Wikipedia:Reference desk/Archives/Science/2011 August 4

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August 4[edit]

Spotting nocturnal animals at night[edit]

So, I recently put up a bird feeder in my yard. It is on ~7 foot pole with a birdhouse/feeder on top in which I put sunflower seeds. The birds love it. But during the night, something eats all the seeds. I put a squirrel guard on the pole, and have personally witnessed (during the day) that it does a good job of keeping squirrels out of ther feeder. So I'm a bit stumped as to what is eating all my birdseed overnight. I had previously heard that there was a certain color light (red, green, blue?) that nocturnal animals can't register, and will approach feeders even though it is illuminated. I would like to know what color light this is so I can put one in my yard. I really just want to sit on my porch and spot the culprit, and not have deal with expensive infrared lights, or motion-cameras. Any assistance would be appreciated. Quinn BEAUTIFUL DAY 00:30, 4 August 2011 (UTC)

I should say that I already have an exterior light fixture in the yard, with a regular old "white" light, so I'm hoping I can just change the bulb to a different color. Quinn BEAUTIFUL DAY 00:32, 4 August 2011 (UTC)
I'm pretty sure it's red. Have you just tried to 'catch them in the act'? I have exactly the same thing happen at my place and it's possums they aren't timid at all, they'll walk on our deck even when the lights are on and we're out there too with guests over. It won't be possums where you are, but maybe whatever it is isn't as shy as you think. Vespine (talk) 01:08, 4 August 2011 (UTC)
Not sure where you think I am, exactly, because possums are pretty common in central Mississippi. Regardless, I don't think it's possums for the very reason you stated; whatever it is, it is very sneaky...won't come out when I have the lights on. I wonder if it could it be some sort of bug (insect) eating the seeds? Quinn BEAUTIFUL DAY 01:23, 4 August 2011 (UTC)
Aah, so you call them possums too, they're technically opossums, we have possums in Australia. Vespine (talk) 03:29, 4 August 2011 (UTC)
A bat? The Northern flying squirrel? Are you sure it isn't just the birds getting up earlier than you? AndyTheGrump (talk) 01:29, 4 August 2011 (UTC)
I'd vote for a bat, too, although they mostly eat insects, but I imagine some might go for bird seed. Just in case it is something on foot, perhaps a raccoon, I suggest spreading some sand at the base of the pole so you can look for tracks the next morning. StuRat (talk) 02:14, 4 August 2011 (UTC)

Chupacabra. Either that or the Southern flying squirrel. Chances are 50/50. μηδείς (talk) 02:04, 4 August 2011 (UTC)

Ooops, yes, wrong squirrel species. :( AndyTheGrump (talk) 02:08, 4 August 2011 (UTC)
A good little mystery. Is the pole smooth metal or climbable? How far from the pole is the nearest tree? Birds can gobble seeds vwery quickly. You have probably thought of all this.
As for color of light, in our neck of the woods they sell strobe lights for the purpose of discouraging wildlife from coming near. The idea is to place the light where the animal cannot approach without looking at it. If something is climbing your pole, a downward-pointing strobe on the pole might have an effect. Wanderer57 (talk) 02:17, 4 August 2011 (UTC)
BTW, how do you know it's not birds eating the seeds ? You said they are eaten at night, but are you always up right at dawn ? The proverbial "early bird" might very well be the "culprit". StuRat (talk) 02:22, 4 August 2011 (UTC)
Could be birds, I suppose. If so, that's fine. That's what the feeder is for. But I'll get up at night and check it, and one minute the feeder is hour later it's completely empty. And it holds a lot of seed. Getting kind of expensive, really. I should clarify, I don't simply want to identify it...I want to figure out the best way to catch it in the act so I can "get rid of it" if you catch my drift. Quinn BEAUTIFUL DAY 02:48, 4 August 2011 (UTC)
So, in a nutshell, my question is: Is there a good way to observe wildlife at night? And again, a FLIR camera is a bit out of my price range. Quinn BEAUTIFUL DAY 02:53, 4 August 2011 (UTC)
At my house (southeastern Canada), raccoons empty out bird feeders regularly, and these are feeders that hold 4 kilos (+/-10 pounds) of sunflower seeds when full. Unlike your predators, though, 'coons are not afraid of lights, even if I turn the lights on as they are feeding. Only opening a door they can see will get them to amble off, and they return minutes after I go back indoors. We finally had to electrify a plate at the base of the pole. 'Coons are smart and they test it every month or so. (For those of you reading this from the U.K. or other European points, don't panic; the shock is very mild from North American voltages.) Bielle (talk) 03:17, 4 August 2011 (UTC)
Maybe the creature eating it couldn't care less whether it is day or night. Therefore empty it out before dark, if possible. Then try to observe it unobtrusively from a distance at frequent intervals during the day. If it is a nocturnal creature it may make an exception and come out during the day, if it has become habituated to finding food at your feeder. Bus stop (talk) 03:28, 4 August 2011 (UTC)
That might work. Though come to think of it, you could simply take the feeder indoors at night, and leave the whatever-it-is to find food elsewhere. After all, I don't suppose it realises it is a bird-feeder. It found a source of food, so it eats it. If you do succeed in whacking it over the head with a baseball bat or something, another one is likely to discover the source of food later (unless you have exterminated the last surviving 'whatever'), so killing it doesn't solve the problem. AndyTheGrump (talk) 03:39, 4 August 2011 (UTC)
I have had the experience with raccoons as Bielle, if there's food they are quite willing to come into lit areas. Is this a tube-style feeder or more of a platform feeder? It could simply be that crows or other larger birds gobbling it up. I once came home to find that a bear had figured out how to open my iron silo feeder, which is metal and cannot be opened while hung up on its hook. The bear appeared to have swatted it down and knocked it around until the lid came off. Now I hang it up where bears can't reach. Beeblebrox (talk) 04:06, 4 August 2011 (UTC)
Beeblebrox, if you have bears, then you shouldn't have bird feeders. If you manage to keep them out, then they will still be in your yard, hungry, and angry, which is a very bad combo. StuRat (talk) 05:28, 4 August 2011 (UTC)
For the record, I think Racoons would eat you if you fell asleep outdoors at night. They aren't particularly aggressive or vicious, just an annoying combination of smart and persistant and not giving a shit. My dad went for YEARS trying to devise novel systems to keep the racoons out of our trashcans, and every year the racoons would figure it out. If we could somehow convince racoons to put on snazzy suits and wear sunglasses, they'd make perfect superspies. If the OP lives in an area with racoons, I'd vote for that as the likely culprit. Where I grew up, racoons weren't spooked by anything. We'd stand on our back steps at night and try to scare them off by throwing sand and rocks at them. They'd just look at us like we were crazy and go back to looting our trashcans. --Jayron32 05:52, 4 August 2011 (UTC)

