Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

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

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

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

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

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

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

March 29

Distance to ULAS J1120+0641 and the age of the universe

The article about ULAS J1120+0641 gives its comoving distance as 28.85 billion light years. The article on the age of the universe gives the age of the universe as 13.75 ± 0.11 billion years. This appears to mean that the light emited by ULAS J1120+0641 can't have reached us yet, and won't for at least another ~15 billion years. I originally thought that the solution was that the space between earth and ULAS J1120+0641 has expanded since it first emitted light in our direction, so the heavily redshifted light that we see from it was emited at a time when it was much closer. But the article on comoving distance says that "Comoving distance factors out the expansion of the universe, giving a distance that does not change in time due to the expansion of space". So how is it that ULAS J1120+0641 is visible given the age of our universe? 203.27.72.5 (talk) 00:42, 29 March 2012 (UTC)

I find this question really hard to get my head around, it's very counter intuitive when you're talking about BOTH distance AND age in terms of light years.. Here is a couple of articles which attempt to explain it... Vespine (talk) 01:15, 29 March 2012 (UTC)

Suppose that you could, at this very moment, freeze the expansion of the universe. If you measure the distance to ULAS J1120+0641, you would get 28.85 billion light years. If you send a radio signal, it will reach the object after 28.85 billion years. However, the light we receive now from that object was emitted billions of years ago. For all of those billions of years, the universe was smaller than it is now, so light travelled, in one year, farther than 1 light year of comoving distance. --140.180.39.146 (talk) 01:56, 29 March 2012 (UTC)

Proper unit and force

Which unit would suit to measure the force that seeks to stop the moving object (can't recall the proper name of that force, maybe that from Newton's 3rd law), specifically by pulling the accelerating object backwards or holding it from the front? And how to calculate that stopping force for any speed and/or acceleration given (such as, theoretically, for a superman who is pulling the accelerating car backwards?) Also in the case of a superman is a frontal stopping of, say, a moving car more advantageous due to better friction or there is no difference?--46.205.11.219 (talk) 00:50, 29 March 2012 (UTC)

That force would be measured in Newtons. Your second question: no difference (if you apply the same force in the same direction). F = m(v_f - v_i)/t. Plasmic Physics (talk) 01:03, 29 March 2012 (UTC)

That's only for the total force though. OP seems to imply there are two forces working against each other, in which case you need to add or subtract a magnitude (say $F=F_{a}-F_{b}$, then $F_{a}=ma+F_{b}$). To stop an accelerating car from accelerating you need to apply a force of equal magnitude and opposite direction. --145.94.77.43 (talk) 08:17, 29 March 2012 (UTC)

Will I need conversion of car's horse powers to newtons in that case or something like that?--46.204.18.135 (talk) 14:05, 29 March 2012 (UTC)

That 'stopping force' is friction, there is no other natural force that has the same effect. You may be confused with inertia, which is a different concept. Plasmic Physics (talk) 01:07, 29 March 2012 (UTC)

Horsepower is a measure of power nor force, and power is alternatively measured in Watts not Newtons. Plasmic Physics (talk) 20:37, 29 March 2012 (UTC)

The first question is really vague. Is the object just moving, or is it actually accelerating? Forces are usually measured in Newtons, but I have a feeling that's not what you're really asking for here. A force of a given magnitude has the same effect as long as it acts in the same direction, so it doesn't matter if it is a pull from the back or a push from the front. As for the question "how to calculate that stopping force for any speed and/or acceleration given "; to over come the acceleration, the stopping force must be greater than the accelerating force. If there is no acceleration, that force is any number greater than zero; F_Stopping > 0. If there is acceleration then stopping force must be equal to the accelerating force plus any number greater than zero; F_Stopping > F_Acceleration. You can calculate the accelerating force by taking the mass of the object m_Object and multiplying it by its acceleration a_Object; F_Acceleration = m_Object x a_Object. 203.27.72.5 (talk) 22:29, 30 March 2012 (UTC)

Genome testing

When submitting your DNA sample for genome testing, is there any way to verify that they actually did it, versus just cashing your check and sending you back randomized results ? For example, can they tell you your eye color, hair color, hair texture, etc. ? StuRat (talk) 06:48, 29 March 2012 (UTC)

In principle, yes. In practice, it will depend on what you are having tested. Unless the purpose of the test is to obtain some sort of comprehensive profile, then they are unlikely to be looking for things like eye color and hair. It would generally be considered an invasion of privacy for the lab to look at traits beyond those they were explicitly asked to examine. Beyond that, there is also the issue that the function of many genes is still unknown and even for some common traits (e.g. eye color) there isn't enough knowledge of all the genes and possible alleles to reliably predict outward appearance with high confidence. However, there are enough traits that we do understand that a testing company could provide the kind of verification that you are looking for, provided they performed the appropriate tests and you had given your permission to do that. Dragons flight (talk) 08:39, 29 March 2012 (UTC)

Actually, if you tested with 23andme, which provides health details as well as genetic results, they will provide you with guesses as to your eye color, blood type, height and other traits. If you tested with FamilyTreeDNA, there will be no traits (but you will have access to their more extensive genetic database, if you are looking for relatives). And if you test at 23andme and transfer your results to FamilyTreeDNA, you will have all of the above. The best way, though certainly not the least expensive, to verify results is to have the test done at two different labs and compare results; testing relatives who should have similar results is another way to be sure actual testing is being done... - Nunh-huh 10:23, 29 March 2012 (UTC)

Some companies will tell you what they can directly, others will give you a file with all your SNPs (or, rather, with all SNPs that their machine can recognize), and you can try to interpret the results on your own.

At the very least, the lab should tell you your mtDNA haplogroup and, if you're a male, Y-DNA haplogroup (and you should have a pretty good idea what Y-DNA haplogroup to expect, if you know your ancestry.)

To give an example, 23andme.com tells me that I have "72% chance of blue eyes; 27% chance of green eyes; 1% chance of brown eyes" because I have GG at the marker rs12913832, and "greatly increased odds of having red hair" because I have TT at the marker rs1805007. But these are characteristics where the connection between genetics and appearance is well understood. They can't tell me anything meaningful about my height, because height is influenced by many genes, most with small effects, and not all of them are known.--Itinerant1 (talk) 10:35, 29 March 2012 (UTC)

Visible physical characteristics would make a very poor check, since if they company is a scam to begin with, obviously they could just look and see. Even health conditions would offer little reassurance in the U.S., where health information is anything but closely guarded. By far the most important check is that the test or part thereof might be repeated for some reason (especially likely when large amounts of information are collected incidentally as part of a standard screen) - any inconsistency would potentially cause them grief. Of course, real scam artists are very good at avoiding scrutiny and gabbing their way out of contradictions. Wnt (talk) 15:17, 29 March 2012 (UTC)

The idea is that you would mail in a DNA swab, anonymously, so they would have no idea what you look like, other than to the extent they derived that info from your DNA. Payment could be done by money order, to keep it all anonymous. You'd want the info to be anonymous anyway, lest they sell info to potential employers on your genetic likelihood to have a foot fetish. :-) StuRat (talk) 17:10, 29 March 2012 (UTC)

Relevant literature for anyone considering sending samples for DNA testing: My Beautiful Genome by Danish author Lone Frank. I've been told it's a good read, and bought the book a week ago, but have only reached page 18, so I cannot really review it. Good reader reviews on Amazon.com. --NorwegianBlue ^talk 16:26, 29 March 2012 (UTC)

german raider "wolf", at the end of first world war

recently i read, a rather well written tale of the german raider "wolf". by the end of her odyssee, she apparantly visited trinidade isl. but fled at the sight of approaching vessels. the book in question is: "wolf" by guilliatt & hohnen, random house 2009, isbn 9780593060759 an entry concerning this episode could be of interest. peter varenhorst — Preceding unsigned comment added by 81.205.241.214 (talk) 10:34, 29 March 2012 (UTC)

SMS Wolf (auxiliary cruiser), which cites the same book you mention. That article doesn't mention a trip to the Caribbean, however. -- Finlay McWalterჷTalk 11:07, 29 March 2012 (UTC)

The Transcript of Naval Staff Intelligence Division Report "Cruise of the German Auxiliary Cruiser WOLF", March 1918 in the UK National Archives might have more information. I haven't had a chance to read through it yet, but the Google search result suggests that the island in question is Trindade and Martim Vaz which is in the Atlantic, not Trinidad in the the Caribbean. Alansplodge (talk) 15:26, 29 March 2012 (UTC)

Unidentified flowers

Could anyone help me with the two flowers linked here? I'm not sure at all on the first, and the second is a species of guava (methinks). Both are fairly good pictures, so it would be a shame to not have them in an article.

Guava?

Yellow flower

Thanks. Crisco 1492 (talk) 12:54, 29 March 2012 (UTC)

Considering the first image, it appears to be an actinomorphic flower, which as best as I can see has four sepals, four small pink petals, and some absurd number, maybe over 100 stamens, hiding any gynoecium that might be present. This gives a floral formula of "Ca⁴Co⁴A^∞G^?" ... I think. After that I just googled "guava indonesia flower" like everybody else and got [1], identified by the poster as a Malay apple flower. Some day I mean to learn botany to the point of being able to actually use a key, really, but by the time I do I think they'll be obsolete. Wnt (talk) 15:45, 29 March 2012 (UTC)

• Thanks, that appears correct. Crisco 1492 (talk) 15:57, 29 March 2012 (UTC)

• The yellow one appears to be Cosmos caudatus. Crisco 1492 (talk) 16:03, 29 March 2012 (UTC)

Titration curve of pure water

What does the titration curve (pH vs volume of acid added) look like? Is it a straight line? (This isn't a homework question, I'm not in school) ike9898 (talk) 17:45, 29 March 2012 (UTC)

Titration curve. TenOfAllTrades(talk) 18:15, 29 March 2012 (UTC)

If you're not going to help, please consider not posting anything at all. The linked article doesn't explicitly answer the question, at least not for someone without a complete understanding of the subject. ike9898 (talk) 20:07, 29 March 2012 (UTC)

Almost all titration curves look approximately the same, the only key differences are the exact position and number of the (comparably) steeper rises along the graph compared to the more gentle slopes between them--these positions are dependent upon the pKa of the substance being titrated (once you account for the actual absolute amount of that substance). If there is any substance present that can react with the solution being added (your acid), the graph will certainly not be just a straight line, because by definition "some" of that substance would be consumed at first but eventually no more could react. Because the graph is a measurement of either the amount of unreacted substance being titrated or the amount of titrant being added (or some complex function of them), different slopes would be present at these two extremes. Water is not an inert solvent when it comes to adding H+ because it is both a weak acid and a weak base. DMacks (talk) 20:19, 29 March 2012 (UTC)

Thanks. The pKa of water is >15. Do you think the titration curve would be 'practically a straight line' in the range of, say, pH 3-10? ike9898 (talk) 20:47, 29 March 2012 (UTC)

Assuming you are adding an acid that dissociates completely in water (a strong acid), and you plot it in the usual manner (pH vs added acid) it won't be a straight line, but rather a logarithmic curve (because pH is logarithmic with regards to acid concentration, and was originally defined for being in water). There are also complications due to the fact that adding acid probably changes the volume perhaps significantly. However, it really isn't appropriate to speak of a titration curve in this regime - a titration curve is typically used either when a buffer is being looked at (theoretically water could be used as a buffer, but I don't know any situations where it is), or where you are doing a titration, trying to fully react the species.

