Wikipedia:Reference desk/Archives/Science/2008 April 19

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April 19

help with short chain fatty acids

I just need to know if short chain fatty acids will remain liquid even at colder temperatures.—————

Define short and define colder. Butyric acid is about as short as they get and has a melting point not far below that of water. Although you also have to consider the structure and saturation. Isobutyric acid has the same chemical formula but a much lower melting point (not that it's considered a fatty acid, as far as I know). Someguy1221 (talk) 02:10, 19 April 2008 (UTC)

Note that the Wikipedia articles on the respective fatty acids usually have information on the melting point in the box at the right. Icek (talk) 03:20, 19 April 2008 (UTC)

horned sheep

In researching breeds of horned sheep, I find that the rams have larger horns than the ewes. Is the larger size and curvature of the horns in the rams a result of the male hormone testosterone or from some other factor? Phil234 (talk) 03:13, 19 April 2008 (UTC)

I doubt if any scientists have studied this in detail, so the answer may not be known. I'd go with testosterone, though, as that's responsible for most masculine traits. StuRat (talk) 19:48, 19 April 2008 (UTC)

In breeds of cattle which are horned, the cows have horns which are virtually as large as the horns on the bulls. Sheep are different as the ewes have much smaller horns than the rams. This is the reason I'm not sure that it is entirely a result of testosterone. Phil234 (talk)

reflection of light by mirror and conservation of momentum.

Please read the question carefully and answer as detailed as you can.

when light is reflected by a mirror, the momentum of the mirror is changed and the mirror have to deflect in order to coserve total momentum. Now consider an arrangement where the mirror is rigidly fastened so that it cannot move in any direction(even the atomic movement is prohibited by any means; say the temperature is absolute zero). Now in this condition if light is incident upon the mirror, waht will be the result then ? As the light can not be reflected by the mirror to maintain law of conservation of momentum. will the light wave simply pass through the mirror ?

You're making the mistaken assumption that a mirror can be perfectly rigid. Let's say you don't make the mirror more rigid, and you merely make it heavier. A lot heavier...like...the mass of the Earth. And your mirror is in space. Anything going to stop it from absorbing the tiniest bit of momentum? Nope. So why do you think fastening the mirror very strongly to something on the Earth would stop it from absorbing momentum? All you actually accomplish is increasing the mass of the momentum absorbing body (which is now the entire planet), and thus decrease its change in velocity. Someguy1221 (talk) 05:09, 19 April 2008 (UTC)

Also, your idea of stopping the mirror from moving by reducing the temperature to 0^oK is flawed. While this removes all random momentum from the atoms of the mirror, it in no way prevents the mirror from absorbing any externally supplied momentum. "Perfectly rigid" is an impossibility, all materials have some elasticity - this question is a new version of the irresistible force paradox. SpinningSpark 07:40, 19 April 2008 (UTC)

Quantum: Determine the Force between the Electrons

According to Coulomb's law, when two electrons are put close to each other, there will be electrostatic forces act on them and the force can be determined as

$F={1 \over 4\pi \varepsilon _{0}}{\frac {q_{1}q_{2}}{r^{2}}}$

where $r$ is the distance between the two electrons. But according to Uncertainty Principle, we can not make sure the positions of the electrons so how can we decide $r$? - Justin545 (talk) 09:18, 19 April 2008 (UTC)

Coulomb's law is a classical approximation and only applies when r is large compared to inter-atomic distances and the charges are stationary or moving slowly compared to the speed of light. For the full quantum Monty, you need quantum electrodynamics, which explains non-classical phenomena such as the Casimir effect. Gandalf61 (talk) 11:45, 19 April 2008 (UTC)

Well, you don't actually need QED to make use of Coulomb's law in quantum mechanics. I just finished an elementary quantum mechanics course (where we never touched QED), and we used Coulomb's law all the time. It turns out that "force" is not a very useful concept in quantum mechanics. Much more often, one speaks of the potential, which is