Um, the problem is the strange desire that only those observed taking advantage of charity deserve it. The feeder's motivation is far from selfless. Next he'll want commercial endorsements and signed releases. Charity is charity, and commercialism commercialism. μηδείς (talk) 05:29, 4 August 2011 (UTC)

  • @StuRat: Don't worry, I am well aware of bear danger (now). I've moved since that incident, at my new place the feeder is 20+ feet off the ground and the neighborhood bear has never even tried to get at it. We don't put seed in it in the spring when they are super-hungry and tend to come to town and get into people's garbage or dog food. Beeblebrox (talk) 18:48, 4 August 2011 (UTC)
Good job, Beebles. Whoop whoop pull up Bitching Betty | Averted crashes 11:51, 5 August 2011 (UTC)
OP again: Doubt anyone is still paying attention to this, but in case you're interested, it turned out to be squirrels. It is a platform feeder on a 7 ft. pole, and even though I have an squirrel guard (an upside down metal cone beneath the feeder), which seemed to keep them out during the day, I caught a couple of squirrels raiding it just before day break. One squirrel would put its hind legs on the pole, and reach up and grab the rim of the cone. The other squirrel would get on it's back, and reach up and rake all of the seed off the platform onto the ground. Then they'd feed. This amazes me for 3 reasons:
  • It's pretty ingenious what they are doing.
  • It requires cooperation, in which the one that could reach the feeder rakes the seeds on the ground for both of them, when it could just as well have jumped from the other squirrels back onto the feeder and had it all to himself.
  • The don't do this during the day when I know they're watching. When I'm on my porch watching the feeder, the squirrels remain on the ground, and act like they can't get around the squirrel guard.
Anyway, I've decided to just put a cupfull of seed in at a time, and figure that the squirrels are just a fact of life. Thanks for the suggestions. Quinn BEAUTIFUL DAY 01:10, 5 August 2011 (UTC)
Not just "a" fact of life. The fact of life. μηδείς (talk) 01:44, 5 August 2011 (UTC)
@Quinn: That's actually pretty awesome. Nature can be amazing quite often. Thanks for sharing! --Jayron32 03:10, 5 August 2011 (UTC)
Now I'm concerned that you've unintentionally created a lab for the development of super-intelligent squirrels who will soon rise and enslave the human race. :-) StuRat (talk) 03:46, 9 August 2011 (UTC)

Response to Creationwiki[edit]

What is's response to Creationwiki's refutations of Index to Creationist Claims? What are its people's response? — Preceding unsigned comment added by (talk) 02:12, 4 August 2011 (UTC)

This is the Wikipedia science reference desk. Is this a question about a science-based matter? AndyTheGrump (talk) 02:16, 4 August 2011 (UTC)
Well, I think this is a science-based matter. But I don't see the need for more responses -- if there are some, will there need to be a response to the response to the response to each item, which is itself a response to a creationist claim? At some point one just has to rest one's case. Looie496 (talk) 02:59, 4 August 2011 (UTC)
This is a science matter but it isn't really something for RD/S. If you want responses, look in the web archives and some usenet archives of like Google Groups. This should be relatively easy. If you can't find any, this likely means none exists. You are welcome to start a thread on, observing appropriate netiquette (both general usenet netiquette and the specific netiquette of that group), if you really want responses but consider what Looie497 has said before you get your hopes up. Note even if anyone here posts to, they shouldn't be giving a response like they would on Bear in mind is just a usenet group, and the archive is primarily someone's archive of selected posts to the usenet group. There is no such thing as an 'official' response and if anyone did want to response, it would ultimately only be the response of that person. 06:42, 4 August 2011 (UTC)
Edit: As I expected, a quick search easily found a response to creationwiki on the archive site here, basically saying what Looie496 said. There is also some mention of creationwiki in this discussion [1] although I don't know if it's something in their rebuttal to the index. Bear in mind the archive has had minimal updating since 2006.
On the other hand, many discussions on the actual usenet group show up in a simple search [2] (safe search off), some of them may relate to the rebuttal to the index.
Nil Einne (talk) 06:55, 4 August 2011 (UTC)
It may be worth mentioning that the talk.* hierarchy was created especially to house discussions that tend to go back and forth forever with nobody ever changing their minds. Along with there's talk.abortion, talk.politics.mideast, etc. These groups have existed for decades, and every possible argument and counterargument has probably appeared there already; it's just a matter of finding it. -- BenRG (talk) 07:57, 4 August 2011 (UTC)

ABO/Rh retype[edit]

i got my medical check-up result,and was curious about the medical terminology.ABO  :O — Preceding unsigned comment added by (talk) 05:32, 4 August 2011 (UTC)

See blood type. StuRat (talk) 05:46, 4 August 2011 (UTC)

