. Ariel. (talk) 18:53, 2 June 2010 (UTC)[reply]
Terraformation of Mars
In this picture, they show an artists conception of the terraformation of mars. In stages 3 and 4, they basically just add more water, making the oceans bigger. What exactly is the advantage of that? Wouldn't it be better to have more land than oceans? ScienceApe (talk) 03:42, 2 June 2010 (UTC)[reply]
Water is also the most important greenhouse gas on Earth, and given how cold Mars is, covering a larger surface area with standing water might contribute to getting more water into the air to help support this warming. (Of course to get an ocean in the first place you already have to add something to the atmosphere to trap heat and keep the water from simply freezing.) Dragons flight (talk) 03:53, 2 June 2010 (UTC)[reply]
There are several reasons to have an ocean. First, the above-mentioned greenhouse effect. Second, water has a very high specific heat capacity, and because it is mostly transparent, serves as a giant heat sink, which keeps the earth's temperatures from fluctuating too much over the course of a day (currently, martian temperatures can change almost 100 °C (180 °F) in a day). Thirdly, if you hope to terraform a planet, and introduce large amounts of life, you're going to need large amounts of water.
Unfortunately, terraforming Mars is unlikely to work. Mars' low mass means that, unlike on earth, important molecules such as nitrogen, oxygen, and, yes, water vapor can escape its gravity directly into space over time. Thus, we would need to constantly replenish any atmosphere we created there. This is of course ignoring the HUGE question of "where the heck to we get a planet's supply of water and oxygen from in the first place?" :-D -RunningOnBrains(talk)05:08, 2 June 2010 (UTC)[reply]
Atmosphere loss is only significant on a geological time scale. Unless the teraforming is planned to take billions of years, replenishing the atmosphere would be trivial compared to the task of creating one in the first place. --Bowlhover (talk) 08:11, 2 June 2010 (UTC)[reply]
To get the water there in the first place (assuming we don't find enough frozen down under the surface already) would probably require bombarding the planet with icy asteroids - no small feat! The whole issue is really about how to warm the planet up - doing that would make it possible to drive water and various gasses out of the soil. There is a lot of frozen CO2 at the poles, melting the icecaps could liberate that and cause enough of a global warming effect to heat up everything else. Once things are warm and there is a denser atmosphere (albeit mostly of CO2) then you'd want to add photosynthesis to the mix to turn CO2 into oxygen. But this is a crazily difficult project. Nobody should ever underestimate the difficulties. SteveBaker (talk) 11:53, 2 June 2010 (UTC)[reply]
Indeed, it is beyond our ability to really conceive of how it would be done. It's not going to be done in the next 25 years, and as far as technology is concerned any predictions more than 25 years ahead are little more than guesses. --Tango (talk) 16:18, 2 June 2010 (UTC)[reply]
There are arguments that the bulk of Mars' former atmosphere has not been lost to space, but rather has become locked up in its rocks because, unlike on the Earth, it does not get recycled by tectonic activity and active vulcanism. Theorists such as Martyn J. Fogg (a personal acquaintance) have proposed releasing significant quantities from appropriate strata by large scale thermonuclear engineering (i.e. bury huge H-bombs and set 'em off, preferably from a distance). Such released gasses might, by positive global warming feedback mechanisms similar to those we ourselves are arguably experiencing, cause further atmospheric evolution and result in a useful atmosphere quite rapidly, which might persist on a timescale of the order of 100,000 years or more before further replenishment became necessary. 87.81.230.195 (talk) 22:09, 2 June 2010 (UTC)[reply]
Linde's chaotic inflation: why only one level of bubble universes?
Andrei Linde's theory of bubble universes (I don't know if "bubble universe" is the acccepted term, but you know what I mean) describes them as emerging from an ur-universe (again, I don't know the accepted term). However, from what I can find on wikipedia, Linde's theory doesn't describe bubble universes emerging FROM the first "level" of bubble universes (The "level" emerging from the ur-universe); and the previous statement can be extended to bubble universes emerging from the bubble universes that emerge from the bubble universes that emerge from the ur-universe. In other words, Linde's description seems to involve only one "level" of bubble universes.
