Wikipedia:Reference desk/Archives/Science/2010 June 19

= June 19 =

Ammonia
What's a chemical which decomposes ammonia but which is harmless to humans? --75.25.103.109 (talk) 00:30, 19 June 2010 (UTC)
 * Sodium bicarbonate: it reacts to form sodium ammonium carbonate, which is harmless. --Chemicalinterest (talk) 00:49, 19 June 2010 (UTC)
 * sodium ammonium carbonate doesn't really exist - carbonate is too basic - so it will deprotonate ammonium.
 * A mild dilute acid will convert ammonia to a salt - eg citric acid will form ammonium citrate - which will get rid of the ammonia smell, but does not decompose the ammonia.87.102.32.15 (talk) 02:36, 19 June 2010 (UTC)
 * It only deprotonates ammonia partially, so there is still a little odor. Try reacting smelly vinegar with smelly ammonia to produce the faintly odored ammonium acetate. --Chemicalinterest (talk) 10:54, 19 June 2010 (UTC)


 * Urine contains urea, which breaks down into ammonia. See also the urea cycle.  Of course, in high enough concentrations, any substance can be harmful to humans.  Nimur (talk) 19:12, 19 June 2010 (UTC)
 * Think they wanted something that decomposes ammonia, not decomposes to ammonia. Not sure now..83.100.252.174 (talk) 21:27, 19 June 2010 (UTC)
 * Vague definitions of harmful aren't needed here; he is obviously asking whether something that is not very toxic. --Chemicalinterest (talk) 20:09, 19 June 2010 (UTC)
 * Decomposes ammonia by removing odor, etc. --Chemicalinterest (talk) 22:41, 19 June 2010 (UTC)

Production of carbon tetrachloride
Can carbon tetrachloride be made by burning a candle in chlorine gas? In oxygen it forms carbon dioxide. --Chemicalinterest (talk) 00:54, 19 June 2010 (UTC)
 * Based on the article you linked, specifically the section on synthesis and the chlorination article it cites, one can generate CCl4 through oxidation reactions using chlorine gas. However, those references suggest that one must use more specific reactants and conditions than simply applying heat to a candle in a chlorine gas atmosphere to obtain the desired products in substantial quantities.  -- Scray (talk) 04:06, 19 June 2010 (UTC)
 * I would imagine that, if you burned a candle in chlorine gas, you would get all sorts of chlorinated products (including some carbon tetrachloride). To get a good yield of pure(ish) carbon tetrachloride, you would need a more specific reaction, such as the chlorination of methane mentioned in the article. Physchim62 (talk) 11:47, 19 June 2010 (UTC)

Potato Chips
How do potato chips companies get their chips crisp, even when they are the baked kind? When I thinly slice mine and cook whether it is frying or baking they come out like au gratin potatoes? —Preceding unsigned comment added by 71.137.252.51 (talk) 03:38, 19 June 2010 (UTC)
 * I don't think you can do the baked kind at home -- they actually powder the potatoes and mix them with other stuff to get something that will be crispy when baked. For the fried ones, it's simply a matter of frying them for a long time at a relatively low oil temperature -- there's an amazing amount of water in potatoes and you have to get it all out or your chips will be soggy. Looie496 (talk) 05:00, 19 June 2010 (UTC)

I haven't made potato chips, but when I fry French Fries, I get them quite hard and crispy. My method is to have plenty of oil to completely, really really submerge whatever you're frying (aka deep frying). Then you have to get the oil really really hot. You should have it on maximum heat on your stove's largest flame (if you have different sizes) and test the oil by dropping a single drop of water into it. If the water does not sizzle IMMEDIATELY when it hits the surface of the deep oil, you have to wait for the oil to get hotter. (when it's not hot enough, the drop of water will fall in, and only a moment or two later cause a reaction. you have to then wait for the oil to get hotter.)  Once the oil is really really hot, so that a drop of water sizzles onto it (you should be testing every minute or two), you drop on whatever you're deep-frying, in this case potato chips: STAND BACK! It will splutter and sizzle like hell when you put the stuff in. But then it will settle down (you keep it on maximum heat) and just fry. You should be frying for about 4-8 minutes, you can stir occasionally, the oil won't pop out at you (juts don't get any water in it), all of this is on your stove's maximum heat, and you check that it's done by the color: your chips shoudl be "golden brown". When they are, turn off the heat and carefully remove the chips onto a kitchen towel (bounty, etc) or you can strain them with a strainer, leaving them oilier. Now, one thing is a little bit of oil will be all over your stove, so don't remove the pan until you've turned off the flame (and, if it's an electric stove, waited for it to cool) as it could ignite the oil - this happened to me. That's about it. So, my advice is really the opposite of the advice to "cook slowly for a long time". Then again, I haven't fried chips yet, so who knwos if this will work :) 92.229.14.159 (talk) 12:03, 19 June 2010 (UTC)