International space station[edit]

Do the space stations have the ability to transform electricity through any equipments to the earth? provide the answers as quickly as posible to my email if any — Preceding unsigned comment added by Ebysebastian (talkcontribs) 06:56, 4 August 2011 (UTC)

The ISS, and previous stations (Skylab, Mir, and the Salyuts) only generate a small amount of power, enough for their own use. People have suggested giant space power stations which beam power down to the earth - see space-based solar power. -- Finlay McWalterTalk 09:13, 4 August 2011 (UTC)
Agreed, they don't have the ability to transfer electricity to the earth. (Well, maybe a tiny amount, if they charged a battery there which returned to Earth with the Shuttle.) StuRat (talk) 22:05, 5 August 2011 (UTC)

humans on other planets[edit]

actually universe is huge...we born on earth .which is in milkyway galaxy and our star about the evidence of the aliens or living creatures on other galaxies ? they too have huge stars and some dwarf galaxies there any evidence or any reports those things? — Preceding unsigned comment added by Pebel vsrk (talkcontribs) 09:05, 4 August 2011 (UTC)

No evidence yet - see SETI. You need to clarify whether you specifically mean "humans" or "any intelligent life form". Humans are definitely unique to Earth. Roger (talk) 09:25, 4 August 2011 (UTC)
You know that how? --Trovatore (talk) 09:49, 4 August 2011 (UTC)
From the Australian Bureau of Statistics, "Our best estimates indicate that roughly 100% of all people live here." HiLo48 (talk) 10:25, 4 August 2011 (UTC)
Doesn't seem to be in the ref given. Anyway you haven't indicated how they would know.
If the physical universe has infinitely many galaxies, which it well may, and if there is a fixed positive probability of humans in any given galaxy, then by analogy to the infinite monkey theorem there is a probability of 1 (which is not the same as certainty — see almost surely) that there are humans in some other galaxy. Of course the "fixed positive probability" bit is a bit of a materialist assumption; it is not a given that "human" is definable in terms of configuration of matter. --Trovatore (talk) 20:45, 4 August 2011 (UTC)
Using the same argument, there must be a planet with intelligent pink flying pigs, or anything else you can imagine, and one identical to Earth except that this question was never asked! Seriously, though, I would remove the positive requirement on Trovatore's probability and get an answer of zero, but that is just my opinion. Estimates are just not valid from our slight knowledge of the origin of life because they "beg the question", and the universe might still turn out to be finite but unbounded. Dbfirs 07:35, 5 August 2011 (UTC)
The universe could turn out to be finite, but it might not. As I understand it the evidence is pretty balanced at the moment. That is, the confidence interval for the curvature includes the value zero — the simplest models for nonpositive curvature are infinite, for positive curvature, finite. There are compact models with negative curvature but in my admittedly non-expert opinion they come across as forced (they're things like a solid dodecahedron with opposite faces identified).
Curious why you think the probability per galaxy should be zero? Remember that you have to get exactly zero (or at least, for any positive ε, only finitely many galaxies where the probability is greater than ε) to avoid the conclusion that it will almost surely happen somewhere if the universe is infinite. Just saying the probability is not greater than one in isn't good enough. --Trovatore (talk) 08:39, 5 August 2011 (UTC)
Yes, I deliberately chose zero because of my opinion on the origin of life (but this is not the place to argue over opinion). The question also arises as to whether the theoretical existence of something (planets, intelligent life, pink flying pigs) at an infinite distance constitutes existence as we know it. I rather liked Andy's comment regarding the Drake Equation in an answer below. Dbfirs 12:02, 5 August 2011 (UTC)
See also our article on extraterrestrial life.--Shantavira|feed me 09:29, 4 August 2011 (UTC)
The only origin I can think of that would have a probability of exactly zero is some sort of deliberate creation, where the creator declined to do it elsewhere. I actually do believe in God, so I won't rule that out; I'm just curious whether that is in fact what you meant. It's a little hard to understand why God would have made such a big universe to put people in only one tiny corner of it, though.
As for infinite distances, there are no infinite distances involved in the scenario I'm talking about. The universe itself would be infinite, but the distance between any two points would be finite. So even if the existence of something infinitely far away would not constitute "existence as we know it", whatever that means, that doesn't change anything. If you meant that existence just so far away that we can never find out about it is not existence, well, that seems dangerously close to the rather discredited notion of logical positivism. --Trovatore (talk) 19:13, 5 August 2011 (UTC)
Yes, that's my reason for believing the zero probability, but I did say that it was only my opinion, not something I would try to prove. On the topology of possible universes, you are no doubt more knowledgeable than I, but I struggle to imagine an infinite universe in which all distances are finite, unless you are thinking of a Multiverse. Perhaps the universe is stranger than I can imagine? Dbfirs 19:49, 5 August 2011 (UTC)
Simplify — think of the real line. The real line itself is infinite, but the distance between any two points on it is finite. --Trovatore (talk) 19:51, 5 August 2011 (UTC)
Yes, sorry, my brain obviously wasn't functioning properly when I wrote the above. Your simplification occurred to me, and I (metaphorically) kicked myself before I read your reply. I should have compared the question of other intelligent life with the well-known question "Are there seven consecutive sevens in the decimal expansion on pi?" since we know the infinite structure of the straight line and mathematical 3- or 4-D space (-time), but we don't know the infinite "pattern" of pi. Dbfirs 06:43, 6 August 2011 (UTC)
... continued to explain my thinking ... The distance of the seventh consecutive seven in the decimal expansion of pi from the decimal point (using a metric of one unit per decimal place) could well be infinite -- no-one knows. By analogy, the distance from us to the nearest planet with pink flying elephants (or pigs or whatever you imagine) could well be infinite -- no-one knows. It all depends on whether an infinite universe is truly random, and that, currently, is a matter of faith, not science. Dbfirs 21:52, 6 August 2011 (UTC)

