Wikipedia:Reference desk/Archives/Science/2011 June 25

Science desk
< June 24	<< May | June | Jul >>	June 26 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 25

Halo effect?

What is the psychology term used to describe when a person's head is encircled in a halo to improve their public image? (Not for religion or the Halo effect) For example, Obama is often portrayed in front of a brightened circle, or out of focus seal.Smallman12q (talk) 00:36, 25 June 2011 (UTC)

I'm not sure there is a term, but I will point out that there are similar photos of Bush as well (do a Google Image search for "Bush halo" -- it seems pretty common given the practice of putting seals in the background). (And for something else entirely, do a Google Image search of "Ashcroft Spirit of Justice".) --Mr.98 (talk) 02:07, 25 June 2011 (UTC)

Well, I think a psychologist would say that that is in fact an example of the halo effect in action. Looie496 (talk) 00:49, 26 June 2011 (UTC)

The halo effect has nothing to do with visual halos. --Mr.98 (talk) 14:00, 27 June 2011 (UTC)

Appeal to authority? Guilt (albeit positive) by association? Imagine Reason (talk) 14:03, 27 June 2011 (UTC)

It gives the appearance that the person is wearing a hat. Hats have been historically associated with power. Bit speculative. ~AH1 ^(discuss!) 01:46, 30 June 2011 (UTC)

Unknown bug

[1] Can anyone tell me what kind of bug this is? The photo was taken in the US state of Connecticut. It's roughly 5+ inches long. Thanks, Dismas|^(talk) 01:00, 25 June 2011 (UTC)

I believe that's a dobsonfly. Looie496 (talk) 03:29, 25 June 2011 (UTC)

Known "for its kingly features and intimidating tusks", apparently. I love Wikipedia.--Shantavira|^{feed me} 07:21, 25 June 2011 (UTC)

Thanks!! Dismas|^(talk) 13:50, 25 June 2011 (UTC)

Why are bird droppings white?

Why are bird droppings generally predominantly white, while those of most other creatures are predominantly brown? -- Jack of Oz ^{[your turn]} 03:03, 25 June 2011 (UTC)

Most mammals (including humans), as well as amphibians, excrete most of their nitrogen waste as urea, in urine. Fish tend to get rid of nitrogen waste as ammonia. Birds and reptiles metabolize nitrogen waste to uric acid. Uric acid is not very soluble in water, so birds don't excrete it dissolved in urine, the way mammals do urea. Rather, it is excreted with other solid waste, in the form of a white paste. Buddy431 (talk) 04:19, 25 June 2011 (UTC)

And because uric acid comes in the form of white crystals, hence the colour. Yes, I wanted to ask this additional question but found out from the article. --Ouro (blah blah) 07:28, 25 June 2011 (UTC)

Lovely, thanks both of you. -- Jack of Oz ^{[your turn]} 08:46, 25 June 2011 (UTC)

Is there anything else you guano know ? StuRat (talk) 18:32, 25 June 2011 (UTC)

Not at the moment, thanks. If I feel so moved, I'll go to the right place.  :) -- Jack of Oz ^{[your turn]} 21:48, 25 June 2011 (UTC)

No, much to the regret of gout sufferers, humans do not excrete urea, or even allantoin like pigs do, but the sparingly soluble uric acid. I remain curious whether the high uric acid levels help account for why so many predators spit humans out, as eating shark meat high in uric acid or other ammonia rich compounds can be harmful. Wnt (talk) 22:23, 25 June 2011 (UTC)

You're wrong - read the articles urea and uric acid. Urea is the waste product in mammals (including humans) for most sources of nitrogen. Uric acid is only the end product for the Purine metabolism. Most mammals further break uric acid (from the Purine metabolism) down into Allantoin via Urate oxidase. Birds and reptiles, on the other hand, convert nearly all of their nitrogenous waste into uric acid (and excrete it along with their feces). Buddy431 (talk) 03:34, 26 June 2011 (UTC)