 * Harold McGee's On Food and Cooking explains both styles of cooking them. He says factory made crisps are cooked at a consistent, high temperature (~170C) for 3..4 minutes (they're on a submerged conveyor). Home cooked crisps (and factory made "kettle chips") are made in batches, with the oil starting at ~120C and rising to 175C in 8..10 minutes.  He explains how the differences in the water and protein behaviour in these two environments account for the kettle chips being harder; this latter method largely resembles the double-frying method that's commonly used for making fully-fledged Belgian fries (example).  As that recipe I cited notes, don't dump in such a massive lot of slices that the oil temperature plummets - use small to medium sized batches.  In general, different cultivars have different water and starch content, so experimenting with locally available types is a good idea.  It's very common to dry the cut potato before frying (to reduce spitting and promote rapid caramelisation) and for some cultivars people wash the cut slices before drying (to reduce excess starch) - I've heard of people who towel dry the cut slices and them leave them out for a couple of hours to really dry out (but overdo this and they'll burn, or disintegrate and contaminate the oil). -- Finlay McWalter • Talk 14:17, 19 June 2010 (UTC)

sperm sorting
I just want to ask a question about sperm sorting. I am not great with negotiating computers so I hope I am doing this right. I understand sperm sorting can be used to determine sex. I am wondering if it would also work to help males with balanced chromosome translocations. Up to 60% of an affected male's sperm will produce miscarriages. Since sex determination looks at the chromosomes or in some way sorts the x from the y sperm, I thought it might work for this too. Any help you can give me will be much appreciated. —Preceding unsigned comment added by Sallygartner (talk • contribs) 04:23, 19 June 2010 (UTC)
 * Have you read the obvious article Sperm sorting? Nil Einne (talk) 10:27, 19 June 2010 (UTC)

Yes, I have read the article. This does not specifically say it would help with chromosome problems. —Preceding unsigned comment added by Sallygartner (talk • contribs) 15:27, 19 June 2010 (UTC)
 * Well the article explains how sex sorting works which you seemed confused about. The sperm are dyed and given a different charge depending on amount of dye absorbed (which varies because of the differing amounts of DNA the dye binds to).
 * So if the sperm have a differing DNA complement, e.g. lack part of one or more chromosome (nullisomy), you may be able to detect them in this way (in particular if the X sperm have what seems a complete complement), but if the sperm chromosomes contain balance translocations, the DNA complement will be the same. seems to discuss this somewhat although you'd need a subscription.
 * The article also mentions "DNA damage in sperm cells may be detected by using Raman spectroscopy. [1] It is not specific enough to detect individual traits, however.[1]" From the ref  it doesn't appear this will help with balanced translocations much since it's detecting DNA damage.
 * Nil Einne (talk) 16:05, 19 June 2010 (UTC)


 * This procedure exposes spermatozoa to a fluorescent dye (Hoechst 33342) and ultraviolet light? Both of those seem like things that could cause chromosomal or genetic damage.  This issue seems to have been brought up letters to the journal Human Reproduction.  This 2005 article states in its title, Hoechst 33342 stain and u.v. laser exposure do not induce genotoxic effects in flow-sorted boar spermatozoa, but I'm unconvinced.   Nimur (talk) 19:22, 19 June 2010 (UTC)