$V={1 \over 4\pi \varepsilon _{0}}{\frac {q_{1}q_{2}}{r}}$

(If you know any vector calculus, the potential is defined so that $F=-\nabla V$, where $\nabla$ is the gradient operator.) So the way you actually use Coulomb's law is that you have a space of possible positions of some particles (say, a proton and an electron in a hydrogen ataom), and you use Coulomb's law to assign a value of the potential to every point of this space. Then you solve the Schrödinger equation on this space to obtain the possible energy states of the system. As you say, the distance between the two particles is uncertain, but this is not a problem because the electrostatic contribution to the energy is also uncertain. It is only the total energy that is certain; it is uncertain what fraction of that is electrostatic potential energy and what fraction is kinetic energy. (If you're confused about how the sum of two uncertain numbers can be uncertain, imagine I flip a penny and a nickel and don't tell you the results, but I tell you I got one head and one tail. The total number of heads is now certain, but the number of pennies or nickels that came up heads is uncertain.) —Keenan Pepper 14:42, 19 April 2008 (UTC)

Suppose a wave function of two electrons is $\psi (x,y)$ where $x$ and $y$ are the postions of the respective electron. Then $|\psi (x,y)|^{2}$ should be the probability density function for finding the first electron at $x$ and the second electron at $y$. And the normalization condition should be $\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }|\psi (x,y)|^{2}\,dx\,dy=1$. The distance between them should be $r=|x-y|$. The probability of finding the first electron at $x'$ and the second electron at $y'$ should be $P(x',y')=\int _{y'}^{y'+dy}\int _{x'}^{x'+dx}|\psi (x,y)|^{2}\,dx\,dy$. So do you mean the potential is determined by the weighted sum in discrete form

$V={1 \over 4\pi \varepsilon _{0}}\left(P_{1}{\frac {q_{1}q_{2}}{r_{1}}}+P_{2}{\frac {q_{1}q_{2}}{r_{2}}}+P_{3}{\frac {q_{1}q_{2}}{r_{3}}}+...\right)$

${\begin{aligned}V=&{1 \over 4\pi \varepsilon _{0}}\left[P(x'_{1},y'_{1}){\frac {q_{1}q_{2}}{|x'_{1}-y'_{1}|}}+P(x'_{1},y'_{2}){\frac {q_{1}q_{2}}{|x'_{1}-y'_{2}|}}+P(x'_{1},y'_{3}){\frac {q_{1}q_{2}}{|x'_{1}-y'_{3}|}}+...\right]\\+&{1 \over 4\pi \varepsilon _{0}}\left[P(x'_{2},y'_{1}){\frac {q_{1}q_{2}}{|x'_{2}-y'_{1}|}}+P(x'_{2},y'_{2}){\frac {q_{1}q_{2}}{|x'_{2}-y'_{2}|}}+P(x'_{2},y'_{3}){\frac {q_{1}q_{2}}{|x'_{2}-y'_{3}|}}+...\right]\\+&{1 \over 4\pi \varepsilon _{0}}\left[P(x'_{3},y'_{1}){\frac {q_{1}q_{2}}{|x'_{3}-y'_{1}|}}+P(x'_{3},y'_{2}){\frac {q_{1}q_{2}}{|x'_{3}-y'_{2}|}}+P(x'_{3},y'_{3}){\frac {q_{1}q_{2}}{|x'_{3}-y'_{3}|}}+...\right]\\&\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\vdots \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\vdots \\\end{aligned}}$

$V={1 \over 4\pi \varepsilon _{0}}\sum _{x'}\sum _{y'}P(x',y'){\frac {q_{1}q_{2}}{|x'-y'|}}$

$V={1 \over 4\pi \varepsilon _{0}}\sum _{x',y'}P(x',y'){\frac {q_{1}q_{2}}{|x'-y'|}}$

or in continuous form

$V={1 \over 4\pi \varepsilon _{0}}\int _{-\infty }^{\infty }\int _{-\infty }^{\infty }|\psi (x,y)|^{2}{\frac {q_{1}q_{2}}{|x-y|}}\,dx\,dy$

? - Justin545 (talk) 06:00, 20 April 2008 (UTC)

Getting out of my depth here so this might be a stupid comment. I don't see how you could use that in a real calculation. ψ(x,y) and hence P(x',y') is not a given. The starting information is usually the potential function V(r,φ,z) which is then fed into Schödinger to get the answer. Also, I cannot understand why you are working in two dimensions only, you need x,y,z in cartesian co-ordinates - or was that just for brevity? SpinningSpark 08:53, 20 April 2008 (UTC)

The use of symbol $y$ would be confusing, but $y$ doesn't mean the y-axis which is perpendicular to the x-axis. For brevity, I assume both of the two electrons lie on the same line so that they can only move in one-dimentional space (imaging two electrons in the same wire of infinite length).

