Wikipedia:Reference desk/Archives/Science/2007 July 15

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July 15

Harnessing rotational energy into stored energy

Strange question, but i am curious if i were to place my bike on a frame, suspending me while i pedal, how would i be able to harness and save this energy, and what equipment exists (if any) that someone knows of that i could to use to convert my mechanical energy into a useful energy source (battery) Thanks if anyone is willing to tackle this.

If I'm correct in understanding your description, you are talking about a standard electrical generator. Have a look at this site to see how they work. - Akamad 01:21, 15 July 2007 (UTC)

Our hub dynamo article specifically answers your question. StuRat 06:09, 15 July 2007 (UTC)

Yes, this will definitely work - although the voltage you get out from a bicycle dynamo might be a bit feeble for doing much other than lighting a couple of flashlight bulbs. With more efficient use of gearing and a better generator, you could do better. According to Human-powered transport The average "in-shape" cyclist can produce about 3 watts/kg for more than an hour (e.g., around 200 watts for a 70 kg rider), with top amateurs producing 5 watts/kg and elite athletes achieving 6 watts/kg for similar lengths of time.. According to Electrical generator bicycle generators are only 40% to 60% efficient - and a car alternator would be a better bet at 90% efficiency. So with optimal gearing and the best available generator, at 180 Watts, you could keep three 60 Watt lightbulbs burning - for "more than an hour" (assuming that you could keep up that rate of exercise). Alternatively, if you tried to power your PC with it - you'd have to pedal pretty hard to keep it running - you'd have to be a "top amateur" cyclist to run a PC for an hour before getting tired out. According to Orders of magnitude (power), two square meters of solar panels would produce more energy - assuming you get an hour of sunlight per day. SteveBaker 18:40, 15 July 2007 (UTC)

I think the best application is providing power for a bicycle to turn on lights for night driving. (It should also have rechargeable batteries so the lights don't go off when you stop.) StuRat 01:23, 16 July 2007 (UTC)

Search using "Flywheel Energy Storage" also .Polypipe Wrangler 07:52, 17 July 2007 (UTC)

Weight

I have noticed an odd phenomenon, and I would like some input. I weigh myself every day -- at roughly the same time of day, wearing the same outfit each day (i.e., my birthday suit). I understand that one's weight will always have minor variations from day to day (say, water retained for example) and even from hour to hour. Due to many factors, and the degree of accuracy on a bathroom scale, one's weight fluctuates constantly, plus or minus a few pounds (I imagine). So, here is my question. I have consistently noticed that when I place the scale on Spot A on the floor in the bathroom, it will always give me a lower weight than when I place the scale on Spot B on the floor in the bathroom. This is very consistent and the difference is sometimes as much as 3, 4, 5 pounds. What on earth could cause this? Spot A and Spot B are barely a foot apart, perhaps 1/2 a foot. The only thing I can think of is that the bathroom floor has some minor inconsistency in not being perfectly level. (But I don't even know if that would contribute to the weight gain/loss recorded.) Nonetheless, it is a "normal" flat bathroom floor -- meaning, there certainly are no glaring inclines/declines. Even if there were a minor difference in how level the floor is, that certainly cannot account for 3, 4, 5 pounds? Does anyone have any ideas? Thanks. (JosephASpadaro 01:09, 15 July 2007 (UTC))

Probably your scale reports a different weight depending on the weight distribution on top of it. Maybe it's a different angle, or maybe you stand on it differently when it is in a different spot. Why don't you try experimenting with standing on different parts of the scale when you weigh yourself? -- JSBillings 01:56, 15 July 2007 (UTC)

No, I make a point to stand on it exactly the same each time. (JosephASpadaro 04:02, 15 July 2007 (UTC))

Maybe you could do a more controlled experiment by placing a couple of books on the scale. At least with books you don't have to worry about the weight distribution -- as long as you make sure the books don't move. If the scale insists that the books are heavier in one place than in another, then the floor might have some defect, as suggested by JSBillings. Beyond that, we could speculate forever and not arrive to an answer. Might as well apply the scientific method. Good luck! --Waldsen 04:29, 15 July 2007 (UTC)