 * I agree with you Nimur; the latter paper is pretty unconvincing. (The fulltext appears to be a free download.)  Their statistics on chromosomal anomalies and sister chromatid exchanges are based on just eight piglets (four stained and four unstained, Table 2), and the amount of scatter in the data values suggests that they desperately need more data to get reliable estimates of the means.  While none of their data are significant at p < 0.05, you really wouldn't expect it to be unless the effect size was enormous. TenOfAllTrades(talk) 22:39, 19 June 2010 (UTC)

why do gas (petrol) stations have the same characteristic roof over the filling area?
Why do gas (petrol) stations all have the characteristic roof (or covering) over the filling area. Specifically, it is flat, held up on pilons, and of a rectangular or other very "square" (right angled corners) footprint. There are many types of roofs on many buildings, but only gas stations have this type as a rule - why? Thank you. 92.229.14.159 (talk) 12:10, 19 June 2010 (UTC)
 * Maybe they are mass produced. --Chemicalinterest (talk) 12:12, 19 June 2010 (UTC)
 * Well this one doesn't. Anyway while I don't know the specific answer to the question I would guess there are some considerations for a petrol station that many other buildings lack, in particular they need high roofs both to accomodate large vehicles and I presume to ensure fumes don't get trapped. The roofs also likely need a degree of fire resistance and perhaps resistance to the petrol (and probably some diesel) fumes. And they do need roofs so people can fill their cars up without getting wet and perhaps for other reasons. Ultimately it may be tradition and the lack of any real advantage to do something else as much as anything. Nil Einne (talk) 15:28, 19 June 2010 (UTC)
 * The roofs are serving the same purpose, so it's not surprising they use the same design. It's probably the best design for the job. It needs to be open on two sides for the vehicles to get in and out and it is beneficial for it to be open on the 3rd side as well for ventilation. That gives them two options for holding it up, columns or a cantilevered design. The former is far easier and there are no real disadvantages, so naturally they choose that. They have a choice between a flat roof or a sloping roof. Flat roofs are easier and cheaper, and clearly work, so naturally they choose flat roofs. Everyone (with a few exceptions, either due to different priorities or a different starting point) that designs petrol stations goes through the same thought process and naturally gets the same result. --Tango (talk) 16:01, 19 June 2010 (UTC)
 * Major gas (petrol) brands aim to provide a distinctive recognizable "welcoming" forecourt for self service. This corporate styling exercise includes a brand logo, pumps, card reader and uniform prefabricated roofs that provide shelter and lighting. Cuddlyable3 (talk) 16:29, 19 June 2010 (UTC)

I (op) don't buy these answers. They lead, perhaps, to the current design, but the current would be the second-to-last step following the above reasoning: the last step would be to add a sloping roof, so that the rain can roll off, instead of accumulating. Why isn't there such a slope? You can make it with $75 of corrugated sheet metal. There has to be something else. 92.229.14.11 (talk) 19:41, 19 June 2010 (UTC)
 * You're sort of right - see this image of a petrol station roof
 * Here's another (much more modern) exception to the rule.
 * Here's a hybrid of the two
 * Here's some more 'old school' flat roof types    street view of last one - looks flat - but has a slight internal slope and internal drainage this seems to be a fairly standard design where I am another - different shape but same internals
 * Note the internal drainage in most of these, I recommend you use an aerial photograph to look at the ones near where you live - it's clear that they are not just simple flat roofs at all; a key feature of the flat type roofs is central drainage that means less space taken up on the forecourt by drainage pipes (they can be close to the pumps near the pillars) - to do this with gutters only on the perimeter is slightly more complicated. 83.100.252.174 (talk) 21:16, 19 June 2010 (UTC)
 * In fact the old style flat roof seems to be going out of fashion (why?) example - I assumed this was a flat roof - becuase it used to be - but is now a sloping tiled roof - 83.100.252.174 (talk) 21:56, 19 June 2010 (UTC)
 * Flat roofs are bad because the rainwater doesn't run off quickly, and pools on the roof. This weight can damage the roof itself. --TammyMoet (talk) 07:33, 20 June 2010 (UTC)
 * C'mon, flat roofs are not level roofs, they always have a slight drainage slope either to one edge, two edges or toward a central gully. My belief has always been that the cost has driven the design. A huge, ugly, square, 'flat' roof is the cheapest option, don't waste money on fancy design if the fancy design is not going to attract custom - and when did anybody ever go down to the Whatever gas station because they loved the roof. Nah, you generally go to the cheapest or nearest. I think local building laws and regulations (in the UK) are now making for a better looking tiled and sloping roof. Caesar&#39;s Daddy (talk) 07:55, 20 June 2010 (UTC)
 * No you're right, they're not level but they're not really "flat" either. (I've owned one or two...) Water does indeed collect in the hollows, but the real issue is that rainwater (especially if the drain's blocked, or if you get really heavy rain) takes time to drain away. This weight causes the roof to fail eventually. Plus the fact that the tar cloth perishes over time, and needs replacing. Flat roofs may well be cheaper but take more maintenance than sloping roofs, and it may well be that this is the part that persuades people to replace them with a more traditional style roof. --TammyMoet (talk) 12:01, 20 June 2010 (UTC)
 * In snowy areas, how do they keep the weight of the snow from collapsing the roof? Do they heat it somehow, or does someone show up with a cherry picker and shovel it?  Googlemeister (talk) 13:51, 21 June 2010 (UTC)
 * The solution to both rain and snow problems is very simple: they build the roof strong enough to take the load. I live in an area that doesn't get much of either, and the building code for flat roofs calls for being able to support ten inches of water or its equivalent in snow.  Areas with serious snowfall require things to be even stronger. --Carnildo (talk) 00:37, 23 June 2010 (UTC)