The starting information, the potential field $V$ is where my qustion came from. For a system which consists of only one charged particle, an electron for example, the potential field $V$ of the particle should be determined by its environment. But consider a system of more than one charged particles, the potential field $V$ should be a function of those charged particles as well as their environment since the charged particles will interact with each other (either attraction or repulsion because of electrostatic forces). - Justin545 (talk) 11:02, 20 April 2008 (UTC)

Camel and crocodile

How long can a crocodile survive without food? How long can a camel survive without water? - Kittybrewster ☎ 09:57, 19 April 2008 (UTC)

A crocodile: seems to be about 3 weeks to a month: see [1]. - Nunh-huh 10:07, 19 April 2008 (UTC)

Camels can lose up to 40% of its body weight in water safely. [2]. Camels lost 97 liters of waters in 11 days of dehydration [3]. A camel weighs 300 to 690 kilograms [4]. That same site says camels can go without water for about 11 days. This is probably a lower limit. - Nunh-huh 10:07, 19 April 2008 (UTC)

Crocs can go much longer than a month without eating. The crocs in that farm were probably fed a chicken, and they can't last too long on just that. Croc farms normally feed them on a chicken each week. However, a croc that eats a large meal (kangaroo, deer etc.) can go a few months. Snakes are the best at it however, and can go up to a year after eating a large meal. --liquidGhoul (talk) 09:22, 20 April 2008 (UTC)

Size matters (but this time, not in a good way)

This question was removed here as it is the exact same question previously asked by a user banned for trolling User:Picture of a cloud [5] Nil Einne (talk) 23:58, 19 April 2008 (UTC)

Spin

Hi, these questions may be stupid, but I had to ask............. I was reading about particles, and one of the major things I did not understand was 'spin'. I did not understand how it can have a value like 1/2 or 1. It could be clockwise or anti-clockwise, but what does the value represent?? please explain in simple terms...........(I'm only 15 yrs old and don't expect me to understand much complicated physics.) And also what exactly is the magnetic quantum number ? I also don't understand how sub-shells can co-exist(How can a single shell be divided again into more shells???).

Spin is actually a pretty complicated atomic principle. However, essentially, it's the total angular momentum of a sub-atomic particle that produces a defined magnetic moment. Wisdom89 _{(T / ^C)} 14:04, 19 April 2008 (UTC)

For your question about shells, you might want to read our article on electron shell. It can explain it better than I ever could. Wisdom89 _{(T / ^C)} 14:06, 19 April 2008 (UTC)

This answer for spin is actually wrong for a few reasons. One, the spin is not the same as the total angular momentum. The total angular momentum is the sum (as quantum operators, not numbers) of the intrinsic spin angular momentum, which is a built-in property of the particle and has nothing to do with spatial motion, and the orbital angular momentum, which is a property of the particle's motion in space. Two, every object has spin, not just sub-atomic particles. You can see the spin of whole molecules, even large ones, with microwave rotational spectroscopy. Spin is the reason why helium-3 becomes a superfluid at a much lower temperature than helium-4. Three, it's not necessary to have a magnetic moment to have spin. Photons have spin, but no magnetic moment. —Keenan Pepper 14:23, 19 April 2008 (UTC)

First of all, these are not stupid questions at all. They're very important and difficult questions, and physicists discussed them for many decades before the answers were generally accepted. Unfortunately, it's impossible to explain the ideas without "much complicated physics". If you can get a hold of a copy of The Feynman Lectures on Physics, you just might be able to understand parts of that, but otherwise I don't know what to tell you. You have to learn quantum mechanics before any of this starts to make sense (and even then parts of it still seem bizarre and counterintuitive). —Keenan Pepper 14:27, 19 April 2008 (UTC)

