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August 1

Block erasure

Why can flash memory be read and written one cell at a time, but only erased in blocks? I've read the flash memory article, and it seems that erasure is just a matter of bringing the control gate low and the drain high, which doesn't seem any more complicated than programming the bit. --140.180.16.144 (talk) 00:19, 1 August 2011 (UTC)

It is a different mechanism. Imagine a flash memory made up of buckets of water. You can ask whether any particular bucket is full. You can fill any particular bucket. Or you can pull the "single" bit of string that opens the bottom of a whole block of buckets to erase the block. Obviously it could be done differently, but memory manufacturers have decided that the block erase method is a commercially satisfactory compromise between being unable to erase at all and being able to erase any particular cell. -- SGBailey (talk) 11:40, 1 August 2011 (UTC)

Disulfiram and fetal alcohol syndrome

I had an episode "Choice" going in the background, where a pregnant woman ends up being sentenced to a court-ordered alcohol treatment program to avoid fetal alcohol syndrome. I became curious whether the notoriously unpleasant combination of Antabuse (disulfiram) and alcohol would increase the risk of FAS, and found some references suggesting that acetaldehyde, which is what builds up when the drug is taken to interfere with alcohol degradation, does indeed have teratogenic effects,^[1][2] though one study found that disulfiram didn't make these worse.^[3] All these studies were quite old, and seemed to mark this as a question of some public health importance, yet I'm reading that disulfiram has remained "FDA pregnancy category C" with no information about whether it is harmful or not to pregnant mothers. How is it that this question has never officially been sorted out one way or the other? Wnt (talk) 01:21, 1 August 2011 (UTC)

Prob'ly 'cause it takes a long, long time to do clinical studies in humans. FWIW 67.169.177.176 (talk) 01:43, 1 August 2011 (UTC)

Well, you certainly can't do a proper clinical trial to look for teratogenicity in fetuses - but you can look retrospectively at what happens when the mother chose to take the drug vs. not, with certain pitfalls. Wnt (talk) 01:50, 1 August 2011 (UTC)

Insane to order her to go on antabuse when she could be incarcerated for nine months and given valium to control the withdrawal symptoms. Rather silly premise. μηδείς (talk) 02:00, 1 August 2011 (UTC)

Incarcerated on what charge? I don't think I saw the episode, but the brief description at the linked article doesn't mention any criminal act on her part. --Trovatore (talk) 08:19, 1 August 2011 (UTC)

The question says "sentenced", does it not? μηδείς (talk) 01:45, 4 August 2011 (UTC)

Sorry - this wasn't really a question about the episode, which never specifies what sort of treatment would be given at all. It just got me wondering whether authorities, one place or another, might be causing fetal alcohol syndrome with their forceful efforts to prevent it. Wnt (talk) 17:11, 1 August 2011 (UTC)

popularizing chemistry

I feel that many natural science branches like biology and physics are more popularized than chemistry.Am I wrong?If so, why is chemistry less popularized? Is it hard or something?--Irrational number (talk) 01:26, 1 August 2011 (UTC)

I dunno -- as a chemist, I don't find it hard at all. Maybe it's just that there's not as much earth-shaking basic research (as opposed to the more mundane but more useful applied research)? 67.169.177.176 (talk) 01:37, 1 August 2011 (UTC)

I think that there's a lot more biology being publicly funded than chemistry, which I think of as being done much more by corporations. Public funds encourage researchers to talk up (if not hype) their research to the public, whereas proprietary research tends to be done in secret, and when discussed by company employees, tends to be disbelieved by a skeptical public. Wnt (talk) 01:41, 1 August 2011 (UTC)

Plus, there are negative stereotypes of chemistry being a "dirty" science (as opposed to biology, which is "natural" and therefore supposedly "green"). 67.169.177.176 (talk) 01:45, 1 August 2011 (UTC)

I would be quite surprised if there was any correlation with amount of public funding received and amount of popularization. The areas of popularization are fairly narrow (a handful of sub-questions of each field, even in physics and biology), whereas the areas of public funding are quite broad. Furthermore, it isn't the case that popularizing your particular discipline (say, physics) is going to result in increased public funding for that discipline, as generally speaking most public funding of science goes into a big NSF pot that is then doled out by the NSF administrators and reviewers, not Congress or "the public" to any degree (and let's thank goodness for that!). --Mr.98 (talk) 01:55, 1 August 2011 (UTC)

This is quite an esoteric question - no way to clearly say exactly which part fits in which branch, and so forth. And, it depends what timeframe you look at, what countries you look at, all the problems of cross-field-studies (is astrophysics chemistry? Molecular modelling? etc) Depending on how you choose to divvy up "The Sciences", you'd get vastly different results. A related article, which might serve as a starting point, is Natural science. Personally, I don't think it is related to difficulty; it could relate to trend/fashion, and could relate to the way subjects (for e.g. Degree-level) are constantly being subdivided. I bet there's a bit of Chemistry included in various Quantum mechanics courses, and in a cooking degree. Is a chef a chemist?  Chzz  ►  01:51, 1 August 2011 (UTC)