From uric acid: "In humans and higher primates, uric acid is the final oxidation (breakdown) product of purine metabolism and is excreted in urine." This is also why humans get uric acid kidney stones. Now I should add, however, that I have some personal doubts about the perfect truth of this statement, because urate oxidase happens to have a "stop codon" right in the catalytic site that happens to use the sequence for selenocysteine, though it doesn't have a good SECIS. I have a feeling humans might just use the very low amounts of RNA produced for this gene to make some amount of functional protein for specialized purposes, and therefore can go on from uric acid in some small percentage of the total metabolism. But that's just personal speculation. Wnt (talk) 07:32, 26 June 2011 (UTC)

Right, the key words being purine metabolism. Humans excrete purine waste products as uric acid, but nearly all other nitrogen waste products as urea. Uric acid only counts for a small amount of human nitrogenous waste (though still enough to cause gout). On the other hand, birds and reptiles excrete nearly all of their nitrogenous waste as uric acid (as a solid, along with the feces). Buddy432 (talk) 03:00, 27 June 2011 (UTC)

Wow. Never so blind as when you think you know... I've looked it up, and yes, urea is described as 20-30 or 25-30 grams per day, whereas uric acid is 250 mg - 750 mg per day.^[2] So yes, indeed, urea is much more important than uric acid in terms of total nitrogen excretion! Wnt (talk) 04:49, 27 June 2011 (UTC)

I think maybe snakes excrete most of their nitrogen as uric acid. That's what sticks in my head from the "Nitrogen" chapter of Primo Levi's mostly-nonfiction-novel (if that makes sense) The Periodic Table. Levi recounts needing a quantity of the stuff, and contacting a zoo with a large snake to see if they'd give him his feces. The zookeepers were quite indignant that this nobody was asking for the precious snake crap, which of course was all spoken for. --Trovatore (talk) 16:55, 27 June 2011 (UTC)

Magnetic field of sun

please compair the magnetic field of sun and earth .Is there any major diffrence between them ?and why?--Akbarmohammadzade (talk) 05:13, 25 June 2011 (UTC)Iran

Is this a homework question? We have articles on the Solar magnetic field and the Earth's magnetic field, go have a read and if you still have specific questions then come back here. Cheers, Ouro (blah blah) 06:56, 25 June 2011 (UTC)

As I was decided to discuss about this subject Ibrought It,here I want to say my idea: The periodical variation of sun body and its convection ,make the sun to have global magnetic fields outside and inside of its body .the plasma body of sun make it not to be able to have magnetic poles such as earth ,in addition its rotation round its axies has defferenet speeds from equarter to pole. The major defference between earth magnetic field and sun's one is that earth has iron core and semi stable solid body . but the magnetic fields in sun are the result of movement of electeric particles .akbarmohammadzade--78.38.28.3 (talk) 07:35, 26 June 2011 (UTC)

The solar wind

It is supposed that the solar wind moves direct planetary orbital .but it might be all around any quarter of sun , then we can suppose that the kuiper belt be sphrical round solar system (not ring ). is it because of Einshtein general relativity that the solar wind have to move in such direction?--Akbarmohammadzade (talk) 05:31, 25 June 2011 (UTC)Iran

Huh? As we read in our article on the Kuiper belt, the belt resembles a torus with the main concentration extending to around ten degrees outside of the plane of the ecliptic. It is not spherical (hence the designation 'belt'). The Solar wind, which I believe radiates in all directions from the star, doesn't really have much to do with its shape as far as I know, though I might be wrong. That's all I could understand from your question. --Ouro (blah blah) 07:03, 25 June 2011 (UTC)

Have a look at Oort cloud. Plasmic Physics (talk) 11:09, 25 June 2011 (UTC)

Indeed, the Oort cloud is spherical. Neither the Oort cloud of the Kuiper belt have anything to do with solar wind, though. --Tango (talk) 13:25, 25 June 2011 (UTC)

And the radiation of particles, like anything else, occurs in all directions from the source. If the solar wind does push the planets outward in their orbit a bit, I would expect only a tiny effect, and for it not to be cumulative, since the orbital speed ultimately controls orbital distance. Think of it like a fan blowing a ball upward. It only moves up a bit, since gravity holds it down. StuRat (talk) 13:43, 25 June 2011 (UTC)