Evidence: Wow! did someone reply to our call? Cuddlyable3 (talk) 12:12, 4 August 2011 (UTC)

Before anyone jumps on to analyzing the atmospheric dynamics of hypothetical planetary systems in the reception-zone of the positive and negative feedhorns of the "Wow!" signal, how about the far simpler analysis of the PSRR of the signal processing circuit? How about the bit error rate of the digital computer that processed it? How about a root locus stability analysis of the analog and digital signal filters? How about intermodulation introducing an out-of-band signal into the spectrum under study? Four spurious samples of low-resolution data, with a duration lasting less than one minute, which have never been reproduced, do not constitute evidence of anything. I have never actually seen the circuits for the Big Ear; but I have spent a good amount of time in the formal and informal study of radio signal processing; and I see interesting bursts of noise every day. In all cases, if I care to investigate the noise, it invariably comes down to one of these benign factors; in other words, the "extraterrestrial signal" is "terrestrial noise." Very often, radio-noise is due to distant lightning strikes; or your neighbor opening their refrigerator door, causing the compressor to turn on, surging a few amps through the shared AC power transformer. The magnitude of these electromagnetic signals is much larger than any signal ever received from Outer Space - and they are noise. If you're lucky, you might be able to pick up extraterrestrial noise. At that stage, you can analyze its properties, compare it to known physics, and usually, you can say "hey, neat! My goofy radio contraption successfully detected ... radio signals from a stray electron in the high atmosphere that got a little hotter than usual because of direct sunlight." And you can publish your results in Science or Nature. Or something. But, to conclude extraterrestrial intelligence from four spurious samples defies any sort of procedural study of the signal. The Wow! signal is noise. This conclusion is obvious. Thorough understanding of radio physics, or at least an elementary primer in basic signal processing, is a prerequisite to legitimate radio-SETI. It is incredibly frustrating when legitimate scientific analysis takes a back-seat to populist sensationalism. Such silly and unfounded claims discredit the entire SETI effort. Or, to rephrase: if you don't know what noise looks like, how can you claim to know what a signal looks like? Nimur (talk) 18:19, 4 August 2011 (UTC)
Nimur you misrepresent the analysis by Dr. Jerry R. Ehman Ph.D. as having "concluded extraterrestrial intelligence from four spurious samples" that you declare are obviously noise. Please read his report to understand better. You are wrong about the received signal duration. Proper evaluation of the Wow! signal involves estimating the probability of a terrestrial source or conceivable combination of sources causing an emission on a frequency that is globally protected for radio astronomy and which, during its detection, matched the scanning lobe shape of a receiving horn that I understood to be calibrated against point sources in space that are not in dispute. You parade a select few signal-to-noise limitations as though they are relevant to faulty design of circuits for the Big Ear that you have not seen! Some extraordinary evidence is needed to back your claims that 1) serious radio astronomy is pursued oblivious to lightning and refrigerator power surges, and 2) you know things about signal processing that were not common knowledge to Ehrman and co-workers at Ohio State University Radio Observatory. Here is where you will find them now and here is more background information. Reading your post gives the impression that you are trying to discredit actual SETI work. Cuddlyable3 (talk) 17:59, 5 August 2011 (UTC)
The report linked above was never subjected to peer review. There is no shortage of academic, industrial, and professional journals that would be happy to publish meritorious, high-quality scientific results related to experimental radioscience. That's all I have to say about this subject. Nimur (talk) 20:08, 5 August 2011 (UTC)
Yes Nimur, professional journals such as Astronomical Journal, Vol. 72, p. 793, Observations of Planetary Nebulae at λ3.75 cm., Author: Ehman, J. R. I believe you have nothing to say about Ehman's work or qualifications. Cuddlyable3 (talk) 21:30, 5 August 2011 (UTC)
Two points: (1) the article you have just linked makes no mention of the Wow! signal; (2) ... because its publication date is 10 years prior to the reported Wow! signal. Did you even read it? It was a brief paragraph about radio observations. I too have authored brief paragraphs about radio observations in peer-reviewed journals; that fact does not mean everything I say about space-aliens is true. The fact that a scientist may have previously presented solid work in a journal does not mean that all his future work is infallible. I did not say anything about Ehman's work or qualifications. I made a very specific statement: this report, which you linked earlier, was not subject to peer review. I don't really feel like your argument is going anywhere; but, you may choose to believe whatever you like. If you want to believe that the Big Ear report and the Wow! signal represent good science, you are entitled to your opinion. Nimur (talk) 23:57, 5 August 2011 (UTC)
Nimur, you complained about Ehman's work in terms of "goofy radio contraption", "populist sensationalism" and "silly and unfounded claims". Some explanation of how a scientist able to present solid work in a peer reviewed professional journal has allegedly decayed so much so fast is called for. What are you saying, if anything, about space-aliens? I indented your post as a reply to mine and hope you don't mind. Cuddlyable3 (talk) 13:49, 6 August 2011 (UTC)
So you argument is... the fact that his work a decade previous was peer reviewed makes up for the fact that the work in question was not? If that's the case, I have some shares in a cold fusion plant I'd like to sell you... and maybe a little intelligent design as well! (As well as some N-rays, if you're feeling flush...) --Mr.98 (talk) 02:41, 7 August 2011 (UTC)
Nimur, somewhere occluded by your mockery you have asserted three - 3 - times that Dr. Ehrman's work report is not peer reviewed and therefore (?) does not represent what you call good science. After defining a question the scientific method starts with observation of data and proceeds to formulating a falsifiable hypothesis. You may find Peirce's explanation of Abductive reasoning enlightening. The SETI activities that you find so discredited has a defined question and is in the data collection phase. It has not yet produced a falsifiable hypothesis for an obvious reason: the present lack of cooperative aliens. When and if these things are in place you may see peer reviewed articles. For now, investigations proceed by the work of many well qualified (but under-funded) workers while you just present your superior thoughts here. Your latest mocking comparisons with cold fusion fraud etc. are offensive. Cuddlyable3 (talk) 10:32, 7 August 2011 (UTC)
There is as of yet no really compelling evidence. As to the likelihood of estimating the probability of anyone being "out there" to receive and reply to a signal, you might check out the Drake equation, which at least helps to clarify exactly what would go into such an estimation of probability. Personally I am pretty pessimistic about the idea of useful two-way communication between Earthlings and anyone else, unless special relativity is very, very, very incorrect or the quantum world grants some kind of work-around. --Mr.98 (talk) 14:22, 4 August 2011 (UTC)

