Wikipedia:Reference desk/Archives/Science/2010 March 18

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March 18

Wild bird with a foot band

Weird. I was sitting in my backyard and I saw a wild sparrow with a metal foot band. I'm guessing it didn't put it on its self. How did it get on there? 198.188.150.134 (talk) 01:29, 18 March 2010 (UTC)

I imagine it was Bird ringing. Never knew it was called that before--Jac16888^Talk 01:33, 18 March 2010 (UTC)

That was a very interesting read, thanks for linking to that article. But I fail to see why researchers would add this tag onto a mere sparrow. I'm pretty sure they already know the migration patters of sparrows, and I don't see how it would be practical to count the population of sparrows, I mean , there must be hundreds of thousands of sparrows, there's no way you can catch that many and be sure you've got them all. 198.188.150.134 (talk) 03:25, 18 March 2010 (UTC)

I found it pretty interesting too. Maybe keep an eye out for it, it might still be around, and see if you can get a close up picture of its band and find out who tagged it. Also, found this link [1] which says its for determining survival rates and populations--Jac16888^Talk 03:34, 18 March 2010 (UTC)

To 198...: You'd be surprised. They tag all sorts of animals, even those that aren't endangered, and keep track of them for the very good reason that they can't know if there is or isn't a problem unless they keep track. Yes, there are lots of sparrows, but they need to know exactly how many is "lots" and if there start to be less, they can stay ahead of the problem. They need baseline numbers of populations to know when something does go wrong. And they aren't trying to tag them all. They tag a representative sample each year, and then see how many tagged animals they catch from year to year. If they tag a constant number every year, and the number they get back is steadily declining, then they can get info on the whole population. --Jayron32 03:51, 18 March 2010 (UTC)

To clarify, that: They determine how many there are by seeing what proportion of sparrows they catch have already been tagged. If, say, they have tagged 100 birds and they find that 10% of the birds they catch are tagged, they can conclude there are about 1000 birds. --Tango (talk) 09:02, 18 March 2010 (UTC)

Wow, this is most interesting, thanks Wikipedia. 198.188.150.134 (talk) 07:13, 19 March 2010 (UTC)

has anyone ever been born completely reversed?

I don't mean dextrocardia, but a more complete reversal, including heart, liver, etc. Has it happened? If not, could it? Why or why not? This is not homework. 82.113.121.93 (talk) 01:40, 18 March 2010 (UTC)

Evidently, as the dextrocardia article links to Situs inversus, affecting "less than 1 in 10,000 people". Apparently, Randy Foye has it, and gets along just fine. Buddy431 (talk) 01:59, 18 March 2010 (UTC)

Indeed. A complete reversal shouldn't cause any problems at all (other than doctors misdiagnosing you because, say, the pain from your appendicitis is on the wrong side, or transplanted organs not fitting properly). Partial reversals cause all kinds of problems because things don't fit together correctly. --Tango (talk) 09:04, 18 March 2010 (UTC)

Further to the OP's interesting question, has anyone ever been born inside out, like the monkey in "The Fly"?[Trevor Loughlin]80.1.80.17 (talk) 11:03, 18 March 2010 (UTC)

I'm not familiar with "They Fly", but I don't see how anyone could be born inside out. If the "internal" organs are outside the skin, what would hold them together? --Tango (talk) 11:34, 18 March 2010 (UTC)

its easy to say situs inversus has no problems apart from the appendix being on the left side. however there are innumerable diseases that go hand in hand with situs inversus - many congenital cardiac anomalies, respiratory problems due to ciliary dysfunction and infertility to name a few... —Preceding unsigned comment added by 213.130.123.30 (talk) 11:25, 18 March 2010 (UTC)

I'm not familiar with "They Fly", but I don't see how anyone could be born inside out. If the "internal" organs are outside the skin, what would hold them together? --Tango (talk) 11:34, 18 March 2010 (UTC)

I believe there is a condition where some of the internal organs, like the intestines, are outside of the skin. As you can imagine, this is quite serious and surgery must be performed to place those organs back inside and sew up the skin. StuRat (talk) 14:13, 18 March 2010 (UTC)

Yes, I have heard of people being born with various kinds of hernia. I can't find any mention of it in our article, though (it mentions congenital diaphragmatic hernia, but that involves things from the abdomen protruding into the chest cavity, rather than outside the body). That is far from being inside-out, though. I'm not really sure what an inside-out person would be like. The concept of being inside-out only really makes sense for hollow objects. --Tango (talk) 14:39, 18 March 2010 (UTC)

Gastroschisis. [2] --TammyMoet (talk) 15:40, 18 March 2010 (UTC)

Well, it would mean the ectoderm develops inside and the endoderm develops outside the body. I suspect such a severe deformity would result in a spontaneous abortion early in the pregnancy. (And people/animals can be modeled as a hollow tube.) StuRat (talk) 15:43, 18 March 2010 (UTC)

Do your feet smell? Does your nose run? You're built upside down! --jpgordon^{::==( o )} 23:47, 20 March 2010 (UTC)

Inflation (cosmology)

Can Inflation (cosmology) be thought of as Refractive index just as various materials like water, air and glass are thought of in terms of their effect on the speed of light since such materials in effect impose the effect of inflation (cosmology) upon the speed of light due to their refractive index? -- 71.100.11.118 (talk) 01:42, 18 March 2010 (UTC)

No, it can't. Dauto (talk) 03:29, 18 March 2010 (UTC)

The how do you explain that in the absence of inflation the furthest source of light would be 13.7 billion light years away whereas with inflation it appears to to have traveled for 43 billion years just like light through glass appears to take longer than light through a vacuum? 71.100.11.118 (talk) 05:10, 18 March 2010 (UTC)

During inflation space/time expanded at far greater than the speed of light. But I'm pretty sure that's not all of it. According to observable universe we can see more than 13.7G light years because of the expansion of space. I take it as this (but I'm not a cosmologist, astrophysicist or astronomer): Star 10G LY away throws out some light, at some point in the 10 billion years the light spends travelling towards us, space expands putting the star an extra 10G LY away, so we see a star 20G LY away (also the wavelength of the light has doubled in that time). Perhaps inflation gave it a head start, too, with ultra-super-fast expansion of space. --Polysylabic Pseudonym (talk) 06:24, 18 March 2010 (UTC)

Dauto's brief answer was correct. Refraction follows certain quantitifiable laws. Cosmological inflation follows a different set of laws, including general relativity. If you want to have a very superficial explanation, then "yes, both effects relate to the way light travels." But they are totally different effects caused by different things. Nimur (talk) 14:47, 18 March 2010 (UTC)

Even without inflation, we could receive light from an object more than 13.7 comoving Glyr away, because some of the Hubble expansion (not inflation) of the universe occurred "behind" the photon as it traveled here. -- Coneslayer (talk) 14:52, 18 March 2010 (UTC)

Trains

Are there any electric freight trains?

Are there any monorail freight trains?

Are there any maglev freight trains?