Put acid added on a log scale and you get your straight line. Alternately, you could remove the log from the pH and just plot [H⁺] vs Acid added, which if you think about it makes it quite clear why it should be a straight line. 203.27.72.5 (talk) 04:36, 30 March 2012 (UTC)

Thanks for the help y'all. ike9898 (talk) 13:15, 30 March 2012 (UTC)

to close this topic, consider this $pK_{W}=pH+pOH$. using $pK_{W}\approx 14$ at room temperature, therefore $pH=14+log(c(OH))$ --Biggerj1 (talk) 16:36, 26 January 2015 (UTC)

chaos

I'm soon gonna be giving a lecture about chaos (and many other things) and there's a point about chaos I want to understand. They generally say that chaotic systems are unpredictable because although they're deterministic, they're very sensitive to changes in the initial conditions and small changes rapidly amplify, making it too difficult to predict the evolution and final conditions of the system. My question is HOW sensitive? Is there a point to which if we know all the details in the conditions of the system, we won't need to know any further details in order to fully predict the behavior of the system (by fully, I mean at least like planetary motions) or does it go all the way to a point that it isn't theoretically possible to measure the conditions of the system? What I mean is, is it right to say "If I know the conditions of the system to a certain degree(not fully of course), I can fully predict the system."?--Irrational number (talk) 17:49, 29 March 2012 (UTC)

I'd say the degree to which you can predict the outcome depends on the degree of knowledge of the initial conditions, and the more time elapses, the more questionable the predictions become. For example, in weather forecasting, today's weather is right maybe 90% of the time, but next week's only 50%. And to put it in terms of the butterfly effect, killing most butterflies won't much matter, but a small portion may be absolutely critical and have a huge effect. StuRat (talk) 18:01, 29 March 2012 (UTC)

You are right, in that sometimes the sensitivity to changes in initial conditions does not pose a problem for prediction of chaotic systems, while sometimes it does. For a given system, the value that tells you how concerned you have to be is the Lyapunov exponent. Also, in my opinion, mentioning quantum mechanics is a red herring here. With respect to the underlying math and physics, the uncertainty principle is completely different from deterministic chaos. The only similarities are extremely hand-wavy and superficial. SemanticMantis (talk) 18:25, 29 March 2012 (UTC)

Thanks for the answers, I've already read the Lyapunov exponent article, my question is that will your predictions become questionable no matter how good your measurement of the initial conditions are? or is it like, if your error is less than, say 0.00000001 percent, you can fully rely on your prediction, and your predictions will become more or less time-independent?--Irrational number (talk) 18:45, 29 March 2012 (UTC)

The former. For any Lyapunov type system, arbitrarily small errors will eventually become arbitrarily large differences. The Lyapunov exponent helps tell you how long that will take for a given level of uncertainty in the initial conditions, but eventually you get large errors regardless of how accurate the initial measurements. This is fundamentally what it means to be sensitive to the initial conditions. Dragons flight (talk) 18:54, 29 March 2012 (UTC)

Consider a system whose state is a real number between zero and one, and changes once per second to the fractional part of ten times the previous state. If the initial state is 0.231486... then the next state is 0.31486... and the next state is 0.1486... and so on. If you can measure the initial state to one part in 10ⁿ then you can predict the system's behavior pretty accurately for n seconds, and after that you can't predict it at all. That's typical of chaotic systems. No particular level of detail is enough to predict the behavior into the indefinite future. -- BenRG (talk) 18:39, 29 March 2012 (UTC)

Well then in some sense every system is more or less chaotic, is it the "aplification" of changes that makes the system more chaotic?--Irrational number (talk) 18:52, 29 March 2012 (UTC)

SemanticMantis, I didn't say that they're related, I just asked do we have to fully know the conditions of the system in order to predict its behavior, and fully measuring a system's conditions, to my limited knowledge, is somehow related to the uncertainty principle, I didn't say that chaotic systems are unpredictable because of the seemingly non-deterministic behavior of small particles, I understand that these are different subjects...(or at least I think I understand...)--Irrational number (talk) 19:02, 29 March 2012 (UTC)

In principle it's not always true that no level of detailed knowledge is enough: if you know the exact initial conditions, that is enough to predict infinitely far into the future if your computer can handle an infinite number of decimal places -- so computer storage capacity is the limiting factor when there is perfectly detailed knowledge.

For you to know the exact initial conditions, they must be rational, and in some cases this is consistent with a chaotic trajectory. For example, if $x_{n+1}=4x_{n}(1-x_{n})$ there is an analytic solution $x_{n}=\sin ^{2}(2^{n}\theta \pi )$ where $\theta$ is such that $x_{0}=\sin ^{2}\theta \pi$. It's chaotic if and only if theta is irrational. If for example $x_{0}$ = 1/3, or almost any rational number, then theta is irrational. Then the trajectory is chaotic, and since theta is irrational the initial condition for theta cannot be known with perfect precision, but the initial condition for x is known with precision so 4x(1-x) can be iterated arbitrarily far into the future until the numbers get too big for the computer to store them. See Chaotic map#Solution in some cases.

Of course, in physical systems there may be no circumstances in which you know the initial conditions, even if rational, perfectly. Duoduoduo (talk) 19:13, 29 March 2012 (UTC)

True, I didn't mean to put words in your mouth. But I stand my my claim: the relationships are superficial; I'd advise that you not go looking there for inspiration, understanding or intuition ;) As to your more specific question, Dragons flight makes a good point above; no amount of partial information gives you predictability forever, but the lyapunov exponent can give you a good indication of how your errors will propagate in time, and therefore on what time horizon you can hope to make decent predictions. SemanticMantis (talk) 00:36, 30 March 2012 (UTC)

Thanks, I kinda get it now, so no matter how much you know the details, given enough time, your predictions will become less and less reliable...--Irrational number (talk) 05:39, 30 March 2012 (UTC)

I think you have to be careful about what you mean by 'prediction'. For example, look at the picture of the Lorenz attractor at the top of the Lorenz system article. If you know the initial condition of this system with a small but finite precision, your predictions of the state of the system (meaning the values of x, y, and z) will get exponentially worse with time, for small times. However, after a long time, you can be sure that the state will be very close to the attractor - in other words, you can narrow the state down to quite a small region. In a practical application, that might be all you need. The concept of fractal dimension is relevant here - if the attractor has a large dimension, then it will tend to fill a large region of space. There is a nice paper that links the dimension of an attractor to the predictability of the system - I think it is this one (you need a subscription to Physical Review Letters - which I don't have). 81.98.43.107 (talk) 17:43, 31 March 2012 (UTC)

Plugging into the sun with carbon nanotubes + what is the world economy's ATP (energy carrier, biology metaphor)

This is a two-part question.

I.

First, assuming that the Sun is a ball of electricity we can plug into and get AC voltage. How much would a one-atom (or however thick it needs to be) carbon nanotube in each direction (positive and negative polarity) from Earth to Sun (1 AU) weigh. If we had such a ball of carbon nanotube and it would unroll slowly and gracefully if we flung it toward the sun, and the two lines got there, then assuming their attraction to each other did not cause the two lines to fall into each other (they were sufficient distance apart) would there be practical problems with orbits that would cause planets to intercept these lines? With a few active movement points (rockets) could we move parts of the line out of planets' ways?

Second, look at our article on sun, we find that it is not in fact a ball of electricity we can plug into and get AC voltage. And that's not because it's DC. Instead, our article informs us that it is hot plasma interwoven with magnetic fields. What interests me is whether these magnetic fields, if they are stonger than Earth's could be harnessed by lassoing our line (the one going form Earth to Sun and back), around and around and around the sun (like someone doing whatever you do when you're jumping/skipping rope) then would we get electricity, or enough for it to be worth our trouble? If not, we will have to do something more drastic at the end of the leads. I'm not sure what, but for part 2, assume we just get AC back to Earth.

II.

Here I am making an analogy with biology. The 'energy carriers' of the Body are ATP which depletes to ADP when used up, and is replenished to ATP as an energy source. My question concerns the world economy. At the moment, instead of having litle carriers of energy that get used up and replenished, instead we have fuels we burn off. So, what would the energy carrier be that is a physical object that gets depleted and centrally replenished, were we to get leads with unlimited AC at some central location on Earth? Would we have to literally have giant transformers and strap this whole thing into the existing electricity grid, or is there some other great physical carrier (whether physical, mechanical [torque, pressure, whatever], electrical, magnetic, chemical, kinetic, biological, whatever) that for example could power a house for a while, a year say, and that you then can send along to be replenished from the AC leads coming from the sun. I am thinking of something small.

Basically, both of these questions are probably not of much interest, but the explanations might enlighten me. Thank you for your time. 188.156.115.197 (talk) 18:18, 29 March 2012 (UTC)

You don't need to run a line all the way to the Sun. The solar wind completes the circuit in some sense. All you need is to tap into the ionosphere, which has a high charge difference from the ground which I believe is ultimately due to the solar wind, and tap into near-limitless energy by shorting out this immense atmospheric capacitor. At least, that's the idea proposed by Nikola Tesla, and still viewed as theoretically possible, I think. (Sort of a more ambitious version of the lightning rocket) Though I would greatly miss the aesthetics of it, as the mythological wedding of Persephone and Prometheus draws nigh, it is about time for once-mortal men to steal Jove's trove of thunderbolts. ;) Wnt (talk) 18:54, 29 March 2012 (UTC)

OP here. Jesus Christ, man, don't do this!!!! Our ionosphere is the ONLY thing protecting us from immediate annihilation. If anyone is reading this - D O N O T D O T H I S. Our system of commerce is not set up to protect public goods such as the ionosphere. No, better get it from the sun. As for my original question: how much nano tubing do we need? 188.157.120.238 (talk) 19:29, 29 March 2012 (UTC)

The ionosphere is not what protects us. The magnetosphere is. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:58, 29 March 2012 (UTC)

I'm no physicist, but I'm reasonably sure that 8 1/3 light-minutes of wires would have enough resistance to nullify any gains we could hope to get. Unless you do superconductors, I guess. Also, wouldn't work when the part of Earth that has the wire's endpoint rotates away from the sun. Writ Keeper ⚇♔ 20:05, 29 March 2012 (UTC)

doesn't space automatically cool everything off to 0 kelvin and superconduct any wire? also aren't carbon nanotubes very good at transferring current. also if it's the sun who cares how much is lost, it could be 7 orders of magnitude and we'd still have enough. if there were an ac jack on the sun to plug into. Finally as to rotation I guess we have to do something about that. 94.27.177.124 (talk) 21:04, 29 March 2012 (UTC)

It is just overall crazy with so many flaws in your logic, I won't even try to explain. Plasmic Physics (talk) 21:08, 29 March 2012 (UTC)

all great ideas start as overall crazy with so many flaws in logic that they are not even worth explaining. Einstein had to go to a friend who paid attention to math he didn't learn properly before he could even work out special relativity. Let alone, let alone, general relativity. Also your name is plasmic physics, which this text field (firefox) redlines. Google returns only your username here on Wikipedia when I put "plasmic physics" in quotes on the search engine. That does not scream nobel prize to me. But hey thanks for your help and insight. 94.27.177.124 (talk) 21:18, 29 March 2012 (UTC)

The article outer space#environment says "The current black body temperature of the background radiation is about 3 K (−270 °C; −454 °F)." Not quite absolute zero, so I don't know if it's low enough to "superconduct any wire", but I doubt it. I think it is low enough to superconduct even the first (low temperature) generation of superconductors.

I personally like your thought experiment. Who knows where thought experiments lead? (To me, maybe this one leads to Earth's rotation being no problem -- just use the Sun's boundless energy to stop the rotation of the Earth. But that's probably just hypothetical.) Duoduoduo (talk) 21:45, 29 March 2012 (UTC)

If Earth stopped spinning it would either collapse (or everyone would be crushed) or explode spewing magma and with everyone flung off into space - only one of those things would happen and this is the type of thing where if you bother to learn it you would know, which I didn't. So: what happens if the Earth stops spinning? Presumably not 'nothing' though maybe so, given that the Moon is rotation locked with us and seems to be doing just fine, though it doesn't have much of any life. 149.200.72.244 (talk) 22:12, 29 March 2012 (UTC)

also (op here) i did not get any answer to the SIMPLE question of how much 2 AU (a unit of length) of carbon nanotubing weighs (when it's sstill on Earth) nor any response to the second part of my qeustion. 94.27.177.124 (talk) 21:14, 29 March 2012 (UTC)

What is the diameter of the nanotube in terms of carbon atoms, and is the wire tensioned? You are essentially asking how long is a piece of string? We need a bit of information before we can calculate an answer. Plasmic Physics (talk) 21:23, 29 March 2012 (UTC)

I'm NOT asking "how long is a piece of string", but out of curiosity how long is it? As to my actual question, say the diameter of the nanotube is 1 carbon atom, 0 stress since in space things float and we get the tension to balance out somehow (naively, since it goes there and back again that cancels out). in this primordial case, how much will 2 au of 1 carbon diameter nanotubing weigh while it's on Earth? Then we can multiply by some factor, Gee, in case any of this is realistic. It's simple enough to go from 1 carbon diameter to 2 or 6, you just multiply whatever answer you're about to give me. It's the 2 AU that is the bigger factor accounting for most of the order of magnitude...so...? how much does a 1 carbon diameter nanotube that is 2 au (a 1 dimensional measure of length) long weigh? 21:36, 29 March 2012 (UTC) — Preceding unsigned comment added by 149.200.72.244 (talk)

I get only .04 grams --Digrpat (talk) 21:59, 29 March 2012 (UTC)

OP here. Pardon my French but are you shitting me? I *thought* it might be some tiny amount, like a few pounds or a ton or two. You did the full 2 AU? See, this is what I expected. Now from 0.04 grams, you know if you want to go from 1 atom to 100 in diameter be by guest, that 4 grams is not going to be impossible to launch. I wonder about the other parts of my question - orbits intersecting our nice little power cord... woudl we have to actively move it? How much transmission loss could we expect? (Again, I think 7 orders of magnitude is fine, given we're dealing with the sun). Then we'll work out the sun and and the Earth end, but let's concentrate onthis. How much current do you think a carbon nanotube can carry, and at what resistance? (or what's the graph look like). 149.200.72.244 (talk) 22:33, 29 March 2012 (UTC)

