Wikipedia:Reference desk/Archives/Science/2007 May 3

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May 3

blood types

What would happen if you were to mix two types of blood groups? —The preceding unsigned comment was added by 24.6.87.25 (talk) 00:07, 3 May 2007 (UTC).

They would have a fight. read the intro V-Man - ^T/_C 00:35, 3 May 2007 (UTC)

no "fight" if they were compatible; big bad fight if they were incompatible. See blood type to see what types are considered compatible, but you'll want further information. If you're mixing blood in the lab (i.e. a petrie dish, rather than in an organism), the blood will agglutinate or hemolyze. If you've transfused incompatible blood into an organism, you will get a transfusion reaction, which might include fever, hemolysis, anaphylaxis, or death. - Nunh-huh 01:55, 3 May 2007 (UTC)

Yeah, it depends on the groups. Some can be mixed without a problem, some cannot. Look at the article. --24.147.86.187 12:01, 3 May 2007 (UTC)

Half Life of a Drug molecule

If the half life of a substance is 60 hours and after many many many hours later, the drug is down to it's last molecule. What does the "half-life" of 60 hours mean physically for a single drug molecule? Does it mean that 60 hours later, there will be half a molecule of that drug? 202.168.50.40 00:27, 3 May 2007 (UTC)

This being answered above - see Wikipedia:Reference_desk/Science#Half_Life_of_a_Drug David Ruben ^Talk 00:31, 3 May 2007 (UTC)

It's sort of answers -- someone said "However, half-life formulas break down for a relatively small number of molecules/particles, as is mentioned in the last section of the half-life article." But perhaps it's worth going into more detail. The point is that the idea of "half-life" as "the time for half of the stuff to be consumed" simply breaks down when the quantity is down to where you're counting individual atoms or molecules. In nuclear physics it is better to think of it as the time during which, for each particular atom, the probability that it will break down is 1/2. For organic systems like drugs in someone's body, where complex reactions can be involved, it's quite possible that the "half-life" model is only an approximation in the first place; but if it does apply exactly, you can say that in 60 hours there is a probability of 1/2 that the last molecule will be gone, and 1/2 that it will still be there. --Anonymous, May 3, 2007, 00:39 (UTC).

Coupling Constants

Is the coupling constant for the colour force greater than 1 at low energies? Thanks, *Max* 00:49, 3 May 2007 (UTC)

As far as I understood it grows arbitrarily close to 1, but remains below it. —The preceding unsigned comment was added by 84.187.43.190 (talk) 02:42, 3 May 2007 (UTC).

Thank you. *Max* 13:45, 3 May 2007 (UTC)

Flexibility

Are females more flexible than males? Why so? A reponse on my talk page or to just let me know would be greatly appreicated.100110100 01:31, 3 May 2007 (UTC)

My crackpot chiropractor said to me that the tendons/nerves in a female just "snap" back to their place when stretched, whereas males after they have been manipulated their tendons etc tend to stay like that more easily. However ultimately I'm not sure. Rfwoolf 12:22, 3 May 2007 (UTC)

The only difference I can think up right now is that Women and Men have a slightly different bone structure. Of importance here is the difference in structure of the pelvis, which makes doing splits easier for women. Other than that I think the main difference stems fromt he fact that women are more likely to practice ballet and gymnastics as a hobby. You might also want to check out the article, contortionist, which states that both men and women are equaly likely to be hyper flexible. PvT 14:02, 3 May 2007 (UTC)

My crackpot chiropractor also said that people with looser tendons aren't very suitable for contact sports such as rugby. I would imagine that women aren't very suitable for that sport either. Rfwoolf 18:40, 3 May 2007 (UTC)

"Flexibility For Sport" - Bob Smith - ISBN 1 85223 804 6 says the different shape of the female pelvis, wider and flatter than the male pelvis means there is greater potential for flexibility. The lighter bone structure is another advantage. Also it says that during pregnancy the increased secretion of the hormone relaxin increases the range of motion, especially around the pelvis. Also the differing levels of oestrogen and progesterone may also play a part in affecting ROM but there is no conclusive evidence. Lifestyle may have a limiting factor on the ROM in the male. This does not mean men are "muscle bound" and thus inflexible; Tom Platz is quite flexible and very muscular. --TrogWoolley 19:38, 3 May 2007 (UTC)

Source of Light in Color Spectrum

5/2/07

Greetings,

Your picture of white light separating into the colored light shows a prism with a very strong source of light to make a very prominent color spectrum see -- http://en.wikipedia.org/wiki/Color_spectrum. However, the picture did not say what is the source of light used. Can you please tell me what is the source of light used to make such a strong color spectrum and where can i get it? I used large flashlights and small flashlights and you can barely see the color spectrum because the light was not strong enough. I am now looking into photography lighting and believing for the best.

Thank you.

Hernandezw 01:38, 3 May 2007 (UTC)

I believe Newton used sunlight. --TotoBaggins 01:46, 3 May 2007 (UTC)

Incandescent bulbs such as the one in a typical flashlight usually output a very yellowish spectrum. -- mattb 01:51, 3 May 2007 (UTC)

The picture in question was taken by NASA. The link given to NASA on the picture's own page no longer works. Sadly, I don't think we have any information on the type of bulb (and, I would guess, lens system) used to create the image. --Tagishsimon (talk)

It is a photography of a still image. Just leave the shutter open for a second or two. —The preceding unsigned comment was added by 84.187.43.190 (talk) 02:45, 3 May 2007 (UTC).

In a classroom I have used a slide projector with a slit where the slide would go For a slit, I used a thin piece of metal painted flat black with high temperature paint (Rust-OLeum "Barbecue black" [1]). Physicists would doubtless have an instrument quality adjustable slit. The slit was focussed to throw its image on the white screen, with a white card horizontally below it. A glass prism was then placed in front of the lens, and rotated such that the slit image was spread out, the shorter wavelengths being bent more. For all that, the students did not seem all that impressed. When Newton wrote about using a prism to create a spectrum from sunlight shining in through a small opening in the shutters of his room, some of his contemporaries said they tried it and it didn't work and that he was probably just seeing a "staining effect" from dirt on the surface of the glass. A great article could be written with contemporary doubters who slowed the progress of science by denying the truth of scientific findings such as this, the Edison effect, the Hall Effect or wireless radio transmissions before Hertz. Edison 02:55, 3 May 2007 (UTC)

Back in high school physics (hi Mr Davidson!) we had actual 35mm slides made from pictures, of presumably of a white line very accurately drawn on a black piece of paper. I'm sure it took some experimentation of the part of some lab tech assistant with camera settings in order to get the desired slit-size on the film. Also worked for 2-slit experiments. DMacks 04:41, 3 May 2007 (UTC)

The page sorta still exists in the archive, but doesn't mention the light source as far as I can see. —Bromskloss 08:37, 3 May 2007 (UTC)

You can make a pretty good optical slit by bringing the sharp edges of two single-edged razor blades nearly together. (These are the sort of blades used in scraper tools.) And because the blades are stainless steel, they're reasonably heat-resistant as well.