Bowei Huang 2 (talk) 01:56, 18 March 2010 (UTC)

Yes, no and no as far as I can tell. The only proof of any of these methods that I can find is the electric freight train through Google. Regards, --—Cyclonenim | Chat  02:16, 18 March 2010 (UTC)

What route does the electric freight train take on its journey through Google? Edison (talk) 03:41, 18 March 2010 (UTC)

^{Left at I'm feeling lucky station. Regards, --—Cyclonenim | Chat  03:44, 18 March 2010 (UTC)}

Please see electric locomotive, monorail, and Maglev.--Shantavira|^{feed me} 08:29, 18 March 2010 (UTC)

The thing that distinguishes freight from people is speed. There are very few - if any - items of rail freight that needs to get there as fast as people do. Electric trains are about efficiency and such - and hence are useful for both people and freight. But monorails and maglevs are all about speed - and they are a costly way to carry freight. Hence, I agree with Cyclonenim - "Yes, No, No". SteveBaker (talk) 00:32, 19 March 2010 (UTC)

Maglevs are about speed, but most monorails are short-distance, low-speed services in an urban area or a still more confined location like an airport or fairground, and what they're about is having an elevated route without the wide structure needed to support a conventional track. However, such systems would not normally have freight traffic either.

However, at least one monorail did historically exist in a rural location and did carry some freight: the bizarre Listowel and Ballybunion Railway. --Anonymous, 20:44 UTC, March 19, 2010.

Purpose

Does any action other than those done by conscious beings have a purpose or are they just reacting to the laws of physics? —Preceding unsigned comment added by 99.254.8.208 (talk) 05:16, 18 March 2010 (UTC)

Science really can't answer that. See teleology. --Trovatore (talk) 05:19, 18 March 2010 (UTC)

Thank you. On a tangentially related topic, do single-celled organisms do things on purpose? 99.254.8.208 (talk) 05:40, 18 March 2010 (UTC)

There is no contradiction between having a purpose and reacting to the laws of physics. A "purpose" is a label attached to certain types of activities in order to make them easier to predict and understand, namely activities that can be understood as promoting some goal. Currently the only systems we know that can usefully be described in terms of purpose are organisms that result from natural selection, and devices that those organisms have created. Looie496 (talk) 05:41, 18 March 2010 (UTC)

On purpose? Some single celled organisms can follow scent trails to food; can cooperate with others to form colonies. Some pathogenic single celled organisms can cooridinate attacks through quorum sensing. Is sensing something and reacting to is "purpose?". In fact, are "conscious" humans doing any more? Perhaps the Humanities desk can offer a better answer to this philosophical question. --Polysylabic Pseudonym (talk) 06:34, 18 March 2010 (UTC)

J. Scott Turner has an interesting book that I read a couple years ago. He talks a bit about purpose/intentionality, and concludes that to be "purposeful", an organism has to have a mental representation of the world, and to be able to try to make the world more like the one they imagine. So basically, anything that's programmed to modify its environment in accordance with some inner plan could be said to "have a purpose". Beavers, ants, and quite a lot of things would probably fall under this definition. *shrug* I thought it was interesting, anyway. Indeterminate (talk) 11:01, 18 March 2010 (UTC)

I don't think you can sensibly speak of purposes where there is no motive force involved. Did the Colorado River 'purposely' wear down the Grand Canyon? Not really. Vranak (talk) 07:15, 18 March 2010 (UTC)

Conscious beings obey laws of physics. They just think they have a choice. 67.243.7.245 (talk) 15:27, 18 March 2010 (UTC)

If one-celled organisms do all that, what is the most simple thing that tries to preserve (or reproduce) itself by choosing between two actions, even if it's a simple if-then decision? --99.254.8.208 (talk) 22:36, 18 March 2010 (UTC)

It depends what you mean by "choose". Take something like an amoeba - it can detect when there is too little food around and "chooses" to turn into a Microbial cyst to wait out the lean times. But what causes that is a relatively simple chain of chemical pathways...amoeba don't have a nervous system - they consist of just a single cell after all. So is this a "choice"? If you think it is then we can go smaller - does a plutonium atom "choose" to preserve itself for (on average) around 14 years and not to decay into Americium? Well, that's certainly a bit of a stretch - it is a simple physical matter. But why is the chemical reaction that serves to cause the amoeba to turn into a cyst more or less valid than what the plutonium atom does? So if we say that the amoeba didn't have a "choice" then you have to say that a tree doesn't have a choice about whether it's going to drop its leaves in autumn...and (most scientists would say) a human doesn't have a "choice" about whether to have a ham sandwich or a cheese sandwich for lunch...it's still a matter of physics/chemistry...albeit a very complicated matter. So this word "choice" doesn't have a good definition. We either have to apply it to the smallest objects in the universe - or we have to avoid applying it to the most complex objects that we are aware of. In the end, it's just a word. SteveBaker (talk) 02:30, 19 March 2010 (UTC)

It's one of those "what is the definition of this word?" questions. What do you really mean by "having a purpose"?

Consider a definitely inanimate object - a computer let's say - does a computer that is programmed to calculate the first million digits of PI have a "purpose"?

• If the answer is "yes" - then your definition of "purpose" certainly encompasses even the simplest life forms and inanimate objects. A rock that becomes detached and bounces down the side of a mountain has just as much "purpose" as a computer - and so do viruses and bacteria...by that definition.
• If you say "no" (presumably because you feel that a computer is a deterministic system and is "inanimate") then I'd have to argue that from everything science has determined, higher life forms and even humans are simply complex machines. Under this definition of "purpose", nothing in the entire universe has a "purpose" because everything is simply slavishly following the mundane laws of physics.

We could turn to the dictionary definition of "purpose" - which (according to Wiktionary) is:

1. An object to be reached; a target; an aim; a goal.
2. A result that is desired; an intention.
3. The act of intending to do something; resolution; determination.
4. The subject of discourse; the point at issue.
5. The reason for which something is done, or the reason it is done in a particular way.

Of these definitions, our pi-calculating computer has a purpose under definitions (1),(2),(4) and (5)...but not (I'd say) under definition (3). But this is no longer a matter of science - it's a matter of linguistics. SteveBaker (talk) 00:26, 19 March 2010 (UTC)

We don't have the capacity to ultimately control ourselves. We can observe what transpires in our experience from things we do. Therefore we don't have "purpose." Living is comparable to an art. In this sense a boulder rolling down a hill has more "purpose" than a well-lived life of a human being. Bus stop (talk) 00:35, 19 March 2010 (UTC)

Multiverse

Can you get to another universe by physically traveling in 3D space out of the area resulting from the big bang, or would you have to travel in a different kind of "direction" to get there? —Preceding unsigned comment added by 99.254.8.208 (talk) 05:34, 18 March 2010 (UTC)

I'm not sure actual scientific theories of "Multiverses" work in the way you seem to think they do. You may want to read Multiverse and Many-worlds interpretation and the works of Hugh Everett III and Max Tegmark. Any actual discussion of parallel universes is purely speculative and without experimental verification. Such possible universes are perfectly consistant with current understandings of how our universe works, but there is also nothing in the current theories that requires them, so by Occam's Razor, there generally isn't much use for hypothetical alternate universes in the current theory. --Jayron32 05:45, 18 March 2010 (UTC)

I'm pretty sure you couldn't travel outside the universe in normal 3D space. The edge of the universe is moving away from you at (or faster than?) the speed of light. You can't go that fast. --Polysylabic Pseudonym (talk) 06:37, 18 March 2010 (UTC)

If the universe has an edge. See Shape of the Universe for a discussion on the various proposed shapes the universe has. There are some models called "Open universe" models that have no edge because they are infinite; there are also "closed edgeless" models as well. --Jayron32 06:42, 18 March 2010 (UTC)