A single nanotube would weigh about 15000 kg over 2 AU, and be able to carry a maximum hypothetical current of about about 6 microamps with a resistance of about 1×10²⁴ Ohms at room temperature. For a transmission loss of around 4×10¹³ W, somewhat larger than the entire world's current energy consumption at present. Dragons flight (talk) 22:44, 29 March 2012 (UTC)

A nanotube of one atom circumference is hardly a tube, more like nanostring. This means that a different typr of bonding may be in order - what is the bond length between the atoms in the carbon nanostring? Will the new bonding type allow for electronic conductivity or inslation? Plasmic Physics (talk) 22:52, 29 March 2012 (UTC)

"doesn't space automatically cool everything off to 0 kelvin and superconduct any wire?" Well that depends on your time horizon. Space contains only a sprinkling of matter since it is almost a total vacuum. The matter that is present is mostly high speed (i.e. high temperature) particles in the solar wind. But even if you ignore the solar wind, any object in a vacuum has nothing around it to act as a heat sink to transfer its heat to. So it doens't get instantly chilled. On the contrary, it can only cool down by emitting electromagnetic radiation (see black body radiation. So the end result is that it cools down at an increasingly slower rate forever. And all that is not taking into account the fact that it will be bathed in EM radiation from the Sun. 203.27.72.5 (talk) 07:52, 30 March 2012 (UTC)

I would think that even synthesizing a nanotube on an astronomical length scale in the first place would fall somewhere between chemically implausible and completely absurd. The real limiting factor isn't the amount of carbon, or the length of tube, but the ridiculous number of defects you'd wind up with. My (somewhat limited) understanding is that a nanotube hundreds of microns long is so full of defects that it may as well be amorphous carbon, to say nothing of a nanotube that you'd have to measure in AUs. If you want a conducting material, that's just not going to work. (+)H₃N-Protein\Chemist-CO₂(-) 14:24, 30 March 2012 (UTC)

Note that linear acetylenic carbon, carbon nanowires, linear carbon, crystalline carbyne, as can be generated by additions into C_nO which produce a resonance structure between C=C=C=C=C=O and -C*C-C*C-C*O+ etc. ... whatever you call it, it's a real thing. [2][3] Carbon nanowires are more stable than fullerenes, less so than carbon nanotubes. However, they can become energetically unstable at lengths over 20 unless confined in carbon nanotubes ... probably an interesting story there. They can also apparently transform a semiconducting SWNT into a metallic one. Wnt (talk) 20:19, 30 March 2012 (UTC)

In general, I'm not sure what I'm talking about with this subject, but some basics at least: we're talking about a circuit here. What's being plugged into? I suppose the emission of plasma from the coronosphere has some intrinsic bias that should charge up the Sun to a certain degree, but that same charge is being transmitted to the Earth via the solar wind. I picture a perfect circuit from the Sun and what would it be? A huge carbon nanotube full of solar wind particles moving straight down the center without hitting anything to carry the charge without resistance.

Now eventually these particles strike the Earth's ionosphere, and the Earth picks up a charge, but I'm still not sure how the circuit works. Why doesn't the whole Earth pick up the same charge? I know the ionosphere varies by day and night, and surely the magnetic field of the Earth must have some differing influence on positive and negative per Van Allen belts - I suppose the charge we're picking up by day must be leaving somehow - but I don't really know at all. Is it discharging back out to space by night, some kind of "terrestrial wind"? We're not hot enough to spew plasma, but what about charge? Hmmm, I suppose not... we must be completing the circuit by intermittently? feeding from those different Van Allen belts of protons and electrons.

My feeling is still that by tapping into the ionosphere we might as well be tapping into the Sun; that conduction from there to here, via solar wind, is not the issue. If we could ground that and tap into that huge power source, the question still remains, how does the current move on from there? There must be some mechanism by which the ionospheric potential is preserved. It might be that getting the current back out is just as important as getting it in for such a scheme.

For that matter, why aren't satellites powered by solar wind? Trail two (widely separated) very fine nanowires, one that passing protons tend to stick to, one that electrons reach more readily, harvest the current, and emit a small amount of atomic or molecular hydrogen gas. Is that a kind of heat engine? The article on the Van Allen belts has a scheme for "removal" - isn't there some less ambitious means to simply harvest such energy?

I'm afraid I'm far, far out to sea on this one. It was indeed a very good thought experiment for the OP to propose this. Wnt (talk) 20:19, 30 March 2012 (UTC)

Just thought I'd point out that all of those pi bonds linking the carbons together are prone to electrophilic attack. And you're sticking them in a proton plasma. 203.27.72.5 (talk) 21:27, 30 March 2012 (UTC)

Hey, I didn't think up this scheme, and I didn't say it was perfect. Maybe a big shade at the Sun end and a strong positive charge (p-doping a linear carbon chain??) would keep away protons... of course, the whole scenario of digging a hole in a conductive medium in order to install a single tiny wire that won't conduct except as a matter of rhetoric is wacky to start with, but... Wnt (talk) 14:11, 31 March 2012 (UTC)

VSEPR theory

What geometry does VSEPR theory predict for molecules with a steric number greater than 9? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:25, 29 March 2012 (UTC)

VSEPR theory is pure geometry: Take X number of objects distributed around a central point, and arange them so they are a maximum distance from each other. Hypothetically, any number of objects could be used, and indeed the shapes so described have almost nothing to do with chemistry, it is just a geometry exercise. There isn't really any need, for a chemist, to describe any molecule which cannot actually exist, but geometrically, one can describe the optimum arangement for any arbitrary number of objects. As a geometry exercise, I would imagine that the solutions for molecules with greater than 9 atoms around the central atom have been solved, but as a chemist I am unfamiliar with those shapes as I never need to use them for any reason. --Jayron32 02:55, 30 March 2012 (UTC)

Apparently, no general solution exists, but you can write a computer program that will arrange any arbitrary number of points onto the surface of a sphere. One example that is easy to find is for 12 atoms around a central one. This will form an icosahedral pattern, equivalent to the hexagonal sphere packing. This paper has more info, though it looks at all n-spheres (i.e. all sphere-like objects in any number of dimensions), and barely touches on the classic 2-sphere (what we'd call a sphere in everyday language). Smurrayinchester 07:46, 30 March 2012 (UTC)

looking to side to yawn

if i look to the side (left or right) with my eyes closed, in the position i'm in, it sounds in my ear like yawning. why is this. what is that sound. does something open or close.

in this case i dont open my mouth at all but it sounds / feels the same. closed mouth yawn. 149.200.72.244 (talk) 21:29, 29 March 2012 (UTC)

At a guess, is its because your eye muscles ( the ones controlled by you're sixth cranial nerve) are tremoring. Yawning muscles of the jaw do the same thing at 'maximum' flexation. Bone and muscle/connective tissue transmits the tremor and back to the ear. This tension may also distort the shape of the ear and changes the amplitude and shape of its dynamic response so that the ambient noise sounds different. Never been asked this question before -so thanks.--Aspro (talk) 21:48, 29 March 2012 (UTC)

Do planes cast full-sized shadows?

do planes cast full-sized shadows? if so/if not is this due to the fact that the sun is not a point source (like a very small candle) but in fact a huge ball of 'light' far larger than Earth? Is it the distance that does it? If so at what distance would planes start casting shadows that weren't/were (opposite of fact) their own size? 149.200.72.244 (talk) 21:54, 29 March 2012 (UTC)

The Sun is so incredibly far away that the light from it is, for all intents and purposes, parallel. So illuminated by the Sun overhead, the size of an aircraft's shadow (on a level surface) is the same as the aircraft. -- Finlay McWalterჷTalk 21:57, 29 March 2012 (UTC)

But even at the distance it is, the Sun isn't a point source. Looked at (with appropriate precautions of course) it's still a disk (because it's s incredibly huge). If it was a point source the aircraft would cast a crisp shadow; as it's not, the shadow has fuzzy edges (areas on the ground for which the plane blocks some, but not all, of the Sun's disc). -- Finlay McWalterჷTalk 22:00, 29 March 2012 (UTC)

This is correct, but unless the plane is quite low the fuzzy area extending from the edges meets in the middle and the whole shadow becomes faint and fuzzy. As Baseball Bugs notes below, to form a dark shadow with reasonably clear edges, the plane has to be low enough to totally eclipse the sun from the point of view of observers on the ground.--Srleffler (talk) 17:53, 2 April 2012 (UTC)

The moon, for example, doesn't cast a "full-sized" shadow, i.e. a cylinder - it's more of a cone. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:58, 29 March 2012 (UTC)

When an aircraft is close to the ground it casts a shadow that is clearly recognisable as the shadow of the aircraft, although it is a little fuzzy around the edges due to the penumbra. Higher above the ground an aircraft doesn't cast a shadow at all, but a Glory (optical phenomenon) which is a bright circular patch on the ground, a bit like there is a searchlight shining brightly at a point on the Earth's surface. The bright patch (the glory) moves across the Earth's surface at the same speed as the aircraft. Dolphin (t) 22:03, 29 March 2012 (UTC)

Looking at it from the other direction, consider looking up at a plane crossing the sun's disk (let's supposed one is immune from being blinded). Unless the plane totally "eclipses" the sun, there's not going to much of a shadow discernible from the ground. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:15, 29 March 2012 (UTC)

If there's no shadow, what if (immune from being blinded) you look up and into the hole of the glory? What do you see? - is the sun occluded there or not? 149.200.72.244 (talk) 22:26, 29 March 2012 (UTC)

There is a shadow, you just can't see it. All you see is the plane, looking black, against the sun - as with, for example, an annular eclipse. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:29, 29 March 2012 (UTC)

I have been on planes where the shadow is clearly visible on the ground, but I believe at a suffieciently high altitude, like cruising altitude for a jet liner, the shadow becomes almost indescernible. The atmosphere also plays a non insignificant part in this question. Even though it "looks" transparent, the air does reflect some light. It was noted that on the moon, shadows appear MUCH darker and "crisper" then on the earth. This effect is ever greater if there are any clouds in the sky which act like big light diffusing boxes. Vespine (talk) 23:19, 29 March 2012 (UTC)

BS. Airplanes do not cast glories on the ground. The glory is an optical phenomenon that happens when light around a shadow falls on water droplets in the air (mist or clouds). The phenomenon is created by the water droplets, and the rainbow pattern is cast back toward the source of the light (which is why you only see it if your shadow is falling on the mist or clouds. You have to be on the plane to see a glory around the plane's shadow). --Srleffler (talk) 17:48, 2 April 2012 (UTC)

Google image [airplane shadow] and you'll see all kinds of interesting stuff. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 30 March 2012 (UTC)

There is a couple of good images of optical effects from aircraft - see Glory (optical phenomenon). Dolphin (t) 01:06, 30 March 2012 (UTC)

Ignoring atmospheric effects, we can pretty easily calculate all the values explicitly. First, I want to know the apparent angle of the diameter of the sun as viewed from Earth. This is just the ratio of its actual diameter to its distance, so that's 1.392×10⁶ km/1.496×10⁸ km = 0.0093 radians. Dark full shadow (umbra) occurs where the plane is fully obscuring the disk of the sun. Supposing the plane is wide-body aircraft let's assume the diameter of the fuselage is about 6m. For the body of the plane to fully obscure the sun at any point on the ground, the distance would have to be less than 6m/0.0093 ≈ 640m away. Above that, no point on the ground will be in full shadow. The "fuzz" on the shadow (penumbra) grows from the edges linearly in the plane's altitude, until eventually it engulfs the whole shadow. Rckrone (talk) 02:45, 30 March 2012 (UTC)

wnhat would happen if the Earth stopped spinning

say over a 72 hour period it wound down and stopped spinning (you can make this slower, a year or two if it helps preserve life and sanity). we need this to harness infinite energy (let's say) and can use it to stop te earth. But what happens if we do? Nows in the interest of fairness (one half would always be dark) we could transfer the power station every 3 months and rotate the Earth by a quarter, to change who gets light. (seasons however are due to the angle with the sun i understand, and aren't due to spin - after all it's day and night in every season). This movement is a massive pain in the ass though so you would only rotate the earth every so often. at other times it becomes locked facing the Sun (s the moon is locked facing us).. in this case would this work, or how often would we have to give the old rotesserie a turn to keep things from burning? Finally are any of the planets (mars, venus, jupiter, etc) locked iwth the sun, and if so how are they dealing with it? 149.200.72.244 (talk) 22:16, 29 March 2012 (UTC)

No, none of the planets are tidally locked to the Sun. People used to think Mercury was (there's an Arthur C. Clarke story about pogo-sticked aliens living in the twilight band between the burning hot and the unliveably chilly), but it's not. To answer your question: in such a short time, we'd all die. But if we have infinite energy, can't we can just live off that? Given more time than your draconian deadline, we can all move a mile or so underground (hey, it's like The Matrix) where geothermal heat predominates, and screw the Sun. -- Finlay McWalterჷTalk 22:22, 29 March 2012 (UTC)

Wouldn't the infinite energy collapse into a black hole and suck us all in? --Trovatore (talk) 23:30, 29 March 2012 (UTC)

see my other question. apparently we only need to stop the earth if we want this infinite energy (which we would also use to stop the earth) but a bit of googling what happens if the earth stops shows that tthe whole thing might not actually be worth it. 149.200.72.244 (talk) 22:29, 29 March 2012 (UTC)

If I may quote myself, from a similar question in September of last year: (I have taken some liberties to modify the quote to increase relevance to the current question)

“ The answer to this type of physics question always depends: how would [the earth stop spinning]? If you can specify that, we can follow through with the consequences by solving the equations of motion for the Earth-Moon[-Sun] system.