World War II US Submarine Equipment[edit]

I would like to know what companies made periscopes and TDC's for US submarines of WW II, please (talk) 11:09, 4 August 2011 (UTC)

On page 280 of U.S. Submarines Through 1945: An Illustrated Design History by Norman Friedman, it states that "C&R" (Convoy and Routing?) called for bids for 10 periscopes to its 1929 specifications in January 1930. It goes on to say that "all three manufacturers bid." This appears to refer to Kollmorgen, Barr and Stroud and Nedinsco (Nederlandsche Instrumentim Compagnie), a subsidiary of Zeiss. Kollmorgen won the bid. Unfortunately, that's as far as Google Books would let me see. This periscope manual published just after World War II lists five manufacturers: the three I've already mentioned, Keuffel and Esser and Bausch & Lomb. According to this Undersea Warfare magazine article, Kollmorgen was also "the dominant U.S. periscope manufacturer" of World War I. Hope that helps. Does TDC stand for Torpedo Data Computer? Clarityfiend (talk) 21:07, 4 August 2011 (UTC)

Temperature inside an atomic nucleus, & what if it were cooled[edit]

Hi, I've heard that a sample of rhodium was recently cooled to 10^(-10)Kelvin, just above absolute zero. That being true, isn't it also true that the temperature inside each of the many nuclei in the sample was higher? Would it be possible someday to cool the nuclei as well, slowing the internal motions inside each nucleus? Thanks, Rich Peterson24.7.28.186 (talk) 11:59, 4 August 2011 (UTC)

Temperature is a property of the bulk material. You really start to get into problems if you try to define temperature for an individual molecule or atom. Furthermore, absolute zero only defines zero molecular motion, not zero energy, so there will still be, for example, exchanges of gluons and mesons inside of the nucleus which are holding it together, and those interactions will occur even at fractional kelvin temperatures as low as you note. --Jayron32 12:35, 4 August 2011 (UTC)
  • So I've heard(about absolut zero and zero point motion). What's your point?-Rich Peterson199.33.32.40 (talk) 00:34, 5 August 2011 (UTC)
I'm not sure what you mean that absolute zero ... defines zero molecular motion. Surely molecules as well have zero-point motion; it's just smaller than it is for smaller particles. This is a good place to remind everyone that temperature, in general, is not about kinetic energy. --Trovatore (talk) 20:58, 4 August 2011 (UTC)
The nuclei of stable isotopes are already in their ground state and cannot be cooled any further. Unstable nuclei release excess energy when they decay which happens spontaneously. The concept of temperature doesn't really make sense for such a small system. Dauto (talk) 14:26, 4 August 2011 (UTC)
  • the thermo article here seems to say that ten fermions is enough. Wouldn't a rhodium nucleus have about 100 fermions?--How do we know a stable nucleus can't be cooled? Are you saying that in principle it can't be cooled further(except, when an alpha particle once in a while tunnels out, say), or that so far it has never been observed or method devised? Thanks. (talk) 00:34, 5 August 2011 (UTC)
It can't be cooled because there are no accessible states with lower energy so no energy can be removed from the nucleus. The number of particles here is not important. What's really important is the distance between energy levels which is of the order of 1 MeV. That means that excited states only become accessible at temperatures around 10 billion Kelvin (Give or take an order of magnitude). At energies much lower than that the nucleus effectively behaves as a single particle with no internal structure. Dauto (talk) 02:59, 5 August 2011 (UTC)
Maybe the OP is thinking of a Bose–Einstein condensate. Roger (talk) 14:36, 4 August 2011 (UTC)
What makes you think that could be the case? There is nothing about that in the question. Dauto (talk) 15:41, 4 August 2011 (UTC)
Hmmm, do nuclear isomers represent a "temperature" of sorts? Wnt (talk) 18:17, 5 August 2011 (UTC)
In principle I suppose they could, if you had enough excited states available that the behavior of the system started to become stochastic. But it doesn't make any sense that I can see to say, for example, that technetium 99m has a "higher nuclear temperature" than techetium 99, because it's just a single step from one to the other. There is no identifiable equilibrium around, and without some notion of (at least approximate) equilibrium, thermodynamics makes no sense. --Trovatore (talk) 19:47, 5 August 2011 (UTC)
Well, what about if we(if we could)heated up a stable isotope of uranium into a million degree plasma and observed a .1% decrease in halflife? Wouldn't that mean tunnelling out of the nucleus was becoming more probable, hence indicating a higher temperature inside?RichPeterson199.33.32.40 (talk) 22:07, 5 August 2011 (UTC)

Green birds in Greater London[edit]

I was startled by the sight of a flock of about 20-30 birds whizzing past my window yesterday. They were all bright green. I'm no bird expert (hoping someone here is) but they put me in mind of parakeets, but I only got a fleeting glimpse, so can't ofer much more description. Any good ideas what they might have been? (Surely not parakeets?) --Dweller (talk) 12:48, 4 August 2011 (UTC)