The notion of an alternate universe suggests a space that exists but is not in any way accessible. And if we cannot access it, then we cannot know it exists. So... pretty much an empty concept, unless I am missing something. Vranak (talk) 07:05, 18 March 2010 (UTC)

There are some theories of "bubble universes", where there are multiple universes separated only by space, but they are always arranged in such a way that it is impossible to travel between them. If you could travel between them, they would be part of the same universe by any reasonable definition. --Tango (talk) 09:08, 18 March 2010 (UTC)

What if they aren't accessible by normal means, but are via wormholes ? StuRat (talk) 14:03, 18 March 2010 (UTC)

Again, wormholes are allowable by, but not necessary for, current theories of how the universe works. That makes them fun for science fiction, but lacking evidentiary support, there's no need to suppose they actually exist. At some level "magic" is also allowable by, but not necessary for, current theories as well. After all "Another land that obeys different physical laws and can only be reached through a cross-dimensional portal" is still basically magic whether its The Lion, The Witch, and the Wardrobe or the work of a well respected cosmologist. Couching the magic with terminology from quantum theory doesn't make it less magical. --Jayron32 14:18, 18 March 2010 (UTC)

What's the difference? As far as I know, there is no difference between a path through "normal" space and one through a wormhole. Locally, space is space, and globally it all depends on your perspective. --Tango (talk) 15:16, 18 March 2010 (UTC)

blue chemical

What is the name of the blue coloring I get after soaking a nickel-copper alloy in white vinegar for a couple of days? Is it copper acetate? Googlemeister (talk) 13:12, 18 March 2010 (UTC)

Our article on copper acetate would seem to imply that that is probably the case - the history section mentions that traditionally copper acetate was prepared using vinegar and copper sheets. I don't know whether the nickel would also react, potentially giving a mixture.131.111.185.69 (talk) 13:31, 18 March 2010 (UTC)

From what I can find on Google, nickel also reacts with acetic acid, and is also bluish. It is probably a mixture of copper(II) acetate and zinc nickel acetate. --Link ^(t•c•m) 13:40, 18 March 2010 (UTC)

zinc acetate? was that a typo? --Ludwigs2 15:04, 18 March 2010 (UTC)

Yes. Blame it on the relative positions of copper and zinc in the periodic table. --Link ^(t•c•m) 22:00, 18 March 2010 (UTC)

bleach

Will two bleached negro parents have white offsprings? —Preceding unsigned comment added by 117.196.140.248 (talk) 14:04, 18 March 2010 (UTC)

No. --Jayron32 14:12, 18 March 2010 (UTC)

Well unless bleached is a bad translation for Albino, in which case maybe? --BozMo talk 14:41, 18 March 2010 (UTC)

More likely the OP is refering to Lamarckism; genetic inheritance doesn't work that way. --Jayron32 14:46, 18 March 2010 (UTC)

In case the OP is a non-native English speaker, he or she may wish to read our article on the word negro to see why this term is not commonly acceptable in modern speech. At the very least, understand the nuances of your word choice. Nimur (talk) 14:51, 18 March 2010 (UTC)

The United Negro College Fund begs to differ. Comet Tuttle (talk) 17:14, 18 March 2010 (UTC)

They probably wouldn't. Like the National Association for the Advancement of Colored People, just because they maintain a historic name does not mean they necessarily think the antiquated terms should be used in other contexts. --Mr.98 (talk) 23:17, 18 March 2010 (UTC)

There is a quote that begins: "If the white man is but a bleached negro,...". If this is what is referred to, it is a trick question and the answer is yes. Other quotes use "bleached negro" to mean a culturally Anglicized African. Rmhermen (talk) 15:29, 18 March 2010 (UTC)

From Doctor Huguet: "And if the taint of the brute origin adheres to the negro, does it not cling to us all? If the son of a murderer stands disgraced, does not his grandson inherit something of the shame? If the white man is but a bleached negro, what right has he to mock his dark progenitor? The credit is due, not to him, but to the cold and clouds of the stormy north, or the darkness of the troglodytes' caves, during myriads of years" (emphasis mine) That's very poetic, if a bit outdated. Buddy431 (talk) 03:10, 19 March 2010 (UTC)

"Bleached negro" could be a non-politically correct version of the also non-politically correct "mulatto", - a person of mixed white and black ancestry. In this case, I would dare to say that yes, they could have child that could be considered white by some standards. However, according to the one drop rule, they could only have black offspring.ProteanEd (talk) 16:33, 18 March 2010 (UTC)

According to the one drop rule everyone on the planet is almost certainly black - see recent African origin 131.111.185.69 (talk) 16:48, 18 March 2010 (UTC)

You are only right if evolution is right. From my experience, however, I know that many racists don't believe in evolution. ProteanEd (talk) 17:41, 18 March 2010 (UTC)

ProteanEd, have you a source for claiming that "mulatto" is non-politically correct? That would be arguable only if you can supply an alternative that expresses the same meaning. The word "quadroon" also has a specific meaning. Cuddlyable3 (talk) 01:21, 20 March 2010 (UTC)

Back to being scientific: If referring to albinoism, wouldn't two albino "black" parents be most certainly have albino children as well? (Our albinoism article doesn't mention this, maybe it isn't necessary true). From what I remember from highschool biology about recessive gene says this would be the case. --Kvasir (talk) 18:02, 18 March 2010 (UTC)

If both parents were affected because of mutations in the same gene, then yes, their children would all be affected (since they could only inherit a mutated copy of the gene from each parent). However, there are several different genes that can be involved in albinism, meaning that if the parents have albinism due to mutations in different genes, then none of their children will be affected, but will all be carriers for two different heterozygous mutations. --- Medical geneticist (talk) 11:29, 19 March 2010 (UTC)

Interesting, thankyou. --Kvasir (talk) 14:54, 19 March 2010 (UTC)

Not sure if it has been mentioned, but actions taken by an individual to change their appearance (i.e. bleaching skin, body building, etc.) would fall under the topic of phenotipic plasticity; those traits do not become part of the individual's genetic make-up. Of course there is some degree of probabilty involved (perhaps a mutation for that allele at an identical locus for each parent), but in short, no, their children won't inherit that trait.161.165.196.84 (talk) 09:52, 21 March 2010 (UTC)

Narcissus in the aquarium

I'm wondering if I can put my post-bloom Narcissus tazetta in the aquarium. I read that narcissus contains the alkaloid poison lycorine. I suppose it's toxic to humans but is it safe for the aquarium? I hope the bulb can soak up the excess nutrient in the tank and also live beyond its normal short flowering life. Thx. --Kvasir (talk) 14:35, 18 March 2010 (UTC)

In my experience, the way to treat indoor narcissi after flowering, is to give them a hefty dose of plant food and then ignore them for about 9 months, until you see a shoot coming from the bulb. They do come back every year, which is what happens in the wild, but they are not repeat flowering. Why would you want to drown a bulb in an aquarium? --TammyMoet (talk) 15:37, 18 March 2010 (UTC)

Mostly to soak up nutrients. I also read you can bury the bulb in a pot. Most Narcissus tazetta were sold submerged in water with pebbles for Chinese new year, not in a pot with soil. Maybe that's why i seem to think the species is aquatic or come from swamp like environment. I havne't found any info to that fact. --Kvasir (talk) 18:10, 18 March 2010 (UTC)