For example, if you hypothesize that a giant comet large and fast enough to change the [Earth's rotation] impacted our planet, .... well, we would need to calculate the effect that such a large comet has on the orbits of Earth and everything else in the solar system, too. We could solve that problem by setting up an n-body problem to model the solar system, including Earth, Moon, Sun, and other planets; and we would use perturbation theory to study how sensitively the system reacts when we add in a new comet on a course to impact the moon. The results are difficult to compute, but this can be done in a reasonable amount of time with a reasonable amount of effort.

...

On the other hand, if you just want to make something up, "just imagine" that the [Earth] magically changes its [rotation], all bets are off. We can't meaningfully speculate what consequences follow when one law of physics breaks "because of magic." Anything could happen. Everything we know about the way the Moon's orbit couples into the Earth's rotation depends on the rules of physics as we currently understand them.

” — Nimur

So - does that answer your question? Anything. Anything could happen. Nimur (talk) 22:44, 29 March 2012 (UTC)

I saw a documentary on exactly this topic, they descibed the weather system shutting down, the oceans receding from the equator, all life on earth dying, etc.. Plasmic Physics (talk) 22:57, 29 March 2012 (UTC)

The English language lacks a word to adequately describe such hyper-speculative programs, which are indeed a staple of science channels the world over. May I suggest "makestuffupumentary"? They've taken a model with hundreds of unrelated variables and woggled the dials around (usually to the most cinematically exciting values) and say "what would happen if". -- Finlay McWalterჷTalk 23:08, 29 March 2012 (UTC)

It would be certain death to anything on the "sun" side in a very short amount of time, far less then 3 months. Without a night time to cool things down, my completely uneducated speculative guess, between the tropics everything would be dead within a week. Vespine (talk) 23:26, 29 March 2012 (UTC)

On the Sun side, temperatures would go up by about the fourth root of 2 times the Kelvin temperature, so a daily average of 20 C would go to 70 C, which I agree is pretty unpleasant. Offhand I think it would take ~2-3 days before it is too hot to be tolerable to humans. Dragons flight (talk) 00:04, 30 March 2012 (UTC)

Nay, it would take much less than one day. :) Really though, there are some factors that would be hard to figure out - for example, 70 C would put so much water vapor into the air - what would that do to the greenhouse effect and albedo? But meanwhile water would be getting lost to the dark side where it would be locked up in ice. There would also be huge salt deposits where I suppose briny water would lurk and defy (almost) all attempts at evaporation. I'm not sure if you end up with Venus or the dark side of Mercury, or something truly weird and novel. I doubt it would look like in the "crockumentary" though. Wnt (talk) 14:36, 30 March 2012 (UTC)

This is the television program. [4] No less inane than any other speculation on the topic, I suppose. Wnt (talk) 23:57, 29 March 2012 (UTC)

By the way, has no one thought to ask Alan Jackson? --Trovatore (talk) 00:39, 30 March 2012 (UTC)

To answer Finlay's question: the term "crockumentary" has been used to describe perceived junk documentaries. Fox News has used it before. 207.6.208.66 (talk) 01:14, 30 March 2012 (UTC)

Fox "News" questioning the academic stridency of anything is pure, unadulterated irony. --Jayron32 02:40, 30 March 2012 (UTC)

there will be wave , Water Nosfim — Preceding unsigned comment added by 81.218.91.170 (talk) 07:58, 30 March 2012 (UTC)

If the Earth were tidally locked, presumably even with no rotation the atmosphere would redistribute heat to the night side. Given the thickness and composition of Earth's atmosphere, I wonder how the day side-night side temperature difference would be mitigated as compared to a situation with a very thin atmosphere. Duoduoduo (talk) 15:08, 30 March 2012 (UTC)

You would end up with very strong winds blowing from the day side to the night side because of convection currents (it's the same process as makes prevailing winds blow from the equator to the poles, just more extreme). That would be enough to transfer a lot of heat. It is very difficult to judge exactly how much, though. What kind of greenhouse effect you end up with would be significant - there isn't a great deal of difference between the day and night side of Venus despite a day lasting several months, and that's because of the greenhouse effect - the night side can't actually cool down much because the heat is trapped. I'm speculating here, but I expect the convection currents would be enough to keep the levels of water vapour reasonably constant on both sides of the Earth, so the night side would be kept reasonably warm. If we compare it to the moon, which has no atmosphere to regulate temperature at all, the day side gets up to +180C and the night side down to -150C. The Earth would show a significantly smaller variation than that, and presumably a fairly similar average to now (depending on exactly what happens to the greenhouse effect), so I think Dragon Flight's estimate of +70C on the day side is reasonably (hotter at the equator and cooler at the poles, the same as it is now). The night side might get down to -50C or so? Those are just educated guesses, though. --Tango (talk) 20:21, 30 March 2012 (UTC)

March 30

Things without Mass

These are probably straightforward questions for any physicists out there, but:

• Have we found or identified things without mass (or matter, if you prefer) in the universe?
• If not, are there not-unproven theories that allow for or expect to find massless or matterless things?
• Where do forces and waves (and torques and etc.) fit in? Are they considered things, or effects of things? 207.6.208.66 (talk) 01:35, 30 March 2012 (UTC)

Well, photons have zero rest mass, or at least that's the current thinking, and by default mass means "rest mass" these days.

If you mean that the things have no mass-energy, I suppose that depends on what you mean by a "thing". I am not aware of any way that a physical object can be detected if it has no mass-energy. But the number seven doesn't seem to have any mass-energy, and has arguably been "found", at least if you're a mathematical realist. --Trovatore (talk) 02:06, 30 March 2012 (UTC)

This question might even boil down to metaphysical naturalism, the theory that the only kind of things that "exist" are made of "physical stuff", i.e. mass and energy. In that respect, nothing has been found which conclusivley proves "non-physical" things exist, but a few things, perhaps the most well known being consciousness, present as yet unsolved problems to the position. Vespine (talk) 03:28, 30 March 2012 (UTC)

Maybe just add that it's probably a question of philosophy as much as physics. Specifically metaphysics. Vespine (talk)

Last one. As to the "not unproven theories that allow massless or matterles things"; Cartesian dualism, or more specifically Substance dualism would fall into that category. Vespine (talk) 03:36, 30 March 2012 (UTC)

See, and I thought only the Catholics had a Mass... --Jayron32 03:50, 30 March 2012 (UTC)

Look up wikt:Mass and wikt:Mess. The original meaning is simply the amount of food put out for a meal. (The symbolic wafer has apparently wandered a way from the Last Supper) But Newton's mass has a different etymology entirely. Wnt (talk) 04:25, 30 March 2012 (UTC)

Er, no. The Wiktionary entry for 'mass' clearly indicates that the name for the church ritual derives from the dismissal sentence 'Ite, missa est'. This has nothing to do with amounts of food; it just means "(You can/should) go, it (our prayer) has been sent." AlexTiefling (talk) 13:23, 30 March 2012 (UTC)

Actually, for 'Mass', which I hadn't read (I guess I should have remembered article names over there are case sensitive!). I find myself very skeptical of this interpretation but it's off topic, and not my field. Wnt (talk) 14:28, 30 March 2012 (UTC)

Hmmm, agreed that all particles have a finite mass-energy. Photons would have zero mass-energy if they stood still, while massive particles would have infinite energy at the speed of light, so we don't see these things. Fundamental forces are mediated by particles - with the possible exception if quantum gravity can't be worked out, and anything else a real physicist might think of... These particles, and forces, have mass, or release mass. For example the binding energy of a nucleus makes it less massive so energy has to go in to bring out the protons and electrons doh! neutrons. Or the negative energy of the Casimir effect (maybe lack of virtual particles?). But potential energy e.g. between two charged objects brought together can also have positive mass...

Hypothetically, if you had a "zero mass electron", and you brought it near a regular electron, I'd expect it to go accelerating away at an infinite rate (zero inertia). But with access to a proton I suppose it would zip to it from any distance based on the most infinitesimal force. It would certainly be very weird - I wonder if there's a stronger way to refute the possibility. Wnt (talk) 04:09, 30 March 2012 (UTC)

Thanks for the responses: I suppose I should have clarified that I was considering detectable phenomena rather than concepts or ideas. Are zero-mass electrons possible? I was lead to believe (by a school no less!) that they had a fixed mass. They also decided that Newtonian physics sufficiently explained how things worked, so I wouldn't be surprised that they were wrong.

Interesting point on the rest mass of photons: though I can't find exactly where in the speed of light article it outright states that photons move at a fixed speed, I'm inferring it from everyone above. Theoretically speaking, then, what would happen to photons caught in black holes? Would they no longer be able to move? (Or if preferred, what do current theories stipulate might happen to photons when they meet with a black hole?) 207.6.208.66 (talk) 05:19, 30 March 2012 (UTC)

Emphatically no, no zero mass electrons have ever been suggested. Photons move at the speed of light, always; this is the key axiom underlying the theory of relativity. Even in black holes they move at the speed of light, relative to the space they're in, until the singularity is reached; and the mathematical description just ends there without explanation. Wnt (talk) 05:36, 30 March 2012 (UTC)

Well, I guess that makes sense then. Thanks a bunch to everyone, especially Wnt! 207.6.208.66 (talk) 05:45, 30 March 2012 (UTC)

Flat, empty spacetime is something that physically exists, yet in non-quantum physics at least doesn't inherently have any mass to it, even if you take the ambiguous term "mass" to mean "relativistic mass". However, in quantum physics spacetime does inherently have a vacuum energy (which is equivalent to a "vacuum relativistic mass"), although how much of that "vacuum relativistic mass" spacetime has is unclear, since looking at vacuum energy from the perspective of quantum field theory or from the perspective of the cosmological constant gives wildly different values for that, for reasons that aren't understood. Red Act (talk) 06:59, 30 March 2012 (UTC)

Photons always move at the speed of light, true, but what that speed is depends on the medium the photons are passing through. When people refer to "the speed of light" without elaboration they mean the speed of light in a vacuum. But scientists can slow down light dramatically, using low temperature mediums. Just recently I read (maybe in Scientific American?) that in a recent experiment light was slowed down to about 38 miles per hour.

Is it conceptually possible to slow light to 0 miles per hour? Would it be massless/energyless then? Duoduoduo (talk) 19:43, 30 March 2012 (UTC)

Look at slow light. The distinction between phase velocity, group velocity, and signal velocity gets really tricky. I've seen different takes on the situation with photons subject to a refractive index - as I understand it, though, all the "slowing" of light has to do with properties of the wave model; whenever you're looking at an actual photon that thing should be moving at the honest to God vacuum speed of light. Note I could well be wrong/confused on that point - I've seen explanations up to and including modeling electric field as a curvature of space to explain the slower speed. Wnt (talk) 21:01, 30 March 2012 (UTC)

eco-friendly utopia

Imagine everything about pollution, greenhouse effect, blah blah... is magically fixed. Now how can we start again and build cities that are completely eco-friendly, without giving up all the technology we have now (like, say, going back into caves). I mean do we have a theoretical idea of what an eco-friendly city, town, whatever, looks like? I mean we scream about global warming and pollution all the time, but what is it that we ultimately want to reach exactly?--Irrational number (talk) 07:41, 30 March 2012 (UTC)

If you have a subscription to New Scientist, this article on "Rebuilding civilisation from scratch" explores this. The engineer's dream (if not necessarily the sociologist's) is an arcology - a largely self-contained planned city which attempts to be as efficient as possible to heat and cool, to water and feed, to light, and to provide transport around. "What we want to reach" is more of a political question, and it'll depend on who you ask, but the technological approach is roughly bright green environmentalism. Smurrayinchester 08:31, 30 March 2012 (UTC)

I believe population is the real problem. If 99% of the people would be good enough to disintegrate, we would still have enough to maintain a technological society yet not enough to create ecological catastrophes. StuRat (talk) 08:37, 30 March 2012 (UTC)

So what your saying is, is that we ought to nuke Zuccotti Park? 203.27.72.5 (talk) 21:00, 30 March 2012 (UTC)