A standard bathroom scale is just a spring scale, and those a notoriously poor. If you intentionally stand on one corner of the scale, you can likely get a 50 pound variation. Thus, a 3-5 pound variation can happen just as a result of imperceptible changes in the weight distribution. This may be because the floor bows a bit, or because you are closer to a wall in one position and naturally lean away from it a bit. StuRat 06:03, 15 July 2007 (UTC)

Good input -- thanks. (JosephASpadaro 17:34, 15 July 2007 (UTC))

Another variation happens when you put the scales on carpet, and the scales are supported all over the base, rather than 4 feet as they were designed. When I first saw this I didn't beleive it - that gravity could change between carpet and tiles! But as StuRat says, its just the design with a spring, and the distortion in the metal case is taken into account with the measurement. GB 21:47, 15 July 2007 (UTC)

Legless Lizards

I'm watching 'Man vs. Wild' and the guy picks up and shows what looks like a snake. He said it was a legless Lizard. I went to the Wiki article, and the intro has '4 legs' in the description. Are there legless lizards? Why aren't they snakes? Thanks! Bmedley Sutler 02:13, 15 July 2007 (UTC)

According to the Pygopodidae (Legless Lizard family), they differ from snakes by having external ear holes and non-forked tongues. -- JSBillings 02:15, 15 July 2007 (UTC)

I think one answer to the question, "why aren't they snakes?" is that they evolved separately, so if we called them "snakes" then "snakes" would be a polyphyletic group, and that's considered bad naming practice. --Allen 14:35, 15 July 2007 (UTC)

Yes, it's important to note that the definition of snakes isn't simply "reptiles that have no legs". It's more complicated than that, as we have to consider other physical and genetic attributes to call something a snake.128.163.171.68 17:51, 15 July 2007 (UTC)

Properties of mercury

Below is the original question and my question is in bold at the end. Thanks NA --75.75.13.217 03:45, 15 July 2007 (UTC)

Mercury is the only metal element that is liquid at room temeratures. Why?

It's melting point is -37.9 °F (= -38.83°C), and its boiling point is 674.11 °F. What is it about this element's atoms, and/or electron layers, that makes it different in this respect from other metails?

The answer has partly to do with the electron configuration of Mercury, and also relativistic effects. The electron configuration of mercury is [Kr] 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s². The last shell labeled 6s is completely full, and is noticibly closer to the nucleus than what would be expected if relativistic effects were not taken into account. The combination of these two factors results in rather tightly bound outer shell of electrons for mercury. Hence, mercury cannot form particularly strong metal-metal bonds. The result is an element which is liquid at room temperature. Contrast this with gold and thallium which are right beside mercury on the periodic table, but are solids. Let the reference desk know if you'd like a more detailed explanation, I hope this answers your question! --HappyCamper 1 July 2005 00:03 (UTC)

Thanks HappyCamper for explaining more clearly than I usually manage! "Relativistic effects" occur in atoms of a high atomic number: the positive charge of the nucleus is so high that some of the electrons in the atoms are moving very fast—fast enough that special relativity has to be taken into account in predicting their movement. This causes a number of changes in the chemistry of the elements concerned, of which the fact that mercury is liquid at room temperature is perhaps the most striking. Physchim62 4 July 2005 08:46 (UTC)

You're welcome, Physchim62 :-) You do great edits on Wikipedia too! --HappyCamper 7 July 2005 04:25 (UTC)

One small quibble, if I may: "electrons moving fast". Well, yes the electrons whether acting particle-like or wave-like do have velocity and momentum data associated with them. But while in an orbital (a standing wave) "moving fast" is a poor way to describe a charge that is not doing what charged particles do when they move fast (in a circle - i.e. accelerating). Visualizing a charged particle zipping about the nucleus like a planet around a sun at a relativistic speed is terribly misleading. (Even if expert chemists who don't care about the physics of charged particle movement DO use that heuristic.) 4.250.168.127 23:04, 25 July 2005 (UTC)

