Wikipedia:Reference desk/Archives/Science/2008 August 1

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August 1

Raindrop

What is the weight of a typical free falling raindrop? —Preceding unsigned comment added by 79.76.185.178 (talk) 00:57, 1 August 2008 (UTC)

According to rain, typical raindrops are approximately spherical, with a diameter of 1-2mm. Thus they have a volume of about 5×10⁻¹⁰–4×10⁻⁹m³, a mass of about 5×10⁻⁷–4×10⁻⁶kg, and a weight of about 5×10⁻⁶–4×10⁻⁵N. Algebraist 01:08, 1 August 2008 (UTC)

Or in more readable units (no offense Algebraist), a raindrop has a mass of about a milligram (and therefore a weight of about 10 micronewtons). —Keenan Pepper 03:35, 1 August 2008 (UTC)

Wait does a free falling raindrop have any weight? I mean it has mass..but does it have weight? As the raindrop basically no longer exists when it goes * splat * does a raindrop ever have any weight to begin with? —Preceding unsigned comment added by PvT (talk • contribs) 08:27, 1 August 2008 (UTC)

Weight is the amount of gravitational force pulling on an object. A raindrop may be in freefall falling, but that's because gravity is acting on it. --Bowlhover (talk) 08:38, 1 August 2008 (UTC)

Everything with mass in a gravitational field has weight. --98.217.8.46 (talk) 13:51, 1 August 2008 (UTC)

Bowlhover, raindrops aren't in freefall. Their terminal velocity is 9 m/s at the highest. After a few seconds, they pretty much stop accelerating at all. — DanielLC 17:09, 1 August 2008 (UTC)

Oops, I used "freefall" to mean "in a fall". --Bowlhover (talk) 18:28, 1 August 2008 (UTC)

Insect identification

What is this insect? It was in Vancouver. Sancho 07:24, 1 August 2008 (UTC)

Oh, I think it's a Firebrat. Sancho 07:36, 1 August 2008 (UTC)

Copper Sulfate as an algacide

I have some copper sulfate I purchased from Southern States Coop and I used it in my pool as an algacide. I was amazed at the quickness which it cleared the pool(overnight) with only about 2 teaspoons of CuSo4. I still have not added any shock in over two months. My pool has 14500gals of water. I have a terrible problem now with algae taking over my small (test)aquarium.I have one fish (left)an he's a Jack Dempsey, who gradually killed the other fish.1) Can I dose the aquarium with him in it? 2)If I must keep him out, for how long? 3) should I just leave him in and OVERdose it for his murder of the other fish? (just kidding) (e-mail removed as per guidelines)—Preceding unsigned comment added by 72.84.241.243 (talk) 12:17, 1 August 2008 (UTC)

You can use it - though it is pH sensitive - there are many guidlines on the web eg http://www.fishyfarmacy.com/Q&A/all_about_copper.html or search 'copper sulphate aquarium', it's also poisonous to snails. http://www.sydneycichlid.com/algae.htm says 0.3ppm 87.102.86.73 (talk) 12:41, 1 August 2008 (UTC)

Loop Quantum Gravity

Why does loop quantum gravity predict that the speed of light depends on its energy? Do all LQG theories make this prediction? Thanks, *Max* (talk) 15:44, 1 August 2008 (UTC).

I'm no expert, but the article section "LQG and string nets" mention that some researchers try to derive photons as analoges to phonons. Phonons are vibrations in a medium that propagate at the Speed of sound, which can in fact depend on frequency in certain media. (And high frequency means high energy). So by the analogue, the speed of photons could depend on their energy too. If I read the article correctly, this is an effect of their model and for instance the "preon approach" would presumably not predict it, so not all LQG theories predict this. EverGreg (talk) 22:02, 1 August 2008 (UTC)

Robert I of Parma's children

Does someone know what was the mental illness of Duke Robert I of Parma's children by his first marriage with princess Maria Pia of the Two Sicilies? His children by his second marriage are all healthy. Maybe the problem is of the Princess Maria Pia? Help me because it's important..... --84.222.154.178 (talk) 17:24, 1 August 2008 (UTC)

The article says mental retardation - that's an intellectual disability. (also read this for a list of possible causes)87.102.86.73 (talk) 17:53, 1 August 2008 (UTC)

It's worth nothing we have no way of knowing if these claims are accurate at least from the information I've seen in the articles. It could be for example that the youngest son or someone else conspired to have them declared mentally retarded for his, her or their own interest. Given that this occured in 1907, I would say it's possible. Also Infanta Maria Antonia of Portugal says two of her children have "issues" (no idea what that means although most of Maria Pia's children has "issues" as well) and one of them was deaf Nil Einne (talk) 18:14, 1 August 2008 (UTC)

Had 'issues' usually means had offspring - not health issues.87.102.86.73 (talk) 18:19, 1 August 2008 (UTC)

See Issue and Issue (legal)87.102.86.73 (talk) 18:21, 1 August 2008 (UTC)

(edit conflict) The problem could be with the union and not specifically with the woman.