In the United States, physics started being really popularized initially after WWII, because of its association with wartime weapons. In more recent years its ability to tell stories about our origins (e.g. cosmology) kept it relevant in the popular mind, and the "mind-blowing" aspects of quantum and relativity make for rather heroic (if often misunderstood) narratives. Biology is mainly popularized via discussions of evolution and genetics, both of which are quite popular in that they again tell stories about our origins and our current selves. Genetics has been of popular interest in the US since the 1920s or so, in part because of its connection with eugenics and race and all that, which really touch pretty deep into major American preoccupations. As for chemistry, there just doesn't seem to be as much popular association. In the best of times it is associated with industry and development; in the worst of times, with all of the excesses and downsides of industry and development (pollution, DDT, whatever). The aspects of it that do pertain to origin stories or selfhood quickly become assimilated into other fields (e.g. cosmology, again). Chemistry does not appear to tell very heroic stories about humanity or its place in the universe, though there is no inherent reason it need not. --Mr.98 (talk) 01:52, 1 August 2011 (UTC)

Here in Australia we have a major political leader who has publicly declared twice in the last week that carbon dioxide is difficult to detect because it's invisible, tasteless, odourless and weightless. That he was able to say it twice without embarrassment shows the poor public situation chemistry is in. HiLo48 (talk) 01:58, 1 August 2011 (UTC)

Wait til he finds out about the insidious chemical, dihydrogen monoxide. :-) StuRat (talk) 02:31, 1 August 2011 (UTC)

Common name, "Copious water"; always labelled "use sparingly" ;-)  Chzz  ►  06:54, 1 August 2011 (UTC)

Simplistic answer: Because as far as the environmentalist, organic food and natural health "industries" (both the crackpot and nominally rational varieties thereof) are concerned, chemistry is the Great Satan!(tm). The major selling point for much of food and "natural" medicines and other products advertising is the claim that they "contain no chemicals" and the gullible uneducated public swallow it whole. The chemical industry has simply been totally and utterly crushed in the propaganda war for public consciousness - probably because they never even noticed there was a war on until after they had already lost it. Roger (talk) 11:29, 1 August 2011 (UTC)

Did anyone tell him carbon monoxide, radon, sarin and a number of other substances he probably does want someone to regulate are also odourless, 'invisible' (presuming this means colourless) and tasteless? Nil Einne (talk) 01:36, 3 August 2011 (UTC)

DNA testing of cremains

On a past set of episodes of the show Dexter, the forensics people performed DNA testing on a very small amount of cremated remains and were able to compare its DNA with the DNA from some nearby saliva and determine the two people were related. Is it actually possible to perform any useful DNA analysis on ashes? To forestall a particularly useless type of response seen pretty often on the Reference Desk, I will note in advance: Yes, I am aware that teleplays are works of fiction, and that authors of fiction often write things that are not possible. Comet Tuttle (talk) 02:50, 1 August 2011 (UTC)

Only if the cremation was done improperly. When a murderer splashes gasoline on a body and lights a match, for example, lots of DNA will likely remain. StuRat (talk) 02:57, 1 August 2011 (UTC)

(edit conflict)Doing a google search, I have found private companies that will take your money to do it for you: Here is but one example. However, others debate that this is normally viable in a properly done cremation: This page says that it isn't possible; This page says that it may be possible if teeth survived the cremation process. Neither of those are what I would call scrupulously reliable, but the College of American Pathology at least has a name that sounds credible, and they say that under normal cremation conditions, there is no way to get DNA. Apparently DNA can survive a "few hundred degrees" for a short time; the reference notes the possibility of recovering DNA from building fires, but cremation conditions (in excess of 2000 degrees C for in excess of 2 hours) doesn't leave anything behind. --Jayron32 03:04, 1 August 2011 (UTC)

Great references - thanks, Jayron32! Comet Tuttle (talk) 16:30, 1 August 2011 (UTC)

energy solution

Suppose public land in each County could be set aside and populated with solar farms and energy storage devices to form a giant power grid sufficient to supply all of the electricity needs of the United States and that this could be done for substantially less cost than the 14 trillion dollar deficit. Is there any reason why this could not be done immediately? --DeeperQA (talk) 04:45, 1 August 2011 (UTC)

Sure, you want to clear all of the nature off of the little bits of greenspace we have left? Turning earth into Coruscant doesn't sound like all that great of an idea... --Jayron32 04:54, 1 August 2011 (UTC)

Besides all other reasons, it is a long term solution, in the short term, it would only make the deficit grow. Plasmic Physics (talk) 04:56, 1 August 2011 (UTC)

Sorry, I did not think it necessary to mention that I am looking for scientific rather than financial or contrived reasons. For instance their are plenty of ways to avoid using green space which produces a little be of oxygen and if you can get rid of the deficit budget and opt for a surplus budget then you can solve two problems with one action. Please try again. --DeeperQA (talk) 05:06, 1 August 2011 (UTC)

So, you've invented a magical world where considerations like money and the environment don't matter, and you're asking us to critique it? With infinite resources and no financial or environmental concerns, you could do anything. By your criteria, you could set up a power grid based on hamster wheels if you wanted. Your solar system could be built if you had literally no other concerns at all. Back here in the real world, these concerns are important... --Jayron32 05:15, 1 August 2011 (UTC)

No need to be sarcastic, you could just have said that you don't perseive any scientific barriers, and that all the possible barriers are economical and evironmental in nature. (or something along these lines) Plasmic Physics (talk) 06:13, 1 August 2011 (UTC)