I took the liberty to take the result of this discussion to Group 12 element, thanks all! V8rik 23:08, 25 November 2006 (UTC)

Hello, I am not sure I understand but maybe you can point me to a good source. Zn ([Ar] 3d10 4s2) and Cd ([Kr] 4d10 5s2) also have full s and d outer shell. So what gives for Hg. Hg from what I have read here can make amalgams with gold and zinc but I am not sure what kind of bonds these are. Also please give a little bit more about how special relativity comes into play here?

Current rate of extinction

hey all, i would like a source that states the current world extinction rate. i have heard in a several different places that there are currently 200 species going extinct a day but never (to my knowledge) with a source. --74.97.142.249 04:30, 15 July 2007 (UTC)

Somewhere between 0.5 and 50 extinctions per day (Stuart L. Pimm; Gareth J. Russell; John L. Gittleman; Thomas M. Brooks (1995). "The Future of Biodiversity". Science. 269: 347–350. {{cite journal}}: Unknown parameter |last-author-amp= ignored (|name-list-style= suggested) (help)). The large uncertainty comes from the assumption that the vast majority of extinctions occur without being noticed. Only 748 extinctions have been documented since 1500 AD. Dragons flight 04:51, 15 July 2007 (UTC)

Do those figures include bacteria ? Viruses ? StuRat 05:55, 15 July 2007 (UTC)

Macroscopic animals and plants. Dragons flight 05:58, 15 July 2007 (UTC)

This brings up the question of where one draws the line between macroscopic and microscopic. Perhaps single-celled organisms versus multicellular organisms would be a good dividing line, but you definitely need a microscope to see some multicellular organisms. StuRat 13:59, 15 July 2007 (UTC)

Well..from what I know, macro means big, while micro means small..is that correct? --Zacharycrimsonwolf 13:03, 16 July 2007 (UTC)

That's true - but they are both relative terms. Relative to a virus, an amoeba is 'big'. Relative to a Californian redwood, an ant is 'small' - but an ant is big compared to an amoeba...so where do you draw the line for the purposes of answering this question? SteveBaker 17:37, 16 July 2007 (UTC)

I believe that as practical matter, "macro" means unaided human eyesight. The stuff we can't see is even less well understood, so we start with those things where we have half a clue. Dragons flight 00:56, 17 July 2007 (UTC)

Even that is a widely variable scale, as some people can see much smaller things than others. There is a species of tiny orange spiders that some people can see and others can't, for example. StuRat 13:39, 17 July 2007 (UTC)

The concept of "species" is rather weak for non-sexually-reproducing individuals, which in turn makes the concept of "extinct" a fuzzy one. --Carnildo 23:09, 16 July 2007 (UTC)

Otto Wilhelm Thomé

I can find no biographical data to go with this article - no date or place of birth or death, no parents, no education...... Any suggestions? Googlesearch doesn't turn up the right answers - perhaps I'm asking the wrong questions Raasgat 06:34, 15 July 2007 (UTC)

At the bottom of this page I found the information he apparently lived 1840-1925. He also published a book entitled Lehrbuch der Zoologie für Gymnasien, Realgymnasien. Not a lot of information I must admit.

/ Mats Halldin (talk) 12:32, 15 July 2007 (UTC)

Thanks Mats - More information than I could come up with! I'm sure there's a full biography around somewhere - I'll keep searching. Raasgat 19:16, 15 July 2007 (UTC)

You could try contacting Kurt Stüber, his page gives you his address. ---Sluzzelin talk 13:23, 16 July 2007 (UTC)

HONEY

WHY doesn't honey go bad(decay) and always stay good?