I think it's a propensity of plants which come from bulbs not to need soil. For example, I have a hyacinth in a hyacinth vase. Its roots are in the water in the bottom of the glass. All the nutrients it needs are contained in the bulb - hence the advice to give the bulb a good feed before letting it die down and dry off naturally. All it needs in order to fulfil its destiny and produce a hyacinth is water and light. If I'd put the whole bulb in water it would rot: it's just the roots that need to be in water. I bet you'd find the water level only came up to the top of the pebbles in the gifts you mention. You might find this site useful: [3]--TammyMoet (talk) 16:22, 19 March 2010 (UTC)

Interesting, never seen these vases before. --Kvasir (talk) 15:48, 22 March 2010 (UTC)

Calculation of lifespan of the sun

Here's my solution, but it's about 5 magnitudes off the accepted value-
solar luminosity(rate at which the sun gives out energy) $=3.839x10^{26}$
let the lifespan of the sun= energy nuclear fusion /solar luminosity
$e=mc^{2}$.
consider only the mass of the solar core, since nuclear fusion only takes place there.
therefore
$m={\text{volume of the core}}\times {\text{density of the core}}$ $=0.24^{3}\times {\text{volume of the sun}}\times 1.5\times 10^{5}$ (Solar core)
$e=2.12841x10^{49}$
${\text{lifespan}}={\frac {2.12841\times 10^{49}\div (3.839\times 10^{26}}{(60\times 60\times 24\times 365)}}=1759{\text{trillion years}}$

this is obviously off, someone pls help!! —Preceding unsigned comment added by Invisiblebug590 (talk • contribs) 15:43, 18 March 2010 (UTC)

Did you use the density of the suns core for the volume of the entire sun, or just for the core of the sun? Googlemeister (talk) 16:01, 18 March 2010 (UTC)

First: e=mc², yes -- but the proton-proton chain is not a full matter-to-energy conversion. Rather, about 0.7% of the initial mass becomes energy, with the remaining 99.3% becoming helium. Additionally, the accumulation of helium in the core accelerates the rate of fusion (see stellar evolution), so a constant rate estimation will be high. Finally, I'd guess that the numbers you're using for "core" may not exactly match the region where fusion occurs. Perhaps the fusing region is smaller, or perhaps hydrogen near the edge of the core doesn't fully fuse. — Lomn 16:01, 18 March 2010 (UTC)

Oops, updating: the bulk of the hydrogen in the sun (that which isn't in the core) will never fuse. There's simply not enough mixing. At some point the helium in the core overwhelms the hydrogen (and being denser, it settles there) and the sun kicks into helium fusion even while still predominantly composed of hydrogen. That's your other missing bit. — Lomn 16:05, 18 March 2010 (UTC)

I have fixed the formatting of your TeX - you need to put \text{} around text or it is treated as lots of variables ("volume" is v*o*l*u*m*e, etc.). The \text command gets rid of the italics and keeps the spaces in. --Tango (talk) 17:35, 18 March 2010 (UTC)

Also, the mass you calculate for the core is already larger than the total mass of the sun! Icek (talk) 03:58, 19 March 2010 (UTC)

expansion exceeding speed of light

If the universe was static and not expanding then it would make sense that the furthest distance one could see would be the age of the universe or at least to the age of the first photon. If the Universe is expanding then at a steady rate of say twice that distance in 13.7 billion light years then it makes sense that we could see light from 27.4 light years away since that light started coming at us only 13.7 billion light years ago. So what if the expansion of the Universe reaches the speed of light, would not this be the point at which we could only see darkness and nothing beyond just like looking into a Black Hole? 71.100.11.118 (talk) 15:51, 18 March 2010 (UTC)

The fault in your explanation is that you are using the universe itself as a frame of reference for measuring the rate of expansion of the universe. The speed of light is based on the current rate of change of the universe - considering the universe to be static. So, if the universe expands or contracts, it is the static frame of reference. The speed of light is measured as though the expansion/contraction of the universe is static. Therefore, light is always light speed in the universe no matter how fast or slow it expands. -- kainaw™ 15:56, 18 March 2010 (UTC)

Well not exactly. Expansion and contraction of the Universe effects the rate at which bodies that emit light are comin toward or going away from us and since some of these bodies emit light if they are ever traveling with the expansion at a rate away from use that exceeds that speed of light then that light being emitted would have to travel faster than the speed of light in order for us to see it. (I am of course assuming that an object traveling away from us faster than the speed of sound can also not be heard.) 71.100.11.118 (talk) 16:49, 18 March 2010 (UTC)

I rarely even belong on the Science desk but I can say that your latter statement isn't true. If there's an airplane 1 mile away from you, travelling at Mach 6 away from you, its sonic boom and the sound of its engines radiates in all directions. The sound will reach you in about 5 seconds, just like any other sound that was emitted from 1 mile away. The sound isn't carried along in the path of the airplane in a "wake" of some sort. (You may have been claiming that the sound couldn't be heard because a quickly expanding universe would keep the sound away from you, but that wasn't how I read your statement.) Comet Tuttle (talk) 16:56, 18 March 2010 (UTC)

Actually a sonic boom and the crack of a whip or lightning occur at a static point in air where the plane or end of the whip or super heated air are compressed and the uncompressed rather than coming out of the plane such a the music from a mp3 player coming out of a speaker that is traveling along at the same speed above the speed of sound which the plane is traveling at. Even if the speaker is pointed in your direction you will not hear the sound coming from it. (I'm pretty sure.) 71.100.11.118 (talk) 17:23, 18 March 2010 (UTC)

You are half right here. There's nothing fundamentally different about a sonic boom from any other type of sound (it's all just compression and decompression of air) so if the plane is playing music you'll still hear it on the ground. But it's also true that sound travels through a medium, which is in this case nearly stationary with respect to the observer, so the fact that the plane is going fast doesn't matter. If on the other hand you're making noise on the ground, the plane can't hear you because it's outrunning the sound. It's also true that using sound as an analogy for light is usually a bad idea. The whole point of relativity is that they can't be treated the same. Rckrone (talk) 18:03, 18 March 2010 (UTC)

I suppose that in the case of the speaker moving with the plane and emitting sound that the frequency reaching the listener's ear would fall below the threshold of human hearing. 71.100.11.118 (talk) 03:00, 20 March 2010 (UTC)

The expansion speed depends on distance. The further something is away, the faster it recedes from us (this is Hubble's law). That means that, if something is far enough away, it will be receding from us faster than the speed of light. This is actually not at all strange. The rule about not going faster than light speed applies to objects moving through space, not the expansion of space. We can still see objects that are receding faster than the speed of light, it just takes longer and longer for the light to reach us. The point where we can't see something because the light hasn't had time to reach us yet is the cosmological horizon (it is very similar to the event horizon of a black hole). --Tango (talk) 17:44, 18 March 2010 (UTC)

In answer to the OP's question, future of an expanding universe says that eventually galaxies and galaxy clusters will be moving away from each other at the speed of light. This will not only make intergalactic travel impossible, but there will basically be no evidence for the big bang for new civilizations to discover. It won't look like looking into a black hole from within any of these galaxies, since you'd still have stars in your own galaxy, but beyond this it would be pitch black. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 22:51, 18 March 2010 (UTC)