Atlant 13:03, 3 May 2007 (UTC)

The orgin of Earth's spin

58.107.36.175 01:56, 3 May 2007 (UTC)RosTHave searched Wikipedia and the Web and the nearest it gets is to attribute the spin of the earth (and other objects) to the collapse of primeval gas clouds but why should these gas clouds spin or rotate in the first place? RosT

See Solar nebula. It seems that as gas clouds shrink due to gravitational collapse, random motion becomes spin due to conservation of angular momentum. --Allen 02:20, 3 May 2007 (UTC)

The question is: Why is the planet spinning *so fast*? In a gas cloud composed of billions of small particles in completely random motion, the expected deviation from zero total angular momentum should be quite small compared to the total mass of the cloud. —The preceding unsigned comment was added by 84.187.43.190 (talk) 02:37, 3 May 2007 (UTC).

Coupla thoughts: What's the frame of reference for declaring that a period of 24h is "fast"?—the earth is pretty light and small on a cosmic scale. Need to be careful that a reasoning of "they should average out" doesn't wind up as a Law of averages fallacy for one specific collection of particles (i.e., "Earth"). By conservation of angular momentum, a large disk spinning slowly becomes a small disk spinning more rapidly—moment of inertia scales as r², so cutting the diameter in half increases ω by a factor by four. DMacks 03:07, 3 May 2007 (UTC)

• Indeed, and the solar nebula probably collapses from an objects that's at least 1000 AU across, you can spin up quite a bit. In general, the problem for astronomers is how to get rid of all the angular momentum the solar system should have, not to account for the small amount it has. WilyD

Grass Of South Africa

I've been told that the South Africans chew a grass for a drug. What is it?100110100 02:04, 3 May 2007 (UTC)

Could you be referring to to Khat (though it is more popular in East Africa, than South Africa.) Rockpocket 02:24, 3 May 2007 (UTC)

Some discussion that is not answering the question. Click the 'show' link, if you want to read it.
The following discussion has been closed. Please do not modify it.
I have no idea what he was refering to.100110100 02:37, 3 May 2007 (UTC) My Cat chews grass apparently as an Emetic to get rid of hairballs. Edison 02:58, 3 May 2007 (UTC) I think your cat chews grass just because it's an idiot. Every dog and cat I have met chews and swallows grass, and it makes them throw up. :) Not making fun of your cat! Why is that, that they eat grass? [Mac Δαvιs] ❖ 05:09, 3 May 2007 (UTC) Didn't you just give us what you think the reason is? Did you click on the emetic link? JackofOz 05:14, 3 May 2007 (UTC) I've read that dogs chew grass because it helps them throw up. For example you're not supposed to feed dogs bread (because it contains yeast) yet a lot of stupid pet owners continue to do this even after I've told them not to. I'm *guessing* that when I saw their dogs eating grass it was for this reason - to throw up. Rfwoolf 12:19, 3 May 2007 (UTC)

Nepeta, maybe. I don't know if they chew it. (I just realize that my answer has absolutely nothing to do with the question. I read the drug thing, then the cat thing and I probably thought the question was about a grass that african cats would chew...) (now I'm scared that I may be swallowed by the big box of tangential discussion) A.Z. 08:27, 3 May 2007 (UTC)

I'm from South Africa, and I'm not sure what you're referring to. Certainly in the urban areas such a thing is highly unlikely. What you're probably referring to is a type of herb or roots or something. There's sugar cane which you can chew and suck on and spit out. Maybe you can give us more information. Are you sure it was a "Grass" ?Rfwoolf 12:19, 3 May 2007 (UTC)

I asked my classmate, 'What drugs have you done?', & then after a while, he said every culture has a drug, then he cited that in South Africa, the people smoke a grass (as far as I remember this conversation).100110100 01:43, 4 May 2007 (UTC)

I'm from South Africa too, and you might be referring to Dagga. Since it is a weed that grows naturally (or illegally) in the bush, it is sometimes referred to as weed or grass. An expression: 'are you smoking grass/weed?' is often heard, meaning 'whacked or drugged or whatever' Sandman30s 13:27, 3 May 2007 (UTC)

Good answer, but would a person chew dagga? Rfwoolf 18:34, 3 May 2007 (UTC)

Good question.100110100 01:43, 4 May 2007 (UTC)

Well that's the only drug I know that's referred to as grass. I've seen people chewing on blades of grass (they'd make good gardeners) but certainly not as a drug. Maybe the OP was misinformed? Sandman30s 12:01, 4 May 2007 (UTC)

Sandman I had read your answer somehow without reading 100110100's comment just before it, where he seems to have 'changed his question from chewing to smoking in which case it seems like your answer was apt. And I agree, smoking 'grass' in South Africa, as far as I understand, is indeed weed/marijuana/dagga. Rfwoolf 13:48, 4 May 2007 (UTC)

What type of heron?

A few years ago I saw a bluish heron in Northern California and was wondering what kind of heron it was. It was not (from my memory) a Great Blue Heron. 67.172.125.250 03:39, 3 May 2007 (UTC)

The Great Blue Heron is fairly common and striking – are you sure that wasn't it? For other alternatives, this page says that 11 of the 12 US species of herons have been sighted in California recently, but that The seven most common species of heron found up and down the West Coast of the United States are the American Bittern, Black-crowned Night Heron, Green Heron, Great Blue Heron, Great Egret, Snowy Egret and the Cattle Egret. Of those seven, only the Black-crowned Night Heron, the Green Heron, and the Great Blue Heron would seem at all likely to be seen as "bluish". Other less common (in California) possibilities are the Little Blue Heron and the Tricolored Heron. You can compare pictures of most of these on their Wikipedia pages or on the web, for example here. --mglg_(talk) 19:11, 3 May 2007 (UTC)

It was probably a little blue heron, as it was bluer than a great blue, but no white area. Thanks 24.10.123.107 23:04, 3 May 2007 (UTC)

Electric Control Device

Hi. What is an electric control device? Thanks. --Mayfare 04:39, 3 May 2007 (UTC)

Could be many many things... A relay, a switch, a transistor, etc. Could you be more specific or give context? -- mattb 04:41, 3 May 2007 (UTC)

There are systems of device numbers for electrical control, such that Device 2 would be a timer, Device 50 would be an overcurrent relay, and various numbers have different functions. Is that what you referred to? Edison 04:11, 4 May 2007 (UTC)

Nuclear fuel effeciency

I have four questions which are linked

1. Given a typical* modern power station, what kind of yield in terms of watts does a ton of uranium produce.

2. Given a typical* modern uranium mine. How much fossil fuel does it require to mine and transport a ton of uranium.

3. Given a typical* modern fossil fuel power station how many watts would the fuel equivalent to the answer to question two produce.