This condition can be, but is not necessarily, inherited (have a genetic cause) see http://specialed.freeyellow.com/YAdaptUse.html

There is also the possibilty of bad luck.

I'll leave as message at the humanities desk to see if anyone knows more about this specifically.87.102.86.73 (talk) 18:19, 1 August 2008 (UTC)

I'm not certain that there was a modern diagnosis-I haven't seen one in reading about it; one could speculate that there was an Rh blood factor incompatibility in the first marriage (and not in the second), or a congenital toxoplasmosis infection (such as that responsible for mental retardation in the French royal pretenders), or any of a number of other possibilities. - Nunh-huh 01:24, 2 August 2008 (UTC)

Gull strength

For its size, is a gull (say, your basic Herring Gull) physically stronger than a human? --Kurt Shaped Box (talk) 19:49, 1 August 2008 (UTC)

Well I can't fly - so at a guess - yes?87.102.86.73 (talk) 20:04, 1 August 2008 (UTC)

I expect that if Kurt were shrunk to the size of a gull, he could kick its ass, (but couldn't fly) and if the gull were enlarged to Kurt's size it would be unable to support its own weight and would fall over (and also be unable to fly). See Square-cube law and "On Being the Right Size " by HaldaneEdison (talk) 20:18, 1 August 2008 (UTC)

I hope not - if Kurt were gull-sized I'd imagine that he would find its claws to be as big as kitchen knives...87.102.86.73 (talk) 21:43, 1 August 2008 (UTC)

I don't know for certain, but I suspect from observation that gulls have faster reflexes and reaction times than humans too. I don't know how effective punches and kicks would be against thick feathers either... --Kurt Shaped Box (talk) 22:09, 1 August 2008 (UTC)

Plus gulls have beaks. —Lowellian (reply) 23:51, 1 August 2008 (UTC)

Could this be adequately modeled by a fight between gull and equally sized primate, such as a small monkey? A Tamarin is approximately the same mass as a gull (at about 1 kg), and they look pretty human-like to me. Nimur (talk) 00:02, 2 August 2008 (UTC)

Due to the shorter nerve paths, Kurt's reflexes and responses to stimuli would become faster. As for the beaks, his musculature is designed to operate an organism many times larger. Read the Haldane ref and consider how things like strength and mass vary by squares and cubes as size is scaled by an order of magnitude. A human, scaled down, would be far stronger than a small primate or a bird. I personaly would pay big bucks to watch the fight on pay per view TV. Edison (talk) 04:19, 2 August 2008 (UTC)

Kurt-shaped or not, a box can't beat a gull in a fight. Not even boxing. — DanielLC 17:26, 2 August 2008 (UTC)

Am I the only one who gets unsettled?

Question restored per Wikipedia talk:Reference desk#Am I the only one who gets unsettled?

When discovering that one's pet parrot not only has sexual thoughts, but has sexual thoughts about humans, namely me? Just to look at a parrot, you wouldn't think it. I'm quite religious and this disturbs me a little. --81.79.21.14 (talk) 19:24, 30 July 2008 (UTC)

If you're asking do parrots exhibit sexual feelings towards their owners, I'd imagine the answer would be yes, in some circumstances, as parrots often form close, affectionate bonds with their owners. There are several interesting answers from this yahoo! answers post on a similar question, and this article also makes for an interesting read. 20I.170.20 (talk) 19:56, 1 August 2008 (UTC)

It seems a bit of a leap assume that thought in parrots is equivalent to thought in humans. I have no idea if they do think, but whatever thinking they do is probably pretty parrot-y. Even if the bird is becoming sexually excited, psittacine morality is likely quite different from your own. This is not to say "you're wrong," only to suggest that you may be applying standards to the parrot that apply mainly to humans.