Probably parakeets. Grandiose (me, talk, contribs) 12:51, 4 August 2011 (UTC)
Rose-ringed Parakeets (aka Ringnecked Parakeets), perhaps? There are several self-sustaining populations of feral parrots in the UK... --Kurt Shaped Box (talk) 13:04, 4 August 2011 (UTC)
That's unbelievable... thank you, it could well be. If you can point me to any photos of a bird (or flock) in flight, that'd be great. --Dweller (talk) 13:10, 4 August 2011 (UTC)
Is File:Psittacula krameri -Whitefield, Bangalore, India -flying-8.jpg of any use to you? Take a look at Alexandrine Parakeet too - it's a similar-looking (but larger), closely-related species that is also sometimes found as a feral bird, though less often. --Kurt Shaped Box (talk) 13:17, 4 August 2011 (UTC)
Ah. Now I'm not so sure. While I only got a fleeting look at the disappearing flock, I don't recall their tail feathers being so fan-like. I thought their shape in flight might, repeat might have been more swallow-like...? --Dweller (talk) 13:50, 4 August 2011 (UTC)
Okay... How about the Monk Parakeet - in flight: File:Myiopsitta monachus -Florida -two flying-8b.jpg, though I suppose that you would have noticed the grey colouration? I believe that there are some in the UK. TBH, I couldn't tell you what they look like when moving - I've only ever seen this parrot in photos. Have you checked out these species on YouTube, btw - I suspect that there will be HQ video of all of them in flight (probably pets flying around someone's front room), and there may even be vids of the specific flock of feral birds that you saw... --Kurt Shaped Box (talk) 15:22, 4 August 2011 (UTC)
I think they must have been parakeets, especially now you've convinced me there's considerable variety in tail feather appearance between varieties. Yes, I'll check out Youtube. How extraordinary. Never seen them before. --Dweller (talk) 15:27, 4 August 2011 (UTC)

Yes they're parakeets. I see them almost every day now. (talk) 14:17, 4 August 2011 (UTC)

They have certainly been there since the 1960s. I recall as a child being told that they escaped from a pet shop on the Goldhawk Road. There was also a flock of Budgerigars but they don't survive cold winters so well.Elen of the Roads (talk) 15:34, 4 August 2011 (UTC)

Yup, Rose-ringed Parakeets. There is a large population from the west London suburbs (see Kingston parakeets), all the way up the Thames valley. A common sight, though they often draw attention more by their noisy calls. If you saw a flock of thirty, I'd suspect that they were roosting nearby. AndyTheGrump (talk) 15:44, 4 August 2011 (UTC)
Also hawks and owls hate Budgerigars for being tame, its a bit harder for them to catch Paras.
There's been a wild flock of wild parakeets at Englefield Green for over ten years now but recently the population seems to have exploded for some reason. Was at a barbee over at Egham on Friday, there were litteraly hundreds of them flying over the garden, some came within 10 feet of us. We were like Whoa!!! So spectacular... If you want to photo them Runnymede Park is a happy hunting ground. FeydHuxtable (talk) 15:58, 4 August 2011 (UTC)
Just to prove the point about how common they are, I've just had two fly past my window (SW London suburbs), squawking loudly... AndyTheGrump (talk) 18:06, 4 August 2011 (UTC)
I can only assume nothing eats them. London clearly needs the return of the Red Kite, successfully reintroduced into Northamptonshire about 10 years ago. Elen of the Roads (talk) 20:23, 4 August 2011 (UTC)
I suspect that a Kite would prefer easier targets. The parakeets gregarious nature will make preying on them difficult, and they are agile fliers - and Kites generally prefer to scavenge anyway. One might be tempted to introduce the parakeets natural predator (whatever that is) to control the population, but that is a tactic that has misfired before. I think the ecosystem of south-east England has bigger problems than the parakeets anyway - and ironically, the London suburbs, where our noisy friends have settled, are probably more ecologically diverse than the small remaining areas of 'nature' we have. Then again, for a bird that evolved in the mountain uplands, an ecosystem consisting of tree-filled gulleys between vertical cliffs is probably ideal - we think we live in a man-made environment, but the parakeets may see it differently. AndyTheGrump (talk) 03:42, 5 August 2011 (UTC)
More info on parakeets in London here, here, and here. What I find unbelievable is that there are some people in London who don't know about them... !! Ghmyrtle (talk) 09:13, 5 August 2011 (UTC)
I live in east London, a mile and a bit from the Olympic Park, and had never seen one until a visit to Kensington Gardens last month. It seems they are fastidious in their choice of neighbourhood! Alansplodge (talk) 16:48, 5 August 2011 (UTC)

what effects onbody organs human hanging death[edit]

dear sir,

human hanging death ,deadd body organs is it use full for donate or transplent like eye,kidney,lungs .
after death how much time for donate human body organs

thanks & regards shivkumar(india) — Preceding unsigned comment added by (talk) 17:47, 4 August 2011 (UTC)

A better question is what effects DON'T onbody organs human hanging death. --Goodbye Galaxy (talk) 18:33, 4 August 2011 (UTC)
A lot depends on the exact method of hanging used. See Hanging#Medical effects for details. Beeblebrox (talk) 18:53, 4 August 2011 (UTC)
At the very least, it pretty much rules out a neck transplant. ←Baseball Bugs What's up, Doc? carrots→ 19:17, 4 August 2011 (UTC)
removed OP's email Bazza (talk) 15:09, 5 August 2011 (UTC)
Good question. I'd think that organs in the head, like the eyes, might be damaged by a spike in blood pressure. The jerk at the bottom isn't so severe that I'd expect it to damage the organs of the abdomen. Then the other issue is that you'd need to remove those organs immediately upon death. This contrasts with cases where somebody is brain dead, but the body lives on in a hospital, where the organs don't need to be removed until the recipient is prepped for surgery. So, this might be a rather limiting factor with hangings. StuRat (talk) 22:01, 5 August 2011 (UTC)
Mike the Headless Chicken lived for 18 months. This suggests that a brain-dead hanged body can be kept alive for a while. Do not try this at home. Cuddlyable3 (talk) 13:32, 6 August 2011 (UTC)