No. What I am asking is that you consider the end results and whether the end results would be sufficient to overcome real world difficulties instead of artificial difficulties such as already mentioned. --DeeperQA (talk) 06:05, 1 August 2011 (UTC)

Okay, how about this... Instead of going to Mars how about constructing such a grid? Would not that be a better project? --DeeperQA (talk) 06:18, 1 August 2011 (UTC)

Better in terms of what? Plasmic Physics (talk) 06:22, 1 August 2011 (UTC)

You name it. --DeeperQA (talk) 06:35, 1 August 2011 (UTC)

...err, I will rule out one: dealing with the aftermath of a giant asteroid hitting the US and blocking the radiation from the Sun. --DeeperQA (talk) 06:38, 1 August 2011 (UTC)

What I mean is, how are you comparing going to Mars against constructing such a grid? I frankly don't know what you want us to tell you. Plasmic Physics (talk) 07:10, 1 August 2011 (UTC)

I can not explain my question further. It seems clear to me that solar offers a global solution to energy needs and that cost can be handled in many ways. That leaves only the question of whether the science and technology at this point in time is sufficient to begin such a project now rather than wait until the only place to live is in outer space. --DeeperQA (talk) 08:25, 1 August 2011 (UTC)

I think if you have all these trillions of dollars available, investing in nuclear fusion would be a more assured long-term solution to energy supply, though there would be a longer delay before the investment paid off. Dbfirs 08:13, 1 August 2011 (UTC)

Obviously you can not create a 14 trillion dollar deficit unless the resources are available to do so and Chernobyl and Fukushima are good reason to avoid conventional fission based nuclear perhaps except for Thorium based fission rectors. --DeeperQA (talk) 08:25, 1 August 2011 (UTC)

If, like you said resources is not an issue, then either a massive scale solar project and colonising space are both possible projects. But, I'm not such what colonising space has to do with the USA's deficit problem. Plasmic Physics (talk) 09:06, 1 August 2011 (UTC)

Except as a questionable expenditure probably nothing. --DeeperQA (talk) 09:10, 1 August 2011 (UTC)

If you're looking to save the US budget by cutting NASA...I got news for you bud: NASA is a drop in the bucket. Its entire yearly budget is less than the military spends on air conditioning. NASA has arguably contributed more scientific innovations than any other organization in the world. There are better things to cut than scientific progress and research that is constantly bettering ALL our lives. How about we cut out some "fraud, waste and abuse"?-RunningOnBrains^(talk) 16:10, 1 August 2011 (UTC)

I agree, like tax breaks, tax cuts and tax loopholes for the rich. --DeeperQA (talk) 07:57, 2 August 2011 (UTC)

However, with electricity too cheap to measure a surplus budget could follow and forever be maintained in absence of perhaps anything except wise Chinese leader. --DeeperQA (talk) 09:13, 1 August 2011 (UTC)

That would be highly optimistic, even if you could do it for free like you said. Plasmic Physics (talk) 10:17, 1 August 2011 (UTC)

What does the US national debt have to do with it? The US government doesn't pay for people's energy. People pay for it themselves. In fact, the government gets a lot of revenue from taxes on energy. --Tango (talk) 11:42, 1 August 2011 (UTC)

The national debt is in the way. --DeeperQA (talk) 16:00, 1 August 2011 (UTC)

How is the national debt in the way? The U.S. is a free-market economy, not a socialist economy, and the government takes no part in the funding or building of industries, including power plants and the electrical grid. The national debt makes not one iota of difference in this matter... --Jayron32 00:34, 2 August 2011 (UTC)

The Manhattan Project gave us a fast track to nuclear power. It was government funded. The TVA project was government funded. Hover Dam project was government funded. The list can continue and is very long. --DeeperQA (talk) 07:55, 2 August 2011 (UTC)

I just did a back-of-the-envelope calculation and came up with a cost of about 10 trillion dollars for enough solar panels to provide all the US's electricity, at current prices. (Don't take that number too seriously, though.) The reason it could not be done immediately is that at current efficiencies, it would require at least 10,000 square kilometers of solar panels, which could not be constructed in a short time. Looie496 (talk) 16:09, 1 August 2011 (UTC)

Current solar technology is crap. They only convert a small portion of the sunlight to electricity, steadily decrease in efficiency, must be cleaned of dust regularly, have no ability to store the electricity until needed, cost too much, must be turned constantly to face the Sun, etc. Improving the technology is the first step required. In the meantime, there are other energy sources which are ready to be built now, such as nuclear reactors built in safe places, like underground in unpopulated areas, rather than above ground, in heavily populated areas, right by active fault lines. With a high enough level of incompetence, any energy source can be made dangerous. StuRat (talk) 16:23, 1 August 2011 (UTC)

Solar thermal energy is not so terrible as all that, but yes, there's a capital cost. Wnt (talk) 17:04, 1 August 2011 (UTC)

better fit?