Strange... That is not what I remember the article referenced says. I'm going to see if our library has it so I can check it again. My memory is that it states that increased acceleration will increase the red shift until gamma rays are longer in wavelength than the universe, so it will not be possible to detect electromagnetic waves as waves anymore. It does not imply that the galaxies will be travelling faster than the speed of light or that there will be no evidence of the Big Bang since everything inside the galaxy will still be visible and known in the same way. Interstellar radiation will be undetectable with current methods. A future civilization will require someone to assume that there is another galaxy that must be red-shifted and figure out some method for proving it to be true. -- kainaw™ 00:13, 19 March 2010 (UTC)

Found the article online. Whomever cited it apparently confused reaching the de Sitter horizon with expanding faster than the speed of light. I'll change the article here to properly represent what the paper being cited says. If another paper cites it differently, that should be used instead of the article currently being used. -- kainaw™ 00:28, 19 March 2010 (UTC)

Hmmm, although the article doesn't back up what I said, this video (at the 51-minute mark) does (which is where I learned this idea in the first place). Remember that it's not that the galaxies are moving away from each other; rather the space between them is expanding, which causes the redshifting (the 10 minute mark of the video does a good job of explaining it). At a certain point, that redshifting will be so extreme that no known method can be used to detect other galaxies or the CMB. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 09:07, 19 March 2010 (UTC)

My main issue isn't that redshift will become extreme - it is the claim that galaxies will be independently travelling faster than the speed of light - which is what the questioner apparently believes. You are very accurate in stating that the distance between the galaxies is expanding. The galaxies are stationary - not moving. So, they are not travelling faster than the speed of light. The way I normally hear it explained is that the galaxy is like a balloon. The galaxies are dots on the outside of the balloon. As the balloon expands, the distance between the dots expands, but the galaxies are still on the same spot on the balloon. So, from the point of view of a galaxy in space, it appears that other galaxies are moving away at incredible speeds, but they aren't actually moving at all. Space is expanding. -- kainaw™ 13:38, 19 March 2010 (UTC)

Kainaw, within the framework of relative your statement "it appears that other galaxies are moving away at incredible speeds, but they aren't actually moving at all" makes no sense since movement is relative. There is nothing wrong with thinking of the movement of the galaxies away from us as real movement. Dauto (talk) 16:17, 20 March 2010 (UTC)

It's an important distinction to make since, according to special relativity, galaxies actually moving at the speed of light is impossible. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 03:45, 21 March 2010 (UTC)

The question remains unanswered then or in disagreement since blowing up a balloon still puts distance between the dots on its surface. By adding space fast enough eventually this distance will force the dots to separate at the speed of light and possibly beyond even though light will retain its speed limit meaning that the dots will become invisible to each other. 71.100.11.118 (talk) 13:09, 22 March 2010 (UTC)

There is no disagreement. Galaxies won't be able to see each other. It'll be pitch black looking beyond one's galaxy/cluster. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 22:36, 22 March 2010 (UTC)

Which converter?

If you have a device (a Set-top box) with the specifications of 12V 15W, which voltage converter should you buy? I saw one 12V 1A, but will it fit this device?--ProteanEd (talk) 16:00, 18 March 2010 (UTC)

Watts = Volts * Amps. Your device potentially draws 1.25 A, so the converter is probably not sufficient. — Lomn 16:02, 18 March 2010 (UTC)

And what if I have the choice of a 1.8A, 12V converter? Can this converter fry the device? Or will the device just use enough power as needed? ProteanEd (talk) 16:07, 18 March 2010 (UTC)

A power supply is usually rated by the volts it delivers and the maximum amps it is capable of supplying. Devices draw however much they draw of that. Consider that your 15-amp fuse/circuit-breaker doesn't blow when you are only driving a small lightbulb. DMacks (talk) 16:12, 18 March 2010 (UTC)

It depends on the type of converter. Simple transformer-based ones are designed to be paired with something drawing close to the rated current (if the current draw is too low, the voltage provided will be higher than rated), while switch-mode and other regulated converters will provide the rated voltage for any current draw. --Carnildo (talk) 00:10, 19 March 2010 (UTC)

It's been a while since I did radio electronics, but I seem to recall that a wire transformer rated at (say) 12V, 5A will deliver 12V at 0.05A, will deliver 12V at 1A, still at 5A, but will deliver less than 12V at 6A (or blow its fuse, or fuse its wire windings). A switch mode transformer (which pretty much any transformer you find will be) should deliver close to its rated voltage anywhere under the rated current.

In answer to the original question, you can safely use a voltage converter (which I've been calling a transformer above) rated at 12V and any amperage (A) above 1.25. So you are safe to buy a 12V 2A voltage converter. --Polysylabic Pseudonym (talk) 02:03, 19 March 2010 (UTC)

I would recommend getting something that can produce at least 50% more amps than you strictly need. Power supplies that are being run close to their maximum amperage tend to get hot - and that shortens their lives considerably. The 1.8A/12V gizmo sounds like just the thing. Carnildo's right about not going crazy, you certainly wouldn't want something that could produce (say) 10 times the current you need - but 50% of excess power is perfectly reasonable. The 1.8A/12V gizmo sounds like just the thing. SteveBaker (talk) 02:06, 19 March 2010 (UTC)

I may be old but there is nothing wrong with my short term memory nor is there anything wrong with my short term memory. The 1.8A/12V gizmo sounds like just the thing. Cuddlyable3 (talk) 01:10, 20 March 2010 (UTC)

auxins - geotropism and photo-tropism

auxins are there in growing tips of plants, at shoot tips. are they at root tips too? nextly what about the growing tips of leaf? Next question what's there in roots that makes them response to gravity(mainly growing towards gravity). and whats there in shoot tip that makes to grow towards light? both of them have auxins(main growth promoting harmone)then what makes the above difference....thanx.--Myownid420 (talk) 16:28, 18 March 2010 (UTC)

Don't roots tend to grow toward water more than down ? As for leaf tips, the amount of photosynthesis would seem to be the proper way to guage which way to grow. StuRat (talk) 16:48, 18 March 2010 (UTC)

Auxin, gravitropism, and phototropism cover this issue with varying quality. I don't know how gravitropism works, but with phototropism the auxins are sent to the shaded side of the plant, which then grows faster, which tends to push the plant away from the shaded side, which sends the plant towards the light. It'll be the same with gravitropism, but I don't know what the mechanism is for the plant to detect gravity. --Sean 19:43, 18 March 2010 (UTC)

I'm sure you can get data from the auxin and gravitropism/phototropism articles, but to put it short: a chemical necessary for growth on the side of the stem that is near the light dissolves and/or becomes deactivated, and so growth is greater on the side of the stem farther from the light and the plant 'tips' towards the light. As for gravitropism, intracellular vesicles were determined to control cellular position -- cells have an affinity for them on their floor (thinking of cells as oversimplified cubes). So the cells grow in order to orient themselves so that these vesicles lay on the bottom of the cell -- roots therefor 'know' which side is down and so do stems. I can't seem to remember the name of these vesicles and can't find it online, but they start with the letter 'a'. DRosenbach ^{(Talk | Contribs)} 19:46, 18 March 2010 (UTC)

Got it -- amyloplast. DRosenbach ^{(Talk | Contribs)} 20:16, 18 March 2010 (UTC)

Fascinating!, thanks. --Sean 13:17, 19 March 2010 (UTC)

Phototropism says auxins on the dark side cause softening of the cell wall which allows the cells to expand and thereby tip towards the light. The light-side-growth-deactivation process you describe seems to be something totally different. Citation? --Sean 13:17, 19 March 2010 (UTC)

string theory and space

Some string theories suggests that they are closed rings. And a sting can have enough energy that it will get stretched and form a membrane i.e. a universe. One more thing to note is that space cant be torn, it can be stretched, twisted, bended but not torn. So the hole in between a string will not get filled as it stretches, where will it go? (i got this doubt when i was watching "The_Elegant_Universe-PartIII-Welcome_to_the_11th_Dimension" from NOVA)

Maybe it will stay the same size, and nobody will ever notice it ? StuRat (talk) 16:51, 18 March 2010 (UTC)

See Membrane (M-Theory) and Brane cosmology for discussions over these theories of the universe. --Jayron32 16:52, 18 March 2010 (UTC)

Freshly-made Bradford Reagent

[/i] Has anyone here made their own Bradford Reagent?