165.146.39.29 13:38, 15 July 2007 (UTC)Lucy

I believe it is the same reason why table sugar (sucrose) doesn't go bad: They are both hygroscopic. Any germs that land on it quickly dry out. --Mdwyer 15:43, 15 July 2007 (UTC)

Honey is also somewhat acidic and has some antibacterial components. (Although you still shouldn't feed a baby honey because it can still contain nasty bacteria like Clostridium botulinum) -- JSBillings 22:10, 15 July 2007 (UTC)

Firstly, there is no therapeutic antibacterial component in honey. Still, no bacteria can survive in honey because of its high concentration of sugar (in water). Honey is a syrup and is a sugar-in-water solution; however, there is more sugar (by weight and by volume) than there is water. Bacterial cell membranes are Semipermeable. When a bacterium is submerged in honey, the concentration of sucrose (the main sugar in honey) is much much higher in the honey than within the bacterium. This concentration difference will equilibrate via diffusion. Since the cell membranes of bacteria are semipermeable, the sugar in the honey is too big to move from the honey into the bacterium. Water is not. So, water moves from the bacterium into the honey, literally crushing and killing the bacteria cells. So, honey never "goes bad" because the bacteria can never live long enough to reproduce and spoil it. This goes for Clostridium botulinum as well. This is not to say that honey is safe for infants though. When bacteria experience harsh conditions in the environment, they can form endospores. Endospores can survive a range of harsh conditions that a regular bacterium could not. Clostiridium botulinum endospores are contained in a significant portion of commercial honey. This is because they are picked up by the bees from vegetation. Such endospores would be eliminated by our immune systems in children and adults, but not by infants. So in infants, the endospores make it all the way to the small intestine and reactivate there feeding on whatever is inside and cause infant botulism. Mrdeath5493 20:51, 16 July 2007 (UTC)

Organic Adult Diapers

OK, this subject requires some actual maturity, so anyone subject to replying with "Ewww, gross", please leave now. My elderly father has entered the stage in life where he needs to wear adult diapers. Unfortunately, most of those contain nasty chemicals (like chlorine) for "odor control". The effect of these is to destroy good bacteria and promote fungal infections. I have no problem finding organic baby diapers without those nasty chemicals, but haven't been able to find organic adult diapers. I either need a brick and mortar store in the Detroit area, or a site which sells online and delivers to the US. Any suggestions as to where I should look ? StuRat 14:10, 15 July 2007 (UTC)

Uh, might be slightly insulting, but have you tried looking at websites that sell BDSM type stuff? They might have something. --L^augh! 14:20, 15 July 2007 (UTC)

Have you asked a medical doctor or health professional? An adult health care center would probably be familiar with this issue and could direct you to a manufacturer or provide an alternative solution altogether. Nimur 15:51, 15 July 2007 (UTC)

Why can't an adult wear baby diapers? Is it simply a matter of size (i.e., a large adult cannot "fit into" a small baby diaper)? If so, can't you manipulate baby diapers in some way (i.e., tape two together) ... or so? (JosephASpadaro 17:38, 15 July 2007 (UTC))

Is it not possible to use towelling (non disposable diapers) instead? You can then control the cleaning/material environment of the product. I know that's probably not the ideal solution but may be an alternative if you struggle to locate your first choice. ny156uk 18:00, 15 July 2007 (UTC)

Hmm, even cloth ones seem to be anti-bacterial. Skittle 12:00, 16 July 2007 (UTC)

That's internally though, surely it won't affect the skin much? Nil Einne 12:58, 16 July 2007 (UTC)

I believe liquids are able to transport the anti-bacterial agents to the skin. StuRat 13:29, 17 July 2007 (UTC)

If these are meant to be reusable, might the anti-bacterial thing be something that doesn't wash away? I'd probably ask them if it was me. Skittle 19:33, 17 July 2007 (UTC)

industrial use of insecticides

What types of insecticides and pesticides are use industrially, specifically in transport containers coming from the eastern countries

Molecular orbital formation

How exactly can two atoms[say,two oxygen atoms] combine to form two molecular orbitals[anti bonding and bonding] when there are only two orbitals combining?