However, theoretically, bubble universes could emerge from within THIS ("our") universe, which implies at least one more "level" of bubble universes.
Have I misunderstood Linde's description? Or, perhaps, are further "levels" implied by Linde, but he leaves the implication unstated in order to simplify his description? Have others theorized further "levels"? If so, have they described this as being different from Linde's description, or just a corollary to it? 63.17.75.70 (talk) 04:04, 2 June 2010 (UTC)[reply]
In the more esoteric but serious sciences called cosmology and superstring theory, there are many theories of bubble universes, these theories sometimes overlap. For a popular science sampling, you could search for "bubble universe" at www.newscientist.com. It's one of their favourite topics, with repeated coverage. From what I've seen, most such theories imply sometimes a chain of bubble universes of unspecified length, towards both the past and the future, and sometimes that our universe bubbled forth from something "simpler" like some kind of vacuum that's not a typical universe in its own right. Sometimes the future bubbling out of our universe involves black holes, sometimes something catastrophic happening to the vacuum energy. It's all theory and you can really pick and choose. EverGreg (talk) 12:07, 2 June 2010 (UTC)[reply]
The diagram I saw (colloquium by someone... perhaps a former student of Linde?) showed sub-universes forming in a sort of bifurcation pattern, so that, if I understand your question right, this universe may already be seeding other universes, but obviously we don't see it (the bubbles form outside our dimensions). That would describe many layers of bubbles. The bifurcation diagram in chaos theory is a nice illustration, though the chaos cutoff doesn't occur I don't think. SamuelRiv (talk) 18:09, 2 June 2010 (UTC)[reply]
Lake Okeechobee
Is there any evidence such as shocked quartz, a gravity anomaly, and tektites in areas surrounding Lake Okeechobee in Florida, USA to suggest the lake might be the sight of an impact creator as far back as the end of the Cretaceous period? 71.100.8.229 (talk) 04:48, 2 June 2010 (UTC)[reply]
Lake Okeechobee hardly even exists, in a geological sense. It is 13 feet deep at its deepest point. There is a geologist named E. J. Petuch who suggested in the 1980s that the Everglades are the remnant of an ancient crater formed by a meteorite strike 38 million years ago, but he seems to have backed away from that idea, and I can't see any serious suggestions that apply to Okeechobee. The only thing in its favor is that it is sort of roundish. Looie496 (talk) 05:34, 2 June 2010 (UTC)[reply]
Reverse jet filter - pressure drop
Hi
Can anyone tell me how to calculate the pressure drop in a reverse jet filter if I know the volume flow rate and dimensions of the filter bags, no and material of bags etc
Thanks —Preceding unsigned comment added by 123.237.93.244 (talk) 05:36, 2 June 2010 (UTC)[reply]
Bernoulli's equation has a term for losses. It is that term which I am interested in. So if anybody has a model or correlation for obtaining the pressure loss in the reverse jet filter I will be grateful if you can share it. Thanks —Preceding unsigned comment added by 123.237.93.244 (talk) 09:44, 2 June 2010 (UTC)[reply]
Yes, it is an indicator of heart disease and diabetes (fatter=more likely . suprised?) specifically it's relation in general to Body mass indexegvery generalised or just google for "waste hip ratio +disease", and choose a disease.