Does Kepler's 3rd Law of Planetary Motion find a better fit if it is changed from p^2 = a^3 to p^2 = a^pi(3.141593...)? --DeeperQA (talk) 09:55, 1 August 2011 (UTC)

If it did, wouldn't the be stated as such? Plasmic Physics (talk) 10:21, 1 August 2011 (UTC)

Kepler's 3rd Law is already a perfect fit (under Newtonian gravity and mechanics). It follows by a pretty simply mathematical derivation from F=GMm/r² and F=ma. If you want to allow for relativity then just changing the power isn't going to help at all. --Tango (talk) 11:45, 1 August 2011 (UTC)

No, of course it doesn't. The question is what makes you think it should or could? Dauto (talk) 13:02, 1 August 2011 (UTC)

I was thinking only about planetary orbit approximations and not about mathematical derivatives. I see it: 2*G*M*m/r^3 from G*M*m/r^2. Thanks. --DeeperQA (talk) 14:50, 1 August 2011 (UTC)

You should look into the modern derivation of the law - I was just talking about something like it with electrons. While Kepler's third law might once have been determined by observation, we now know that the radius of an orbit is proportional to the square of the angular momentum of the object, and the length of time it takes to complete that orbit (the orbital period) is proportional to the cube. It's not some arbitrary ratio we can just change or adjust; each of these things is the necessary mathematical consequence of other physical laws. Wnt (talk) 17:07, 1 August 2011 (UTC)

You are right. Its called creative thinking (or speculation) which happened before first coffee and was applied out of place. I must have been asking myself how Kepler came up with the law using empirical data before the Calculus was invented. As for going deeper, yes, it is angular momentum that I was looking for to better connect the third law to electron orbits (atoms) but what my ultimate question is, is whether Kepler's third law is (or can be) applied to subatomic partials or are subatomic particles not regarded in terms of orbits? --DeeperQA (talk) 21:57, 1 August 2011 (UTC)

...Which has already been answered. No. Plasmic Physics (talk) 08:55, 2 August 2011 (UTC)

Statistics on Human Penis Size

Most of the charts I've seen look at stats for length or girth by themselves, I was wondering if there was any availible stats on both together. For example, what percentage of men have 6 inches length and 4 inches circumference, etc. 209.252.235.206 (talk) 10:32, 1 August 2011 (UTC)

A sad percentage. So smarr.

I don't know the answer, but have you read "Human penis size"? There are several references. One of them might have your answer. Axl ¤ [Talk] 06:20, 2 August 2011 (UTC)

What is an airlift system

Apparently fish are moved up the Haneji Dam using an airlift rather than a fish ladder. I've seen and understand a fish ladder. What is how does an airlift work? Is it an Airlift pump? If so, don't the bubbles harm the fish? -- SGBailey (talk) 11:33, 1 August 2011 (UTC)

I think "air lift" may be an artefact of the dam's page's Janglish (which also calls a fish ladder a "stared-fish ways") rather than a correct technical term. It may simply be some kind of pumped siphon system; this company has a bunch of fish-sucking equipment including a siphon fish ladder. I can't find specific information about what's deployed at Haneji. -- Finlay McWalter ☻ Talk 13:47, 1 August 2011 (UTC)

Current Control vs. Voltage control

Hello. I am currently reading up on cochlear implants, but had little luck in finding different control mechanisms. What are some advantages of current control vs voltage control (for cochlear implants specifically, but also in general) ?

Many thanks. 114.77.39.141 (talk) 11:53, 1 August 2011 (UTC)

This paper gives some of the answers. --Heron (talk) 17:33, 1 August 2011 (UTC)

Hmm it does answer some of my questions but it doesn't really go into too much depth. Thanks a lot though; i did try to search for these answers and came up very short. 114.77.39.141 (talk) 10:32, 3 August 2011 (UTC)

Resurecting extinct species

Could species like the saber-toothed tiger or the mastodon be resurrected? There are some similar species which could get a genetically modified fetus contained the genome of them.Quest09 (talk) 12:15, 1 August 2011 (UTC)

There has been some talk of cloning up a moa (brief mention) and the Pleistocene Park guy wants a woolly mammoth. Right now we can clone mammals from a living cell: cloning up an extinct animal presents two major additional problems - firstly is getting a viable genome from something that has been dead for hundreds or thousands of years (that's surely easier for recently extinct things like the dodo and the thylacine than for mammoths, never mind dinosaurs), and secondly getting that genome into an egg and getting a clone to take from it. -- Finlay McWalter ☻ Talk 13:19, 1 August 2011 (UTC)

Mammoths have the advantages of being recently extinct as well as having lived in cold areas. Therefore, intact flesh of a mammoth may be found in the Siberian permafrost. However, DNA may still be found in bones and teeth of animals only a few thousand years old, provided they were properly preserved. This usually means they were encased in rock, before decomposition could work it's way into the interior of the bones and teeth.