I hope you can see what I am getting at.

4. Seeing as there is no obvious substitute for fossil fuel in the mining/transporting of uranium and the construction/decommissioning of power stations. Could nuclear power be defined as a convoluted way of turning fossil fuel into electricity?

• Hard to define I am sure, but I only a rough guideline.

Hope that's OK

Pet Dane —The preceding unsigned comment was added by Petdane (talk • contribs) 05:40, 3 May 2007 (UTC).

Nuclear power could be self-sustaining in a hydrogen economy, but it is true that *everything* is distorted by how cheap oil is. Michael Pollan's excellent book The Omnivore's Dilemma makes a good case that industrial agriculture is a convoluted way of turning fossil fuel into food, outweighing even sunlight as an input. --TotoBaggins 12:55, 3 May 2007 (UTC)

This is an excellent question, and it's always worth remembering that some cost in input is required. However, nuclear energy is so many orders of magnitude more efficient than chemical fuels that it's nearly impossible these days for it to be a net energy loss. I ran some quick numbers for the Ranger Uranium Mine based on their 2006 annual report[2], a page from Syracuse on energy density of fuels[3], and some miscellaneous references (such as the refining rate of crude oil to gasoline, etc). Granted there are a lot of assumptions and estimates I've made, but I've tried to be conservative: for instance, I assumed the entire consumables budget for Ranger was gasoline. Anyway, a rough upper band for Ranger's fossil fuel energy expenditure is 2.2 terawatt-hours (TWh). The 5000 tonnes of U₃O₈ produced by Ranger that year has an approximate energy potential of 100 000 TWh. Nuclear energy is, by any measure, a net energy gain. — Lomn 13:12, 3 May 2007 (UTC)

[EC] Let's suppose that one U-235 fission reaction liberates about 200 MeV of energy. One ton of U-235 would contain about 2.56×10²⁷ U-235 nuclei. If all the nuclei undergo fission, the liberated energy would be 8.2×10¹⁶ J. I'd say a "typical" power station would have 35% efficiency, so the useful energy would be around 2.9×10¹⁶ J.

I don't really know how much fuel it takes to mine and transport one ton of uranium. But it's easy to find a work-around:

In an ideal power station, the amount of fossil fuel (let's assume regular gasoline here) needed to produce the same amount of energy as one ton of uranium is roughly 653,000 tons (enough to fill the largest oil tanker in the world). I think it's safe to assume that a much smaller amount of fossil fuel is involved in the mining and transportation of uranium. —LestatdeLioncourt 13:19, 3 May 2007 (UTC)

Remember that you have to calculate also the costs associated with refining the uranium, 1 tonne e fissionable uranium isotopes.Bastard Soap 13:03, 4 May 2007 (UTC)

The Little Albert Experiment

Why was it aloud to happen when it was so un ethical —The preceding unsigned comment was added by 124.177.179.178 (talk) 06:07, 3 May 2007 (UTC).

You could first check out the Wikipedia page on the Little Albert Experiment.--droptone 06:38, 3 May 2007 (UTC)

And you might as well be told that research ethics in 1920 were not exactly what the would later become in the 20th century after the horrors of Nazi experimentation, Tuskeegee, etc. For a long time researchers didn't give a lot of thought to the ethics of their work on human subjects. Now unfortunately the pendulum has swung ridiculously the other direction where an IRB can reject a proposal that involves asking prisoners something that might be uncomfortable to them— after all, life in prison would be wonderful if it weren't for those pesky sociologists asking the inmates how often they had been raped there and etc. --24.147.86.187 12:04, 3 May 2007 (UTC)

electrolyte mud

where can I found electrolyte mud? —The preceding unsigned comment was added by 125.160.98.78 (talk) 08:04, 3 May 2007 (UTC).

Never heard of "electrolyte mud." Assuming that's just mud with electrolytes in it, pour saltwater onto dirt ;-) Someguy1221 10:39, 3 May 2007 (UTC)

I'm actually impressed—the phrase "electrolyte mud" draws absolutely no Google hits. Are you sure that's what you're looking for? The only thing I can think of is that it might be an overpriced gimmick at a day spa: "Enjoy our electrolyte mud facial mask, followed by a hot iguana massage...". TenOfAllTrades(talk) 13:56, 3 May 2007 (UTC)

I don't think I'd care to massage an iguana, even if it did look hot. :-) StuRat 18:27, 3 May 2007 (UTC)

I think this refers to the mud collecting at the bottom of a Lead-acid battery (look at the bottom of construction section.Polypipe Wrangler 22:47, 3 May 2007 (UTC)

or maybe it is copper (or any other metal) electrolytic refining byproducts -Yyy 06:26, 4 May 2007 (UTC)

Photosynthesis

Is there anyway you could construct human cells so that the too could photosynthesise?

Thank You

89.241.1.180 09:11, 3 May 2007 (UTC)

You might be able to pull this off in a petri dish (still some issues), but not in a whole person. And even if you could, the energy provided would be miniscule compared to eating instead. The amount of phosynthesis that occurs is, among a great many other things, somewhat proportional to the surface area of the organism. Not only do we require a lot more energy per unit volume than a plant does, but we have a much smaller surface area to volume ratio than most plants (if you consider only living matter). Further, it's generally easier to steal other organisms' sugar than to make your own, presuming such organisms are plentiful and don't fight back. Simply put, it would be very hard, certainly wouldn't work, and wouldn't make sense even if it did. A much better bet would be to try and redesign ATP synthase to be powered by light, but good luck with that. Someguy1221 11:16, 3 May 2007 (UTC)

Agreed. I recall there being some plant that "turns into an animal at night" and eats other plants. I believe this was a single celled plant. Does anyone recall the name ? StuRat 18:21, 3 May 2007 (UTC)

Are you thinking of a Euglena? if so, it's worth noting that they're not single celled plants, in so much as they're protists--VectorPotential^Talk 19:00, 3 May 2007 (UTC)

I'm not sure, that might be it. StuRat 19:05, 3 May 2007 (UTC)