Skinnys die too - and the percentage of death is close to 100% :)
LOL... the picture caught me by surprise... the article suggests that there is a correlation between WHR and offspring intelligence due possibly to more polyunsaturated fats the fetus needs for brain development. Maybe the real reason is that the fetus just wants to find ways to attract a mate with large quarters. :-] 71.100.0.241 (talk) 15:15, 2 June 2010 (UTC)[reply]
more[45] suggests 0.95 for men and 0.80 women is a good bet, these figures are for specific causes of death , this [46] for all causes of mortality death rate increases with waste to hip ratio.87.102.114.166 (talk) 13:11, 2 June 2010 (UTC)[reply]
When I placed copper in a solution of iron(III) chloride, the brownish yellow solution turned green. Is it due to this oxidation reaction: Cu + 2 FeCl3 → CuCl2 + 2 FeCl2 Thank you. --Chemicalinterest (talk) 11:14, 2 June 2010 (UTC)[reply]
Think so Fe3/Fe2 standard potential is 0.77V , Cu2/Cu is 0.34V - the reaction would go, copper (II) chloride is green , ferrous chloride is pale. The potentials for chloride complexes are different, and I haven't bothered to find them since there's no big difference between copper and iron in this respect.87.102.114.166 (talk) 12:35, 2 June 2010 (UTC)[reply]
That's where I got my idea from; it was used as a copper etchant. It is unlike other metal-metal salt redox reactions in that another metal is not formed. I didn't see any copper(I) chloride intermediate like they stated in the article. --Chemicalinterest (talk) 13:33, 2 June 2010 (UTC)[reply]
I don't think the CuCl will be present in large amounts - it might not dissolve depending on the concentration of Cl- in solution. There might be some on the surface of the copper - eg use copper + FeCl3 dilute - remove the copper and wash the surface with (pure) water - a patina of CuCl (might) be present - any CuCl2 would be washed away by the water.
I perhaps did not make myself clear in a previous question regarding Phenylephrine, which is given to dilate pupils and has the side effect of restricting blood vessels and Simvastatin, which is given to reduce high Cholesterol which is the intended effect. Although there is no direct interaction between Phenylephrine and Simvastatin for a drug interaction checker to find it does not appear that any drug interaction checker will also look for the combination of blood vessel restriction from high Cholesterol and from the side effect of Phenylephrine which could be deadly. Is there a program or method which checks for these types of deadly interactions since drug interaction checkers appears to ignore such interactions? 71.100.0.241 (talk) 13:11, 2 June 2010 (UTC)[reply]
Because I can find all sorts of drug interaction and WHR and BMI warning check sites on the Internet but not any that warn of this problem. 71.100.0.241 (talk) 16:49, 2 June 2010 (UTC)[reply]
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.--Tagishsimon(talk)16:04, 2 June 2010 (UTC)[reply]
History of Science: What did Islamic Science invent or discover?
Does anyone on Wikipedia, have a list of scientific discoveries that can be directly attributed to scientific researchers working in the Islamic world?
Hmm, Reading that led me to a question on a tangent...
Could the Islamic World have developed a self-contained powered vehicle before the Industrial Revolution in Western Europe?
Sfan00 IMG (talk) 21:37, 2 June 2010 (UTC)[reply]
Hero invented a cart that moved around by itself, the path could be programmed by winding a string round pegs on a barrel. Dmcq (talk) 21:59, 2 June 2010 (UTC)[reply]
A steam engine - probably not able to make a boiler that withstood the pressures, and more importantly make pistons to the correct accuracy - but maybe they could have if they'd tried. Similar problem with internal combustion
Electrical - this seems more likely - they almost certainly had the battery - I assume the knew about magnets - however I don't thing they had made the connection between electricity and magnetism necessary to - make big magnets, and make motors.
I'm not entirly sure an Arab steam engine is as implausible as you suggest, given that 'distillation' was a chemistry technique discovered in the Arab world (and would thus have needed appropriate vessels).
The articles linked also note that there were automata that ran on steam so...
I'm not saying that the self propelled vehicle has to be 'useful' ..
Sfan00 IMG (talk) 22:33, 2 June 2010 (UTC)
Other forms of power...
- Water...
- Sand ...
Clockwork mechanisms - Comments on the #wikipedia-en IRC suggested mechanical clockwork power needs a coil spring which would
need a certain level of metalworking. That said, simple mechanical power storage like a twisted cord could be built on fairly
simple technology...[reply]
density of liquid mixture
i would like to know how do we calculate the density of liquid mixture.for eg how do i calculate density of 40 % ethanol v/v?we know the density of absolute ethanol and that of water but how do we apply this knowledge to calculate density of the mixture?please guide. —Preceding unsigned comment added by 180.149.53.9 (talk) 19:40, 2 June 2010 (UTC)[reply]
It's not easy or impossible - you can estimate the density by averaging the densities of the components eg for 40%v/v ethanol water the density would be estimated to be 0.40 x density ethanol + 0.60 x density water.