The solar wind doesn't have much effect on orbits, but radiation pressure does. It's particularly significant for asteroids. Also, the solar wind isn't going to completely spherically symmetrical because it is affected by the sun's magnetic field, which isn't spherically symmetrical. --Tango (talk) 18:47, 25 June 2011 (UTC)

well the O'ort belt is far from us , but we can see the effects of Kuiper belt where that first send water here to earth. ( in fact I am studying about the efects of solar wind on production of water in solar system , which cased the existance of life in this system) Akbarmohammadzade (talk 08:52, 26 June 2011 (UTC)

You may be interested in the Heliopause. ~AH1 ^(discuss!) 01:43, 30 June 2011 (UTC)

Standard enthalpy of formation

How much is C(g)'s standard heat of formation?--M940504 (talk) 10:24, 25 June 2011 (UTC)

The same as graphite's standard heat of vaporisation. Plasmic Physics (talk) 11:06, 25 June 2011 (UTC)

Use of figures from copyright protected references

I am referring to figures which I personally drafted in the first place and which ended up in published articles that I coauthored (e.g., in Journal of Inorganic Biochemistry, etc., not someone else's articles). Is this forbidden by Wikipedia? Figures certainly help to clarify concepts in any review-type article.

A am attempting to write an account of a specific area of chemistry. I see figures used this way in review articles all the time (e.g., page 8 of the Encyclopedia of Vitamin-E used images from a paper I coauthored, which was published in Biochimica et Biophysica Acta. originally). Jrwright72626 (talk) 11:27, 25 June 2011 (UTC)

See WP:DCM. This sort of question is generally better asked on the Help Desk. Tevildo (talk) 12:44, 25 June 2011 (UTC)

Yes, see the help desk in the first instance. DCM may not be necessary; it depends what you mean by 'figures', if, as one might think, you mean illustrations of some kind, then DCM may be necessary. Grandiose (me, talk, contribs) 12:49, 25 June 2011 (UTC)

DCM probably doesn't apply in this case, since most journal publications require authors to transfer their ownership/copyright of all published material to the journal. Figures that are reproduced in a review article without any substantial changes require the permission of the original journal (that's why it often says "reproduced with permission from ..."). I doubt that a journal would donate their materials to be freely reproduced on Wikipedia, and if a copyrighted image is found in an article it will most likely be removed. If you are interested in contributing figures to Wikipedia, it would probably be best to create new figures and publish them into the Wikimedia Commons so that they can be freely used. --- Medical geneticist (talk) 13:40, 25 June 2011 (UTC)

While the help desk is the best place for questions concerning using or contributing to wikipedia in general, the best place for this specific question is probably Wikipedia:Media copyright questions, I suspect you may be directed the if you asked at the help desk. Nil Einne (talk) 13:55, 25 June 2011 (UTC)

Medical geneticist is right -- I should create entirely new figures. I do have some photos and diagrams (of a spectroscopic display, electrophoretic separations, etc.) that have not been published anywhere. Obviously I could use those without having to go through a lot of letter writing. Jrwright72626 (talk) 16:19, 25 June 2011 (UTC)

Fortunately the US doesn't have database copyright, but for those unfortunately living in countries that do, I don't know if even redrafting a graph would be legal - it might be that the journal claims to own the results themselves. Though I would not criticize someone for posting the data here anyway, nor would I support any effort of Wikipedia to collude in the enforcement of such regulations. Wnt (talk) 21:10, 25 June 2011 (UTC)

Lasalocid

I looked for further information on this chicken food additive because a local stock food company has just recalled several batches after accidentally adding lasalocid to chicken mash and feed pellets. One of the warnings in their advertisement was that it should not be fed to dogs. I thought this might be a useful addition to the Wikipedia entry.

Regards, Heather March — Preceding unsigned comment added by 218.101.90.35 (talk) 21:35, 25 June 2011 (UTC)

There are many references to this problem and I have amended the article with an appropriate reference from the Veterinary Record of the British Veterinary Association. Thanks for that Heather, for future reference it is usually better to leave a note like this on the 'talk' page of the article which will bring it to the attention of any watchers of that page. Richard Avery (talk) 10:12, 26 June 2011 (UTC)

Permian–Triassic extinction event

Hi, I couldn't help but compare the data of this event with human impact and climate change. The extinction figures were pretty much as they are today according to the estimates and there was afterwards a huge geological event which began as a *greenhouse effect* and countiniued into a super hot world that even any trace of humanity would probably not survive.