There are many who would argue that anything less than giving up all technology is pollution. --145.94.77.43 (talk) 09:35, 30 March 2012 (UTC)

There are lots of positions one could take as to the outcome, but the essential goal of all of them is some form of sustainability — e.g., a system that can continue without eventually destroying itself. The problems with global warming and pollution in their current forms is that they are rapidly becoming unsustainable, and the consequences of that are going to be massive in terms of human health, lived environments, and human economies. There are practical solutions, for example, towards reducing carbon dioxide output substantially that would keep the base temperature deviation within holocene levels, for example. They don't involve becoming an eco-topia or anything like that; they involve capturing emissions, improving efficiency, using other forms of energy generation, etc. (e.g. the Stabilization Wedge Game). --Mr.98 (talk) 13:24, 30 March 2012 (UTC)

Tangential, but I wanted to pull this quote from Mr.98's link (emphasis mine):

• "A final criticism is that the Wedge Game focuses on technological fixes rather than fundamentally challenging the endless growth economy that is at the heart of global climate change.The 2007 IPCC reports state clearly that economic and demographic growth are the fundamental drivers of global climate change." I think this aspect is often overlooked. Our basic economic principles which equate growth with wealth and prosperity inherently lead to unstable, unstustainable resource exploitation. SemanticMantis (talk) 15:09, 30 March 2012 (UTC)

I was looking for something more... detailed. I mean I know an eco-friendly system is such that it won't destroy itself and all of those things, but what exactly would it be like? Do we know enough about what it must look like?--Irrational number (talk) 17:39, 30 March 2012 (UTC)

With a lower population, it would work pretty much like it does now. That is, people would continue to cut down trees to plant crops, but this would now only take a small portion of the total land, because of the much smaller population. Fossil fuels would still be unsustainable, though, in that we are currently using them up at something like a million times the rate at which they are formed, and we can't cut our usage to 1 millionth merely by reducing population. The good news is, renewable energy sources like solar and hydro work far better with lower populations. That is, there's just as much sunlight and water, but far less energy is needed. Creating greenhouse gases would no longer be a concern at 1% of our current population, as that lower rate wouldn't have a measurable effect on the climate. Of course, if population began to grow, then the ecology would again be threatened, so we would need controls in place to prevent that. My point is, that it's fundamentally our current population which is unsustainable, and the effects on the environment are just a symptom of this problem. StuRat (talk) 17:54, 30 March 2012 (UTC)

StuRat, you make a good point about population. However, it's not just our population, it's our population and our rate of resource use. There are indeed two factors that can in principle be adjusted. SemanticMantis (talk) 18:12, 30 March 2012 (UTC)

True, but we often make this mistake of thinking that, say, American Indians, lived in a totally sustainable way, when, if they had the same population we do, they would have had environmental problems, too. For example, all those feces, if not sent through a sewage treatment plant, would pollute all the rivers, lakes, and aquifers. That population would also quickly kill off all the wild game. StuRat (talk) 20:07, 30 March 2012 (UTC)

Then we are agreed. While per capita rate of resource usage is the important factor for a fixed population size, the total resource usage rate goes up linearly with population, if they use resources at a fixed per capita rate. Given a certain total target usage rate (which is really what sustainability is), we must then use less per capita to support more people. SemanticMantis (talk) 20:18, 30 March 2012 (UTC)

Right, but I don't know if it's possible to reduce our level of consumption per capita to be sustainable at the current population, much less with an ever-expanding population. At out current pop, about the best we can do is use up one resource, then move on to the next, like from oil to natural gas, to coal, and hope global warming isn't too bad. There's basically no hope we can maintain our current population without having a major ecological impact. StuRat (talk) 00:50, 31 March 2012 (UTC)

The answers to your revised question have more to do with sociology and culture than engineering and hard science. As such, you're basically asking for a political and cultural philosophy that supports sustainable practices. This is basically the realm of speculative fiction. If that angle interests you, I highly recommend this book [5], which (in great detail) posits a societal system that is truly sustainable. Spoiler alert: it involves no urban/rural divide, no cars or fossil fuels, no beasts of burden, and no eating meat ;) SemanticMantis (talk) 20:26, 30 March 2012 (UTC)

Sustainability depends on time horizon. Ultimately, only maximum entropy condition is sustainable. 203.27.72.5 (talk) 21:08, 30 March 2012 (UTC)

let me put it this way: we leave the earth, and meet a fancy beautiful, non-poluted planet just like our earth, with (for the sake of the question) identical conditions. Now we want to build cities, what would the city be like? I want a picture detailed enough to be able to be analyzed for seeing whether it's practical or not (horrible phrasing, sorry!!)--Irrational number (talk) 21:34, 30 March 2012 (UTC)

It really depends on what your goals are. If your only consideration is minimising pollution, then fairly obviously the solution is not to build a city at all and just leave the planet alone. Clearly, you want the minimise pollution while still having humans living there, but how many humans? In what level of comfort? If you want a similar population and standard of living as we have now, then your main problem really isn't the design of the cities. It's power generation. Your main priority would be to find a means of power generation that doesn't rely on burning fossil fuels. We have plenty of those now (nuclear, solar, wind, tidal, hydro, biomass, etc.), they just tend to be more expensive and less convenient than fossil fuels so they aren't used as much. There are other forms of pollution, but getting rid of fossil fuels would get you 90% of the way there. --Tango (talk) 21:50, 30 March 2012 (UTC)

Well, living underground and leaving the surface alone would be nice. I happen to think underground nuclear power is less destructive to the environment than massive solar farms, wind farms, and dams, so I'd go that way. Mines should be the traditional type, not strip mines or mountaintop removal. Food should be grown hydroponically. Transportation would be subways and elevators. StuRat (talk) 01:08, 31 March 2012 (UTC)

I think that suggestion just belies a subjective preference for protecting superterranean environments. Why is destroying the environment of earthworms, plants' root structures and soil microbes objectively better than destroying that of any other organism? 203.27.72.5 (talk) 04:19, 31 March 2012 (UTC)

The earthworms and roots would stay relatively close to the surface, so would be safe. I'm talking about hundreds of meters/yards down. StuRat (talk) 05:26, 31 March 2012 (UTC)

I think what you really need to define (and not just you, but environmentalists in general) is what you want to avoid. Do you want to avoid causing pain, killing individual organisms, causing the extinction of species, influencing behaviours or evolution? Do you only want to avoid affecting life, or are you also adverse to polluting places that don't host life? If you try to take this all to its logical conclusion, you just end up with a paradox; people ought not to exist (as per the Voluntary Human Extinction Movement ) so as to avoid changing the natural environment, but people exist naturally so removing them would in itself be changing the natural environment. 203.27.72.5 (talk) 06:45, 31 March 2012 (UTC)

If human beings, governed by the laws of nature as are any other form of life, are going to be part of this utopia, the idea of anything being sustained but high population growth is pretty dubious. One would have to modify humans to create a society of people averse to having children above the replacement rate for a society which had a minimal impact on the ecology of this new planet. These modified humans could live in rammed earth and cob houses and bike everywhere, or they could live in brick subdivisions and drive 500cu Eldorados. Regardless of the technology they used, the only thing stopping them from naturally expanding to fill the space available would be genetic engineering or some kind of mandated psychological programming. Even these measures would fail given enough generations of mutation. Nevard (talk) 20:53, 31 March 2012 (UTC)

Ironic how all attempts to preserve nature inherently involve fighting against the natural processes that tend to destroy it. 203.27.72.5 (talk) 02:07, 1 April 2012 (UTC)

Two questions about plastic bag bans

The city where I live banned plastic bags in June last year, and so far it seems to have good public support. Plastic bag bans seem to be all the rage in the Philippines right now, with cities like Angeles, Muntinlupa, Pasig and Makati implementing them. I have two questions about such bans:

• 1. What are the short-term and long-term ecological effects of such bans? (both good and bad)

One of the advantages of plastic bag bans is that it cleans up the environment, or does it? I read somewhere that in the long-term, plastic bag bans are actually harmful to the environment, since making paper bags takes up more water and cuts more trees. However, at least they biodegrade easily. So, have there ever been studies about the effects of bans, both short-term and long-term? I'm not asking for opinions, but actual results from studies or experiences.

• 2. Which was the first location in the world to ban plastic bags, and where?

I know San Francisco was the first city in the United States to ban plastic bags, and Bangladesh was among the first countries to ban their use, but where was the first place in the world to ban them, and when? I could not find enough information about this online, but according to some sources, it was a small village in Australia (whose name I forgot), but is this true?

Narutolovehinata5 ^tccsdnew 13:55, 30 March 2012 (UTC)

I think that more information with regard to the proposed legal status of alternatives, as explained in Oxo Biodegradable, Biodegradable bag, and Bioplastic, is necessary to evaluate the effect of such a ban. Presently it appears that degradability is not well defined with some international standard (and more importantly, there's no clear logical dividing line either), so exactly where the line is drawn is important. Wnt (talk) 14:18, 30 March 2012 (UTC)

I read somewhere (unfortunately I can't remember where) that paper bags take a very long time to degrade, which would mean that biodegradability is at best a long term but not short term advantage of paper over plastic.

My understanding is that paper is made of some pretty nasty chemicals. Would that mean that biodegradability is a bad thing?

A disadvantage of plastic bags is that animals eat them and die as a result of a clogged up digestive system. Duoduoduo (talk) 14:57, 30 March 2012 (UTC)

Paper is made with some nasty chemicals more than of them, depending in part on what is done with it - see environmental impact of paper, bleaching of wood pulp. In landfill conditions, denied access to oxygen and nutrients, biodegradation of many things is difficult.

In practice, I think that the urban dweller's main objection to plastic bags is when they end up in every tree, crinkling away in the wind like the flag of some small trashy nation, or when they appear visibly at the shoreline of a river. Any sort of photo- or bio-degradation is enough to help with that. Wnt (talk) 15:23, 30 March 2012 (UTC)

I think the best idea is to get everyone to use reusable bags. (Of course, if they feel the need to wash them after each use, with detergent, this has a high environmental cost, too.) Brown paper bags aren't bleached, which is better for the environment and they biodegrade quickly. The glossy, bleached and dyed paper bags from high-end stores are more of a problem. One other advantage of paper bags is that they quickly get soaked and flattened and thus stop blowing around, unlike plastic bags, which seems to blow around until they hit a chain linked fence or something like that. StuRat (talk) 15:29, 30 March 2012 (UTC)

Actually guys, I'm asking about the effects of plastic bag bans, not about the bags themselves. I'm asking what are the good and bad short and long-term effects of plastic bag bans, not arguments in favor and against recyclable bags. Narutolovehinata5 ^tccsdnew 15:34, 30 March 2012 (UTC)

Well, to reiterate, the specifics depend on the ban. Will a patchwork of overbroad local bans damage demand for oxydegradable bags and thus create more long-term trash elsewhere? Will they encourage the use of paper which then leads to more deforestation? Even with a single known law in your hands it is very hard to work out what it will do, and when it is unspecified... Wnt (talk) 16:55, 30 March 2012 (UTC)

Belgium banned "free" shopping bags years ago, customers have to ask specifically for them and shops have to charge for them. Not sure if they were the first to do it. Since then most shops only have "reusable" bags, though you could question the reusability of the cheapest ones (0.10€), they're made from that stretchable plastic that you know won't last too long if you carry something heavy. This only appies to supermarkets, other shops like fashion, electronics etc. don't mind paying for the bags themselves. Ever since the Greens were in the government some 10 to 15 years ago (??), an eco-tax was introduced on all "avoidable" non-recyclable packaging. That meant 0.50€ for plastic bottles, since recycled glass is an alternative, high taxes on non-rechargeable batteries, on razors with a fixed handle and so on. Basically, all the cheapest products got much more expensive... Ssscienccce (84.197.178.75) (talk) 21:38, 2 April 2012 (UTC)

Duck with face texture like a chicken's wattle

The other day at a pond in northern Virginia I saw a duck and instead of feathers on the front of its head above its bill and around its eyes there was red bumpy skin like unto a chicken's wattle or a turkey's head. This was only around the face area; it had feathers on the rest of its head. What species of duck have red skin on their faces? 20.137.18.53 (talk) 14:09, 30 March 2012 (UTC)

A Muscovy Duck. (+)H₃N-Protein\Chemist-CO₂(-) 14:16, 30 March 2012 (UTC)

Thank you. 20.137.18.53 (talk) 14:46, 30 March 2012 (UTC)

Or possibly a churkendoose.[6] ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:37, 31 March 2012 (UTC)

Visual range of animals that differs from humans

I understand that some birds can see into the UV spectrum. Do they have a wider visual range than humans, or is their whole visual range just shifted up a bit? To put it another way, can birds see all the same colors as us plus UV light, or are they "missing" some of the colors we can see? I'd also like to know about other animals that have a different range than us. Are there any that go the other way, seeing infrared instead of UV? And what do you think it would look like to have such different kinds of vision? 151.163.2.8 (talk) 15:36, 30 March 2012 (UTC)