Shouting Over High Pitched Sounds

As you all know, if you can hear a loud noise, you have to shout to people that are stood reasonably close to you in order for them to hear you, even though they would normally be able to hear you if you spoke normally when the noise was not being made. Is this still the case when the noise is inaudible (i.e. it has a pitch of over 20,000Hz)? In other words, is the need to shout generated by the actual vibration of the air, or by the overloading of the human ears? --80.229.152.246 14:05, 3 May 2007 (UTC)

No, you would not need to shout in that case. Sounds, being a purely wave phenomenon, don't interfere with one another, but pass right past each other like ripples on water (it is possible to "cancel" a sound by sending the reverse sound, but that's something different). The need to shout is because you can't hear those frequencies which are "overloaded", as you said, in your ears, by the loud noise. StuRat 18:18, 3 May 2007 (UTC)

Waves certainly do interfere with each other- see wave interference. Friday (talk) 18:25, 3 May 2007 (UTC)

Perhaps I used the wrong words to describe what I mean. One wave hitting another doesn't destroy it, but they pass right over each other. That said, at the point where they are on top of one another, they are additive. So, if the peak of one wave hits the trough of another equal sized wave, they will, at that point only, cancel each other. Once they pass each other, there is no residual effect of each wave on the other. StuRat 19:00, 3 May 2007 (UTC)

Sufficiently high amplitude sound waves do not act like perfect waves (air particles will experience net motion, as opposed to oscillating in place) and will permanently alter or destroy low amplitude waves. I'm not sure how strong the sound has to be for this, though, you might need a bomb or a speaker system that can shake the earth. Someguy1221 20:14, 3 May 2007 (UTC)

Thanks for the info. I forgot about the fact that waves don't interfere with one another. --80.229.152.246 19:35, 3 May 2007 (UTC)

I think it should be made very clear: waves can interfere with each other, but waves of different frequencies do not interact (in the simplest, linear system analysis, of course). As Someguy1221 pointed out, sufficiently high amplitudes may have nonlinear interference. Nimur 01:40, 6 May 2007 (UTC)

Fall speed of parachutes

As far as I understand a parachute works by causing air resistance and thereby slowing the object that it's carrying down, it also seems to me that it's the ratio between air resistance and weight of the parachute and the object the defines your fall speed, so my question is: How do you calculate the air resistance needed to slow an object to a certain speed?

Second question: How big does a parachute have to be to cause a certain level of air resistance? Thanks for everything, Jeffrey.Kleykamp 14:10, 3 May 2007 (UTC)

Our article on terminal velocity has formulae that you can use. The only hard part is knowing what the appropriate drag coefficient is, but for a 'blunt' object like a parachute canopy assuming a value around 1.0 is probably not a terrible approximation. TenOfAllTrades(talk) 14:24, 3 May 2007 (UTC)

Also note that there is something called a paraglider, which both increases air resistance and also provides lift via a wing shape. This provides a degree of control over the landing site which is not available with a traditional parachute. Stunt parachutes often employ this technology, allowing for acrobatics during descent. StuRat 18:06, 3 May 2007 (UTC)

Black hole

As far as I understand a black hole's gravity bends light and right before the event horizon you see light coming from your position, so my question is has anyone tried to look at the light that left earth a long time ago, say 100 million years, by looking at a black hole that's 50 million light years away, I know it could be hard, maybe even very hard, to find a black hole that's exactly 50 million light years, but that's not the question. And I also understand that the light won't look like a crystal clear picture, and more like a line, but computers can calculate away any errors. Thanks for everything, Jeffrey.Kleykamp 14:34, 3 May 2007 (UTC)

• This wouldn't work, for a variety of reasons - firstly, the image would be very faint - I'd be surprised even we got even 1 photon a year from such a trick - secondly, the image (if there were several photons) would be fundamentally distorted in an uncorrectable way - both from very minor gravitational lensing and the chaoticness of the process, but also because you're stuck with a diffraction limited telescope. Cheers. WilyD 15:05, 3 May 2007 (UTC)

Also: unfortunately, black holes are quite far away. After a bit of searching on Google, the nearest black hole seems to be about 1600 lightyears away. After a bit of rough calculation, this would mean that the Earth would have an angular diameter of about 8x10^-13' (or if you don't like scientific notation, about 0.0000000000008'). When you consider that the Sun has an angular diameter of about 30', you can see how small that is. As such, only a piddly (yes, that's a scientific term) amount of light would reach the black hole. Even if the improbable event of completely accurate bending of the light could occur (even the tiniest error would result in the light that has been bent from the black hole from reaching us due to the large distance involved), there would not be enough light there for us to detect. I hope that answers your question. --80.229.152.246 15:13, 3 May 2007 (UTC)

Thanks! Jeffrey.Kleykamp 15:22, 3 May 2007 (UTC)

Remember how tiny photons are! Taking the Earth's magnitude (at 1 AU) to be -4 as a Google search suggests, and using the solar luminosity value as a number of 550 nm (green) photons (which should underestimate their number), I calculate that there should be nearly 9 billion photons per second thrown into even such a tiny solid angle by the Earth when it is "full". (I believe that for ideal lensing using the Earth's size as viewed by the lens is correct for this calculation.) That said, that's over the whole spectrum, and there's no guarantee that any given black hole acts as a high-quality lens, or that the Earth's image formed by it would be at all distinguishable from the billions of other images. --Tardis 19:58, 3 May 2007 (UTC)

Are you saying it's possible to see earth, just a matter of the light being sent back properly? Jeffrey.Kleykamp 20:37, 3 May 2007 (UTC)

I'm saying that in principle there are enough photons to go around for the appropriate fraction of them to be detectable. However, I would consider it, practically speaking, completely impossible to (a) distinguish that light from other light in the vicinity, (b) work out the optics of its retrorefraction well enough to form what could be called an "image", and (c) resolve the image in any useful fashion (given the practical limits on telescopes and the absurd distances/relative velocities/etc. involved). --Tardis 22:40, 3 May 2007 (UTC)

Bear in mind that both the earth and the black hole have been moving for the entire 100 million years - the speed of both bodies has probably been varying in subtle and hard to calculate ways. It would be very surprising if the lensing effect happened to shoot the light right back at us. SteveBaker 01:50, 4 May 2007 (UTC)

I see... Jeffrey.Kleykamp 12:10, 4 May 2007 (UTC)

Impossible to calculate ways, actually, since we don't know the distribution of more than 5% of the mass. WilyD 12:46, 4 May 2007 (UTC)

What do you mean? Jeffrey.Kleykamp 13:21, 4 May 2007 (UTC)