The atomic orbitals don't combine in the simple "overlap or merge" physical sense, but rather recombine in various proportions to form molecular orbitals. This recombination can be constructive or destructive: the atomic orbitals could reinforce each other or cancel each other out. So there's the answer: two AO, two ways to combine them, now you have two MO. There's more detail and several examples on the molecular orbital page. DMacks 01:39, 16 July 2007 (UTC)

There are in this case two ways the O orbitals can combine giving two types of resultant orbital, if say the atomic orbitals cn each hold one electron, then each resultant molecular orbital can hold 2 electrons.

Each atomic orbital can hold two electrons, just like each molecular orbital. That's another sign that two atomics become two moleculars: gotta have a place to put all the electrons (start with "space" for four, wind up with space for four). DMacks 03:11, 18 July 2007 (UTC)

Unusual bird behavior

Hi all! There's a bird outside my kitchen window, I believe it's a goldfinch, that keeps on trying to fly through the (closed, unopenable) kitchen window. Someone else told me that it's been doing this for over a week. It keeps on making attempts to enter the house on a very regular, rapid basis. There are some bird feeders in the area, but strangely, this bird is mostly hanging from a hummingbird feeder. What's causing this odd behavior, and is there anyway I can effectively get this bird to stop? - RedWordSmith 17:25, 15 July 2007 (UTC)

It's possible that the bird can see its reflection in the glass and is trying to attack the perceived intruder it in order to defend its territory. Is it by any chance the breeding season for this type of bird where you live? Is it a cock bird? Quite a lot of male songbirds get 'antsy' and 'hormonal' at that time of the year. --Kurt Shaped Box 17:32, 15 July 2007 (UTC)

If it's attacking a reflection in the window, then you could try putting a picture of a predator on the wall. Bart133 ^{(t) (c)} 17:34, 15 July 2007 (UTC)

Editing conflict. I agree with our sea gull expert Kurt. The best thing to do is to cover the window so that the image is not visible. --Eriastrum 17:37, 15 July 2007 (UTC)

When I was a kid, my bedroom window had a *very* reflective anti-glare coating (it was pretty much a two-way mirror on the outside). While it did get the odd small songbird crashing into it, most interesting was the way the mapgies would perch on the windowsill at dawn and hammer on the glass with their beaks. Sometimes there were ten birds lined up and tapping away. I didn't need an alarm clock. :) After a few months, the coating was chipped away in several places and the glass was beginning to spiderweb. I'm still not 100% sure what they were doing - it didn't look like aggressive, territorial behaviour. More like fun. --Kurt Shaped Box 17:50, 15 July 2007 (UTC)

(Edit conflict me too). You could also try tacking a piece of chicken wire or other similar mesh over the window on the outside, in order to break up the reflection. Many songbirds die every year after flying head-first into windows in pursuit of themselves. --Kurt Shaped Box 17:41, 15 July 2007 (UTC)

I thought this kind of thing only happened in movies and comic books. Kittens tend to play with the cat in the mirror, for a while Nil Einne 19:53, 15 July 2007 (UTC)

Anyone that's ever owned a parrot or parakeet will know that birds can become totally obsessed with their own reflections. They don't even need a proper mirror - anything shiny that they can see a little glint of themselves in becomes an object of fascination. They'll try to fight their reflection, feed it, snuggle up to it, or sometimes even try to mate with it. Most birds seem to be unable to grasp the concept that the bird in the mirror is actually itself. --Kurt Shaped Box 20:07, 15 July 2007 (UTC)

I'd be impressed by any that did. Elephants and apes are the only animals recorded to recognise their own reflections, as I recall. Bendž|Ť 22:46, 15 July 2007 (UTC)

I believe mirrors are used to judge the intelligence of animals. The lowest level is animals that always see an enemy and attack it, and never learn. This sounds like what we are dealing with here. The next level is animals that learn it's them in the mirror, then have no more interest in it (no introspection), like cats and dogs. The highest level is animals that become fascinated with their own reflection and use it to look at themselves constantly, such as happens with some primates (including humans). Incidentally, I've also seen a bird do the same thing, trying to get into a glass-walled cafeteria. It kept trying until the glass door was opened by a customer and it got in, at which point it started doing the same thing, only flying at the glass from the inside this time. StuRat 01:13, 16 July 2007 (UTC)