Also note that finding a surrogate mother can be tricky, for mammals larger than any living today. Perhaps a mammoth could be placed in an African elephant, or a saber-toothed tiger in a Siberian tiger, but a c-section would be needed before the offspring became too large, with "premie" medical care performed after that. Birds are easier, as you only need an incubator for the eggs. You'd just have to guess at the ideal temperature, though. StuRat (talk) 16:02, 1 August 2011 (UTC)

Don't the eggs need to be laid? -- 203.82.81.54 (talk) 20:41, 1 August 2011 (UTC)

Yes: part of the problem of using a surrogate mother of another species is that there is a great deal of interaction between the physiologies of mother and festus during gestation, so by virtue of their being different species, mismatches fatal to a successful gestation are likely, and even if the fetus is successfully born, it likely won't have developed in quite the same way as if it had been gestated in a mother of its own species. Incidentally, the loose term Sabre-toothed tiger covers several families of extinct mammals, none of which were anywhere near as closely related to the modern Tigers as, say, modern Lions. Similarly, Mastodons were not even in the same family as modern Elephants, and Mammoths were in the same family but not either of the same genera, so again the relationships are less close (though genetic closeness is not completely correlated with the "distance" of these taxonomic ranks), and the barriers likely to be greater, than is popularly supposed. {The poster formerly known as 87.81.230.195} 90.201.110.81 (talk) 19:50, 1 August 2011 (UTC)

Interaction between "mother and festus" ? I hate to picture that interaction: [4]. StuRat (talk) 10:46, 2 August 2011 (UTC)

The interaction is limited, though, otherwise offspring with mothers of different blood types would not be viable, and male offspring would be thoroughly messed up by the female hormones of the mother, all being born with female genitalia. StuRat (talk) 10:49, 2 August 2011 (UTC)

Hemolytic_disease_of_the_newborn, and I've read of interesting studies on younger sons having a less comfortable time in the womb than older sons, due to the whole male/female thing (I can't remember enough to find an article though). Do we have an article on the battle between the mother and fetus? And this is all within one species, a species with little genetic variability. This is a completely different scale to the problems with different species, or different genera, or even different families. 86.163.1.126 (talk) 13:16, 2 August 2011 (UTC)

If mother and baby have different blood types, then mixing of the blood may be fatal to the baby. That's as bad as it gets, same species or different. In rare cases this does happen, but obviously most of us survive, due to the placental barrier. I don't understand your "young son"/"older son" comment. Also, for other examples of cross-species reproduction, look at grafting in trees, and hybrid animals, like the mule/hinny or tiglon/liger. StuRat (talk) 13:44, 2 August 2011 (UTC)

Most of us do not survive. I cannot remember enough about the son thing to link to a fuller explanation. Basically, it was found that as a woman had more sons, she was in some sense 'primed' to reject the male hormones (as I recall, I read this years ago), and her womb became a more hostile place for subsequent sons. The whole thing about the battle for resources between mother and child, and the interaction between them that battles at the edge of parasitism, is mainstream. 212.183.128.5 (talk) 15:04, 2 August 2011 (UTC)

The Pyrenean Ibex was briefly resurrected through cloning in 2009. However there are closely related living animals, the DNA was extracted from a living Pyrenean Ibex and the clone died seven minutes after birth due to a defect. Hut 8.5 17:00, 3 August 2011 (UTC)

To clarify, the DNA was extracted before the last member of the species died off. However, they have a problem of no male sample, so they can't easily create a breeding pair via cloning. And, for proper genetic diversity, you'd want many clones, not just 2. StuRat (talk) 17:40, 3 August 2011 (UTC)

Leptinella/Cotula

Hi there,

I am a very keen gardener from Newcastle, NSW Australia. I have no botany training at all, but I am interested in plants (Australian natives in particular). I bought a plant called Cotula purpusilla and I have been trying to sort out whether it is native to Australia or not. On the Wiki pages for Cotula and for Leptinella the information is a bit confusing as to which plants are called what and why there has been a change in the names and whether or not the changes have been accepted or not. And I still don't know whether my plant is native to Australia or not!

Don't get me wrong - I love Wiki! I guess it is just frustrating when the information given seems a bit muddled (in regard to the names). I suppose the other thing that would be really helpful on the plant info. pages would be to ensure that plant's country/state of origin as well as natural habitat is included.

Thanks so much for your time and effort, Fmcrowe (talk) 12:17, 1 August 2011 (UTC)

This page and others (note the correct spelling of perpusilla) indicate that the plant is native to New Zealand. This page says that the binomial name is a synonym of Leptinella pusilla. When taxonomists try to split or combine taxa, the results are often confusing. Deor (talk) 12:48, 1 August 2011 (UTC)

Weedicides

How does a weedicide know which is the required plant and which is the useless, unwanted plant? I asked this to my biology teacher but she too couldn't answer me. ID: (email removed) Name: Divesh Paryani — Preceding unsigned comment added by 41.58.128.95 (talk) 14:42, 1 August 2011 (UTC)

It doesn't. Many weedkillers kill all green plants, but common selective weedkillers tend to have little effect on plants of the grass family. Some crops are genetically modified to be resistant to general weedkillers such as glyphosate. The article on Herbicide might be of some interest, but it doesn't explain the biochemistry of resistance. Dbfirs 15:46, 1 August 2011 (UTC)

Glyphosate kills plants because it inhibits an enzyme involved in amino acid biosynthesis. (Humans and other animals aren't killed by it because we get such amino acids from our food - an option a plant doesn't have.) Glyphosate resistant (e.g. "Roundup Ready") plants, for the most part, have been modified with a different version of the enzyme (usually from bacteria) which isn't inhibited by glyphosate. In the presence of glyphosate, they can use this other enzyme to make the amino acids. Likewise with glufosinate (Liberty/Basta), which inhibits a different amino acid synthesis gene, which is also replaced/supplemented in resistant plants (e.g. "LibertyLink"). Other specific herbicides function the same way. For example atrazine kills most plants by interfering with photosynthesis, but doesn't kill maize because maize has a naturally occurring ability to detoxify it [5]. 2,4-D is a hormone mimic which promotes uncontrolled growth in broadleaf plants, but doesn't affect the hormone system of grasses, due to the natural differences between the two types of plants. There are also herbicides which affect different stages of plant growth. For example, preemergent herbicides inhibit seed germination. They won't affect plants that are already growing (e.g. your lawn, already sprouted crops) but will prevent the weed seeds that are in the ground from sprouting. -- 140.142.20.229 (talk) 20:42, 1 August 2011 (UTC)