You could try to follow references from Bruce MacEvoy,'s Color vision pages, chapter 1. – b_jonas 16:07, 30 March 2012 (UTC)

Humans can see ultraviolet after cataract surgery. Reputedly this was used by British intelligence, which recruited such people to "coastwatch" for signalling by German submarines - but the truth of that story seems to be hard to determine. [7] Wnt (talk) 16:52, 30 March 2012 (UTC)

For infrared, lots of animals can see that, like the pit viper. I imagine it looks similar to what we see when using an infrared scope. StuRat (talk) 19:58, 30 March 2012 (UTC)

I believe pit vipers can just detect what direction heat is coming from in a fairly vague way. They don't have any kind of lens, so they won't get a clear image. --Tango (talk) 21:53, 30 March 2012 (UTC)

Fair web info at [8] [9] . The latter sort of gets my imagination going, because it points out that the pits of a pit viper work more by their structure than any special heat receptors. It makes me wonder whether using a tissue printer and doing nothing more absurd than existing sex-change 'therapy', you might take a sensitive area of a blind person (e.g. fingertip) and replace it with a functioning pit sensor. Not saying that's a winning idea, just interesting. Wnt (talk) 20:30, 30 March 2012 (UTC)

That page says pit vipers have a resolution of about 5 degrees, or roughly the your hand held at arm's length. That kind of resolution would be a lot better than nothing for a blind person, but it wouldn't be any near a replacement for sight. And remember, you're just seeing heat, which isn't a very precise way of seeing things anyway (the long wavelength doesn't help). I don't think a pit-fingered blind person would be able to do much more than identify where doors and windows are, which many of them can do with their eyes anyway (what we call "blind" isn't usually no sight at all, although it can be in some cases). --Tango (talk) 22:03, 30 March 2012 (UTC)

Another thing is that many animals are sensitive to polarization of light, so they can see visual structure that is invisible to us. Looie496 (talk) 21:42, 30 March 2012 (UTC)

Most Birds have four types of pigments unlike the the three that humans have. So they don't have any missing colours. In fact with more receptors, they can distinguish more colours. ( mathematically, i think of it this way: with three receptors, all the colours you can see fall in a 3D space; for a given intensity, all the possible shades will fall on 2D space. see RGB-> HSV coding of colours; with more receptors, you get more shades) As a concrete example, you don't distinguish blue+yellow light from green as they both activate red, green and blue receptors, maximally activating the green receptors. birds will be able to tell apart certain pure shades from a mixture that humans can't tell apart. As an aside, birds have two types of red receptors: both have the same rhodopsin sensor, but each has a differently coloured oil droplet that gives the whole cell a different sensitivity. So the longest wavelength peak for the filtered red cell is around 610nm, a bit lower than ours. But a total of 5 primary colours! hope this answers your questionStaticd (talk) 18:31, 31 March 2012 (UTC)

There are probably human tetrachromats too. --ColinFine (talk) 11:57, 1 April 2012 (UTC)

Bees can see UV light which has led some flowers to evolve patterns which are not visible to humans. Vespine (talk) 23:57, 1 April 2012 (UTC)

Help with bird identification

I saw this bird at a park in Southern California. It was maybe six inches long, and appears to be a juvenile, though it doesn't resemble the juveniles of the other bird species that were around. Can anyone tell what it is? 69.111.79.119 (talk) 15:47, 30 March 2012 (UTC)

What were the other adult birds you saw around? Coots?, grebes? My current best guess is Pied-billed_Grebe, note the distinctive dark patch on the beak. (Yes, I know the chick pictured in our article doesn't look much like yours... but this google image search shows how much the chicks can vary [10]) SemanticMantis (talk) 16:01, 30 March 2012 (UTC)

Heavy water plant

What is the purpose of the pipes running up the hillside at the Vemork plant? I am asssuming they have nothing to do with heavy water production: maybe connected with the factory's original purpose of fertilizer production? SpinningSpark 17:17, 30 March 2012 (UTC)

Its a hydro-electric plant. These are the pipes delivering the water from the reservoir to the turbines.--Aspro (talk) 17:36, 30 March 2012 (UTC)

That is, the Penstocks. DMacks (talk) 19:05, 30 March 2012 (UTC)

second part of question: distributing energy in the world economy via carriers

Guys and gals, thanks for the detailed responses to the first part of my question above. The second part was not addressed at all - could someone answer it? (About depletable/refillable energy carriers for the world economy akin to a biological ATP/ADP energy carrier analogue.) Please assume infinite energy is available at a single point on Earth only, and all these 'atp' analogues have to be routed there to be recharged. what would work in practice? If you have any other ideas for addressing my thinking in the second part of the question, or references, I welcome them. Thank you! 188.157.72.10 (talk) 18:29, 30 March 2012 (UTC)

"Transporting energy from a single point source" is a perfectly reasonable simplification of our present energy infrastructure. Sure, we've got multiple point sources, but you can generalize it as "one to many" and it makes sense. And we transport energy around. And that's without getting into "infinite" energy; once you posit that, you can do pretty much whatever you feel like doing, because waste becomes an utter non-factor. So yeah, stick the infinite energy thingamabob on the coastline, crack water into hydrogen, ship it, and burn it. Nice clean fuel cycle that'll power more or less anything. Note that we're not talking anything fundamentally distinct from my local swap-a-propane-can program that I use to run my grill, so I don't see the need to reinvent much terminology. — Lomn 18:38, 30 March 2012 (UTC)

If you want to transport large amounts of energy around the world, I suggest copper wires carrying electricity (your "ATP" could be converted into electricity first). They do lose a bit over the course of the transport, but, so long as you have an infinite energy supply, that's not a problem. This isn't currently done between continents, but I see no reason why oceanic cables similar to the ones which carry phone and Internet signals couldn't also transfer power. Laying all this cable would cost quite a bit, up front, but then we would no longer need to send oil tankers all over the world, endangering the environment, etc. Electricity is also the most useful form of energy for most applications. For those applications where we still need another form, like airplane fuel, it could be created using electricity, close to where it's needed. See synthetic fuel. Electricity would make more sense in cars than gasoline, if it was almost free. Each parking space could then charge you a few pennies to recharge your car as it sits. StuRat (talk) 19:32, 30 March 2012 (UTC)

having more rem dreaming or at least additive From-dream awakemenment

how could i get this?.. thanks!. 109.65.39.161 (talk) 19:39, 30 March 2012 (UTC)

You need to ask your question more clearly. I have no idea what "additive from-dream awakenment" is. See REM sleep for basics. I wonder if lucid dreaming is what you're really interested in. Note that we can't give you specific medical advice for treating some sleep related illness, but we can answer general questions about such an illness. Wnt (talk) 20:35, 30 March 2012 (UTC)

I believe most people dream about the same amount, the main difference is how much they remember their dreams. Keeping a dream diary is supposed to be a good way of learning to remember dreams. --Tango (talk) 20:48, 30 March 2012 (UTC)

March 31

Pupil Dilation

Is it true that one of the causes of the pupil's dilation is when the subject is romantically interested in another person with whom they are in contact?186.28.49.19 (talk) 00:49, 31 March 2012 (UTC)

See pupil dilation. The first paragraph says it "may indicate interest in the subject of attention or indicate sexual stimulation", and a scientific reference is provided. Relatedly, some cultures have believed that dilated pupils make a person more attractive, perhaps because it creates the impression of increased interest, see Belladonna_(plant)#Cosmetics. Indeed, Belladonna is so named because it was used to make a lady look beautiful. SemanticMantis (talk) 03:43, 31 March 2012 (UTC)

Back pain is common because we sleep on mattresses?

My personal experience and some thinking about this issue suggests that we're better off sleeping on the floor. When I bought a new mattress, I was adviced to get one of soft to medium firmness, these are supposed to be good for the back. I weigh 60 kg, and then a soft to medium mattress should give the best support. Firm mattresses are recommended for people over 100 kg, and super firm mattresses for people who are heavier than 160 kg. I ended up choosing one of medium firmness.

However, after several weeks sleeping on this expensive mattress, I got horrible back pains. I never had back pain before. Since my old mattress was a lot firmer than the new mattress, I was convinced that my back needs to rest on a firm mattress. I decided to sleep on my mattress back and the back pain was completely gone in a matter of a week.

Then, I still needed to buy a good mattress that would fit in my new bed, so I went back to the dealer, explaining the problem. A new super firm mattress was ordered. Unfortunately for me, these are also much more expensive than the medium firmness mattresses. The end result is that I now sleep on a super firm mattress, which also costs a super amount of money :( .

During the time I had back pain while sleeping on the medium matress, I noted the following. If you sleep on a hard mattress or lay on the floor, you can move your hand beneath the lower part of your back. But on a mattress of medium firmness, what happens is that this space is filled up by the mattress, so the mattress keeps your back in that position.

This is the only relevant difference that I noted, so it seems to me that the lower back should not be supported by the mattress. Gravity will pull your back a bit straight and that, I guess, allows the muscles in your back to relax. A medium firmness mattress will, by supporting the lower back in its naturally bent position, prevent the muscles from relaxing properly during sleep.

Now, mattresses are a recent invention, so one has to wonder if the fact that so many people complain about back pain has something to do with sleeping on mattresses. Surely, people living in the Stone Age did not suffer as much from back pain as we do today?

Now, if sleeping on super firm mattresses is indeed good for the back, then you could just as well sleep on the floor. That is only a little less comfortable, but much cheaper. And then I'm only 60 kg, if you weigh 100 kg or more, then a super firm mattress would still be way too soft.

So, should we all do away with beds and mattresses and sleep on the ground? Count Iblis (talk) 02:34, 31 March 2012 (UTC)

There is a problem with firm mattresses, though, in that they can cause pressure points. That is, the bits of flesh squeezed between your bones and the firm mattress can have too much pressure on them. This either results in constant turning, which interrupts sleep, or in damage to those areas, like bruises. It works out that lightweight people can typically tolerate a wider range of mattresses, while the obese may not have any firmness which doesn't cause one problem or another. For a nice compromise on firmness, I suggest a mattress directly on the floor, with no bed-spring underneath. The mattress can be a thin, soft one, making it inexpensive. This also avoids the occasional problem with squeaky springs. :-) Falling out of bed is also less painful, but getting up can be more of an effort.

Note that the underlying cause of back pain in humans is that we are bipedal, but with a spine designed for quadrupedal motion, which has been modified just enough to get it to barely work. Imagine a suspension bridge balanced on it's end, then shored up until it (barely) manages to stay upright. StuRat (talk) 02:43, 31 March 2012 (UTC)

About your last point, did bipedal animals like T-Rex have some special features preventing it from getting back pain that we don't have? Count Iblis (talk) 03:07, 31 March 2012 (UTC)

Yes, their spine wasn't upright like ours, but remained relatively horizontal, with a massive tail balancing against their head and torso. For birds like the ostrich, most of the spine is also horizontal, although it often turns vertical at the head. StuRat (talk) 03:14, 31 March 2012 (UTC)

From my experience, the common types of mattresses varies quite significantly from country to country. It's generally suggested that mattresses in large parts of Asia (e.g. China, India, Malaysia) are much more firm then those in countries like NZ, the UK and the US. And the construction of mattresses also varies (although there's also usually choice), e.g. springs with foam or latex support, all latex or all foam, a combination of latex and foam etc. (With various kinds of springs such as pocket springs and inner springs, foams and fibres.) There's also fancy stuff like memory foam. I don't really understand StuRat's suggestion, if you want to save money or prefer not to use a bed then fine, but if not, just choose a bed with a solid based if that's what you prefer. Also from my experience here in NZ, the recommendations when choosing a bed seem to vary from store to store and probably sales person to sales person, but weight doesn't generally seem to be a big consideration, rather personal comfort and preference as well as sleeping position and spinal alignment when laying down. Of course trying to work out how comfortable a mattress is from lying on it for a few minutes isn't that successful, but I guess it's better then nothing. (And I don't know if it's the same in the US but here most chains including bed shop chains seem to have exclusive mattresses, the range or at least names of the mattresses are completely different between chains even if the brand is the same. It sounds like there's a lot of dodgy stuff going on with warranties in the US [11].) Nil Einne (talk) 05:11, 31 March 2012 (UTC)

My point was that the bed frame, box spring, and mattress are only needed if you want a very soft bed. If you want a firm bed, much of that is unnecessary. Just a comforter on a shag carpet with padding might even be sufficient. But, if you want to spend extra money to be conventional, you certainly can. StuRat (talk) 05:20, 31 March 2012 (UTC)

I don't think it's just a matter of being conventional, having the bed too low down can make it difficult to get in and out of, particularly if you're old. Being so low down also makes engaging with other people in the room that aren't on the bed odd. Elevating the mattress may also allow stuff to be stored under the bed and makes cleaning easier (putting the mattress directly on the floor isn't going to completely stop dust and dirt going under it). In some countries the 'box spring' you keep speaking of is fairy uncommon, possibly present in fold out beds but little else. If you have flexible supports it's usually in the form of flexible slats, but in other cases, any sort flexible base is rare, when people do have mattress on the floor, it's primarily to save money, not because they think it's better. Nil Einne (talk) 08:33, 31 March 2012 (UTC)

If the box spring has a use I have yet to figure it out; I think it's basically cosmetic, a bustle for a piece of furniture. My gut reaction is that having beds raised off the ground at all is an elaborate contraption designed to keep people free from rats and thus the bubonic plague, but I'm unaware of evidence for this. But checking our article on bed it does mention that in Germany raised beds became popular around the 13th century as "luxury increased" (which indeed was a consequence of the plague, which relieved the earth of some of its burden). I suppose it's even possible that the change was accomplished by natural selection, with no conscious awareness of the reason! Wnt (talk) 14:06, 31 March 2012 (UTC)

To solve the issue of the top of the bed being too low, perhaps placing the mattress above a set of drawers would make most sense. This would dramatically increase storage area in the bedroom and not allow dust to accumulate underneath. (You wouldn't want handles that stick out, but rather indentations in the front of each drawer that could be used as hand-holds.) I've seen this approach done with waterbeds, but not with a regular mattress. I wonder why not. Is there a concern that bedbugs would have more places to hide ? StuRat (talk) 14:16, 31 March 2012 (UTC)

You haven't seen this done with a regular matress, Stu? In my (UK) experience it's very common. The base of the bed comprises a fabric-covered wooden frame (usually on castors) with 4 large recessed-handled drawers, two each side, occupying its full volume, and with a solid, fabric covered top about 15" off the floor on which any design of mattress matching its dimensions (which are standardised to the standard bed sizes) can be placed. (Single-bed versions may have only two drawers.)