I'm pretty sure that I read somewhere that African greys and some of the larger macaws and cockatoos were capable of recognising their own reflections. Sorry, I can't remember where now - I do read a lot of stuff-stroke-crap. --Kurt Shaped Box 07:29, 16 July 2007 (UTC)

The study is mentioned here [1] and elsewhere (Google). So far, the only animals showns to have this sort of reflection self awareness are dolphins, (Asian) elephants and various primates at least according to the source. Do note though that it's easily possible other animals may possess it, it simply hasn't been demonstrated yet. Also, while obviously related to intelligence, it's important to remember it's only one factor. I.E. Just because a cat is capable of learning that attacking its reflection is pointless doesn't mean it's more intelligent than a bird which isn't (also see bird intelligence too). While there is probably no directly evolved component, it is possible there is some influence and I presume a bird which is usually flying has less need to learn about reflections then an animal like a cat on the ground. Nil Einne 12:08, 16 July 2007 (UTC)

I wonder if seabirds are aware of their own reflections? Thinking about it, they must see themselves reflected in the water reasonably often - and crash-landing in the sea every five minutes in an attempt to fight themselves would be pretty counter-productive. Thinking about 'my' gulls (i.e. the ones I feed every day, I have never had one attacking my windows - and they do come very close. Sometimes they've even been right up to the glass to peer in at me and squawk for my attention. Is a gull technically a 'seabird' anyway? As I understand it (aside from the very strange little Kittiwakes), they never actually go 'out to sea', as such. --Kurt Shaped Box 23:27, 16 July 2007 (UTC)

I didn't think seabirds were terratorial (at least not while at sea!) - so why would they be attacking others of the same breed in the first place? SteveBaker 02:15, 17 July 2007 (UTC)

Have you ever watched the seagulls, man? They look for any excuse to have a fight. If one just looks at another the wrong way or walks a bit too close they end up flapping, screeching, pecking and bickering. Would they really hold back on that because they were over the water? --62.136.231.228 13:56, 17 July 2007 (UTC)

Okay, I figured something like that might be responsible. Covering up the whole window doesn't seem like an option at this point (it's very large!), but I've covered up the bird's favorite spot to perch in front of and attack with a page from a catalog (do songbirds like tea?). We'll see how it works. Thanks for your help so far. - RedWordSmith 20:19, 15 July 2007 (UTC)

I've definitely seen video footage of a chimpanzee recognising itself. The way they test the theory is to aneathetise the animal and while it's unconscious they put a smudge of coloured makeup on it's forehead (imagine a big red dot of lipstick or something). When it wakes up, the chimp is totally unaware that the smudge is there. When it looks into a mirror, it sees "another" chimpanzee with a smudge of colour on it's forehead. If the chimp rubs it's own forehead to get rid of the smudge - then it clearly recognised that the thing it's seeing is a reflection of itself - and not some other animal. I've seen that done with chimps and the result is really conclusive. The problem with doing the experiment with dogs (and maybe cats too) is that dogs live in a sensory environment that's totally dominated by smell. A mirror doesn't easily fool them because it doesn't smell like another dog. So if they care at all about the reflection - it's not because "they think it's another dog". If they care at all (and my dogs never did) then it's just because there is something moving back there that doesn't smell...which is weird to them. I'd imagine dolphins would get a similar cue because their echolocation isn't showing the distinctive sonar image of another dolphin, this is certainly helpful in distinguishing that the mirror isn't just a window onto another world with another dolphin in it. SteveBaker 17:34, 16 July 2007 (UTC)

If researchers have started putting lipstick on chimps I'd say they've been locked up in the laboratory a bit too long. :-) StuRat 13:47, 17 July 2007 (UTC)