Freeview signal, UK[edit]

1) Why do some channels have a stronger signal than others? Shouldnt they all be the same? 2) How many Freeview channels could be encoded into one analogue TV channel? (talk) 19:41, 4 August 2011 (UTC)

The answer to 1 is that it still depends how far you are from the television mast, and what the intervening terrain is like. As to 2 - I'll leave that to the engineers among us. --Elen of the Roads (talk) 20:26, 4 August 2011 (UTC)
Almost all UK TV terrestrial TV reception antennas are directional Yagi antennas with reflectors. They have to be pointed at the broadcasting tower. To receive signals from two different towers you'd need two different antennas feeding the same outlet, which is a very rare thing to do. So, for a given receiver, if you're receiving two channels they're still from the same tower. -- Finlay McWalterTalk 20:42, 4 August 2011 (UTC)
Freeview (that's UK Digital Terrestrial Television broadcast using the DVB-T standard) broadcasts a bunch of channels in one digital stream, at a given frequency. That's called a "multiplex" - this page lists the different multiplexes. So you'd expect to see the same signal strength for BBC1, BBC2, BBC3, BBC-News, and the others in the same miltiplex (because they're all carried on the same stream on the same frequency). A different multiplex, at a different frequency, is going to have somewhat different strength: so ITV1 and Five should be the same as one another, but not necessarily the same as BBC1. Wikipedia has some pretty detailed articles about specific transmitter towers - looking for example at Emley Moor it lists the frequencies at which each multiplex is broadcast; with a bit of digging you should be able to figure out the tower and frequencies that you're receiving. As you can see in the Emley Moor article they don't broadcast all the muxes with the same power. Even if they did, radio signals at different frequencies propagate differently: they interact differently with the atmosphere and with water suspended in it, they diffract over the terrain differently, and interact differently with your general-purpose TV antenna. -- Finlay McWalterTalk 20:28, 4 August 2011 (UTC)
As to your second question (about how many digital channels one can fit into the space freed by turning off an analog TV channel in analog switchoff) - it depends on how they configure the MPEG compression for a given subchannel - they're currently fitting 7 conventional subchannels onto MUX2, for example. HD channels will typically consume much more bandwidth, and so you'd expect to see fewer on a given MUX. This is much the same arrangement for digital radio (T-DAB); the UK's DAB service has been criticised for having too many channels and so having to reduce the effective bitrate for each stream (see this article). A very informative paper about analog switchoff in Europe is here. -- Finlay McWalterTalk 21:09, 4 August 2011 (UTC)

Brownian ratchet[edit]

Hi, I have a couple of questions about the Brownian ratchet setup, but with ratchet disconnected, leaving just the paddle wheel, free to rotate as it chooses. Assume the paddle wheel is massless and frictionless.

1. Does the paddle wheel do a random walk, so that eventually it will inevitably have rotated by any given amount, just as tossing a coin will inevitably eventually produce any given surplus of heads over tails or vice versa? If so, does this rotation occur at zero energy cost?

2. As the vanes of the paddle increase in size (remember it's massless and frictionless), all other things being equal, do the random movements of the wheel, measured as angular displacement, become larger, smaller, or remain the same? (talk) 19:59, 4 August 2011 (UTC)

  1. Yes, and yes.
  2. The random movements become smaller because the number of collisions grow proportionally to the area but the surplus collisions in one direction due to random walk only grows proportionally to the square root of the number of collisions becoming statistically less important for larger objects.
Dauto (talk) 20:17, 4 August 2011 (UTC)
Thanks. As regards (2), I can see the surplus grows on average with the square root, but isn't the surplus the only thing that matters? More surplus = greater movement? (talk) 21:13, 4 August 2011 (UTC)
If the paddle wheel is massless, its behavior when a particle hits it doesn't seem to be very well defined. What happens to it and to the particle? Rckrone (talk) 23:22, 4 August 2011 (UTC)
The massless thing was inspired by the article Brownian ratchet, but looking more carefully, I see that actually only the conecting rod is said to be massless. I don't exactly understand why, if the other parts have mass, it's necessary to specify that the rod is massless. But, in any case, if it makes no sense for the paddle mass to be actually zero, then can we just say that it is negligibly small? I guess really I just didn't want the increasing mass of a huge real physical wheel to be taken into account when calculating the scaling behaviour that I was asking about. (talk) 23:41, 4 August 2011 (UTC)
Yeah, after thinking about it I realized that if you just take it to be vanishingly small, the spot on the wheel where the particle hit would get velocity twice the component of the particle's velocity in the angular direction, so it's not really a problem. Anyway, the angular velocity of the paddle wheel after a collision would depend on how far from the axis the particle hit it. If the wheel is bigger, more particles are hitting farther from the axis so the angular speed after each collision would be smaller on average. Rckrone (talk) 23:48, 4 August 2011 (UTC)
So, if k^2 is the vane area, we're first of all saying that average surplus collisions is proportional to k. Then these collisions are evenly distributed over radial distance 0 to some number proportional to k. And this all adds up to a net decrease in average angular motion as k increases? (talk) 00:53, 5 August 2011 (UTC)
If the mass of the paddle wheel is small compared to the particles, its angular velocity doesn't really accumulate. Instead the angular velocity at any given time is completely determined by the last particle to have hit it. That said, the average angular speed depends only on the speed of the particles and the radius at which they hit the paddles. The number of collisions doesn't matter. Rckrone (talk) 01:59, 5 August 2011 (UTC)
No wait, this isn't quite right. The paddle wheel basically gets pushed around bouncing of the particles, but if two particles come pushing it from opposite directions they can pinch the paddle wheel and be deflected in some way. I think the paddle wheel speed will get very high in this situation as it gets reflected back and forth, but I'm not sure what the speed will be after the particles are deflected. I think the moral of the story is that the wheel behaves weirdly if it doesn't have appreciable inertia. Rckrone (talk) 02:10, 5 August 2011 (UTC)
The wheel speed can be calculated using the Equipartition theorem which gives
Where omega is the angular speed. That gives unsurprisingly an infinite speed for a massless wheel. Dauto (talk) 03:11, 5 August 2011 (UTC)
Although the momentary speed might have to be factored in somewhere in the calculations, what I'm ultimately interested in is the overall rate of progress of the wheel. I may have this wrong, but if it's a random walk, then I think there should be a single parameter characterising the "speed" of the walk. To model this we can say that in each very small timestep Δt, the wheel will move c*sqrt(Δt) radians in a random direction, then c is the number I'm interested in (does that sound right?) (talk) 02:34, 5 August 2011 (UTC)