If you have more specific questions, I'd be happy to try to answer them. —Keenan Pepper 14:27, 19 April 2008 (UTC)

At the risk of confusing you with yet another answer, let me try to answer your questions clearly. First of all, before you will understand any of this, you have to understand what angular momentum is. So if you haven't already got that straight, read the article. Next you need to understand that angular momentum can only exist in whole multiples of a number called $\hbar$ (say it as haich-bar). How many $\hbar$s in total is the "l" quantum number. Spin is the angular momentum the particle has which is not due to its motion (just like a spinning top has angular momentum but is not going anywhere - but also read the first part of the spin article). Now this is where I have to tell you I lied to you, angular momentum has to be whole multiples of $\hbar$ but spin, the "s" quantum number can be ½$\hbar$ which is where the ½ spin comes from. The magnetic moment quantum number ("m") is the number of $\hbar$ in a particular direction (angular momentum is a vector). This also has to be a whole number and must also be less than "l" because that is the total. It is called the magnetic moment number because it is this attribute which causes the spectral lines of a substance to split when exposed to a magnetic field. So sub-shells should be easy now. A shell is all the electrons whith the same energy, a sub-shell is all the electrons with the same energy AND angular momentum. Hope that was helpful. SpinningSpark 16:49, 19 April 2008 (UTC)

The angular momentum corresponding to a quantum number x (either spin or an azimuthal quantum number) is actually $\hbar \cdot {\sqrt {x\cdot (x+1)}}$. Icek (talk) 02:12, 20 April 2008 (UTC)

Sorry, my bad, too keen to simplify something that can't be simplified. SpinningSpark 11:32, 20 April 2008 (UTC)

Thanks a lot for answering my questions, and I believe I'll understand more after finishing school first! Anyway all of you have made it easier for me to understand. I love physics and was curious to know what it all meant. Thanks again. [:)]

Memory

Does anyone know where in the brain memory is stored? Thanks. --Freiberg, Let's talk!, contribs 14:16, 19 April 2008 (UTC)

Sort of, but not fully. See Long_term_memory#Types_of_memory, hippocampus, entorhinal cortex, perirhinal cortex. - Nunh-huh 14:23, 19 April 2008 (UTC)

The grey matter. —Preceding unsigned comment added by Catolog of buggery (talk • contribs) 15:39, April 19, 2008 (UTC)

A anecdote I've heard many times in talks about the brain is that a man (they rarely have a specific name - just "a man") had to have the left side of his brain removed. He lost no memory afterward. A women (again, just some random woman) had to have the right side of her brain removed. She lost no memory. Therefore, memories must not be stored in either the left or right side of the brain. This is considered a joke to brain surgeons because it is based on truth. There are people who have large portions of their brain removed and do not lose memories. The assumption that it means memories are not stored in the brain is, of course, a false assumption. -- kainaw™ 18:18, 19 April 2008 (UTC)

It might also be that each memory is stored in many locations, so removing (or damaging) one part of the brain has little effect. StuRat (talk) 19:38, 19 April 2008 (UTC)

Just to heap on the clarifications: Normally when they talk about removing one or the other "half of the brain", what they're usually talking about removing is just half of the cerebral cortex, while the hippocampus and other parts of the brain are left untouched. Also, this is often done in cases where there has been sufficient damage to that portion of the brain so that other parts of the brain have taken over many of the functions that the damaged/diseased portion would normally control. Furthermore, there are also plenty of people who have had surgery or damage done to their brain that has affected their ability to store and retrieve memories, so clearly the memory is stored in the brain. -- HiEv 20:58, 19 April 2008 (UTC)

This bit about the Hippocampus is interesting[6] and the article mentions it's the first to go in Alzheimer's. Julia Rossi (talk) 09:09, 20 April 2008 (UTC)

Cellular memory is also interesting.--Shantavira|^{feed me} 11:39, 20 April 2008 (UTC)