The frame usually comprises two 2-drawer halves (head and foot ends) for ease of transport, which are firmly attached together in situ; the drawers are commonly used to store spare bed linen and clothes: bedbugs are not very common in the UK, and in any case I understand that they prefer crevices and cracks in walls and furniture rather than clothes, so this type of bed would not increase their prevalence; a bigger worry would be clothes moths, but one takes the usual elementary precautions against them as in any other clothes drawer or wardrobe.

I've been sleeping on such a bed for nearly 25 years (and for several years one of the family cats liked to sleep on my socks in the drawer immediately under my head end/side, which I therefore left open a few inches for her convenience).

Oddly, our main article Bed doesn't describe or name this exact type, but it's briefly described at the end of Platform bed as a "storage platform bed". Examples can currently be seen in any furniture or specialist bedding shop in the UK. {The poster formerly known as 87.81.230.195} — Preceding unsigned comment added by 90.197.66.209 (talk) 17:53, 31 March 2012 (UTC)

Yes, those beds are quite common. The flaw I've found with them is that you need the bedroom to be about twice as wide as the bed if you're going to be able to make full use of the drawers without needing to move the bed in order to get into them. --Tango (talk) 19:03, 31 March 2012 (UTC)

Well, it's only a flaw if you actually have a very narrow bedroom. Obviously, one should always choose furniture suitable for the room in which it's to be used. {The poster formerly known as 87.81.230.195} 90.197.66.209 (talk) 23:13, 31 March 2012 (UTC)

You can also get a storage bed where the mattress lifts up and the whole of the bottom of the bed becomes accessible. This would solve the problem of narrow rooms. --TammyMoet (talk) 08:25, 1 April 2012 (UTC)

Bed#Types of beds includes:

A captain's bed (also known as a chest bed or cabin bed) is a platform bed with drawers and storage compartments built in underneath.

Captain's bed (currently a redlink) may not be the more common name for this, but it is the one I am familiar with. -- ToE 01:11, 1 April 2012 (UTC)

Yes, I noticed that that was the nearest description in the Bed article to what we're talking about, but to me the term implies one side being flush against the wall (or bulkhead), rather than with drawers etc on both sides. When I went shopping today I meant to ask in a bedding shop what they call it, but it being Sunday that particular shop was closed. {The poster formerly known as 87.81.230.195} 90.197.66.103 (talk) 14:41, 1 April 2012 (UTC)

Silicone rubber lids

I have a nice set of cookware from Anchor Hocking. They are glass bowls suitable for storing, microwaving, and serving food. However, one deficiency is that they have plastic lids which warp if subjected to microwaving. This makes it necessary to remove the lids and place paper towels over the top to catch any splashes, and the paper towels sometimes fall into the food. So, I'm wondering why they didn't make the lids out of silicone rubber.

1) Is it prohibitively expensive ?

2) Does silicone rubber have a coefficient of thermal expansion that doesn't work with glass ?

3) I read that fillers used for silicone rubber can emit annoying fumes, would that be the reason ? Are there no fillers which don't do this ?

4) Also, could the lids be made of clear silicone rubber, or would they need to be colored ?

StuRat (talk) 14:28, 31 March 2012 (UTC)

I don't see why it couldn't be done. In fact, if I'm not mistaken, we (meaning my wife and I) have a lid made of silicone for a glass bowl. Dismas|^(talk) 14:41, 31 March 2012 (UTC)

Clear or colored ? Have you microwaved it with the lid on ? If so, were there any fumes ? StuRat (talk) 15:13, 31 March 2012 (UTC)

I looked in our cabinets but can't find the lid right now. But I do remember it being less rigid than plastic. It's blue in color and there were no fumes. When I microwaved with it, I popped the top to keep it from building pressure. But yes, I microwaved with it. Dismas|^(talk) 15:23, 31 March 2012 (UTC)

I have this silicone lid product [12], which has several uses. I use it on the stove top, in the microwave, and as a jar opener. I've never noticed any fumes, and it comes into contact with hot food all the time, yet does not stain or discolor. SemanticMantis (talk) 15:48, 31 March 2012 (UTC)

April 1

exponential power of 2 and number of ancestors 30 generations ago

I'm sure the answer to this is simple, but for some reason I just can't think of it.

A person has 2 parents, 4 grandparents, 8 great-grandparents, and so on. So it's 2 to the power of the number of generations. Yet it wasn't until 1800ish that there were a billion people on earth. All you have to do is go back 30 generations for 2-to-the-30th to equal a billion; that's at least 600 years, conservatively. So how could you have a billion great-great-great-to the thirtieth-power-grandparents, when there weren't that many people on earth?

I will feel really stupid when someone explains this, because it must be obvious.

It's March 31st where I am, so, no, this isn't some kind of April Fool's trick.76.218.9.50 (talk) 00:48, 1 April 2012 (UTC)

Inbreeding. At some point in the past, the same person occupies multiple places in your family tree; i.e. one man is your great-9x-grandfather multiple ways (i.e. you decend via his son on one side of your family, and via his daughter on the other side). The further back you go, the more likely this is to happen. It is unlikely that this would work for 3-4 generations, where people generally know each other and try to avoid marrying close cousins. But when you get back 9-10 generations, there's no way that you know who you are related to, so it is quite likely for your parents to have shared some many-centuries-old ancestor, likely several. --Jayron32 00:52, 1 April 2012 (UTC)

Actually, I thought of this right after I posted -- by taking the question from the other direction. I thought, let's say in year A.D. XXXX there were 100 million people on earth. By definition, everyone alive now descends from those 100 million; yet there are many times more "slots" in the family tree than 100 million; therefore, many people occupy many different slots in the genealogical table. Somehow, this is still pretty mind-boggling, but it basically comes down to lots of people marrying their own (say) third- or fourth- (or tenth- or (gasp) first-)cousin. It would be interesting to know at what point the number of people on earth equaled exactly as many as, on average, we all have "slots" in our tree AS OF that date; clearly, it was sometime between 30 generations ago and 1800ish. That would be the tipping point toward less fourth-cousin-marriage, wouldn't it?76.218.9.50 (talk) 01:02, 1 April 2012 (UTC)

Jayron, your link led me to Pedigree collapse. Very interesting!76.218.9.50 (talk) 01:07, 1 April 2012 (UTC)

The classic example of pedigree collapse is Charles II of Spain, who I believe only had two great-great-grandparents (i.e. all 16 possible positions in the family tree are taken up by one man and one woman.) --Jayron32 01:09, 1 April 2012 (UTC)

Family tree of Charles II of Spain

Our article says "The inbreeding was so widespread in his case that all of his eight great-grandparents were descendants of Joanna of Aragon and Duke Phillip of Austria." That doesn't mean he only had two great-great-grandparents, though. His inbreeding involved a lot of uncle-niece marriages, rather than just cousin-cousin marriages, so the generations are all messed up. Joanna and Phillip will have occupied a lot of slots, but they won't all have been in the same generation (they were his great-great-great-grandparents and his great-great-great-great-great-grandparents, I haven't checked the other lines). This is his family tree. --Tango (talk) 01:44, 1 April 2012 (UTC)

In otherwords, FUBAR. --Jayron32 01:50, 1 April 2012 (UTC)

(edit conflict) All his eight great-grandparents were descendants, not children, of Joanna of Aragon and Duke Phillip of Austria; in fact, none were their children, and Charles II had 14 distinct great-great-grandparents. By my best count, Joanna of Aragon and Duke Phillip of Austria did each occupy 14 positions in his family tree: as 2 of his possible g-g-g-grandparents, 6 of his g-g-g-g-grandparents, and 6 of his g-g-g-g-g-grandparents. (Is there an easy of doing this, say by counting the cycles in the tree?)-- ToE 02:17, 1 April 2012 (UTC) (corrected from 2, 6, 5, & 1. -- ToE 02:35, 1 April 2012 (UTC))

You might also enjoy most recent common ancestor. Dragons flight (talk) 01:10, 1 April 2012 (UTC)

If you go back 29 generations, you have 2^29=537 million "slots". If we assume 20 years per generation (ie. women on average have children when they are aged 20, which is a fairly standard assumption and is about right until recently), that is 29*20=580 years ago, or about 1430. According to World population was around 450 million in 1400, but dropped significantly due to the Black Death and didn't recover for 200 years. That means the world population was more than 2^28 and less than 2^29 for around 300 years or so, which means 29 generations is the closest we'll get. I don't think there is anything particularly significant about that, though, especially since that 450 million people includes people in multiple generations - you have to fill slots in the 29th, 30th and some of the 31st out of people alive at that time (and don't forget generations will be different lengths in different parts of your family tree, so someone 20 generations above you and someone 25 generations above you could easily have been alive at the same time). It's an interesting bit of trivia, but that's all! --Tango (talk) 01:30, 1 April 2012 (UTC)

Also significant is that, until quite recently, there was very little mixing between populations. The actual number of generations to actual pedigree collapse needs to be adjudged within a specific population, and not across all humanity. Until fairly recently, for example, it would be unlikely that an Australian Aborigine and an Aztec would have any chance to share an ancestor closer than about 10,000 years to either; so any calculations made across all humanity likely overshoot the actual result by many generations. --Jayron32 01:40, 1 April 2012 (UTC)

I suspect the average generation is greater than 20 years, since women tended to have lots of kids, so their "average" age of childbirth would probably have been somewhat higher. But to return to my question: "It would be interesting to know at what point the number of people on earth equaled exactly as many as, on average, we all have 'slots' in our tree AS OF that date; clearly, it was sometime between 30 generations ago and 1800ish. That would be the tipping point toward less fourth-cousin-marriage, wouldn't it?" It is interesting to think that the "coefficient of inbreeding" (so to speak) would be decreasing with each passing moment from some date in the past, particularly since the invention of the car plus decent roads. This must have some sort of implication greater than trivia? And particularly so after a few more centuries? A good thing, I'd guess, for those of us who love our common race's diversity.76.218.9.50 (talk) 01:57, 1 April 2012 (UTC)

Pedigree collapse is indeed the term that's used. If you know your tree back a ways, you may be surprised at how many instances you'll discover of first-cousins marrying, for example - a common occurrence, at least until around 1900 when genetic issues finally came to be noticed. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:14, 1 April 2012 (UTC)

I was kidding when I used the phrase "coefficient of inbreeding" above -- but it turns out that's exactly what it's called! (Talk about successfully faking it.) Check this out, about Charles II of Spain -- an article that should be added to several different WP articles, but I'm too lazy: http://blogs.discovermagazine.com/gnxp/2009/04/inbreeding-the-downfall-of-the-spanish-hapsburgs76.218.9.50 (talk) 02:26, 1 April 2012 (UTC)