We can only see and measure about 5% of the mass that makes up the universe - we have no idea where the other 95% is. Hence we can't calculate how things move around the universe because they are being pulled hither and thither by gravitational forces from things that we don't even know exist! If the black hole is 50 million years away, we need to know where the earth was 100 million years ago - and where the black hole was 50 million years ago. We can't calculate that with any precision whatever because of all this dark matter, invisible gas clouds and so on. SteveBaker 16:33, 5 May 2007 (UTC)

I understand it now, thank you very much! Jeffrey.Kleykamp 18:11, 5 May 2007 (UTC)

Color Perception

If we were looking at a green chair, how do we know that blue and yellow are being absorbed and not green? All three of these colors are on the electromagnetic spectrum, correct? Nick 16:27, 3 May 2007 (UTC)nicholassayshi

See color vision. Also note that if you see green, green is being reflected (or re-emitted) from the chair, not absorbed. --Kainaw ^(talk) 16:30, 3 May 2007 (UTC)

Be sure to also see Tetrachromacy. --Atlant 17:07, 3 May 2007 (UTC)

Atlant, don't you mean Trichromacy? Humans are trichromatic. See also Trichromatic color vision. I don't see why its a seperate article than Trichromacy, they should be merged.  Adam2288  T  C  20:25, 3 May 2007 (UTC)

No, I really meant it. I figured the questioner would get let to Trichromacy via Color vision, but for a tetrachromat, they may be able to actually tell the difference between fake yellor (primary red + primary green) and real, monchromatic yellow. We mere mortals can't do that without a spectrograph, a colorimeter, monochromatic lights sources, or some such.

Atlant 15:51, 4 May 2007 (UTC)

The short answer is that you can't tell, by looking at it, whether the colored light that you is "pure" or a mixture of two other colors. When you see yellow on a computer or TV screen, for example, it's typically a mixture of red and green. But it looks the same as a pure yellow light. That's simply how the human visual system works, which is what all the links above are about.

In the case of a typical screen, the red and green light actually comes from separate colored dots, so if you look very close at the screen you can tell. But in general, if the mix of red and green was coming from the same source, the only way you could tell it isn't pure yellow is to apply some sort of instrument; for example, a prism that will separate different colors of light. --Anonymous, May 4, 2007, 00:35 (UTC).

Star Ownership

Situation: Billions of years ago, a dwarf galaxy got stars taken away by the Milky Way (NewScientist). Question: How can we theoretically define the precise moment when the owner of a star changes from one galaxy to an other?--JLdesAlpins 16:42, 3 May 2007 (UTC)

Check the deed. It's in one of the Vogon's filing cabinets.

Atlant 17:04, 3 May 2007 (UTC)

Someone removed this, but I was gently nudging in the same direction that SteveBaker eventually made explicit; the question is more metaphysical than answerable.

Atlant 15:48, 4 May 2007 (UTC)

You could always rustle something up involving the gravitational attractions between the star in question, and the two galaxies - when the force of the new galaxy on the star overcomes the force of the initial galaxy on it, you could define that as the moment at which the star "swaps" galaxies. Of course this is probably far too simple a treatment of the situation. Icthyos 17:38, 3 May 2007 (UTC)

No, I'd say that's a fair treatment - something along the lines of constructing the Roche lobe for the two galaxies. The real point, of course, is that you'd never need to define the "precise moment" - these things are measured in such long timescales that "moments" are millennia long. Spiral Wave 18:47, 3 May 2007 (UTC)

Who cares? The "precise moment" of something so vague would be entirely arbitary - and because of the problems of simultenaety over large distances and high speeds - it's probably entirely dependent on where you happen to be observing the event from. It doesn't matter and you can't measure it. SteveBaker 01:45, 4 May 2007 (UTC)

SteveBaker's comments are (unfortunately) the most accurate description of astrophysics I've yet encountered on the reference desk. I was once enthusiastic about the interesting topics that are studied; but as I learned more about them, I realized that they are mostly studied in a very vague and approximate (and largely speculative) fashion. There is good science to be done! But most of the "neat questions" are best answered as Steve mentioned - "so vague..." and "entirely arbitrary" and "...doesn't matter and you can't measure it." I hope this is not to disappointing for enthusiastic science fans; on the contrary, you should start conditioning your mind to think in vague terms NOW, if you actually want to pursue space-science any farther :) Nimur 01:56, 4 May 2007 (UTC)

There are astrophysics topics where people are concerned about order unity corrections. THey're ... Well, like the CMB anisotropy. WilyD 12:48, 4 May 2007 (UTC)

Mobile Phone Batteries

I've just bought a new battery for my phone after having problems with a poor memory on the last one. I know I'm supposed to charge it for 16 hours the first time but should I just do this straight away or should I drain the new battery before its first charge? --Kiltman67 17:27, 3 May 2007 (UTC)

I understand it's best to do it straight away.--Shantavira 18:06, 3 May 2007 (UTC)

So even if the battery came almost fully charged? --Kiltman67 18:07, 3 May 2007 (UTC)

Well it depends on the type of battery, but asuming its a Li-ion battery, like the vast majority of new cellphone batteries, it's better not to drain it. For increased life, you should avoid draining Li-ion batteries, and if you're going to store it unused for a long time, it should be roughly 50% full, so new batteries are usually 50% or less full (they lose some charge when they're not being used).  Adam2288  T  C  20:20, 3 May 2007 (UTC)

Thanks for the advice, that's the opposite to the advice I was given when I bought the phone originally which seems like it might have been the reason I've had memory problems in the first place. Do you know if it makes a difference to charge the battery for the first time when it's on, rather then when the phone is off? --Kiltman67 20:44, 3 May 2007 (UTC)

This will depend on your specific model; you might get such answers from the owner's manual. If the phone is designed with a "smart" power-supply, it will adjust its charge cycle and power consumption; if not, your manual will probably instruct you on proper procedure. Nimur 02:05, 4 May 2007 (UTC)

Unfortunately the manual didn't say anything about the first charge. I decided the safest option was to just charge it with the phone switched off. --Kiltman67 03:55, 4 May 2007 (UTC)

From my memory and understanding you're supposed to charge it with the phone switched off. It's a huge pain I know, I've been there... you buy a phone and you're so excited to switch it on and start using it - but the stupid manual says you have to charge it for for X hours. But you have to do it. Go home, charge the blasted thing for however long, then switch it on and enjoy! Rfwoolf 14:09, 4 May 2007 (UTC)

Does anybody know if there's any merit to letting the batteries second recharging last as long as the first? I've heard some people say you should give it two long recharges but other people seem to think once is fine. --Kiltman67 22:08, 4 May 2007 (UTC)