(ec) To answer your question, the herbicide doesn't "know". Rather, many herbicides (known as "selective herbicides") are specifically engineered to be ineffective against some desirable plants, or the desirable plants are themselves engineered to be resistant to particular herbicides. We note that glyphosate, sold as "RoundUp", was conceived as a non-selective herbicide (that is, it killed all plants), but that its popularity led to the development of glyphosate-resistant plants such that it can now operate as a selective herbicide. Note also that selective herbicides require specific intentional pairings of appropriate crops and herbicides; one cannot simply use a weedkiller at will with the expectation that it won't harm everything in sight. — Lomn 15:50, 1 August 2011 (UTC)

Some herbicides are absorbed through the leaves of the plant. Those with waxy or narrow leaves absorb less of the herbicide than other plants. It happens that grass is narrow-leaved and most garden weeds are broad-leaved. Thus these herbicides kill garden weeds but not the grass, however, they also kill clover, which may-or-may-not be a weed, depending on your point of view. CS Miller (talk) 21:31, 1 August 2011 (UTC)

It's not really a difference in absorption for grasses, though waxy leaves certainly help survival. See the excellent explanation from 140.142.20.229 above. Dbfirs 22:41, 1 August 2011 (UTC)

I've removed your email address; as you can see, answers will be posted here. I found a couple of articles, one here and also one here that might be useful. --some jerk on the Internet (talk) 16:34, 1 August 2011 (UTC)

Blushing

Hello. My name is Ian, I am vacationing right now in my mother's home city of Moscow and everyone is noticeably lighter here than back in the States, hence this question popping into my head. Because of my descent (mixed Russian-Finnish), I have a very light complexion, and furthermore I blush easily and to the smallest things; even more so, I've noticed, than even other Russians. A problem I have at home in the States is that when I blush it is more noticeable to others and it is often misinterpreted in social situations by my darker American companions. I know blushing is for the most part an unconscious action but is there anything I can do to reduce the frequency or exercise some control over it? My girlfriend advised me to get a tan but that didn't go so well-- apparently I don't tan, I just burn. Thanks in advance, and a happy summer to all! --Ian — Preceding unsigned comment added by 93.94.234.152 (talk) 17:10, 1 August 2011 (UTC)

Blushing is a signal of shame, and so being ashamed of blushing will only make you blush more. So don't be ashamed of it! Be proud of your blushes! Nobody except you really cares anyway. Looie496 (talk) 17:33, 1 August 2011 (UTC)

Wikipedia has an article about Blushing that describes what is known about its causes and possible treatments. You may take comfort (?) in the fact that no animal can blush, only humans do it. Animals don't have anything to blush about. Cuddlyable3 (talk) 17:39, 1 August 2011 (UTC)

"Man is the only animal which blushes ... or needs to." - Mark Twain StuRat (talk) 17:44, 1 August 2011 (UTC)

Well, make-up would do the trick, but you might find that objectionable (perhaps you could paint your face in your favorite team's colors, at sports events). There's also the "spray on tan" chemicals, although I wouldn't recommend them, personally. StuRat (talk) 17:46, 1 August 2011 (UTC)

Certainly a light foundation, as in the sort of skin-coloured make up you apply over your whole face, would reduce how noticeable the blushes were. This is, after all, why women add blusher on top of foundation. While you might find it objectionable, if you're doing it right, with a carefully chosen 'light' foundation or tinted moisturiser, chosen to match your facial skin (not the skin on your hand) and lightly and evenly applied, will be invisible to observers and still mask the blushing (as well as giving a smoother appearance to your complexion). It would, however, be cheaper and more wholesome to come to terms with your blushing and 'own' it as a personal attribute: "I am someone who clearly signals my moods and reactions, rather than disguising them". 86.163.1.126 (talk) 19:07, 1 August 2011 (UTC)

yes but my problem is that I might blush at something random and whoever I happen to be talking to might interpret to mean I am lying or I am ashamed of something relevant to the conversation, where I'm really not, then I have to explain (and might not be believed!), which causes much more embarrassment and fuss. Thanks for the answers (although I'd prefer not to use makeup!); new ones are welcome. --Ian 93.94.234.152 (talk) 00:27, 2 August 2011 (UTC)

Trying to explain away a blush is a case of continuing to dig when you're already in a hole. Really, don't worry about it: that some people blush more than others and some (like you) blush through momentary social embarrassment is well known and understood by other socially competent people, who likely will take no notice or regard it as merely a small component of your overall personality, assuming they even notice in the first place. Those who are so socially retarded as to misinterpret or want to make something out of it - well, why should you care what they think? {The poster formerly known as 87.81.230.195} 90.197.66.109 (talk) 09:42, 2 August 2011 (UTC)