The bird that migrants farthest

I was just watching an episode of Planet Earth (in HD, which is quite an experience) on that dealt with the two poles, and the raspy, Gandalf-like voice of David Attenborough informed me that "The Sandhill Crane has flown here all the way from New Mexico". Quite impressive, I thought. It got me thinking: what bird migrates the longest distance? I suppose there is a hard limit, there would be no point flying further south than the equator, or further north of the pole (well, I guess you can't fly further north than the pole, I mean continuing flying in a straight line once you get there) --Oskar 14:38, 19 April 2008 (UTC)

The Arctic Tern is a strong candidate. You can't tell them not to go farther south than the equator—they go pole-to-pole. The award for longest journey not a migration might go to the Albatross. --Milkbreath (talk) 15:04, 19 April 2008 (UTC)

Holy crap, pole to pole! That's some long distance flying! I had no idea. Impressive bird. --Oskar 15:34, 19 April 2008 (UTC)

Take a look at the Sooty Shearwater [7]. It nests on islands in the far south and routinely flys around the entire Pacific Ocean every year--40,000 miles or so. --Eriastrum (talk) 17:58, 19 April 2008 (UTC)

THAT's the bird I was trying to think of. I looked up Sooty Tern, instead, though. --Milkbreath (talk) 18:17, 19 April 2008 (UTC)

Is there any bird that goes the long way, so to speak? Like starts off in the south pacific somewhere (e.g. NZ, Australia) and the north pacific (e.g. Canada) but goes past Asia, Europe and the Atlantic to get there? Nil Einne (talk) 08:44, 21 April 2008 (UTC)

I can't think of one; migration is mainly a winter-driven north-south thing. But check out the Northern Wheatear that goes from Alaska to South Africa across the whole of Asia and Africa. The Bar-tailed Godwit of New Zealand is said to perform the longest non-stop journey of any animal and the longest migration without pausing to feed of any bird. I still say some albatross or other flies farther. They can soar for a year without landing. And there are the swifts, some of whom never land except to nest in their entire lives, so miles-on-the-wing is going to be darned high even if they don't go very far as that other big, black bird flies. --Milkbreath (talk) 11:39, 21 April 2008 (UTC)

pH

Can pH be below one or above 7, live a 0.5 pH?

Yes. See the "pH scale" diagram in the pH article. --Heron (talk) 15:55, 19 April 2008 (UTC)

Thanks. So it is infinite or is -1 the lowerist?

Again, I direct your attention to the pH article, which states "Thus the most acidic of liquids encountered can have a pH as low as −5." That means a concentration of 10⁵ moles of H⁺ per liter. But pH isn't really a practical description for such ultra-acidic solutions (likewise for ultra-basic solutions at the high end of the scale) because it's very difficult to measure. Further, most real-world use of pH involves the acid (or base) dissolved in water, which itself affects the measurement: the water reacts with the acid or base, so one is not measuring "the acidicity of the acid" but rather "the acidicy of the aqueous acid solution". Thus, a superacid "can produce solutions with a pH down to –25" but that kind of thing doesn't exist in water. Out of curiosity, what was your basis for proposing -1 as the lowest possible pH value? DMacks (talk) 19:16, 19 April 2008 (UTC)

Also note that 7 is only neutral, so pH's can go well above that, and even above 14. StuRat (talk) 19:30, 19 April 2008 (UTC)

Thanks for that.

Job Opportunities

Hello all,

I am a highschool student and plan to pursue a career in the field of quantum physics. I would like to know the pros and cons and also the job opportunities and locations (within the US) of someone with a doctorate in this feild would have.