I'm trying to make sure the color's right - it's supposed to be a brownish-red.

So far I have:

1. Added 100 mg Coomassie Brilliant Blue G-250 to 50 ml of 95% Ethanol

2. Added 100 ml of 85% Phosphoric Acid to the above

3. Slowly (dripwise) added DI water to volume of 1000 ml

The results of step 3 are a dark purplish blue color, while the results of step 2 are the dark brownish red. So the next step:

4. Filter through Whatman #1 filter paper

...and it's still blue. I'm trying the filtration step again, in the hopes that a second filtration will help, but I'm wondering if anyone has done this before and might have a tip or two.

Thanks! Wevets (talk) 16:46, 18 March 2010 (UTC)

Have you checked the pH of your Bradford reagent after step 3? If higher than 2 that's a problem (how sure are you of your DI water source?). How long did you stir before step 3? It's possible the CBBG did not have enough time (e.g. overnight) to go into solution. -- Scray (talk) 23:35, 18 March 2010 (UTC)

Thanks! Haven't checked the pH after step 3 - I'll try that next - it should be less than 2 you say? The DI water source should be good, and I've tried it with two independent sources... even trying millipore water in a dilution going on now. I took a lot of time with step 3, since I heard it may be a problem (added 500 ml over 14 hours,) but I haven't tried to take much time with step 2... haven't seen any mention of it not going into solution - is that likely to be a problem? Should I mix the phosphoric acid and ethanol and CBBG overnight, then dilute overnight?

Incidentally, a second filtration didn't help. Still blue. Starting to wonder if the dye or the Phosphoric Acid could be too old - I'm not a chemist so I don't know how long these things last. Dye is 5 yrs old according to the bottle. Phosphoric Acid looks very old - can't find a date on the bottle, and the style of the label looks very old.

Wevets (talk) 00:49, 19 March 2010 (UTC)

It sounds like the dye is too dilute. I run this assay (you're doing protein quantitation, right?) at a 1:5 dilution in DI water. Just checking this now in the lab, diluting it too much does indeed alter the colour. I'm not a chemist either, but it seems the pH is raised too much and you shift the dye to it's anionic state (which is blue). Maybe try lowering the volume of DI water? Not sure that it needs to be added dropwise though. Also, the filtration step is just to remove particulate matter, it shouldn't have any bearing on the dissolution of the dye.

Incidentally, we use a commercially prepared solution, and they use methanol instead of ethanol- again, I don't know if that makes much difference chemically. And as for phosphoric acid, that does definitely seem to be somewhat perishable.Wrex-beater (talk) 08:45, 19 March 2010 (UTC)

Thanks - how dilute should the dye be? Maybe 0.1 mg/ml as a final dilution isn't so hot after all. Checking the pH is the first thing I'll do on Monday, so we'll see about that.

Do you use the Bio-Rad Protein Assay #500-0006, I think? That's similar to Bradford and has got Methanol in it. I tried diluting some of that with our DI water for comparison, and similarly, it turns a bit blue (though not the same bright blue/purple I'm seeing in the homemade.) Of course, someone hid the instructions that come with the bottle, so I'm going to download those to see if it recommends anything different. Wevets (talk) 14:31, 19 March 2010 (UTC)

3D TV and Animals

Would dogs or other animals enjoy 3D TV? TheFutureAwaits (talk) 17:38, 18 March 2010 (UTC)

I shouldn't think that they would take too kindly to having the requisite glasses put on them. Vranak (talk) 17:54, 18 March 2010 (UTC)

Koko (gorilla) enjoyed 3D Viewmaster views, so similarly tame gorillas might enjoy 3D TV as well. Edison (talk) 19:02, 18 March 2010 (UTC)

Some dogs will allow glasses to be put on them, if only for a little while. —Pie4all88 ^{T C} 19:05, 18 March 2010 (UTC)

Do dogs see at the same framerate people do? If a dog can see at a faster framerate, the TV picture would seem choppy. Googlemeister (talk) 19:24, 18 March 2010 (UTC)

People don't have a frame rate. Your eyes are being lit up as fast as photons can plink your photoreceptors, and some of those plinks get passed on to higher-level vision equipment, but your brain is definitely not getting a full-frame cinematic update every N microseconds. --Sean 19:48, 18 March 2010 (UTC)

Frame rate explains the 'frame rate of your eyes' (sort of), but it looks like that part of the article needs to be fixed. -Pete5x5 (talk) 19:59, 18 March 2010 (UTC)

Your eyes do not have a Frame rate, they have Persistence of vision. At the article Animation the top illustration of a bouncing ball has about the minumum frame rate 10 fps that can give an illusion of motion. The first surviving movie was shot at 12 fps. Cuddlyable3 (talk) 21:15, 18 March 2010 (UTC)

Even the concept of persistence of vision is kinda archaic - it implies the kind of situation where some light hits your eye and the signal that results from it slowly decays away unless more light hits it within a tenth of a second or so - such that if an image flickers fast enough, it'll seem to be a "continuous" stream of light. But that's not how it works at all. Your eyes are perfectly capable of seeing the light/dark/light/dark of a very high frame rate image - certainly into the 100 to 120Hz range. But it's now understood that the visual system can interpolate the missing data of a flickering image to produce the impression of a continuous image to higher brain functions. This is a useful adaptation when (for example) you're trying to hunt a small, fast moving animal in long grass where the blades of grass chop up the image into vertical strips that come and go as they are hidden and revealed between the blades of grass. There are some elegant experiments that demonstrate this - but the simplest is that even in a system that's updating a moving image 30 times a second on a 60 frames per second display (like many computer games do), most people see double-imaging of fast moving objects. If it were only necessary to update the image 10 times a second to get continuous motion (which is somewhat true) then there wouldn't be a problem. But because each image appears twice at the same position on the screen - then jumps forward a bit and appears twice in a row at the next position, our eyes/brain can't do simple linear interpolation and get the impression of uniform motion. Instead, what happens is that our visual system is forced to deduce that there are two objects moving along close together at uniform speed and each is flickering on and off 30 times a second. The fact that we can see this kind of double-imaging artifact at amazingly high frame rates is proof that we're able to see very short flashes of data and interpolate between them. Further evidence for this is due to interpolation and not something weird to do with having two eyeballs is that if you update the image only 20 times a second and display the video at 60Hz, many people will see triple-imaging. The term "persistence of vision" has come to be a handy short-hand for that - but it's not really the right concept for what's really going on. SteveBaker (talk) 23:59, 18 March 2010 (UTC)