Not according to my knowledge - because with your phone on (or in many cases off) it should tell you how full/empty your battery is. But let's be clear, when you get the phone you keep it off and you recharge it for 14 million hours and see that its battery indicates full. Then switch it on and you should see your battery on full. (At this point if the battery isn't full, it didn't charge properly or you didn't charge it long enough and you may have a bad battery or your charger isn't good, or there was no power to the charger). Then use it as needed and charge it as needed - you can stop charging when the battery indicates that it is full. The only problem is that if you don't do that initial charging properly, with the phone off, and for 14 million hours, you mind find your battery life isn't as good as it should be in the long run - which is rather unfortunate and very annoying. Rfwoolf 14:15, 5 May 2007 (UTC)

Angle of the string of a kite

A kite makes a force(lift) to stay up, so I'm wondering what's the relation of the string's angle to the ground, I'm guessing that at 45° the kite is using half it's force to stay up and the other half to pull and move the holder or if it can't, it transfers the energy to the lift or simply losses it, so is it just a right triangle with the hypotenuse being the total force, and to find out the force on the horizontal part you solve for the bottom of the triangle and the vertical force you solve for the right part of the triangle? Thanks for everything, Jeffrey.Kleykamp 19:33, 3 May 2007 (UTC)

If it can't move away from the holder in the horizontal direction, the force increases the tension in the string. The upward force (lift) equall (in magnitude) to a fraction of that tension based on the angle of the string.  Adam2288  T  C  20:16, 3 May 2007 (UTC)

I don't understand, is it correct that the horizontal force is equal to the opposite of the Pythagorean Theorem or (total force² - vertical force²)^0.5. Thanks again, Jeffrey.Kleykamp 20:25, 3 May 2007 (UTC)

Yes, assuming that the kite is stationary (and staying that way), the force on the kite must exactly balance the force applied by the string (same magnitude, opposite direction). Note that for a real kite, the string has mass, and the problem gets much more complicated. (The string will follow a curved path, called a catenary.) TenOfAllTrades(talk) 20:37, 3 May 2007 (UTC)

Thanks that helped me a lot, Jeffrey.Kleykamp 20:53, 3 May 2007 (UTC)

Female/Male Species

I don't know the correct terms but I know that there are several species of birds in which the males are multicolored and "flashy" compared to the females. Are there other species (besides birds) that have the same attributes between male and female counterparts? Are there species that have the females possessing these physical attrubutes instead of the male counterpart? —The preceding unsigned comment was added by Juliet5935 (talk • contribs) 19:46, 3 May 2007 (UTC).

It seems to me that the specific physical attributes of the male are transferred through the Y chromosomes and therefore not in the females, see XY sex-determination system. Jeffrey.Kleykamp 19:53, 3 May 2007 (UTC)

That's not correct, since birds have no Y chromosome, and it is the male that is homogametic (ZZ) and the female that is heterogametic (WZ) - the opposite of human sex determination. - Nunh-huh 19:59, 3 May 2007 (UTC)

See Sex-determination system for more information on that; however, even in mammals the Y chromosome does not necessarily contain the "specific physical attributes" as much as it controls other genes that do, largely through the use of sex hormones. --Tardis 20:17, 3 May 2007 (UTC)

Sexual dimorphism is the attribute of one gender of a species looking significantly different from the other. In birds that exhibit sexual dimorphism, males are more colorful, groom themselves more, and in some species perform intricate dances to attract females.  Adam2288  T  C  19:56, 3 May 2007 (UTC)

I don't know for sure, but I'd assume that the "flashy" attributes are unique to males in species with a strict male/female divide. Since the female can only carry one litter at a time, while the male can impregnate as many females as he likes simultaneously, it's her who needs to select a mate so she doesn't need to be flashy. --Kiltman67 20:03, 3 May 2007 (UTC)

True for the most part but not always. Insects like bees, wasps, and ants are the opposite. One female mates with many males, and the only "flashy" one in a colony is the queen, a female.  Adam2288  T  C  20:09, 3 May 2007 (UTC)

Thank you, Adam. That was what i was looking for!

Kiltman, are you sure about that? I thought most bird species were seasonally monogamous, since taking care of the children requires the cooperation of both parents; one to sit on the eggs, and the other to bring food.--Kirby♥time 06:31, 4 May 2007 (UTC)

Even in monogamous species the female must choose a mate who she thinks will provide the best genes for her offspring. --Kiltman67 14:01, 5 May 2007 (UTC)

Déjà vu

I occasionally experience déjà vu (just feeling that the experience is familiar, rather than any great epiphany), and I seem to find it occurs more often when I'm tired. Friends and family also say that this is their pattern. Is this common? Does it match the neurological basis of déjà vu? -- LukeSurl ^{t c} 20:28, 3 May 2007 (UTC)

Yes, deja vu is associated with fatigue (and with stress). See this, which also speculates on the neurology involved. - Nunh-huh 20:57, 3 May 2007 (UTC)

Ha ha ha! DMacks 00:31, 4 May 2007 (UTC)

I don't get it... Aaadddaaammm 01:11, 4 May 2007 (UTC)

Wait till next time you're fatigued and stressed, then come back to this page and you'll see the joke then. (Note: I didn't say come back to this thread.)  :) JackofOz 01:20, 4 May 2007 (UTC)

Now, that I didn't get. —Bromskloss 08:54, 4 May 2007 (UTC)

It wasn't incredibly witty I suppose, but I think JackOfOz was saying that if a Question is a "thread" then he wasn't saying "Come back to this thread" because there are two of the same thread... Instead he said come back to this [web]page. Rfwoolf 13:40, 4 May 2007 (UTC)

Whoa two threads =) heh pretty easy joke to reconize =). its good i needed a laugh User:Maverick423 If It Looks Good Nuke It 17:31, 4 May 2007 (UTC)

Déjà vu

I occasionally experience déjà vu (just feeling that the experience is familiar, rather than any great epiphany), and I seem to find it occurs more often when I'm tired. Friends and family also say that this is their pattern. Is this common? Does it match the neurological basis of déjà vu? -- LukeSurl ^{t c} 20:28, 3 May 2007 (UTC)

Yes, deja vu is associated with fatigue (and with stress). See this, which also speculates on the neurology involved. - Nunh-huh 20:57, 3 May 2007 (UTC)

Ha ha ha! DMacks 00:31, 4 May 2007 (UTC)

I don't get it... Aaadddaaammm 01:11, 4 May 2007 (UTC)

Wait till next time you're fatigued and stressed, then come back to this page and you'll see the joke then. (Note: I didn't say come back to this thread.)  :) JackofOz 01:20, 4 May 2007 (UTC)

Now, that I didn't get. —Bromskloss 08:54, 4 May 2007 (UTC)

It wasn't incredibly witty I suppose, but I think JackOfOz was saying that if a Question is a "thread" then he wasn't saying "Come back to this thread" because there are two of the same thread... Instead he said come back to this [web]page. Rfwoolf 13:40, 4 May 2007 (UTC)

Whoa two threads =) heh pretty easy joke to reconize =). its good i needed a laugh User:Maverick423 If It Looks Good Nuke It 17:30, 4 May 2007 (UTC)

I *hate* having to repeat myself ... Rfwoolf 14:17, 5 May 2007 (UTC)

Speed of light

Is the reason the speed of lite is thought to be the fastest posible thing just because its how people observe things so they take it as instantaneous. —The preceding unsigned comment was added by 71.185.139.138 (talk) 21:03, 3 May 2007 (UTC).