From that link: Charles II's coefficient of inbreeding was (F = 0.254), where the higher the number, the more inbreeding. "What [you are] doing here is summing up through all of the distinct paths to common ancestors. You weight this by the number of individuals between the common ancestor and the individual whose inbreeding coefficient you are calculating (note that, for example, some of Charles’ lines up ancestry back up to his common ancestors have different numbers of generations). Finally you have to include in the inbreeding coefficient of that common ancestor. Let’s play this out for a brother-sister mating. Assuming that the grandparents, of whom there are only two, are unrelated. So FA = 0. Then, it simplifies to: FI = (0.5)3 X ( 1 ) + (0.5)3 X ( 1 ) = 0.25 In other words, Charles II was moderately more inbred than the average among the offspring from brother-sister matings!" Please, somebody, start the inbreeding coefficient article! (And again, this isn't a joke -- just a coincidence; I didn't notice the April 1 thing till after I first posted above, and the link is a real one.) Start here!: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0005174 76.218.9.50 (talk) 02:38, 1 April 2012 (UTC)

I don't think anyone needs to start a new article: see Coefficient of relationship - Nunh-huh 03:14, 1 April 2012 (UTC)

... to which Inbreeding coefficient redirects. -- ToE 03:19, 1 April 2012 (UTC)

Well, thanks for patronizing me ... that's always fun. But where exactly in that article do you find THIS?: FI = Σ (0.5)i X (1 + FA) 76.218.9.50 (talk) 03:28, 1 April 2012 (UTC)

Nowhere, until you add it. Wikipedia never gets better until you make it better. --Jayron32 15:24, 1 April 2012 (UTC)

Our current theory of Common descent basically means that if you go back far enough, all life can trace its ancestry back to just one common progenitor. That article actually touches on the OP's question. Vespine (talk) 04:48, 2 April 2012 (UTC)

fine structure

why is it important to know the fine structure of an element when its wavelengths are unique to identify it. — Preceding unsigned comment added by 197.255.118.206 (talk) 01:30, 1 April 2012 (UTC)

Fine structure has technical details, but basically it allows one to probe the detailed organization of the electrons in an atom, in general all of the quantum numbers more specific than the principal quantum number. In other words, though you can identify the element by its gross structure, you can know how the electrons of that specific element are organized via the fine structure. Fine structure allows one to know specific information about a specific state of that element, for example, to distinguish between triplet oxygen and singlet oxygen. --Jayron32 01:32, 1 April 2012 (UTC)

In Situ Generation of Acid Catalyst in Esterification

Hello. Why does the acid catalyst in esterifications need to be generated in situ? If I directly add the acid, what side reactions can occur? Thanks in advance. --Mayfare (talk) 03:58, 1 April 2012 (UTC)

It doesn't need to be generated in situ. What makes you think it does? 203.27.72.5 (talk) 04:18, 1 April 2012 (UTC)

(edit conflict) Most acid catalysts used for things like Fischer esterification are common mineral acids, like sulfuric acid. Those acids are significantly hygroscopic to the point where the water they bring to the party is enough to mess up the slow, and highly equilibrium dependent, esterification process. Remember that ester hydrolysis directly competes with esterification: they both function in acidic environments, and the factor which controls the equilibrium shift is the relative amounts of alcohol to water; too much water and the reaction system won't produce good yields of ester. Indeed, in esterification you need to find ways to deal with the fact that it produces water as a byproduct, and that water itself has to be dealt with. Introducing additional water that comes with, say, the water always present in a bottle of sulfuric acid which is sitting on the shelf (so-called "concentrated sulfuric acid" is 98% acid and still has 2% water in it; lower water concentration spontaneously lose excess SO3 until the concentration settles back to a 98/2 ratio). You can use enough dessicant in the reaction to deal with the produced water, and I suppose that can also deal with the water present in the acid; but generation in situ removes one of the sources of water, which helps drive the reaction to make more product more efficiently. --Jayron32 04:22, 1 April 2012 (UTC)

Considering how exothermic the reaction of concentrated sulfuric with water is, I doubt using sulfuric acid is going to add any significant free water to the reacting mixture. According to Esterification#Preparation, sulfuric acid helps the reaction by sequestering water. 203.27.72.5 (talk) 04:51, 1 April 2012 (UTC)

Indeed. Good point. --Jayron32 04:53, 1 April 2012 (UTC)

So coming back to the OP's question, you can use externally sourced acids provided they are either also a dehydrating agent or aren't in aqeuous solution. Sometimes those acid aren't suitable e.g. if acid sensitive functional groups are present, so in that case you can get a mild acid without adding any aqeuous solution by in situ generation. If you want to get an idea of the side reactions, look at the reactants' functional groups. 203.27.72.5 (talk) 05:57, 1 April 2012 (UTC)

Say I had a simple carboxylic acid and a simple alcohol. --Mayfare (talk) 17:08, 1 April 2012 (UTC)

Regarding Common Emitter BJT configuration.

I recently came across a paragraph in an engineering textbook regarding BJT transistor configuration. According to the text, when a BJT is in common emitter configuration, and operating within the active region of the output characteristics curve , the current at the output or collector terminal is not affected by any resistor placed in series with the output. Instead, the collector current is only affected by a change in the current at the base terminal. However, according to my logic, if the resistance at the collector is increased to a large enough value or a small enough value, the collector current should change. I am really confused on this one and I just don't know how changing resistance level of a pathway doesn't change the current in the pathway. Please help. — Preceding unsigned comment added by 210.4.65.52 (talk) 09:11, 1 April 2012 (UTC)

In the active region, the transistor collector is a high impedance terminal and thus acts like a current source. The collector current will be relatively constant (assuming Vbe is constant) as long as the collector resistor does not go too high. The collector resistor and the output resistance at the collector (in h parameter terms: hoe) can be considered to be in parallel as far as the signal is concerned so there will actually be a division of current between the two resistances, but as long as Rc is small compared with hoe, essentailly all the current from the internal current source will flow through the load resistor. If the load resistor goes high enough, then the transistor will enter the saturation region. In the case of very low resistances down to zero, most of the current from the internal current source will go through the load as it is much smaller than hoe.--92.28.78.70 (talk) 13:26, 1 April 2012 (UTC)

FYI, the above user 92-something has been blocked as a sock of a banned user. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:47, 1 April 2012 (UTC)

Canning timing

Hi. I'm making a mango-lime chutney. The recipe fills 8 jars. When it comes to the processing part of the recipe, I can only fit 5 jars into my big pot of boiling water. The processing takes 15 minutes. I need to find out if it's ok to fill the other three jars at once, then wait 15 minutes for their turn to process, or wait and fill and process them, or something else. I need a source that answers this question. Thank you for your help.

I would fill 4 jars, process them and keep the chutney warm while that's happening. Then process the others. However, I wouldn't bother processing a chutney mix. When I make chutney, I sterilise the jars using a microwave method and fill them, seal and store. The vinegar and sugar in the mix preserves and prevents mould forming. My guide in all things preserving is Marguerite Patten's books. You must have a recipe there for your chutney: if it's in a book, what does the book say? --TammyMoet (talk) 12:43, 1 April 2012 (UTC)

Thank you for your advice. I appreciate that it is sourced. I have no book; the recipe was in my aunt's papers.

I would appreciate any other sources that I could read. Thank you again. — Preceding unsigned comment added by 184.147.123.69 (talk) 17:53, 1 April 2012 (UTC)

This might help, looks worth reading the linked page and other linked articles. --TammyMoet (talk) 20:09, 1 April 2012 (UTC)

Metallicity of stars

Will the increasing metalicity of stars mean the formation of earthlike planets, and eventually life, is inevivitable.? — Preceding unsigned comment added by 99.146.124.35 (talk) 14:27, 1 April 2012 (UTC)

It has already happened once. Depending on how you read the Drake equation, it is may have already happened many times. --Jayron32 15:22, 1 April 2012 (UTC)

Sound c ards

Are we really to believe that an ordinary sound card costing say $100 with some cheap spectrum analyser software, can out perform an expensive Audio analyser like the Audio Precision 1?--92.28.78.70 (talk) 16:24, 1 April 2012 (UTC)

As always, one needs specific data and details of the experiment to support any claim. Look at exactly what was compared and what the specific results were to see if "out perform" is a valid conclusion or is specific to certain types of performance in certain situations. But note well that cost is not a good measure of quality (or more precisely, that only expensive things can be good or that cheaper things cannot also be good). To a certain approximation, RedHat's made a fortune selling software that is available for free:) DMacks (talk) 16:57, 1 April 2012 (UTC)

Another important point to keep in mind: audio electronics are quite simple, compared to other domains of electronic engineering. Audio signals have very narrow bandwidths - only a hundred kilohertz will provide very sufficient oversampling. The signal center-frequency is at 0 hertz... when digitized, a low bit-rate is sufficient... even in the analog domain, the signal to noise ratio need not be any better than the perceptual noise sensitivity of the human ear - only maybe 40 dB (about 10 or 12 bits, for the digitally-minded; though CDs and others use 14- or 16-bit samples)... so from this standpoint, every specification is trivial to design. It doesn't take cutting-edge analog or digital hardware; and with today's computer horsepower, even a naively-implemented software can trivially process the entire data representation of the human audible range. A general-purpose, low-end $200 oscilloscope will probably outperform an "audio analyzer" on most technical specifications.

The "value-add" of professional audio equipment tends to come in the form of other intangible goods: reliability; brand-recognition, and the consequent perceived status for the bearer. In the case of audio processing systems, usability and user interface may be better on a high-end system. While I know how to perform any arbitrary signal processing on my audio-card in C, most people find the process a bit convoluted, and prefer user-interfaces with things like sampling loops, sliders, and one-button effects processors. So, there's a market for expensive audio hardware. Even I have been known to spend more money than I should on a tube-amp, whose complicated, "nonlinear" analog system-response is easily modeled by a cheap DSP; I bought my tube-amp "because it was awesome," not really because its tone was any better or different than my mini DSP-driven practice amp. It's 2012; the MOS transistor is, for all purposes, perfectly ideal in the kilohertz range; and the microprocessor can run arbitrarily complex software on each sample; so these facts really invalidate the old-fogey claims about tube tone quality. The same logic applies to sound-cards. Nimur (talk) 17:50, 1 April 2012 (UTC)

FYI, the OP has been blocked as a sock of a banned user. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:44, 1 April 2012 (UTC)

Dogs who howl at the phone

Why do dogs sometimes have a tendency to howl when the phone rings? 98.235.166.47 (talk) 22:14, 1 April 2012 (UTC)

Because it startles them. --Jayron32 22:55, 1 April 2012 (UTC)

Cats and dogs have much better hearing than humans, and as annoying and ear-piercing the phone may be to us, it can be downright scary to the animal whose ears it has assaulted. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:45, 1 April 2012 (UTC)

According to an urban legend, some dogs who are tied to (or standing in a puddle of water adjacent to) telecommunications poles, will bark or yelp when the phone is ringing to indicate an incoming call, because the electricity involved stimulates them in a painful way. In theory, this should only be the case if the telecommunications equipment is faulty or unsafe in some way. --Demiurge1000 (talk) 23:50, 1 April 2012 (UTC)

Subjective biking effort

Is there any rough metric of the subjective effort required to bike X meters up a slope of Y degrees? From experience, I know the metric must be highly nonlinear in Y, because a 20 degree slope feels much more than twice as hard as a 10 degree slope. --140.180.39.146 (talk) 22:36, 1 April 2012 (UTC)

Subjective effort is unique and subjective, by definition. It sounds like you want us to quantify your unique experience. Simple trigonometry can be used to calculate the effect of different slopes on the objective (i.e. actual) force you need to exert in order to move your bike a certain speed. It sounds like your asking for the effect on how hard it feels like to you; quantifying your "feelings" is only something you can do, since this is a highly individualized effect. --Jayron32 22:54, 1 April 2012 (UTC)

It's partly a function of gearing. My experience is that with a normally geared road bike, I can handle a slope of up to 6 degrees with the same effort as flat riding, by going slow enough. If the slope is steeper, I can't go slow enough to equal the effort level of flat riding without having trouble staying upright. A slope of 10 degrees is hard work, and 15 degrees takes major fitness to sustain for more than a few minutes -- 20 degrees is deadly. With a mountain bike, though, the equation changes, because the gearing is different and it's easier to stay upright. Looie496 (talk) 00:31, 2 April 2012 (UTC)

April 2

What is the effective population size of the United Kingdom?

And what about the world? Anyone who fails to read the question properly and gives me the population will be shot. Egg Centric 01:19, 2 April 2012 (UTC)

Maybe you could read the cited article and provide the answer yourself? :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:15, 2 April 2012 (UTC)

I doubt it. I seriously doubt that the data exist to allow the question to be answered. Even if that's wrong, the answer would require fancy analysis of genetic frequency databases for the UK population. Looie496 (talk) 03:11, 2 April 2012 (UTC)

Glow leak

How do you break open a glow stick? I couldn't find any information in Wikipedia's article about breaking open a glow stick. Also—when broken—are the chemicals toxic? If so, in what way (e.g., when touched, inhaled, swallowed, etc.)? 71.146.8.88 (talk) 06:08, 2 April 2012 (UTC)