That describes temporal aliasing that is avoidable by reducing the resolution (blurring) of the object in the direction of its movement. I can tell the difference between my 100Hz TV display and a continuous illumination by waggling my finger in front of my view but that does not mean I can see light/dark/light/dark flicker at 100Hz. The articles Flicker fusion threshold and this in Scholarpedia may be of interest.Cuddlyable3 (talk) 01:06, 20 March 2010 (UTC)

Nope - temporal aliassing is a completely different phenomenon. Temporal aliassing is a physical phenomenon related to the nyquist limit. The double-imaging effect happens entirely inside your eye/brain. Appropriate motion blur will indeed eliminate temporal aliassing - but not double-imaging. I didn't say that waggling your finger in front of the TV proved or disproved anything - but since you mention it, if you couldn't "see" 100Hz flicker, then it would appear continuous and the finger waggling trick wouldn't work. But we have to be super-cautious about the word "see". What our eyes can detect and what our consciousness is informed of are two very different things. SteveBaker (talk) 15:22, 20 March 2010 (UTC)

There are lots of reasons why most animals don't really like TV. With some, it's because they live in a world dominated by scent or that they have very precise hearing that isn't fooled even by stereo sound. Stereo vision is mostly important to predatory or arboreal animals like dogs and humans - but of very little interest to herd animals and herbivores who are more concerned with having a wide field of view. Those kinds of animals probably wouldn't even realise that the TV was in 3D. SteveBaker (talk) 00:08, 19 March 2010 (UTC)

Current over large distances

You know how electricity will not travel down a path that leads to a dead end, and it generally takes the path of least resistance? Does electricity decide which path it will take instantly, or is the information conveyed to it at the speed of light? For example, say some current suddenly had the option to travel in one or more of three paths: one that lead to effectively a dead end, one that had a large amount of resistance at the end of it, and one that did not. These paths are several light-years long and are essentially straight. Would the light mostly travel down the path without the large amount of resistance? Sorry if I'm not explaining this well, and thanks in advance for your response. —Pie4all88 ^{T C} 19:05, 18 March 2010 (UTC)

The information is limited by the speed of light. If we think about how the electrons "decide" where to flow, what's happening is that each electron is pushed locally by the electric field of the particles around it. A path that leads to a positive charge means that electrons at the end get pulled toward the positive charge, and leave a positive "gap" behind, which pulls other electrons along and so on. Electric fields can't travel faster than the speed of light. If we cut the wire at one end, electrons would still flow for a bit at the other end until the changes caused in the electric fields could propagate down to them. Rckrone (talk) 19:21, 18 March 2010 (UTC)

If the length of the wire (or other pathway for current) is large compared to the wavelength of the electromagnetic wave (or equivalently, if the switching happens "fast" relative to size of the circuit), then a lumped element model is inappropriate, and a transmission line model is more accurate. This can be approximated with the Telegrapher's equations. Using these models, or a full-blown solution of Maxwell's equations, results in a more physically accurate, conceptually consistent result and shows that changes in the circuit (such as opening or closing a switch, creating the "dead end" the OP is referring to) will propagate at the speed of electromagnetic waves in the medium. Or, to put it very simply, if there were a wire that were extraordinarily long, even if it terminated in an open circuit, electricity would flow down the wire, because that wire would have a capacitance. This current would represent the transient response of the system; clearly, once the current reaches the end of the wire, it has nowhere to go, so "something has to change". This would result in a reflection (of voltage, current, or both, depending on the type of "dead end"). After some characteristic period of time, steady state would be reached (depending on the type of input current, this could be a standing wave at the input frequency, or a DC valued voltage and zero current, etc.) Nimur (talk) 20:12, 18 March 2010 (UTC)

I do not "know how electricity will not travel down a path that leads to a dead end" because that is not the case. Assuming a conducting line that is long, though not necessarily as absurdly long as several light-years, an electric voltage step (or pulse) entering the line will travel along the line. See the article Transmission line. What you may call a "dead end" is a discontinuity on the line, such as an open circuit or a short circuit. When the voltage step reaches the discontinuity it is reflected. The reflection is seen at the input after the round trip of twice the line length. That is the principle of the Time-domain reflectometer instrument for testing electric paths.

Where there are several paths it is not true that electricity has to decide to take only the path of least resistance. Electric current is shared across parallel paths in inverse proportion to the resistances of the paths. See Ohm's law. An Electric arc (such as Lightning) might seem to be an exception but it is not. The arc appears when a path of Plasma (physics) forms that has much less resistance than any other path. Cuddlyable3 (talk) 20:21, 18 March 2010 (UTC)

Also, to the questuon of electrons "deciding" which path to travel down; it happens the same way that water molecules will decide which pipe to go down when approaching a fork in a pipe. The information comes from the electrons already in those wires. Electricity isn't one electron flying down a tunnel. Its a chain of electrons sliding down the wire, so when a lone electron is faced with a junction, it will "choose" the path that at that moment has an opening for it. --Jayron32 21:01, 18 March 2010 (UTC)

Ok, I understand this much better now. Thanks, everyone, for your very informative answers. —Pie4all88 ^{T C} 22:48, 18 March 2010 (UTC)

One last point - the electrons themself do not travel down the wire. Their "push" does. Each electron pushes its neighbor and so on. The push happens at the speed of light (or pretty close). There is also a pull, which works the same way, but in reverse. In a normal circuit both happen at the same time. If the circuit is long enough there is a slight delay, where you have just one but not both. I think measuring effects of this helped figure out which direction electricity travels. Ariel. (talk) 21:08, 19 March 2010 (UTC)

That's not quite true - the electrons do travel down the wire - but very VERY slowly. The best analogy is to imagine a 20 foot-long hose pipe (the wire) that's completely full of half-inch ball-bearings (the electrons). If you push another ball-bearing into the end of the pipe, it'll force one out of the other end. You could imagine that this process happens pretty much instantly - much faster than a ball could roll down an empty pipe an pop out of the other end. But you paint one of your ball bearings red and push it into the pipe, you have to spend an hour pushing more ball bearings into the pipe before the red one pops out of the other end. So while the 'flow' of ball bearings travels really fast - an individual ball bearing takes a heck of a long time to make the journey. Hence, when you turn on a light switch, the delay before the electricity reaches the other end of the wire is as fast as the speed of light - but it could take a very long time for a particular electron to travel from one end to the other.

This analogy also answers the OP's original question. If you have a 'Y' joint in your pipe and cap off one arm of the Y - then how do the ball bearings "know" to travel down the other arm? It's obviously because the capped off arm is already full of balls. Same kinda deal with electrons and a wire that doesn't go anywhere.

SteveBaker (talk) 02:33, 21 March 2010 (UTC)

How long does a snake need to be in order to constrict an average-sized man?