 * Sloped roofs would lead to water dumping over onto people driving in and out, which they wouldn't like. That setup works okay on your house because it has an eaves trough and a fairly small footprint from which to collect the water. Matt Deres (talk) 14:52, 21 June 2010 (UTC

@ every other person in this thread, hypothesising and digressing does not answer the question!!! and I want to know the answer, ahhh if only I knew a petrol garage architect.

Spindle cell rhabdomyosarcoma
What is the outlook for metastatic spindle cell rhabdomyosarcoma? —Preceding unsigned comment added by 64.223.235.196 (talk) 13:47, 19 June 2010 (UTC) I am not asking for medical advice, just info. —Preceding unsigned comment added by 70.16.107.144 (talk) 14:10, 19 June 2010 (UTC)
 * Not sure if this will answer your question: "Two types of ERMS, botryoid and spindle cell rhabdomyosarcomas, tend to have a better prognosis (outlook) than the more common forms." Taken from this page. --TammyMoet (talk) 15:28, 19 June 2010 (UTC)

but does that apply to cases that have metastasized —Preceding unsigned comment added by 70.16.107.144 (talk) 16:15, 19 June 2010 (UTC)
 * I think that crosses the line into medical advice. Ask your oncologist. --TammyMoet (talk) 16:57, 19 June 2010 (UTC)
 * We understand that you are just looking for information, but honestly there is no way anyone on the Ref Desk can intelligently answer what the prognosis would be for any given person's metastatic cancer. There are simply too many variables.  There is some information in the soft tissue sarcoma article, and this reference discusses factors associated with prognosis in metastatic rhabdomyosarcoma, but your best option (as usual) is to ask a physician. --- Medical geneticist (talk) 19:36, 19 June 2010 (UTC)

Simulator
I need to simulate a microprocessor based system. The system would have some external devices interfaced to the microprocessor. What are the software that can do this type of a simulation ? —Preceding unsigned comment added by 218.248.80.62 (talk) 14:05, 19 June 2010 (UTC)


 * Nisan and Schocken's The Elements of Computing Systems has a free multi-layered simulator (here) which has both hardware level simulation and a simulated CPU. People have designed various components in the book's HDL (a simplified counterpart of VHDL), which the forum should be able to help you find. -- Finlay McWalter • Talk 14:28, 19 June 2010 (UTC)
 * Something from Category:Electronic circuit simulators might help. DMacks (talk) 16:51, 19 June 2010 (UTC)


 * The Computing Ref Desk would be a better place for this question, but in short, what you are hoping to do is to create an emulator. There is software available to use as a starting point, but I'm not very familiar with it. Looie496 (talk) 17:43, 19 June 2010 (UTC)


 * Thanks. I will be posting to the computing RD. 59.93.207.169 (talk) 06:36, 20 June 2010 (UTC)