<crank theory> I feel as if the "emotion" of shame is actually just the sensation of vasoconstriction of the left middle cerebral artery, upstream of its supply to Broca's area, thus shutting down (or responding to a shutdown of?) speech. I feel as if I've been able to counter it to some extent by willing vasodilation in the same area, but I've never tried this with the equipment to test, so it might be delusion. I've seen a few people touch that region of their head when experiencing shame; Facepalm is a stylized example (though not to the left). I wonder whether the constriction of one or several arteries in the brain could lead to a shift of blood into the external carotid artery, and from there the face.</crank theory> Wnt (talk) 17:13, 2 August 2011 (UTC)

aspirin

Is aspirin an NSAID? — Preceding unsigned comment added by 99.70.40.100 (talk) 17:28, 1 August 2011 (UTC)

Yes, as our aspirin article states in its lead. Looie496 (talk) 17:30, 1 August 2011 (UTC)

(Keep in mind the `N' stands for NON, and the abbreviation NSAID is used to describe things in terms of what they are not. To paraphrase Ulam, saying Aspirin is an NSAID is like referring to the bulk of zoology as the study of non-elephant animals.) SemanticMantis (talk) 18:17, 1 August 2011 (UTC)

That answer is good enough to not be in <small>s. 64.134.228.55 (talk) 00:56, 2 August 2011 (UTC)

I disagree. The "NSAID" designation identifies a group of compounds that share side effects, mechanisms of action, etc in a manner that is useful. To the extent that the NSAID term is useful, it is quite a bit different from referring to the bulk of zoology as the study of non-elephant animals. So, that answer does highlight a pedantic issue with the term "NSAID", but doesn't really answer the question. I think the choice of font size was appropriate. -- Scray (talk) 01:04, 2 August 2011 (UTC)

That comparison would be non-specious if it referred instead to "non-mammal animals", and if there were only three or four classes of animals. TenOfAllTrades(talk) 03:06, 2 August 2011 (UTC)

This debate is giving me a headache. ;-) AndyTheGrump (talk) 03:08, 2 August 2011 (UTC)

Take an aspirin. Ooops, no medical advice allowed. DON'T take an aspirin. Cuddlyable3 (talk) 09:45, 2 August 2011 (UTC)

That's medical advice, too! --Stephan Schulz (talk) 09:56, 2 August 2011 (UTC)

The ref.desk advises the OP not to take any advice seen on the ref.desk. Cuddlyable3 (talk) 09:27, 3 August 2011 (UTC)

Perhaps something like fish is a slightly simpler comparison. Nil Einne (talk) 01:25, 3 August 2011 (UTC)

Ok, I'll compare an aspirin to a fish then: on average, an aspirin is more likely to be soluble than a fish is ;-) AndyTheGrump (talk) 01:30, 3 August 2011 (UTC)

Instantaneous force

Hi, I'm designing a small plane; I'm working on the landing gear specifically. Suppose my plane is descending at a rate of 30 m/s at an angle of 45 degrees; What is the instantaneous force acting parallel to the ground, the moment the plane touches the ground? (Ask me if you need any extra data). 117.192.212.48 (talk) 18:00, 1 August 2011 (UTC)

I hope you're not designing a real plane, if you think that's a meaningful question. Looie496 (talk) 18:09, 1 August 2011 (UTC)

Planes don't usually land with a 45 degree glide slope but if yours does, its horizontal velocity is 30 m/s. The horizontal component of the instantaneous force on the landing wheels is whatever causes them to skid. Cuddlyable3 (talk) 18:19, 1 August 2011 (UTC)

I know; the descent angle is way too large. I mean to ask this as a simple physics question. I mentioned 45 degrees because the calculations will be easier. 117.192.212.48 (talk) 18:22, 1 August 2011 (UTC)

i want to know the instantaneous force at the time of impact. 117.192.212.48 (talk) 18:25, 1 August 2011 (UTC)

If your landing gear is rigid it will break. You cannot have instant deceleration of either the vertical or horizontal components of the plane's speed. Cuddlyable3 (talk) 18:28, 1 August 2011 (UTC)

We would need to know the mass of the plane (or the weight, from which the mass may be derived). The mass and radius of the wheels is also important, since they presumably will need to be accelerated from no rotation. I agree with the above comments, that descending at 45 degrees at 30 m/s will result in a crater. StuRat (talk) 18:41, 1 August 2011 (UTC)

Forgetting about the 45 degree angle that others pointed out isn't realistic, and assuming that the mass of the wheels are negligible compared to the mass of the plane, its clear without having to do any actual calculation that the instantaneous force acting parallel to the ground is negligible. Dauto (talk) 19:34, 1 August 2011 (UTC)

Yes, the horizontal force acts only to accelerate the wheels from initial skidding to rolling speed. Unless the wheels have a large moment of inertia, the force will be small compared with the braking force subsequently applied. To calculate the average force, you need to know the radius and moment of inertia of the wheels, the horizontal ground-speed at touchdown, and the skid time or distance. Once the wheels are up to speed, the only horizontal force is from friction in the bearings (and air resistance on the plane). Of course, if the brakes are already on as the plane touches down, rubber will be torn from the tyres by the greater friction force. Dbfirs 20:11, 1 August 2011 (UTC)

A simpler question contains the same basic issue: "Two blocks collide at 1 m/s. What is the instantaneous force between them at the moment of collision?" The answer must be that it depends on the mass of the blocks, Young's modulus, etc. The nearest parts of the blocks inevitably must match speeds first, and then transmit this force outward, in quite a complex way. The wheels of a plane add the additional variable that the force of friction is limited and they may slide over the landing strip as they first touch. Wnt (talk) 20:30, 1 August 2011 (UTC)

I think everybody missed the obvious. Assuming the ground is reasonably smooth, the force at the moment the plane touches the ground is zero. See Friction#Laws of dry friction. At the moment the plane first touches the ground, there is no applied load. The load will increase rapidly after contact, however. The speed of the plane is irrelevant.

