Wikipedia:Reference desk/Archives/Science/2008 July 18

= July 18 =

Over-the-counter diet pills/supplements
Do any of these things actually work? Just browsing my usual online pharmacy site whilst making my monthly nicotine gum order and I stumbled across several claims about 'fat burning', 'fat binding' and 'speeding up metabolism' by various products (some 'herbal', some 'scientific') that sound somewhat improbable... --Kurt Shaped Box (talk) 00:04, 18 July 2008 (UTC)


 * In general, they're of variable safety but minimally effective. Many contain stimulants of some sort (caffeine, ephedra, etc.); stimulants have a long history of use in weight loss products (and plenty of side effects that have limited their legal availability--ephedra & fen phen, for example). "Herbal" stuff is almost assuredly worthless: at best it's an unknown dose of caffeine, at worst the unregulated product is laced with more powerful stimulants and compounds that can cause serious drug interaction issues/side effects. &mdash; Scientizzle 00:22, 18 July 2008 (UTC)


 * (edit conflict) We can't give medical advice. You should probably talk to your doctor if you are looking for a way to lose weight. Personally, I would be doubtful of such claims - the only kind of diet pill I can see working is an appetite suppressant. --Tango (talk) 00:24, 18 July 2008 (UTC)


 * No, I'm not looking to lose weight. I saw this stuff on the web and wondered how they manage to get away with making the sort of claims they are making about their products. It's quite common in UK pharmacies (real, brick and mortar ones too) to see products that I would personally file away in the quackery/placebo effect bin alongside the healing magnets and activated water. --Kurt Shaped Box (talk) 00:37, 18 July 2008 (UTC)


 * I think questions of efficacy can be handled without delving into handing out medical advice, but (of course) a physician would be an appropriate source of information regarding these products. Stimulants, by the way, are often appetite suppressants, having the duel effect of upping energy consumption while decreasing intake (and many unwanted effects, as well). I'd also note that, in the US, there is currently only one FDA approved, over-the-counter weight loss product: Orlistat. &mdash; Scientizzle 00:41, 18 July 2008 (UTC)


 * Interesting, thanks. Some of the pills sold on the site were described as being able to bind to fats in the GI tract, creating large, inabsorbable (is that a word?) molecules which will merely 'pass through'. Does that sound like 'bunk' to you? --Kurt Shaped Box (talk) 00:47, 18 July 2008 (UTC)


 * Orlistat does work to prevent fat absorption, so it's possible that in the UK there are similar things on the market that actually do that. However, its method of action is to inhibit an enzyme that makes fats readily abosorbable, not work as some sort of fat aggregator--that sounds psudoscience-esque (but without more information, I can't be sure). &mdash; Scientizzle 00:54, 18 July 2008 (UTC)


 * Incidentally, do they sell these in the UK? :) &mdash; Scientizzle 00:57, 18 July 2008 (UTC)


 * That page talks about them being on sale in the UK (in the last line), so I guess so... There's one born every minute. --Tango (talk) 01:06, 18 July 2008 (UTC)


 * (edit conflict) I've never seen them personally. I noticed the other day that my local pharmacy sells magnetic wristbands for arthritis relief though (FFS!). I've seen ear candles for sale in more than one place too. I'm currently reading through http://www.dietfraud.com/ - a lot of the stuff I've seen advertised does indeed sound like classic 'bunk', according to their writings... --Kurt Shaped Box (talk) 01:07, 18 July 2008 (UTC)


 * When you have a minute KSB take a wander round here, a place you might find interesting. Richard Avery (talk) 07:12, 18 July 2008 (UTC)


 * Heh, I was actually browsing through that site after I finished posting here last night/early this morning. It's amazing what some people will believe, isn't it? --Kurt Shaped Box (talk) 12:58, 18 July 2008 (UTC)


 * As someone pointed out somewhere (I forget exactly where), a lot of these things talk about 'unleashing the bodies natural healing abilities'. Magnetic wristbands often do, among others. Anyway, the point is... how would you describe the placebo effect? 79.66.90.252 (talk) 23:08, 18 July 2008 (UTC)