Radioactive minerals on other planets?
Has any attempt been made to find commercially exploitable radioactive minerals on any of the moons or planets of our solar system? Solar powered robots and rail-guns could parachute this back to Earth for atomic power. What about Mercury- could its high density mean that dense minerals such as Uranium might exist there?[Trevor Loughlin]80.1.88.6 (talk) 14:36, 19 June 2010 (UTC)
 * No attempt has been made. There's vanishingly little possibility that it would yield product at a lower cost than on earth. --Tagishsimon (talk) 14:40, 19 June 2010 (UTC)


 * Why would anybody do that when uranium still is a fairly common element on earth? Dauto (talk) 15:26, 19 June 2010 (UTC)


 * Something like Uranium is best found on the Earth - it's already here in great quantities. The closest serious idea to what you describe is finding Helium-3 on the Moon (deposited there by solar wind) for use in nuclear fusion (we need to invent a fusion reactor that actually produces more energy than it uses for that to be useful, of course). Apart from Helium-3, there isn't much on the Moon that we can't get easier on Earth, so most ideas about exploiting resources of the Moon are about either using them on the Moon or in space. There are lots of ideas about asteroid mining, including sending resources back to Earth - it's much cheaper (in terms of energy requirement) to get resources from an asteroid to Earth than from another planet (or even the Moon) to Earth, due to weaker gravity. --Tango (talk) 16:16, 19 June 2010 (UTC)


 * Mining of elements or isotopes in space so that they could be brought back to Earth makes no economic sense, and probably won't make one for many more years. Mining makes sense, however, if the materials are to be used locally. To build a research colony on Mars you would want to use Martian materials as much as possible, rather than the ones brought from Earth. Same goes for the water and oxygen used by the colony. --Dr Dima (talk) 02:32, 20 June 2010 (UTC)
 * Uranium on Earth is more common then silver so it's not exactly hard to come by. And considering we don't even use mining robots and interplanetary rail-guns on earth, it doesn't seem like sending them to space is something that's going to be happening any time soon. Vespine (talk) 01:00, 21 June 2010 (UTC)
 * I think that uranium and other radioactive elements have been mapped on the moon by detecting the gamma rays emitted. This can only work where the surface is exposed in a vacuum. Space: 1999 describes what happened when too much radioactivity in one spot on the moon (in fiction). (and could only happen in a really far fetched non realistic fiction) Graeme Bartlett (talk) 11:43, 21 June 2010 (UTC)

Purpose of Addiction
Why can the body become addicted to certain substances and what purpose does this serve? Addictions don't seen to benefit the body in any way. So why does the body crave something? Here I'm talking about physical addictions, not psychological ones. Thanks! Stripey the crab (talk) 14:53, 19 June 2010 (UTC)


 * You probably want to read Substance_dependence, such as the Role of dopamine subsection. --Tagishsimon (talk) 14:58, 19 June 2010 (UTC)
 * The neurotransmitter Dopamine is closely associated with reward-seeking behaviors including basic desires for survival such as sex, eating and family, without which none of us would be alive. It is also involved pathologically in physical addictions. Human neurobiology has not evolved enough to be fool-proof. Cuddlyable3 (talk) 15:57, 19 June 2010 (UTC)
 * Expanding on that, I think the original poster has as a premise the idea that everything in the body has some purpose, which is untrue. The human body has various weird properties that don't serve a great purpose; they just didn't interfere with our ancestors enough to stop them from being able to breed.  See the "Evolutionary baggage" section of Evolution of the eye, or see Recurrent laryngeal nerve, a nerve that runs from your brain to your voice box to control it, but it idiotically goes down into your chest cavity first and then loops back up.  Comet Tuttle (talk) 16:02, 19 June 2010 (UTC)
 * Right, addictions are malfunctions of the biological reward system caused by putting substances into the body that it is not equipped to handle. They don't have a purpose any more than the breakdown of a car after you put water into the gas tank has a purpose. Looie496 (talk) 16:49, 19 June 2010 (UTC)


 * See, in real life turkeys won't come across heads stuck onto sticks to make love with. We're little different, evolution hasn't fitted us to resist all drugs purified in a laboratory where analogues have a useful purpose in the brain. Dmcq (talk) 19:00, 19 June 2010 (UTC)