Thanks, Zrs 12 (talk) 19:19, 19 April 2008 (UTC)

The American Physics society website may help you answer some of your questions. Sifaka ^talk 20:55, 19 April 2008 (UTC)

Diluting toxins

Does drinking lots of some usual beverages (water, tea, juice) help in diluting lethal dose of toxin in blood, thus in avoiding death? Particularly taking into consideration any biotoxin (of mushrooms, snakes, jellyfish etc). --85.132.14.38 (talk) 19:45, 19 April 2008 (UTC)

I don't know about toxins, but I know if you drink enough water before a urine drug test, you can pass due to the drug being diluted. Zrs 12 (talk) 19:56, 19 April 2008 (UTC)

That would be diluted in the urine, not the blood. StuRat (talk) 19:58, 19 April 2008 (UTC)

But urine is waste filtered from the blood by the kidneys, right? Zrs 12 (talk) 20:02, 19 April 2008 (UTC)

Yes, but that doesn't mean that diluted urine means diluted blood. Unless you drink water at a dangerous rate, your kidneys will remove it as quickly as your stomach absorbs it, thus keeping your blood at a constant concentration. StuRat (talk) 20:13, 19 April 2008 (UTC)

Oh, ok. I see now. Zrs 12 (talk) 20:17, 19 April 2008 (UTC)

That would depend on the type of poison. Dilution is recommended for some poisons, but not others. However, this dilution method targets the stomach, not the blood. You can't really dilute the blood since your body regulates closely the amount of water in the blood (by the kidneys removing excess water, for instance). Also note that excess tea consumption can by harmful in itself, due to tannins which can build up. I've had sharp pains in my kidneys from this myself. StuRat (talk) 19:58, 19 April 2008 (UTC)

I would imagine the oxalic acid present in tea as the main cause of kidney pain, not tannins. --Mark PEA (talk) 11:02, 20 April 2008 (UTC)

Possibly, but our article does mention that excess tannins can cause kidney pain in sensitive people, and, if you're talking about the formation of kidney stones from oxalic acid, I'd expect that to take some time to manifest, while the kidney pain I'd get was almost immediately after drinking large quantities of tea. StuRat (talk) 15:35, 25 April 2008 (UTC)

Potentially, but not universally and certainly not reliably. Depending on the type of toxin and how the toxin entered the body, it may be of some use, but there are virtually always better methods. The best bet is to contact local poison control immediately. 9-1-1 (or the relevant local emergency number) can direct calls there. — Lomn 19:59, 19 April 2008 (UTC)

1-1-2 is a useful all-purpose emergency number for many countries, or check out the list at emergency telephone number :) 79.66.99.37 (talk) 12:22, 20 April 2008 (UTC)

It is possible to poison yourself by drinking water. This is not the only case, and maybe not even the most reliable source, just one example: http://www.knbc.com/news/10761800/detail.html So your antidote might turn out to be deadlier than the poison. Drinking too much can also seriously imbalance your electrolytes I don't know if that is what causes most of the fatalities. On the other hand it might get you nominated for a Darwin Award. --Lisa4edit (talk) 07:19, 22 April 2008 (UTC)

It would be more effective to isolate the part of the body exposed to the toxin (hopefull arm/leg) by using compression bandages and raising the limb above the heart, most toxins kill by damaging the internal organs, not the limbs. By drinking a lot you may expose kidneys/heart/brain/liver etc to more of the toxin than you would have otherwise, thus worsening the result.(Please no one take this as medical advice I am no expert but this is basic first aid of a snake bite)--Shniken1 (talk) 01:15, 23 April 2008 (UTC)

As I was walking up the stair...

Your peculiar question for the day. If you walk up a step on an upward-moving escalator, are you expending the same amount of energy as walking up a step on a set of fixed stairs, or more energy, or less? My gut feeling is that it's the same amount, since your "stationary" foot is being propelled upwards to counteract any difference in height relative to the earth's surface, but I'm not certain. Any thought?

Thanks in advance, Grutness...wha? 21:41, 19 April 2008 (UTC)

Good gut feeling. Yeah, it's the same amount (as for a stationary step of the same height; of course escalator steps tend to be larger than fixed ones), except of course for quibbles about air resistance and smaller effects. --Trovatore (talk) 21:58, 19 April 2008 (UTC)

Note of course the total amount of energy you spend walking up the same height would be less since part of the distace travelled comes from the escalator. Nil Einne (talk) 23:22, 19 April 2008 (UTC)

Off-topic rant occasioned by the question: Could I please invite anyone who doesn't want to walk up the escalator to stand to one side? Few things are more irritating than to have a big clump of people jump onto the escalator right in front of you and stop dead. --Trovatore (talk) 23:32, 19 April 2008 (UTC)