 * I'd say many of those might work in the short term, say by having you burn more energy as a result of taking a stimulant or causing you to eat less fat since now you crap your pants if you eat fat (because you're taking a fat binder that causes "anal leakage"). However, as soon as your body adapts and finds other calorie sources to make up for those lost, you likely will gain all the weight back and more. StuRat (talk) 21:25, 20 July 2008 (UTC)

Carbon dioxide benefit
What articles describe experiments using additional carbon dioxide to help grow more lush plants and what is the maximum percent concentration of CO2 that can be used? -- adaptron  (talk) 02:25, 18 July 2008 (UTC)
 * Photosynthesis might help a little. — CycloneNimrod Talk? 08:58, 18 July 2008 (UTC)
 * Also see Free-Air Concentration Enrichment, though those experiments are designed to test the general physiological and ecological effects of higher CO2 environments, not to look at deliberately using CO2 to increase agricultural productivity, which it sounds like you might be talking about. I'd also point you to Phytotron but it's just a single sentence right now.  --Allen (talk) 16:31, 18 July 2008 (UTC)

first human lunar mission
why does this NASA pdf expect the first human lunar mission a decade from now?

http://www.nasa.gov/pdf/54873main_budget_chart_14jan04.pdf —Preceding unsigned comment added by 71.147.39.139 (talk) 02:42, 18 July 2008 (UTC)
 * This question ignores the fact that the "first human lunar mission" occurred in the 1960's. Get real! Edison (talk) 04:37, 18 July 2008 (UTC)
 * exactly, why has NASA of all organizations ignored this fact in their pdf? —Preceding unsigned comment added by 71.147.39.139 (talk) 05:11, 18 July 2008 (UTC)
 * Apollo Moon Landing hoax conspiracy theories? Either that or Neil Armstrong, Buzz Aldrin and the rest are aliens - take your pick. Clarityfiend (talk) 07:18, 18 July 2008 (UTC)


 * Since the file in question shows the anticipated allocation of NASA's budget, "first human lunar mission" implies more than one future manned mission to the Moon is expected. --Bowlhover (talk) 08:13, 18 July 2008 (UTC)


 * I imagine that it was so obvious that they left off the "... after Apollo" bit :) &mdash; QuantumEleven 13:55, 18 July 2008 (UTC)


 * I think it's pretty obvious that they mean "first" only in the context of their new push to return to exploration as a primary goal. APL (talk) 14:14, 18 July 2008 (UTC)

Carbon dioxide risk
The article on Carbon dioxide states that for indoor levels of CO2, "Concentrations higher than 1,000 ppm will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration." ... "At 2,000 ppm the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches. The CO2 concentration between 300 and 2,500 ppm is used as an indicator of indoor air quality."

Can anyone confirm that since the article shows CO2 levels were 315 in 1960 and are 387 now there is a .004 exponential rate increase and that in 115 years levels will reach 600 ppm if this rate is maintained and there is no catastrophic change due to some unknown phenomenon? -- adaptron  (talk) 06:22, 18 July 2008 (UTC)


 * No, it's not currect to state that "since the article shows CO2 levels were 315 in 1960 and are 387 now there is a .004 exponential rate increase". In order to conclude from the measured data that the CO2 level was increasing exponentially and that it therefore would probably continue to increase exponentially, you would need many data points, not just two.  Or to reach that conclusion on theoretical grounds, you would need a sound theory to support the hypothesis.  --Anonymous, 21:20 UTC, July 18, 2008.