 * It maybe because we are creatures of habit, and we resist change.  MacOfJesus (talk) 19:31, 19 June 2010 (UTC)


 * I think the answer to this question is a textbook example of proofs of evolution. It's a fundamental part of evolution, it perfectly explains why many of our biological systems are not perfect and often seem trivially fallible, cobbled together, or coopted or adapted from other purposes; because that's exactly what they are. Let see the creationists and ID-ers try to explain something like addiction, if there is one thing that addiction is NOT is intelligently designed. Vespine (talk) 00:45, 21 June 2010 (UTC)


 * Don't forget man has intelligence and free will, has an imagination to plan for the future. Please see C. G. Jung on the section under addiction.  Some people managed a complete cure.  MacOfJesus (talk) 14:13, 21 June 2010 (UTC)


 * For what it's worth, if I understand correctly, Jung never tried to validate any of his notions by means of testing. I mean, he never even tried.  He was far from the scientific method.  Comet Tuttle (talk) 18:36, 21 June 2010 (UTC)


 * If you look at the page I suggested under the section, you would find he ran clinics and had some addicts to treat. His methods and advice has proven itself as his patients went on to found the AA and The Oxford Group.  He had a distinct empathy with the patient, respecting their dignity.  Have you looked at the steps?  Time has proved them.  And as I said there has been some complete cures.  Jung was top in his field and obtained a Ph.D from the top European University, and is today considered the Master of his Science, and one we go back to time and time again.   His methods are the ones used in every such Clinics today!  The methods you suggest in testing and validating would be counter-productive in the human subject.  MacOfJesus (talk) 22:54, 21 June 2010 (UTC)


 * It is unlikely that any person would purposely become an addict, but a drug dealer might contribute to the addiction of another person and have the purpose of deriving continued business from the addict. (http://www.multilingualbible.com/2_timothy/3-6.htm; http://www.multilingualbible.com/2_peter/2-19.htm) -- Wavelength (talk) 00:55, 22 June 2010 (UTC)

Experiments in quantum mechanics?
What aspects of quantum mechanics have actually been experimentally verified?

If that's a contentious question with a debatable answer, where might one find a list of the most well-known experiments of quantum mechanics? 96.255.178.76 (talk) 15:56, 19 June 2010 (UTC)
 * If I may add the contra-positive: what open questions still exist in quantum mechanics that have not been experimentally verified? Zunaid 16:20, 19 June 2010 (UTC)
 * The double-slit experiment is a famous one that demonstrates wave-particle duality, which is a fundamental feature of quantum mechanics. Pretty much all of quantum mechanics has been experimentally verified - that's a requirement to be considered a scientific theory. --Tango (talk) 16:25, 19 June 2010 (UTC)
 * Many of these experiments are still open to contending interpretations. Cuddlyable3 (talk) 16:35, 19 June 2010 (UTC)
 * Indeed. Things like the Copenhagen interpretation aren't theories, they are interpretations of theories. Theories have evidence for them, interpretations don't (once you get significant evidence for an interpretation over the others, that interpretation just becomes part of the theory and you stop using the word "interpretation"). --Tango (talk) 16:40, 19 June 2010 (UTC)


 * Spin (physics) has been confirmed experimentally - so much so that it's used in NMR spectroscopy, Electron paramagnetic resonance spectroscopy, as well as Magnetic resonance imaging. The Stern–Gerlach experiment is the classic experiment. These are examples of quantisation of spin.


 * Quantum tunnelling is an example of an experimentally obtained results that are explained in terms of a quantum mechanical wavefunction. I'm not aware of other explanations - but that doesn't mean they don't exist - 'QM' represents a good theoretical basis for this phenonoma though.83.100.252.174 (talk) 16:52, 19 June 2010 (UTC)

The list is too long even to summarize. Our article on Theoretical and experimental justification for the Schrödinger equation is probably the best resource here as far as I can see, but it is written at a pretty advanced level. (The Schrödinger equation is the basic mathematical formulation of quantum mechanics). Looie496 (talk) 16:54, 19 June 2010 (UTC)