On a serious note, since smell only works up close, dogs do use sight at a distance, so just do the test with the dogs 10 meters away from the mirror. StuRat 13:47, 17 July 2007 (UTC)

Dogs have a sense of smell that is (allegedly) 1,000,000 times more sensitive than ours. 10 meters is simultaneously not far enough to disable the sense of smell - and too far to allow their (relatively poor) eyesight to operate. SteveBaker 13:57, 17 July 2007 (UTC)

And both dogs and dolphins would have a hard time rubbing a spot off of their foreheads? Capuchin 12:06, 17 July 2007 (UTC)

Yes - but there was a variation of the experiment that was performed with dolphins, see: Cetacean_intelligence#Self-awareness for details. SteveBaker 13:55, 17 July 2007 (UTC)

Need help with evaporation rate.

I've looked around a few placees, specifically the pages on Evaporation, Absolute Humidity and Relative Humidity, and see a couple of formulas, but am not quite sure how to apply them.

My question is: Say I have a pool of water with surface area A and temp T, with air temp T', relative humidity R and pressure P (assume no-wind, closed system, no external energy sources, ideal conditions.) I want to calculate how much water I expect to evaporate over a given time M.

I'm doing this for a grossly simplified wx-sim for a game, so wild approximations are ok, although I'd like to have at least some understanding of the "real" physics behind it, so that I can make intelligent adjustments and choices about what factors to include/exclude.

By way of example, my sim will be doing things like: "over this kM^2 of ocean, temp T, air-temp T', pressure=1atm, X-amount of water evaporated (contributing to the RH of that block of air) over the past hour." We'll be ignoring things like wind, extra-evaporation from unsmooth ocean surface, etc. So, you can see, there are lots & lots of shortcuts being taken. The goal is to create something "realistic-seeming it its effects", not necessarily "100% true to life."

Thanks! Oliepedia 18:20, 15 July 2007 (UTC)

Go for a formula like $rate=cARe^{T}$ GB 22:01, 15 July 2007 (UTC)

Term meanings? (I got A & T, and maybe P. Is e "e"? c?) Can you point me at a reference to read more?

Thanks! Oliepedia 04:01, 16 July 2007 (UTC)

I'm pretty sure he just wanted to spell carpet. But e would be e and c would be c. Capuchin 06:40, 16 July 2007 (UTC)

Sorry I had to stop work on the question abruptly! ok its not carpet - its caret, e is the mathematical constant, c is a constant - not the speed of light, but a figure that might give about cm of evaperation per day at about 40°C. However are there extreme conditions involved? It the temperature wildly different to the earth surface? If you get a big difference between water and air temperature you will get fog - are you interested in that? The Pressure (P) of the air will make little difference in the rate, so I should not have put it in. GB 10:24, 16 July 2007 (UTC)

Uh... ok. Can you help me out with the application? (Is there a standard way, on these pages, to abbreviate "I'm pretty smart, and understand math and more physics than the average Joe, but I don't do this every day, and it's certainly not fresh in my head!"?) My sim/game-planet is Earth-like, so temp extremes in that general range.

Ok, let's try this...

Pool area = $1m^{2}$

Pool Temp = 20°C

Air temp = 25°C

You said to ignore pressure, then replaced with "R" -- what's that? RH%? Let's say 60%

So now I have

rate=c*1*R*(2.71828^20)

Or is T the temp differential (5)? And if R is, indeed, RH%, then I have:

rate = c*1*.60*(2.71828^20)

or

rate ~= c * 291,099,117

So, if I knew what R was, I could work out a c that gave me ...uh... what? "1" (cc per day)? Is "rate" in "cc per day"? Do I have the other terms right? My answer looks big, like it would need nano-units to come out.

Thanks! Oliepedia 02:45, 17 July 2007 (UTC)

FWIW, I found some really good info in this Hydrology Textbook and surrounding pages. 63.201.144.200 21:15, 23 July 2007 (UTC)Oliepedia (forgot my password, again!)