Thanks folks. Oh, and in response to trovatore's comments, IIRC, thinking back to when i was a young kid in London, there is (or was) a set rule at tube stations that people standing on the escalators had to stand to the right, to allow people to walk up or down on them to the left. Not sure how good my memory is, or whether it still implies, but ISTR it worked very well. Grutness...wha? 00:11, 20 April 2008 (UTC)

That first step up always seems so much harder though. 200.127.59.151 (talk) 03:10, 20 April 2008 (UTC)

Stand on the right, walk on the left is indeed the rule on the London Underground and it's usually followed except by tourists. Astronaut (talk) 04:08, 20 April 2008 (UTC)

I lived in London for a few months and when I moved back home I was always terribly annoyed by people standing on both sides of the escalators (the nerve of it...) I still am sometimes. Joe^Talk_Work 16:11, 22 April 2008 (UTC)

You will actually use a very tiny bit less energy stepping up on the escalator. As the step proceeds, the escalator also moves you upwards, thus the force of gravity lessens ever so slightly. If I'm calculating right, every foot you move upwards makes you weigh .00001% less. Franamax (talk) 07:04, 20 April 2008 (UTC) (And do please stand to the right!)

You will weigh the same. You will, however, have to compute a net force which includes the upward normal-force of the escalator; this is sometimes confused for "weighing less" but it is actually the net sum of weight + external force. How can you even calculate a value, though, unless you know some parameter about the escalator (velocity, stair height.. something?) In any case, conserve energy - and note that both you AND the escalator are doing work. You gain a gravitational potential energy m g h proportional to the total height of the escalator (regardless of the stair-step sizes). The escalator does work on you, by lifting you up somewhat. Your muscles must perform the rest of the work. However many stairs you climb will define how far you travel in the moving-reference frame of the stairs (work done by you); the escalator will perform the remainder of the work. Nimur (talk) 17:22, 24 April 2008 (UTC)

Part two

OK, how about if you're walking up the down escalator at a rate sufficient to remain stationary? More, less, or the same as going the same rate on stairs? --69.134.124.30 (talk) 01:20, 20 April 2008 (UTC)

Also, how about a little Mitch Hedburg?: I like escalators because an escalator can never break: it can only become stairs. You'll never see an Escalator Temporarily Out Of Order sign, just Escalator Temporarily Stairs. Sorry for the convenience. We apologize that you can still get up there. --69.134.124.30 (talk) 01:20, 20 April 2008 (UTC)

I love Mitch Hedburg, and I would have thought that this joke was both hilarious and correct, but I know from experience it is merely hilarious. I once saw a seriously broken escalator in an airport. It seemed like several of the steps had fallen down in a jumbled pile at the bottom. It was confusing and hard to describe, like something out of a cartoon. --Allen (talk) 03:22, 20 April 2008 (UTC)

When an escalator is stopped, it can still be used as a stairway. However, when the escalator is being repaired, it is usually taken out of service, because the repairmen need to remove some of the steps to access the motors or the drive train. When this occurs, you will generally see a barrier at the top of the escalator and a larger barrier at the bottom, where the repairmen will have removed three stairs. If you see this, go ahead and look into the work area: there is a lot of interesting stuff in there. -Arch dude (talk) 06:19, 20 April 2008 (UTC)

Yeah right, we all love to have somoeone leaning over and watching when we are trying to fix something. Especially when struggling to understand why the hell it's not working, it really helps to know that someone is taking an interest. SpinningSpark 08:33, 20 April 2008 (UTC)

Just push the barrier aside, jump onto the nearest step, and berate the workers. Don't watch what they're doing, just ask why they're not done yet :) Franamax (talk) 12:40, 20 April 2008 (UTC)

Yeah, 98% of the public will ignore the repairmen, 1% will make stupid counterproductive remarks, 0.9% will be interested but will remain silent. The other 0.1% will look and say something encouraging. Even something as simple as "thanks, guys" might counteract the assholes that make stupid remarks. -70.177.166.200 (talk) 23:55, 20 April 2008 (UTC)