 * Our article on global warming shows projected levels between 541ppm and 971ppm by 2100, based on a large number of variables and potential actions. As the anon poster says above, you can draw any curve you want between 2 points, however your projection doesn't look all that far off. Franamax (talk) 21:30, 18 July 2008 (UTC)


 * It's always incorrect to assume unbounded exponential growth. I'm sure we've got an article on that logical fallacy somewhere. --Carnildo (talk) 21:32, 18 July 2008 (UTC)


 * Logistic function appears exponential at first. Here is an example applied to modelling wikipedia growth. -84user (talk) 22:30, 18 July 2008 (UTC)

Blood supply
If the blood supply is so important, why do institutions like the Red Cross base it on donations? Wouldn't it be smarter to pay people to donate? And if the shelf life is so limited, why don't they keep a DB of donors and ask them to donate in emergencies? Mr.K. (talk) 10:10, 18 July 2008 (UTC)
 * I believe Freakonomics discusses this sort of thing. Once you add a monetary incentive, you remove the incentive of the "feel-good factor" of doing a good deed, and you add an incentive to cheat the system somehow. Plus, you have to spend money on paying donors and running the payments system. 81.174.226.229 (talk) 10:55, 18 July 2008 (UTC)
 * Our article blood donation explains that it is World Health Organization policy for all countries to move to a volunteer-only system. I believe the thinking is that paid donation creates an incentive for poorer people to give blood, and on average they are less healthy people, hence the greater potential for disease to be spread. My guess is that in most developed countries donors' contact details are kept on a database (unless they take a privacy opt-out). That's certainly the case in the UK. Itsmejudith (talk) 11:00, 18 July 2008 (UTC)


 * As for a database of donors, I receive a text message every so often from the Irish Blood Transfusion Board telling me that the blood stocks for my blood group are low, and to go and donate. It may be the same in your country (?). Fribbler (talk) 11:02, 18 July 2008 (UTC)


 * No, but perhaps they are never low on my blood group (A neg.). Mr.K. (talk) 11:08, 18 July 2008 (UTC)


 * I don't donate personally but I've seen people receive cards before when there's a drive near where they live. My guess is O- donors may receive special requests when there's an emergency Nil Einne (talk) 07:44, 19 July 2008 (UTC)


 * On the other hand, I believe selling blood plasma is common in the USA. (All this reminds me, I need to donate again) AlmostReadytoFly (talk) 11:13, 18 July 2008 (UTC)


 * In France, the "reward" for donating blood is a breakfast/lunch afterwards, and sometimes a coupon for a free ice cream :) &mdash; QuantumEleven 13:52, 18 July 2008 (UTC)
 * In Ireland it's a bottle of Guinness (no joke) and a packet of crisps. Fribbler (talk) 13:54, 18 July 2008 (UTC)
 * Normally, in the US, the Red Cross or Lifeline Blood Services or whoever has free orange juice and cookies. Occasionally, they'll give away free t-shirts and other small prizes.  I think the last time that the Red Cross came to my workplace to get blood donations, they offered free tickets to the local minor league baseball team's games.  Dismas |(talk) 14:37, 18 July 2008 (UTC)


 * From what I know in the US from my experiences is that they usually give SODA and cookies, even though you're not recommended to drink it after giving blood. And there are often organizations (radio, police, frats, schools) that organize blood drives, and that's usually when you see the tickets and t-shirts. --Wirbelwind ヴィルヴェルヴィント (talk) 18:12, 18 July 2008 (UTC)


 * Who says soda is contra-indicated for recovering blood donors? It provides a much needed sugar boost. --Shaggorama (talk) 20:08, 18 July 2008 (UTC)
 * Tea and biscuits in England. Doesn't it provide a unique insight into our national cultures? Itsmejudith (talk) 21:18, 18 July 2008 (UTC)


 * The drinks and snacks aren't to thank you for giving blood, they're to stop you fainting on the way home! It's important to replace the fluids, etc. you've just lost. You sometimes get vouchers for ice cream in the UK - particularly in student towns, I think. Ben and Jerry's is a common way of bribing students to do things! --Tango (talk) 21:20, 18 July 2008 (UTC)


 * I guess soda would provide a sugar boost...if it weren't diet soda (at least at my local donor-center). DMacks (talk) 23:05, 18 July 2008 (UTC)


 * I would guess most of these gifts to donors are in turn donated by whoeever they're coming from so it depends somewhat on who's willing to donate gifts for drive organisers to give to donors. Nil Einne (talk) 07:44, 19 July 2008 (UTC)