Sort of. The speed of light has such significance due to special relativity. Faster-than-light might be an interesting read for you. -- mattb 21:10, 3 May 2007 (UTC)

It isn't instantaneous. It's "the fastest speed there is" (except for hypothetical things which can only go faster than the speed of light, and could never slow down, see tachyons), but when you are talking about distances the size of galaxies it seems remarkably slow at times. Light is reaching us today that took billions of years to travel across the whole of the universe! As for why it is fastest, there are some subtle answers to that. The easiest to understand is that the speed of light holds a special relationship in respect to how space and time are related to one another, but even that would need some more discussion to make a lot of sense to someone who hasn't had any exposure to Einstein's theory of special relativity. --24.147.86.187 23:16, 3 May 2007 (UTC)

The classic experiment for measuring the speed of light is a messy affair involving spinning mirrors, lasers and interference patterns - and it would be pointless to try to explain how it proves that light isn't instantaneous. But you don't need all of that - you can tell it's not instantaneous just by listening to the old tapes of the moon landings - there is a L-O-N-G radio delay between NASA on the ground and the moon lander. Radio waves travel at the speed of light - and the distance between earth and moon is so huge that the delay is obviously perceptable even without special equipment. Even a transatlantic phone call (or more obviously, a computer communication between continents) which goes via a satellite has a noticable and sometimes annoying delay.

It's a little confusing that we say that "nothing can go faster than light" - people always ask what's so special about light. It would be better to say that the nature of the universe (and the theory of relativity) imposes a "cosmic speed limit" for all things - and light (and radio waves, etc) happen to be the fastest thing there is - but even light can't exceed the cosmic speed limit - so light happens to travel "at the speed of light". SteveBaker 00:56, 4 May 2007 (UTC)

Even light often travels slower than the physical constant "speed of light", due to properties of the material through which the light is travelling (something that can sort-of be thought as analogous in effect to "drag"). A good college physics lab is measuring the speed of light using a laser, a single stationary mirror across the room from it, and an oscilloscope...can observe the propagation delay just from a classroom or two's distance. DMacks 04:03, 4 May 2007 (UTC)

Steve, what do you mean by the classical experiment? One of the earliest attempts to measure the speed of light was Galileo; he used the hill/lantern method, which admittedly is very poor as it relies on human reaction time. The first time the speed of light was measured within a reasonable accuracy was by Ole Rømer, who used Jupiter's moon Io to pin down the speed of light to around 140,000 miles per second (compare that to the modern value of 186,282 miles per second).--Kirby♥time 06:26, 4 May 2007 (UTC)

"Classic" - not "Classical". As best I can recall - the experiment I did in high school was with a laser and a fast-spinning 8-sided prism with mirrors on each face. A complicated arrangements of mirrors bounced the laser off the spinning mirror - back to a plane mirror next to the laser, back off the spinning mirror and then onto viewing surface that could be examined with a microscope. Measuring the point there the laser spot hits the microscope when the spinning mirror is turned off - then measuring it again when the mirror is spinning allows you to figure out how much the angle the mirror turned through during the trip from the first reflection off to the plane mirror and back to the spinning mirror again. If you know how fast the mirror is spinning and the distance to the plane mirror and such - you can figure out the speed of light. As I recall, we didn't measure the deflection angle directly - but using some kind of interference fringing effect where some of the light from the original laser was interfered with the light entering the microscope - noting how the interference fringing changed allowed more precise calculation of the deflection of the light beam. Messy - ugly - complicated - probably very accurate. SteveBaker 16:24, 5 May 2007 (UTC)

• Michelson-Morley experiment WilyD 12:51, 4 May 2007 (UTC) Err, just Michelson, but that's the best wikipage I found. WilyD 12:53, 4 May 2007 (UTC)

  Michelson-Morley is not so much about measuring the speed of light per-se - but of measuring the speed of light from a distant star and noting it's speed when measured when the earth is moving towards it in our orbit around the sun - then again six months later as we're moving away from it. If the speed of light were not constant, the two measurements would differ by twice the speed of the Earth in its orbit. However, the experiment produced exactly the same results both times - and to a precision much better than the speed of the Earth. This experiment is the one that started Einstein on his quest to explain the consequences of a fixed speed of light...from whence we get relativity and a bunch of other stuff. It's a very cool example of an 'accidental' experimental finding that changed the world. SteveBaker 16:24, 5 May 2007 (UTC)

I suggest SteveBaker read the Michelson-Morley Experiment again. He has completely misinterpreted it. It attempted to show that the aether existed. "Measuring the speed of light from a distant star" - not even sure where you got this from? 84.9.45.27 17:54, 5 May 2007 (UTC)

No - I'm pretty sure I have it right. They weren't TRYING to prove the invarient speed of light - they were trying to show that the aether existed - but the experiment "failed" - in that it didn't show the existance of aether - but instead showed the invarience of the speed of light. SteveBaker 04:06, 6 May 2007 (UTC)

Box of light

Is it possible to make a box of light by using one-way mirrors as the box's sides? Regardless of if it is, theoretically which part of the mirror would be on the outside, the mirror side or the seethrough side? —The preceding unsigned comment was added by 71.185.139.138 (talk) 21:06, 3 May 2007 (UTC).

Not entirely sure what you're after, but a "box of light" formed by two facing mirrors is usually called a Fabry-Pérot optical cavity and is used extensively in lasers. Of course, there's no such thing as a perfect mirror or perfect alignment, and there is always mirror loss (of course, in a laser you want significant transmittance through one mirror, otherwise you can't get the light out!). I'm not sure what the second part of your question is asking... -- mattb 21:14, 3 May 2007 (UTC)

A more clear question please...?

You need to understand that a one-way mirror is simply a mirror where the layer of shiny metal is so thin that some of the light leaks through it. The mirror itself is not directional; what makes it "one-way" is that it's placed between a dark room and a brightly lit room. Say that 1/2 of the light is reflected and 1/2 passes through, and that the bright room has 50 times as much light as the dark one. Then no matter which side you're on, there will be 50 times as much light originating from the brightly lit side, so you'll see what's on that side and maybe just a faint trace of the dark side. There is nothing about one-way mirrors that would enable them to "make a box of light". --Anonymous, May 4, 2007, 00:41, edited 00:44 (UTC).