Let's say that at that time an intellegent life form became dominant over the earth causing the extinction event, not dissimilar to the corresponding present figures which are showing massive extinctions that we cannot even explain. Let's say that this civilisation caused a greenhouse effect, much in the way that present day earth is believed to be going. No coal seams are recovered from that time as though something not only made the trees extinct, but also performed the magic of making them disappear as well?

Excerpt:

"This pattern is consistent with what is known about the effects of hypoxia, a shortage but not a total absence of oxygen. However, hypoxia cannot have been the only killing mechanism for marine organisms. Nearly all of the continental shelf waters would have had to become severely hypoxic to account for the magnitude of the extinction, but such a catastrophe would make it difficult to explain the very selective pattern of the extinction. Models of the Late Permian and Early Triassic atmospheres show a significant but protracted decline in atmospheric oxygen levels, with no acceleration near the P-Tr boundary. Minimum atmospheric oxygen levels in the Early Triassic are never less than present day levels—the decline in oxygen levels does not match the temporal pattern of the extinction."

Is it not a good theory that intelligent life evolved and destroyed the planets ecology, themselves with it, and so on from there?

~ R.T.G 22:37, 25 June 2011 (UTC)

Note: Colony collapse disorder, Decline in amphibian populations etc etc ~ R.T.G 22:41, 25 June 2011 (UTC)

This makes a good sci-fi story, but there are problems. First, I'd think that sentient species at any time would have been fairly likely to invent clay pots, and the broken shards of clay pots should have turned up in sediments somewhere. Next, I'd kind of expect whatever species involved would develop a larger brain, which would be noted as remarkable by paleontologists - and I'd expect their remains to be found, because it's hard to destroy the Earth if you don't have numbers. And when found, shouldn't they have something, some weapon or possessions, some part of the time? Last, how do the Siberian Traps fit into this scheme? It seems as easy to believe that two spaceships were having a war and a stray shot found its way to Earth, creating the Traps and causing all the atmospheric changes. Wnt (talk) 23:56, 25 June 2011 (UTC)

To answer your question directly. No! it's not a good theory because there is no supporting evidence. The (It's all happened before theory) was popular in the sixties, hence the great thoughtfull song [Year 2525].190.148.136.161 (talk) 00:30, 26 June 2011 (UTC)

(ec) To get an idea of why it's pretty implausible, consider what the fossil record millions of years from now would look like if humans did end up wiping themselves out due to climate change sometime over the next few centuries. There would be more than a bit of evidence of our civilization: buildings, roads, technology, not to mention the shear scale of the number of humans that would leave their skeletal remains behind. You're suggesting some creatures had a climate impact on the planet on that scale or larger but left no trace at all of their existence. What was all that coal being burned by/for? Rckrone (talk) 00:35, 26 June 2011 (UTC)

I don't think that's true. What evidence do you think will be left in the fossil record millions of years from now? Perhaps a few human skeletons (fossilisation is a fairly rare event), which someone expert in mammals (assuming such still exist) might possibly note showed signs of little hard labour, but then again we'd expect most of the human skeletons that have ever existed to show signs of a normal workload. Perhaps they'd puzzle over the large skull and small pelvis? But I wouldn't expect any fossil record of our roads or buildings or technology, except maybe a curious thin layer (representing a very brief time) higher than usual in hydrocarbons and radioactive elements. If we're lucky. A million years is a very long time: flint cutting tools might survive, but concrete won't. Even looking at Roman artifacts in Britain, nowhere near that old, shows the problem of missing artifacts made from iron (which have long since corroded to nothing. Maybe, with all the digging we've done, we'll show up as a puzzling mismatch of eras for several layers in a few locations, followed by more sensible, chronological layers on top.

There was an interesting TV series exploring this topic not long ago. Was it Life after us? Or something like that. 86.164.67.252 (talk) 12:45, 27 June 2011 (UTC)