How is body mass index really defined?
The article can't seem to make up its mind. Let $$m$$ be a person's mass and let $$h$$ be their height. Is BMI defined as the dimensionless number
 * $$\frac{m/(1\,\mathrm{kg})}{(h/(1\,\mathrm{m}))^2}$$

or as
 * $$\frac{m}{h^2}$$,

having dimension $$\mathrm{mass}/\mathrm{length}^2$$? You might say the distinction is unimportant, but I like to be precise in how I think about things. —Bromskloss (talk) 10:11, 18 July 2008 (UTC)

These units do not cancel $$\frac{kg}{m^2}$$ is the same as $$\frac{mass}{length^2}$$. Jdrewitt (talk) 10:21, 18 July 2008 (UTC)


 * The first example is dimensionless; he is explicitly dividing out the units. If my mass is 70 kg, the numerator of the first expression is (70 kg)/(1 kg) = 70, a dimensionless number.  The denominator works similarly.  The result of the division is thus also dimensionless.  To answer the question, I've never seen a BMI with units attached, so I would guess that it is a dimensionless number, as produced by the first equation.   But I have no source.  -- Coneslayer (talk) 11:19, 18 July 2008 (UTC)


 * Body mass index is an index, not a measurement. That is why it doesn't have units.  Unlike unit measurements where 1 meter is 1 meter regardless of who is measuring it, BMI is a statistical index based on the population.  If anything, it could have been designed as a percentile.  However, a simply index was chosen which is easily turned into a percentile. --  k a i n a w &trade; 12:08, 18 July 2008 (UTC)
 * BMI doesn't depend on the population, it's a number calculated from measurable properties of a person. What's considered healthy might depend on the population, but the number itself doesn't. The reason it isn't usually seen with units is simply because the units are always metres and kilograms, so there is no need to state them. --Tango (talk) 21:24, 18 July 2008 (UTC)


 * You are misreading what I probably miswrote. Perhaps the article states it clearer: "The body mass index (BMI), or Quetelet index, is a statistical measure of the weight of a person scaled according to height. As such, it is useful as a population measure only, and is not appropriate for diagnosing individuals." --  k a i n a w &trade; 03:31, 23 July 2008 (UTC)


 * BMI can be considered either as dimensionless or as having the unit kg/m^2. Take your pick between these two views:
 * (1) A person's BMI has the unit is kg/m^2 regardless of whether it's written. Dimensionless numbers result from comparing too identical types of quantities, such as two lengths or two velocities, so the units used in measurement do not affect the dimensionless number.  For the body mass index, on the other hand, only kg and m can be used without introducing conversion factors.
 * (2) If we make the simple assumption that a person's BMI is (weight/height^2)/(1 kg/m^2), the BMI would be unitless, and the index is indeed almost always reported without any units. --Bowlhover (talk) 09:09, 19 July 2008 (UTC)

A Possible Method for Tachyon Formation and A Possible Method for Superluminal information transfer
Today while I was reading an article on tachyons, I suddenly thought about tachyon pairs appearing beside a black hole due to quantum fluctuations, and becomes "real" being sent by Hawking Radiation, which the article said "real" tachyons do not exist. Is this method of tachyon formation possible? please reply! And, I also thought that humans could create a machine that ejects multiple tachyons at different rates and places, and another receiver collects the tachyons, and "reads" their shapes and converts them into pictures or words that are understandable by humans. Perhaps, the sender may be able to send a line of tachyons coded with Morse code(special thanks to Morse!) like telegraph, and the receiver receives the data and decodes the pattern of tachyons into understandable symbols or words. Is this method of superluminal information transfer possible? Please reply!!! —Preceding unsigned comment added by Superwj5 (talk • contribs) 13:18, 18 July 2008 (UTC)


 * You realize that tachyons are hypothetical particles? That is to say, no one has ever seen one, and they may not exist, and if they do, we don't really know their properties. Could someone do this? Uh, maybe? But you're not going to get any kind of a real answer to that here, because you're essentially asking about science fiction. -- Captain Disdain (talk) 15:24, 18 July 2008 (UTC)