Do parrots looking at their reflection in a mirror act as though they're seeing themselves, or another parrot? I'm thinking of the elephant self-awareness discussed here (an elephant touched a painted mark on her forehead that she could only see in a mirror; she did not touch a similar mark made with "colorless paint"). Lack of such awareness would suggest the parrot isn't all that responsible for its actions. OtherDave (talk) 20:17, 1 August 2008 (UTC)

I'll tell you what unsettles me. "If the insects had hit on a plan for driving air through their tissues instead of letting it soak in, they might well have become as large as lobsters,..." from the essay linked earlier about animal sizes. Insects the size of lobsters? Gahh. That's really unsettling. Imagine walking through the forest and seeing a mosquito the size of a small raccoon... Nimur (talk) 23:52, 1 August 2008 (UTC)

Heh, insects were that big during the Carboniferous period, due to higher oxygen levels. ;) —Lowellian (reply) 00:42, 2 August 2008 (UTC)

Imagine if a mosquito the size of a small raccoon decided that it would like to feed on your blood! Man! It would be the similarly scaled-up centipedes that I'd have a real problem with - I think I've mentioned before that I have a phobia of those particular creatures. I'd have to carry a machete with me everywhere (handguns are illegal here) - just in case I came face-to-face with a skittering 4-foot length of legs, armour-plating and malevolence... --Kurt Shaped Box (talk) 11:26, 2 August 2008 (UTC)

Male budgies will certainly attempt to copulate with their human's hands or head (if their human is their closest flockmate). It's not something I encourage. I know that some owners find it amusing - but to me, it's a bit like bestiality-lite. I certainly don't know many dog-owners who would willingly allow their pet to hump their leg to the point of climax... --Kurt Shaped Box (talk) 11:33, 2 August 2008 (UTC)

Many animals, birds included, have very simple sexual triggers, so anyone making the right gestures or sounds, or having the right smell, "turns them on". Maybe this is what happened in this case. It's similar to how baby birds decide that anyone nearby who happens to be handy is their mother. StuRat (talk) 13:22, 3 August 2008 (UTC)

Astronomy - Solar Eclipse

I was reading an article on the solar eclipse presently underway, and it discussed the rarity of solar eclipses in the universe. It explained that the only reason that we have a precise solar eclipse is that the "...moon is 100 moon diameters away from Earth and the sun is 100 sun diameters from Earth and that that is how it works."

The Solar Eclipse article adds weight to this statement of rarity by discussing how, because of tidal acceleration (the moon's orbit slowly increasing) and that the sun will slowly increase in size over this timescale (presumably because the spent nuclear fuel reduces it's mass and therefore gravitational pull?) full eclipses will no longer occur on earth in slightly less than 600 million years, then never again.

So I wonder if anyone has any comments on the likelihood of this rare little spot in time and space that we happen to be in. How did the moon form at its' present size? Has any statistical work been done on estimating the chance that a randomly selected planet-moon pair in the universe would have these properties? (I know how imprecise planet estimates are.)

I just found this all very interesting. 24.68.246.113 (talk) 20:15, 1 August 2008 (UTC)

To the best of my knowledge, the approximately "same" (~ 30 arc-minutes) angular diameter of Earth's moon and the sun we orbit is nothing more than "dumb luck", but you can probably expand a variety of Drake equation style estimates to determine likelihood. As far as I am concerned, the likelihood is empirically measured as, "100% of known inhabited planets exhibit this coincidental phenomenon." Alternatively, consider the anthropic approach, "100% of intelligent life evolved visual acuity that could not perceive or distinguish the apparent difference of angular diameter between the two largest astronomical objects visible in the sky of the planet on which it developed." Nimur (talk) 00:07, 2 August 2008 (UTC)

The chances that a solar eclipse would occur on other planets with moons is quite high. The unusual part is that our Moon and Sun have almost the same apparent diameter, which makes for a very interesting solar eclipse where the body of the Sun is blocked, but the corona is still visible. StuRat (talk) 03:52, 2 August 2008 (UTC)

Every planet has its own unique characteristics. Mercury's inclination is 7.005 degrees, and 7.005 is very nearly a whole number. Mars is covered with iron oxide and has the solar system's tallest mountain. Jupiter has 4 Gallilean moons with the very distinctive characteristic of having around the same, very high, brightness; the 5th brightest moon is much dimmer. Neptune has the only major retrograde moon, Triton.

It may not be a coincidence, though, that Earth has a large moon. Tides on the early Earth may have created isolated potholes of water rich in organic molecules. This water, when it evaporated, would concentrate these molecules to a much greater extent than was possible in the open ocean. The molecules would react to form more complex structures, which would in turn be carried into the ocean, and so repeats the process until life formed. --Bowlhover (talk) 04:38, 6 August 2008 (UTC)

Very interesting last insight there, Bowlhover. I think that if this were Yahoo Answers, I would award best answer to "...100% of known inhabited planets exhibit this coincidental phenomenon." Nice NByz (talk) 21:43, 6 August 2008 (UTC)

Sunburn

What causes the outermost layer of the skin to peel off after sunburn? JIP | Talk 21:28, 1 August 2008 (UTC)

Apoptosis: programmed cell death. In essence, the body decides that the top layer(s) of skin cells (keratinocytes) are irreversibly damaged by solar radiation and those cells are killed. Some time later, they slough off. TenOfAllTrades(talk) 21:47, 1 August 2008 (UTC)