Living liquid[edit]

Would it be possible to have a living liquid? Whoop whoop pull up Bitching Betty | Averted crashes 20:47, 4 August 2011 (UTC)

Do you mean like a Changeling? Dauto (talk) 20:53, 4 August 2011 (UTC)

Or an amoeba? --Jayron32 20:55, 4 August 2011 (UTC)
Yeast frequently exists as a liquid. Those eternal cell lines that the oncologists use are liquids. Amoebae are just liquid in a bag - but then the human body is mostly water. I suppose it depends on how you define 'liquid' in a biological, rather than a physical sense. --Elen of the Roads (talk) 21:17, 4 August 2011 (UTC)
Yeasts (and other laboratory cell lines) exist as cells suspended in a liquid; it is incorrect to describe them as liquids. Cells don't exist as single phases of matter. They contain several distinct solid, liquid, and 'fluid' phases. TenOfAllTrades(talk) 23:31, 4 August 2011 (UTC)
This is a somewhat complicated question to answer. When the molecules suspended in a liquid become too large, it starts to be called a "colloid"; if they're large enough it becomes a "solid" (like plastic). I vaguely remember reading that around the turn of the 20th century much was made of the colloidal nature of life, before thinking about it that way became passe. In somewhat a similar way, a cell is made up of a droplet of liquid surrounded in a membrane which is also liquid (though without more reinforcement from extracellular matrix (more or less a solid) such a cell is quite vulnerable anyway) - but is a vesicle or a liposome a "liquid" in the same sense that a homogenous solution would be considered one? So when asking how to make liquid life... well, it seems like mostly a matter of creative description. If you want to avoid the cell membrane, you might consider a virus; or you could imagine some complex "cell" in which all the biochemical components are covalently linked together so no membrane is needed; but if it's too big it would sediment in a test tube on standing and would that count as a liquid? ... I think the boundary blurs as you look at it. Wnt (talk) 05:18, 5 August 2011 (UTC)
I meant (sort of) a large multicellular organism that is held together only by surface tension and the other forces holding liquids together. Whoop whoop pull up Bitching Betty | Averted crashes 11:50, 5 August 2011 (UTC)
How about some slime mold? Wouldn't that be a viscous liquid for some species anyway? Googlemeister (talk) 16:21, 5 August 2011 (UTC)
Well, the issue is, what's the difference between a dissolved solid and a wet solid? Especially when it contains a vast range of different compounds? Because proteins crystallize, we know that their interactions are sufficient to make them solid; so in order to exclude forces that hold solids together, the hypothetical lifeform should have no protein-protein interactions - or at least none on a large scale (how large?). Non-Newtonian fluids are confusing enough with just one or two ingredients. Wnt (talk) 16:44, 5 August 2011 (UTC)

Hanging: suicide or execution?[edit]

If someone is about to be judicially hanged, but they jump off the platform themselves, is it considered suicide or execution? Whoop whoop pull up Bitching Betty | Averted crashes 20:50, 4 August 2011 (UTC)

You're thinking of the last man to enter Parliament with honorable intentions? --Trovatore (talk) 20:51, 4 August 2011 (UTC)
In UK law it made no difference - death on the scaffold was always considered to be execution, particularly as the death penalty usually specified what was to be done with the body. In any case, suicide was until recently considered a mortal sin by the Christian church, while the abovementioned Guido Johnson was (possibly still is) hailed as a martyr. --Elen of the Roads (talk) 21:38, 4 August 2011 (UTC)
1) The Catholic Church does not consider Guy Fawkes a martyr, and I'm not sure it ever did. He was executed for trying to kill people, not for his faith. 2) The official position of the Catholic Church on suicide includes "Grave psychological disturbances, anguish, or grave fear of hardship, suffering, or torture can diminish the responsibility of the one committing suicide." [3] I think avoiding being drawn and quartered is a pretty fair 'grave fear' of 'torture', especially given that the torture was intended to imminently kill him anyway. (talk) 12:20, 5 August 2011 (UTC)
Surely a person who jumps away from certain death is no suicide, whether he breaks his neck or not. It makes me wonder, though, whether we would be unpleasantly surprised to find out who is celebrated as a martyr on September 11, 2201... Wnt (talk) 23:23, 5 August 2011 (UTC)
We would be pleasantly surprised just to be alive in 2201. Cuddlyable3 (talk) 13:26, 6 August 2011 (UTC)
At least as far as the long drop method formerly used in the UK is concerned, there was no platform to jump off: the drop was achieved by a large double trapdoor that opened under the victim. Picture here. AndrewWTaylor (talk) 11:29, 5 August 2011 (UTC)