 * Also, your "questions" have more "I have a crazy theory" than "I have a question" to them. It makes it very clear that you are looking for discussion, not references.  This is a reference desk.  If you simply want to discuss your theories, there are thousands (if not millions) of discussion forums on the Internet just for that purpose. --  k a i n a w &trade; 15:31, 18 July 2008 (UTC)


 * Our tachyon article indicates that there are theoretical arguments that tachyons would not permit superluminal communication. -- Coneslayer (talk) 15:34, 18 July 2008 (UTC)


 * I think you're being confused by two different uses of the word "real" in physics. Tachyons are not real in the same sense that Santa Claus is not real, whereas the particles in Hawking radiation are real in the sense that they're not virtual. -- BenRG (talk) 16:39, 21 July 2008 (UTC)

hypopthetical global warming
Hi. This is not homework, and is viewed from a theoretical standpoint. Consider 17°C (30°F) of global warming. What would happen to Earth's Flora and Fauna, its microorganisms, and humanity? What if this happened in 10,000 years? 4,000 years? 1,000 years? 600 years? 500 years? 300 years? Would we survive? Could negative feedbacks eventually bring on a cooling trend? What would happen with 5,000 ppm CO2? What about 60 metres of sea level rise? Thanks. ~ A H  1 (TCU) 17:26, 18 July 2008 (UTC)


 * That sort of temperature rise would lead to a major mass extinction event. There was a minor one associated with a 6°C rise 65 million years ago, which is the sort of rise expected soon with global warming (and all the older official estimates have turned out to be underestimates). Perhaps humans would survive, I'm not sure. It would make a good disaster movie. Dmcq (talk) 21:01, 18 July 2008 (UTC)


 * It's worth considering that before you consider "Could negative feedbacks eventually bring on a cooling trend" you likely have to consider how you got 17°C rise in the first place (if a negative feedback does kick in, why didn't it kick in earlier? Or did it already kick in but we somehow managed to release such an extreme amount of CO2 that we still managed to achieve such a rise?). I'm not sure but I think our current knowledge re: such an extreme rise is limited since must studies are concentrated on what is expected with what we're doing now or may be doing in the future rather then what conditions may lead to such an extreme rise (according to the latest IPCC "IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C". Of course we know that if we do have such a rise, it would be catastrophic Nil Einne (talk) 07:34, 19 July 2008 (UTC)


 * One of the possible causes of the Permian-Triassic extinction event, the largest extinction in Earth's history, is a temperature increase of 10 to 30 degrees Celsius (see http://news.bbc.co.uk/2/hi/science/nature/4184110.stm). Although the cause of the extinction is still not known with certainty, the scientists who proposed the above-mentioned warming as a hypothesis presumably had evidence that a 10-degree rise in temperature can cause 80% of species to perish.
 * 5000 ppm is 18 times the pre-industrial CO2 level. Earth's temperature rises approximately 3 degrees for every doubling of CO2 concentration, so 5000 ppm implies a warming of 12 degrees. Of course, positive and negative feedback systems would have a great impact in such an extreme climate.
 * As for sea level rise, http://merkel.zoneo.net/Topo/Applet/ is a crude interactive tool that displays geographical maps for any user-entered sea level increase.
 * Dmcq: I'm doubtful that Earth will warm by 6 degrees within any short period of time. Do you have a source?  --Bowlhover (talk) 08:42, 19 July 2008 (UTC)
 * Hi. Yes, IPCC predicts 1.4 - 5.8C of warming within 100 years, and 6C would still be catastropic as Six Degrees: Our Future on a Hotter Planet says 6C is all it took for the P-T extinction to occur, and please say if you're using C or F, and Fred Pearce's book With Speed and Violence: Why Scientists fear tipping points in Climate Change details that the Hadley Centre predicts upwards of 10C (21F) within 100 years. Thanks. ~ A H  1 (TCU) 18:32, 19 July 2008 (UTC)


 * Sorry about the 6C I'd been thinking of his lowest timescale of 300 years which considering there's lots of coal tars etc will be hard to avoid. I should really have stuck to the IPCC limit of 2100. However the IPCC does has 6C within its error range which is quite worrying. Dmcq (talk) 19:34, 19 July 2008 (UTC)