The actual figure may be different due to the way different shaped molecules fit together as well as short range bonding interactions that differ between different types of molecule, and other factors.
It's separate from miscibility...the question (and solutions (sorry:) ) offered apply for any ratio that does give a solution, even if the components are not soluble at other/all concentrations (miscible). DMacks (talk) 20:12, 2 June 2010 (UTC)[reply]
The gory math for "actual" (non-"ideal") liquids is in our volume of mixing article--the intro/definition gives a nice qualitative overview (and specific example for ethanol/water) and then quickly gets to illustrating just now "not easy" the real situation is. DMacks (talk) 20:09, 2 June 2010 (UTC)[reply]
The deviation from simple "sum of parts" is noticeable enough for ethanol/water that there are official tables for converting measured density of such mixtures into their component ratio--wouldn't need that if it were directly additive because could just solve the linear combination I guess? DMacks (talk) 20:20, 2 June 2010 (UTC)[reply]
(EC with all above) For this example you would take the average of 4 parts ethanol and 6 parts water (since that is what it is composed of. The density of water is 1 g/cm3 and ethanol is 0.789 g/cm3. It would come out to (1 g/cm3·6) + (0.789 g/cm3·4) = 9.156 ÷ 10 = 0.9156 g/cm3 --Chemicalinterest (talk) 20:12, 2 June 2010 (UTC)[reply]
i have black plumbers putty sealing my bathroom sink. my sink handle was creaking so i sprayed some pam on it. the next day the pam appeared to eat away the plumbers putty and turn it brown. how is this possible? --Alexsmith44 (talk) 19:53, 2 June 2010 (UTC)[reply]
What's 'pam' did you mean PAM (cooking oil) ? If so the oil in 'pam' will have diluted/dissolved the linseed oil in the Plumber's Mait
eg as an experiment add oil (any) to putty - you'll see that it gets thinner and more runny the more you add.
yes i mean PAM (cooking oil). even if the pam dilutes the linsead oil why does it turn brown? and how does it eat away at it if the outer layer is hard? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 22:04, 2 June 2010 (UTC)[reply]
yes - putty goes hard over time - it may be evaporation, though it may also be polymerisation of the linseed oil - nevertheless hard things can be softened by things that dissolve them.
As for the brown colour - it was black before? Maybe the spray is diluting or washing away the pigment (v dark brown = black). It's difficult to say when I can't see it.
Have you got any spare putty - if so put a little in some oil and see what happens - it's possible that the colour in it will leach out (like dyes running from clothes in the wash). There still might be another explanation.
If you get stuck here you could as a last resort contact the manufacturer of the putty - they might even be interested that the colour is fading if its a flaw in their product.87.102.114.166 (talk) 22:10, 2 June 2010 (UTC)[reply]
Trigonal Bipyramidal Molecular Geometry
Hello. How was the trigonal bipyramid derived as the shape that allows bonding electrons stay as far from each other as possible? The bond angles in tetrahedral molecules equal. Why can't trigonal bipyramids? Thanks in advance. --Mayfare (talk) 21:35, 2 June 2010 (UTC)[reply]
Well we all know that the sun is mostly hydrogen. But hydrogen is invisible, and when hydrogen burns, it burns invisible too I believe. So what exactly are we looking at when we look at the sun? ScienceApe (talk) 22:24, 2 June 2010 (UTC)[reply]
Thermal Radiation, essentially. Anything with a temperature above absolute zero "glows". That is, it releases electromagnetic radiation at a variety of wavelengths dependent on how hot it is. Humans glow mostly in the Infrared range. The sun glows across a wide range of wavelengths, including Visible light. Buddy431 (talk) 22:36, 2 June 2010 (UTC)[reply]
Contents of Organic Pesticide
I just used an organic pesticide that contains the potassium salt of various fatty acids as its main ingredient. Will this actually kill/repel/do something to insect pests or did I just waste my money on some oily, salty water?24.88.87.41 (talk) 22:41, 2 June 2010 (UTC)[reply]
Please do your own homework.
![[43]](http://www.socalvalue.com/airace/stuka/ju87b_cross.jpg){kind=link}