No mirror is perfect. A percent will be lost as heat with every reflection. For the best dielectric mirrors around, I would estimate from what I've read that one can expect losses on the order of one part per million, i.e. 99.9999% reflectivity.[4] With this ultra-high efficiency (I would assume the bandwidth over which this level of refelctivity would be maintained would be very low, requiring the light being refected to be a laser pulse, such as what has been mentioned before), that the light could reflect about 693,000 times before it halved in intensity. If you know the mean free path between reflections (this would be proportional to the radius of the cube, you can figure out the time it would require for the pulse to halve in power. Let's say it was a good room-sized box, and that the mean free path was 10 meters: the intensity would halve every .02 seconds. If you have a huge room, 100 meters, you could get that up to .2 seconds. So you can see, the smaller the box, the quick the light dies inside, because more of it is absorbed by the mirrored walls. [Mac Δαvιs] ❖ 06:19, 4 May 2007 (UTC)

And if it needs to be added, more importantly, you wouldn't ever actually see this light for the effect to work, since seeing it would involve your eye absorbing it. Vespine 06:56, 4 May 2007 (UTC)

Acids/Bases

At the end of one of my experiments doing an acid and base titration, I converted the moles of HCL to moles of NaOH using a stoichiometry problem with the equation of HCL + NaOH -->NaCl+ H20.

My question is: Why are these acid and base titrations done like stoichiometry problems?

Please help, thank you! —The preceding unsigned comment was added by 76.188.176.32 (talk) 21:39, 3 May 2007 (UTC).

I'm afraid I can't understand what you are asking. How else would you do them? - Nunh-huh 23:55, 3 May 2007 (UTC)

Your question is indeed somewhat unclear, but one thing you might want to consider is that, if the resulting solution is supposed to be neutral, then you don't want to have any acid or base left over. That means the equation has to balance. Conversely, if you know the end product is neutral (because you put some acid-base indicator in it and it changed color) and you know how many moles of acid you put in, then you can calculate how many moles of base there must've been to begin with. —Ilmari Karonen (talk) 00:01, 4 May 2007 (UTC)

Or, to be a little more concise: they are done like stoichiometry problems, because they are stoichiometry problems. Tugbug 00:10, 4 May 2007 (UTC)

Parrots have a different idea as to what is considered 'food' to us - why?

Someone mentioned something a while back about how their parrot would shred an entire orange, just to get at the pips inside and completely ignore the fruit. I noticed something similar today with my hyacinth macaw when I gave her a slice of watermelon. Instead of doing what I would, eating the flesh and spitting out the seeds, she did the opposite. To her, the fruit was just something to dig through and fling away to get at the yummy(?) seeds. She made a real mess, as she always does. :)

(The previous thread was here. —Steve Summit (talk) 05:09, 5 May 2007 (UTC))

Probably related to my question - if I give her a chicken drumstick (it's good for her to eat meat every so often), she doesn't seem to be that interested in the meat itself. She tears most of it off and thows it on the floor. Then she cracks the bone and goes for the marrow.

Any ideas why parrots have such different opinions to us on what is 'food'? --81.77.94.75 23:53, 3 May 2007 (UTC)

I'm not sure I'm grasping the mystery here, different animals have different diets, what they eat is a result of the niche they occupy in the environment. IMHO it would be a much bigger mystery if all animals ate the exactly the same things. Vespine 00:00, 4 May 2007 (UTC)

Yes, different animals occupy different ecological niches, so they eat different things. This is because our world is inhomogeneous. Vespine says it would be mysterious if all creatures ate the same thing, but I imagine a hypothetical explanation that is the inevitable result of convergent evolution, if all natural barriers and obstacles were removed. In the absence of any perturbing forces, I imagine there would be no reason for species differentiation; of course biology and real experience teaches us that even minute perturbations of an ecosystem can drastically give evolutionary advantages to certain species. Nimur 01:43, 4 May 2007 (UTC)

Yes, the real mystery is how anyone could suppose that differing diets are somehow odd. Physiology dictates what nutrients are needed, these needs correspond to psychological cravings, thus the parrot eats what it eats. I suppose it should not be surprising that a human supposes that their diet is somehow the right diet, and that different diets present an enigma. Vranak

Sorry, I wasn't deliberately being dense. It's just that I spend a lot of my free time with my parrot and I want to understand how she sees the world and what makes her tick. I've had her for nearly 30 years now (my macaw has been the only constant in my life) and I still don't understand everything about her. I know how to take care of her, feed her and play with her and I understand her habits (and she's picked up some of mine - e.g. swearing, as I mentioned before) but sometimes I wish I could really connect. Maybe this is one for the humanities desk. :) --90.240.102.39 09:02, 4 May 2007 (UTC)

I see this as a two part questions:

1) Why don't humans tend to eat seeds ? This one is fairly simple, people don't get much from seeds with hard shells, as they tend to come out much the same way as they went in. In order to open the shell, people would need to gnaw on them, possibly wearing down their teeth in the process, for very little food benefit. Many birds tend to have beaks or stones in their crops designed specifically to break through the hard shells of seeds, so can make use of them.

2) Why don't parrots eat the flesh of fruit ? This one is a bit harder, and will require speculation on my part. I would guess that they can't handle all that sugar at once, lacking the large pancreas of humans which can rapidly release insulin to counter the sugar rush. They might also get diarrhea with such a diet, not being designed to handle all that moisture in their food. Another factor might be that birds which fly can't afford to be bloated with water, even temporarily, due to the added weight. StuRat 00:07, 5 May 2007 (UTC)

A couple of ideas of my own. Hyacinth macaws are slightly different to other parrots in that they're specifically 'designed' to run on a high fat, high protein diet - as I understand it, the majority of the diet of a pet HM should consist of walnuts, brazils and macadamia, plus meat and cheese every so often. Given this, it would make sense that the bird would go for the seeds, rather than the fruit. Also consider that your bird simply has her own preferences when it comes to food, or is flinging pieces of fruit around the room just to make your expression change. Man, I'd love to own a hyacinth macaw - my dream bird. Ever seen one cracking open a coconut or one of those big brazil nut pods (the thing that contains the nuts) with its beak? Very cool. --Kurt Shaped Box 09:13, 5 May 2007 (UTC)

It wouldn't be quite so cool when the bird is mad at you and gets hold of your finger. StuRat 08:17, 6 May 2007 (UTC)