A non-sourced photo caption in sunburn says, "the dehydration of the epidermis causes the top layer to flake off." I am going to guess that the cells, which have presumably died all around the same time as TenOfAllTrades described above, shrink, lose their flexibility, and detach from the lower layers as they dry. The combination causes them to flake off in big sheets rather than in small pieces like normal. 71.77.4.75 (talk) 22:11, 1 August 2008 (UTC)

creation of the universe

why is this universe created? —Preceding unsigned comment added by Pramod tiwari (talk • contribs) 21:28, 1 August 2008 (UTC)

Wouldn't this be better listed on the Humanities desk? Nyttend (talk) 21:33, 1 August 2008 (UTC)

Possibly.87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)

I asked God to come by here and give an answer. If he's not too busy playing mmorgs, perhaps we'll get an answer soon. -- kainaw™ 22:03, 1 August 2008 (UTC)

(I'm not too busy)87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)

There are many responses to this question but none I've heard that could be described as an final and only answer.

One response is basically summed up by the response "It must".

Alternatively you may consider that the universe is never created, if you meant 'why is it created' as being different from 'why does it exist'.

Finally I can suggest that the answer (if it exists) may be beyond human comprehension.

There are other responses, no doubt, that I hope others will be able to link to for you to read - we have numerous articles relating to this - both scientific, spiritual and religious.

I hope that some one does know - for this I leave the space below blank:87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)

There are several possible answers in our article on creation myths. You may also find a number of useful links in our article on cosmogeny. TenOfAllTrades(talk) 22:14, 1 August 2008 (UTC)

You need to make the question more specific. Then again for every interpretation of your question I can think of except why god created the universe (in which case there is no generally accepted answer, and AFAIK few religions give an answer at all), the question is pretty much meaningless and there is no reason. If there where laws of metaphysics that explained the laws of physics, then you could just count them as the laws of physics and you'd be back to square one. If you were going to use infinite recursion and have meta-meta-physics, meta-meta-meta-physics, ... for ever, it just wouldn't be logically sound. — DanielLC 17:16, 2 August 2008 (UTC)

Usually the grand origin of the universe is credited to a quantum-mechanical separation of energy and anti-energy, enough of which is created to put us into a stable false vacuum state and start the Big Bang. That's at least according to every colloquium I've been to on the topic, though while interesting much of the debate has degraded into a philosophical discussion of the logical validity of arguments such as the Anthropic principle. SamuelRiv (talk) 02:32, 3 August 2008 (UTC)

Large Hadron Collider

Some have suggested that the Large Hadron Collider could create small black holes. If this does happen, what could this cause? 67.150.168.139 (talk) 23:20, 1 August 2008 (UTC)

Micro black hole talks about this issue. "According to the standard calculations these (micro black holes) are harmless because they would quickly decay by Hawking radiation." Someone else with more understanding in this area will have to explain what sorts of particles/products a decaying micro-black-hole would produce... 71.77.4.75 (talk) 23:31, 1 August 2008 (UTC)

The rule for quantum mechanical decays is "everything not forbidden is compulsory", i.e. any decay that doesn't violate any conservation law has a nonzero probability of happening. A free muon can decay into an electron plus neutrinos because all the conserved properties add up correctly, but a free electron can't decay into a muon plus neutrinos because that would violate the conservation of mass-energy, and it can't decay into particles lighter than itself because, for one thing, all the lighter particles have no electric charge. That's why the electron is stable and the muon isn't. A micro black hole, because of its large mass, would have the whole Standard Model particle zoo to choose from, and presumably would decay pretty quickly into some assortment of everyday particles, there being no conservation law to prevent it. If small black holes dramatically violate the approximate conservation laws, as large black holes are believed to, they might be easy to spot. Otherwise, they would behave much like any other quantum particle with the same mass, electric charge, etc, and I'm not sure how you would even tell that they were black holes. My secret hope is that particles and black holes are actually the same thing, and Standard Model decays are the same thing as evaporation by Hawking radiation. This isn't a completely kooky idea; it has been investigated by real physicists. It runs into serious theoretical difficulties, like the fact that the electron violates $a^{2}+Q^{2}\leq M^{2}$ by many orders of magnitude, but I still hope it's somehow true. At any rate, thinking of the electrons and nucleons that make up your body as tiny stable black holes might help some people get over their fear of a tiny stable black hole destroying the Earth/Universe. -- BenRG (talk) 01:35, 2 August 2008 (UTC)

Or perhaps the fact that if the LHC could create it, then it's already been created countless times by cosmic rays in the atmosphere, which often collide at much much higher energies. —Preceding unsigned comment added by SamuelRiv (talk • contribs) 02:35, 3 August 2008 (UTC)