 * Quantum mechanics is a rather wide umbrella term that can cover any theory in physics which is based on the principles of the wave function, gauge symmetry and quantum field theory. We have quantum mechanical theories of three of the four fundamental forces - electromagnetism, the strong force and the weak interaction. All of these have been extensively tested. In particular, the quantum theory of electromagnetism, quantum electrodynamics, has been verified to a higher degree of precision than any other theory in physics, I think. These quantum theories together make up the Standard Model of particle physics. A confirmation of the existence of the Higgs boson would fill one of the few experimental gaps in this model. However, what we lack is a quantum mechanical theory of gravity. There are various candidate theories, but each of these is either inconsistent with known facts, too vague to be testable, or not testable with current technology. Gandalf61 (talk) 16:55, 19 June 2010 (UTC)


 * Quantum mechanics (like special relativity) is a simple set of rules that one requires one's physical theories to follow. It's not a physical theory by itself. A theory that follows the rules might be called "quantum" (or "relativistic"). The basic quantum-mechanical (and relativistic) rules are ludicrously well confirmed; basically every high-energy physics experiment in the last century tests these rules. As for individual quantum theories, it depends on the theory; it's the same as asking "how well has physics been tested?".


 * Gauge symmetry is not an intrinsically quantum idea. It happens that the most famous gauge theory (the Standard Model) is also quantum, but Maxwell's electrodynamics is a U(1) gauge theory, and the equivalence principle in general relativity is related to the gauge principle. -- BenRG (talk) 18:26, 19 June 2010 (UTC)

An experiment proposed by David Deutsch in which an observer is able to reversibly forget the outcome of a measurement, while not forgetting that the measurment was performed, thus disproving the Copenhagen Interpretation (because the measured system would be back in the original state, rather than its wavefunction having irreversibly collapsed because of the measurement), has not yet been performed. Count Iblis (talk) 16:58, 19 June 2010 (UTC)


 * David Deutsch's Request for a Photon Experiment Cuddlyable3 (talk) 17:12, 19 June 2010 (UTC)
 * As far as I can tell that page was not written by Deutsch but by some random Internet crank. Deutsch himself is also kind of crankish. -- BenRG (talk) 18:26, 19 June 2010 (UTC)


 * That experiment was not designed to test quatum mechanics. I t was not designed to test an interpretation of quatum mechanics either. It was designed to test a misunderstanding view of an interpretation of quatum mechanics. Neither quantum mechanics nor any of its main stream interpretations has nothing to say about observers forgeting the outcome of an experiment. Dauto (talk) 02:18, 20 June 2010 (UTC)


 * Forget the cranck experiment. Quantum mechanics in the MWI does make an unambiguous prediction in case of the thought experiment proposed by Deutsch. Count Iblis (talk) 17:25, 20 June 2010 (UTC)