 * I would think the total amount of habitable land would be about the same. Portions of the tropics and coastal areas would become uninhabitable due to high temperatures or flooding, but, at the same time, vast areas of Canada, Greenland, Russia, Sweden, Norway, Finland, and even Antarctica, would become habitable.  The greatest threat to humanity might be indirect, as competition for those new resources could lead to global war.  StuRat (talk) 21:12, 20 July 2008 (UTC)


 * I think that most places inhabited now would become uninhabitable or unpleasant. The loss of species would probably cause ecological collapse and therefore mass starvation. 98.198.9.137 (talk) 14:47, 23 July 2008 (UTC)


 * It may be true that the total inhabitable area will not change much, but the current economy is adjusted to the current climate. If fertile farmland becomes unusable for farming, agricultural output would decrease, the associated industries would suffer, and a recession would occur until the economy adapts.  An economy established in Greenland or northern Canada would not produce in great quantities until far into the future.  --Bowlhover (talk) 08:22, 24 July 2008 (UTC)

Peruvian tropical cyclones and the Humboldt current?
Hi. Why don't tropical cyclones ever occur in the southeastern Pacific? Yes, I know it's because the Humboldt current keeps the water there cold, even more so than in the South Atlantic, but what about during an El Niño? Wouldn't the water be almost as warm as the southwest Pacific? Or, is there too much wind shear? In a globally-warmed world, with stronger El Niños, would tropical cyclones develop there as in the South Atlantic? Or, does something else keep cyclones from forming there? Is it a high pressure system? If it is, then why when hurricanes in the Atlantic form occasionally where the Bermuda high should be, none form near the South American coast? Do Antarctic cold currents and winds keep the South Hemisphere too cold? Also, is the Humboldt current the main reason why the Galapagos islands are so diverse? Thanks. ~ A H  1 (TCU) 17:35, 18 July 2008 (UTC)


 * I could't find direct sources, but El Nino is defined by a surface temperature deviation of at least 0.5°C. The Humboldt current is about 7-8°C colder than one would expect water at this latitude to be. So even with El Nino going strong, the water is still quite cold. --Stephan Schulz (talk) 22:43, 20 July 2008 (UTC)


 * See this map. Even during the strong 1998 El Nino, the ocean temperature in the southeastern Pacific was only above the lower limit for hurricane formation, 28 degrees, north of 10 degrees south. Note that the ocean in the area was colder during a strong El Nino than the southwest Pacific was during a strong La Nina.
 * The second unfavorable condition preventing the formation of cyclones is indeed wind shear. See this paper, which addresses the issue of why tropical cyclones don't form in the southeastern Pacific.
 * This image shows that mean atmospheric pressure is not higher in the southeastern Pacific than in other hurricane basins, such as the northern Atlantic. --Bowlhover (talk) 09:54, 21 July 2008 (UTC)

CP-violation and the shape of the universe
This question probably just indicates my lack of understanding on CP-violation and 3-manifolds, but here it goes:

Let's say there was a group of flat-landers living on a Mobius strip, or if you like, a klein bottle. Now let's say one of the said flat-landers embarks on a journey around his universe. When the he returns, the other flat-landers find that his left and right sides have been switched, i.e. assuming flat-landers are anatomically similar to us, his heart is now on his right side. Of course to his point of view, his heart is on his left side, and left and right everywhere else is switched.

Now let's take this to a three dimensional universe on some kind of a generalized klein bottle. Another journeyman goes across the universe, this time with a bottle of kaons (Ignore in difficulties caused by their decaying and the likes.) When he comes back the kaons will violate CP-symmetry the other way now (and his heart would be switched too, I think). Would this be like having one side of a Mobius strip red and the other side blue, meaning there has to be a boundary somewhere, or could it prove that the universe is orientable? If I've got any of these facts or assumptions wrong, please let me know because I am trying to learn and I do not understand this stuff very well yet.