Just thinking back to someone I used to know who had a python (poss. boa constrictor) that tried to constrict him when he was playing with it, whilst drunk. Apparently, the snake wasn't long enough to get into a position where it had enough coils around him at once to make it impossible to unwind, or something. --Kurt Shaped Box (talk) 20:56, 18 March 2010 (UTC)

Indeed, a small sized snake needs about 38 years on the average to constrict an average-sized man. A very big anaconda needs about one minute on the average. So if we tell you that the average snake would need about 19 years and 30 seconds on the average, would that be a helpful answer? DVdm (talk) 21:06, 18 March 2010 (UTC)

I think he's asking for snake length, not constriction duration. Vimescarrot (talk) 21:08, 18 March 2010 (UTC)

Oops. Sorry. Struck. DVdm (talk) 21:11, 18 March 2010 (UTC)

No worries. None at all. --Kurt Shaped Box (talk) 21:15, 18 March 2010 (UTC)

you write "A very big anaconda needs about one minute on the average [to constrict a man]". is it possible to escape during that one minute in typical amaconda habitat settings and how should you do it?. Thanks. 80.187.107.89 (talk) 21:50, 19 March 2010 (UTC)

I think it only needs to be long enough to wrap around the person's neck. But I don't think snakes are smart enough to target that. Well, except for this snake. --Kvasir (talk) 21:26, 18 March 2010 (UTC)

It's not just length though. A Garter snake is long enough to wrap around someone's neck, but just doesn't have the strength needed to kill someone. --The High Fin Sperm Whale 21:52, 18 March 2010 (UTC)

I have watched one video this week of a man versus a python, and the python did indeed go for the neck. Vranak (talk) 01:34, 19 March 2010 (UTC)

most constrictors work by immobilizing the chest cavity, not by actual strangulation. assuming 3 to 4 wraps around the chest, and given a chest size of 42 inches, that would imply a minimum of 10 ft (for 3 wraps) or 14 feet (for 4 wraps) of main body length - add a few feet for tail and head/neck and it seems you'd need a minimum 14 to 18 foot snake to kill an adult male human. Of course, I'm not certain that a snake of that size could capture and pin an adult male - humans aren't strong as animals go, but hands allow for some fairly unique modes of defense (even without weapons) - but it would have to be at least that large to have the possibility of immobilizing the chest and lungs. --Ludwigs2 21:55, 18 March 2010 (UTC)

Going for the chest rather than the neck is actually a rather clever trick that the snake is using quite deliberately. What it does is to wrap initially rather loosly around your chest - but when you exhale, the pressure on its coils reduces and it is able to tighten up just a little bit more. Thus it can use friction between its coils to avoid needing so much muscle power to crush your chest. Some species have interlocking scales to help that process. So with each breath you take, you have to breathe more and more shallowly...not a nice way to die. However, since the snakes muscles aren't that strong - it's possible to unwind it one coil at a time if your hands are free. Most of the prey that constrictors go for don't have hands! SteveBaker (talk) 03:38, 19 March 2010 (UTC)

That said, snakes are apparently a *lot* faster and stronger than they would first appear. I once remember reading that it took five guys to unwind a python than had attached itself to its owner and started to squeeze him until he creaked. I believe that the near-fatal mistake he had made was to handle live rabbits (i.e. the snake's dinner) directly before interacting with the snake - which then smelled rabbit and jumped to conclusions, due to its poor eyesight. --Kurt Shaped Box (talk) 23:03, 18 March 2010 (UTC)

Isn't that a lesson that men should not play with their pythons whilst alone?--79.76.137.66 (talk) 23:49, 18 March 2010 (UTC)

I've read of smallish constrictors, like 10 feet, killing their owners by wrapping around the throat. I would recommend they not kill their owner unless they are prepared to eat him.Edison (talk) 00:01, 19 March 2010 (UTC)

The 'never attempt to swallow anything larger than your own head' rule doesn't apply to snakes, or so I hear. On account of them being able to pop their jawbones out of their sockets... --Kurt Shaped Box (talk) 00:13, 19 March 2010 (UTC)

I misinterpreted your first sentence...I was trying to imagine how it was safe for me to attempt to swallow a snake that was bigger than my head...Mmm'k - never mind! SteveBaker (talk) 03:29, 19 March 2010 (UTC)

OR: I had a corn snake as a kid that I managed to kill by giving it a too-big mouse to eat. It got the thing into its belly, but was dead the next day. :( --Sean 13:26, 19 March 2010 (UTC)

My recollection of snake-handling rules is that you need one handler for snakes up to ten feet in length, and an additional handler for each further five feet of snake. Based on that, I'd guess that ten feet is about the minimum to successfully constrict a person. --Carnildo (talk) 00:23, 19 March 2010 (UTC)

Isn't it easier just to kill the damn snake? --Kvasir (talk) 04:49, 19 March 2010 (UTC)

At the risk of sounding obvious...not if you want to keep it alive. You mean while it's trying to constrict you? Well, either your hands are free, in which case you can just unwind it (sounds easy enough to me, since apparently they aren't all that strong), or they aren't free, in which case - how do you propose killing it? Vimescarrot (talk) 06:38, 19 March 2010 (UTC)

I was referring to having one handler per 5 feet of snake. One spotter would be enough to kill one when it's out of control? Decapitate it or one stab in the heart. Or have I watched too many movies. :) I'm this close to quoting Snakes on a Plane. --Kvasir (talk) 06:54, 19 March 2010 (UTC)

Snakes that long -- and the business disruption of killing one -- are likely to be much more expensive than simply hiring another handler. --Sean 13:26, 19 March 2010 (UTC)

You guys are overlooking another obvious reason not to try and kill the snake - if it's a pet, the owner likely loves the thing to bits and doesn't want it to die... --Kurt Shaped Box (talk) 01:07, 20 March 2010 (UTC)

Decay of large dead animal in water

If a large animal(let's say elephant-sized) drowns in a lake where there are bacteria but no scavenging animals, how long does it take for the carcass to become skeletonized? Assuming that scavengers were introduced to the region, how early would they have to arrive before the corpse no longer had edible flesh on it? 137.151.174.128 (talk) 22:02, 18 March 2010 (UTC)

For starters, our decomposition article says: A basic guide for the effect of environment on decomposition is given as Casper's Law (or Ratio): if all other factors are equal, then, when there is free access of air a body decomposes twice as fast than if immersed in water and eight times faster than if buried in earth. Comet Tuttle (talk) 23:10, 18 March 2010 (UTC)

Anatomists and anthropologists may use "maceration" to clean flesh from bones, by simply placing them in water and pouring off the liquid with the decayed flesh periodically.[4]. They do not give a timetable for large versus small animals. Some 19th century anatomists would place tadpoles in water with the dead animal to remove the flesh. Other 19th century anatomists would place an animal or human in a metal cage and secure it to the bottom of a pond or lake for a year, by which time natural processes and small creatures would have cleaned the bones. The mesh of the cage should be small enough to contain the smaller bones. Could not find schedules or timetables or recipes more precise. Edison (talk) 23:59, 18 March 2010 (UTC)

We have a forensic entomology article, but no forensic ichthyology article. Comet Tuttle (talk) 00:22, 19 March 2010 (UTC)

February 2010 Scientific American magazine has an article called "The Prolific Afterlife of Whales." It is a very good article. Excerpt: "On the deep seafloor, the carcasses of the largest mammals give life to unique ecosystems…" Bus stop (talk) 03:34, 19 March 2010 (UTC)

Our whale fall article covers this topic. --Sean 13:33, 19 March 2010 (UTC)

Aquarium bugs above the waterline

There are hundreds of these specs of brownish, needle head size bugs with antennae 1/2 to 1/3 of their body length crawling about above the waterline on the wet glass of my aquarium. Adult and young, i assume they are all the same. Some might fall onto the water but soon return even after I try to wash them down by sloshing water on them. They seem to be very good at staying above water (probably due to surface tension) and hopping back onto the glass. What are they? I hope my fish will find them as snack if they are quick enough. I guess once I figure out what they are I'll be able to see if it's any indication of my water quality. thx. --Kvasir (talk) 22:03, 18 March 2010 (UTC)