 * You can experimentally verify quantum theory any time you want. The only problem is that for the more complicated parts, it's difficult to take accurate enough measurements and you have to spend a lot of time learning how to do the math.  If you pursue a university-level course in physics (which is an excellent idea, and I encourage everyone to try!), electronics, optics, certain branches of chemistry, and so on, you will undoubtedly have class and laboratory work where you apply quantum theories to your measurements.  As has been stated above, "quantum mechanics" is an umbrella term for an entire class of mathematical methods that describe certain physical measurements (typically measured in the regime of atomic or sub-atomic systems).  Probably the simplest experiment, which is even conducted in introductory chemistry or physics classes in high school, is measuring photoelectric effect.  Here is a version you can probably do with home equipment.  I recall other experiments in physics, ranging from measuring mass-to-charge ratios (Oil drop experiment); magnetic field effects on optics; double slit experiments; and so on.  Where I went to school, we had an undergraduate physics lab where we did basic quantum physics experiments, and as we got more advanced, we had access to a nuclear reactor, a TUNL nuclear lab, a semiconductor fab, and so on; so as undergraduate physicists, we had the opportunity to do some serious nuke and quantum experimental lab work.  As I got farther and farther down in size/farther up the energy spectrum, experimental verification required need bigger and more expensive devices; and after awhile I lost interest in independently verifying every theory.  Inevitably, you have to accept on faith that just about all of quantum theory has been pretty darned well confirmed experimentally by other scientists - there simply isn't enough time to verify the whole of the modern body of scientific knowledge yourself.  If such experimental facilities are unavailable, there are dozens of exercises you can do as a student to experimentally verify the basic quantum principles yourself.  One of the big "transitions" in comprehending modern physics is understanding exactly what is meant by an "observable." In physics, especially in quantum mechanics, the whole purpose is to sit around and think about invisible, tiny concepts that are literally on the edge of "existing."  (What exactly is energy, for example?)  You have to figure out some way to do something so that you end up making an observation that either verifies or refutes some mathematical representation of what you thought is occurring.  In other words, if somebody tells you that "atomic nuclei exist" or "atomic nuclei don't exist", how do you design an experiment to prove this one way or the other?  (Hint).  As you refine this experiment farther and farther, you start describing more details of the atomic nucleus, and applying more sophisticated methods until you explain every last decimal-place of accuracy that you can measure with your machine.  After just a few decimal places (for most experiments), you need quantum mechanics.  Invariably, at some point, you reach the limit of your experimental accuracy (and have to find someone to pay for a better machine).  Or, you become an applied physicist and worry about different kinds of problems.  Nimur (talk) 20:42, 19 June 2010 (UTC)
 * What exactly is energy? Cuddlyable3 (talk) 22:51, 19 June 2010 (UTC)
 * Energy is a thing that is quantized. It affects other things, an effect we call work.  Energy can have a position (also quantized), but its position is best described by a wave-function; so its position is uncertain with respect to the amount and character of the energy.  We know from experiment that energy is a conserved quantity in all interactions - or at least, if energy disappears, something else manifests to keep things balanced.  Like all questions of physics and philosophy, this question at some point will devolve into "... and here is a set of data we measured experimentally, can you see the pattern?"  Nimur (talk) 15:18, 20 June 2010 (UTC)
 * Using the links I see you wrote "Energy is a Concept that (is a) Photon. It affects Matter, an effect we call Work (physics)." But was energy around before there were any humans to have concepts i.e. which came first, the energy or the concept? Does a falling body receive energy from gravity and if so are photons involved? Cuddlyable3 (talk) 21:21, 20 June 2010 (UTC)
 * Well, a photon is a quantum of energy for a particular kind of interaction. And, strictly speaking, a photon isn't "energy" - it's a particle that carries energy during an electromagnetic interaction.  It was sloppy of me to "imply" that all energy is in the form of photons - this is clearly not the case.  In my defense, I never actually said that, but your expansion of my wikilinks demonstrates that my explanation was not clear.  There are actually many different kinds of quantized energy - phonons, photons, and so on.  You can even say that other things "are" energy, if you want - in a sense, a hadron is also a bundle of "energy", combined in a particular way out of even more elementary "things" (I'm reluctant to use the term "particle" because even elementary particles seem to be nothing more than particular immutable combinations of energy, momentum, spin, and so on).  Combinations of these "things" result in more macroscopic properties, like mass, charge, velocity, and so on.  As far as your other question - energy, like the rest of the universe, existed before humans ever conceived or explained it.  And as for gravity - gee, that's a tough one, because we still don't have a quantum theory of gravity.  But, I wouldn't be surprised if we are able at some point to come up with an unencumbered, experimentally verifiable way to say that "yes, when an object changes its position relative to another object with mass, an exchange of gravitational energy is mediated by a particle."  At present, we have no such theory that can tie up the loose-end implications of such a statement.  At present, the best we have is general relativity, which does not (in its vanilla incarnation) imply that a particle exchange mediates the warping of space-time to cause the effects we call gravity.   Nimur (talk) 22:46, 20 June 2010 (UTC)
 * By far the coolest experiments which both verifies the predictions of some models of QM and actually falsifies the predictions of some other models of QM are the Bell test experiments, which test Bell's theorem. It takes quite a bit of work for someone new to figure out what is going on there, but the results are actually quite profound. The short answer is that you can even determine experimentally between certain interpretations of quantum mechanics (what had been long thought to fall under the heading of "philosophy" more than physics—like the Einstein/Bohr debate), much less between QM and the "classical" theories (the latter of which is so old of an experimental achievement as to no longer be interesting). --Mr.98 (talk) 07:21, 20 June 2010 (UTC)