Thanks in advance,  J kasd  18:38, 18 July 2008 (UTC)


 * Forgive me if this is off-topic of your questions. I stopped reading after your assumption of the flat-lander's anatomy being switched.  If you travel around a Mobius strip, you will not know you are doing so.  You set off on a straight line.  When you reach the point on the strip where you started - from the point of view of a 3-dimensional being - you are on the opposite side of the strip.  Nobody was sitting around at your starting point will know you are there.  You continue on another lap and return to the starting point and meet your friends.  So, if the true circumference of the strip is 100m, you will claim it is 200m because you had no means of knowing you passed your starting point on the opposite side of the strip. --  k a i n a w &trade; 18:43, 18 July 2008 (UTC)
 * I'm not 100% sure on this, but I think that on a strictly 2 dimensional Mobius strip, you would be visible as a mirror image. At least the orientable article leads me to believe so.  J kasd  18:49, 18 July 2008 (UTC)
 * No, sorry Kainaw, you're taking the "paper strip" image too literally. A mathematical Möbius strip does not have any thickness; when you get around to where you started you do see your friends, but you are now oriented differently with respect to them. --Trovatore (talk) 18:50, 18 July 2008 (UTC)
 * We have an article: non-orientable wormhole. Algebraist 19:29, 18 July 2008 (UTC)

Wow, Wikipedia really does have an article about everything. Although the article doesn't mention CP-symmetry, I'm guessing that no global distinction can be made for it as well. Now I have a new question: does anyone know if there are good reasons that the universe may be orientable or not. I realize it probably makes the physics cleaner if it is orientable, but maybe there is some evidence to the contrary perhaps? Anyways, thanks for the article Algebraist.  J kasd  19:54, 18 July 2008 (UTC)

Zipcodezoo
Hello, Refdeskers! I hope this is the appropriate place to begin this discussion. I was wondering if any of you have an opinion on ZipcodeZoo. It's beginning to come to the top of the list on google searches for species and genera and thus is also beginning to show up on Wikipedia. There are about 190 pages on Wikipedia that mention or link to zipcodezoo. Personally, I've found this resource to be unreliable to some extent. I believe it gathers data from various sources and presents it without a human eye looking over it, leading to situations where synonyms for species are wildly incorrect. Taxonomy is just as bad. See specific concerns at an archived discussion with WP:PLANTS: Wikipedia talk:WikiProject Plants/Archive18. I'd appreciate your thoughts on this. Is removal on sight acceptable? Hopefully with time it will become more reliable, but over the past year it hasn't changed much. --Rkitko (talk) 23:50, 18 July 2008 (UTC)


 * Having reliable sources is one of the core policies of Wikipedia. I'd say ZipcodeZoo is neither authoritative nor reliable. Therefore, it shouldn't be used in citations, although the citations that ZipcodeZoo references may be good to use. It looks like the makings of a good resource, though, so I can see it in a list of external links. ~Amatulić (talk) 21:44, 21 July 2008 (UTC)


 * Thanks for your reply. Is there a better to post this question? WP:PUMP? I think it's a relatively small phenomenon so far, but I'd feel better with more input. Cheers, Rkitko (talk) 22:40, 21 July 2008 (UTC)

Disadvantages of coilguns and railguns
What are the disadvantages of modern coilguns and railguns that need to be overcomed for possible infantry use? --Whuzatt 23:52, 18 July 2008 (UTC)


 * The railgun page on wikipedia should give some insight. For larger applications, incredible amounts of energy is needed. launching projectiles also damages the tracks. Coolotter88 (talk) 02:17, 19 July 2008 (UTC)


 * The amount of energy needed is currently a technological hurdle. There needs to be improvements in portable energy before e-mag cannons see widespread use. Railguns can deliver more force, but the friction cause by the projectile sliding against the rails causes a lot of damage. Maybe if there were a way to coat the rails or the projectile in conductive plasma, that might solve the problem. ScienceApe (talk) 17:12, 19 July 2008 (UTC)


 * Then there is the magnetic field generated, which could permanently damage nearby equipment or make it temporarily inoperable. The magnetic pulse might also be detectable by the enemy (for them to use in target-acquisition or as a warning to take cover). StuRat (talk) 20:54, 20 July 2008 (UTC)