This wouldn't happen to be a homework question, would it?--Srleffler (talk) 23:12, 1 August 2011 (UTC)

Ah, phoooey - meant to mention that when I commented but forgot. I assume that the "moment of collision" is supposed to be defined as the moment when the force is greatest, not at the moment when the objects first touch. Wnt (talk) 04:58, 3 August 2011 (UTC)

Even before the plane touches the ground a layer of air between them is being compressed. Cuddlyable3 (talk) 01:01, 2 August 2011 (UTC)

Yes, the force builds up gradually over a tiny fraction of a second as the air is compressed under the tyres, and as the weight of the plane comes to be supported by the tyres rather than by the wings. The concept of "the moment the plane touches the ground" is not clearly defined. Dbfirs 06:26, 2 August 2011 (UTC)

I'll make it simpler (No Srleffler this ain't a homework question :P ) . A body of mass 10 kg is travelling on a frictionless surface at a constant velocity of 20 m/s. Suddenly, it encounters a rough surface (say, coefficient of friction is 0.5). What would be the value of deceleration. 117.192.199.186 (talk) 06:35, 2 August 2011 (UTC)

See Friction#Coefficient of friction: "The 'coefficient of friction' (COF), also known as a 'frictional coefficient' or 'friction coefficient' and symbolized by the Greek letter µ, is a dimensionless scalar value which describes the ratio of the force of friction between two bodies and the force pressing them together". You haven't given 'the force pressing them together', so there isn't an answer. AndyTheGrump (talk) 07:13, 2 August 2011 (UTC)

Ah, but I have. The mass is 10 kg. The force pressing the surfaces together would be 10* 9.8= 98 Newton. 117.192.199.186 (talk) 07:16, 2 August 2011 (UTC)

You didn't - you are assuming a 1 G gravitational force, which you didn't state. Still, I think you have enough information to answer the question now. What is 10 * 9.8 * 0.5? This is the force. Now what is the acceleration/deceleration that results from applying this force to a 10 kg mass (actually, most of this cancels out, unless I am being even more stupid than usual)? AndyTheGrump (talk) 07:24, 2 August 2011 (UTC)

The OP has not made the original question simpler and has instead substituted an entirely different question. Cuddlyable3 (talk) 09:42, 2 August 2011 (UTC)

It is simpler, but it's also sufficiently different to call it an entirely new question. StuRat (talk) 10:34, 2 August 2011 (UTC)

The missing piece of information in this new question is the assumption that the surface is horizontal, but, taking that as given, the answer is 4.9 m/s/s for the 40.8 metres (approx) that is takes for the block to come to rest. The mass of the block is irrelevant, so exactly the same would apply to an object such as a plane, except that the undercarriage might be torn off and the sudden jerk (rate of change of acceleration) would probably cause injury to anyone not wearing a seatbelt. Dbfirs 00:40, 3 August 2011 (UTC)

So my 'physics from a bloke with a social science degree' was right: 4.9 m/s/s, or g * 0.5. It all cancels out. Actually, I'll have to ask how how you came to the conclusion that the block will ever come to rest, according to the formula you use (yes, I know, the formula is an approximation that doesn't work at the limits etc...) AndyTheGrump (talk) 00:50, 3 August 2011 (UTC)

Yes, you were correct. In the simplification where the coefficient of friction is independent of speed (a good approximation in many situations), the rate of decrease in speed is constant until the instant when the body stops. In practice, static friction tends to be marginally greater than sliding friction so in the last millisecond there may be a slight jerk and a coming to rest marginally before the calculated 40.8 m (I just used v² = 2as with "a" as you calculated - simplified from Equations of motion). In a different model where braking force is proportional to speed, as in regenerative braking, the body never actually comes to rest (in theory). Dbfirs 06:13, 3 August 2011 (UTC)

I have some Astronomy Questions:

1. Is it true the clouds of Venus are mainly composed of sulfur dioxide and sulfuric acid?

2. Is it also true Jupiter is also notable for its turbulent weather (e.g. huge storms, lightning, etc?

Thanks!

Neptunekh2 (talk) 20:27, 1 August 2011 (UTC)

I think the articles you linked cover those pretty well, and if not Atmosphere of Venus and Atmosphere of Jupiter should.

Control-F or Apple-F ("Find" in your browser) are your friends. ;) Wnt (talk) 20:34, 1 August 2011 (UTC)

How much does gravity hold the human body together?

If an astronaut floating in deep space floated into a fictional region where the force of gravity stopped working, would the tissues of his body maintain their structural integrity? I.e., is gravity at all significant in its contribution to holding the body together? 76.27.175.80 (talk) 21:49, 1 August 2011 (UTC)

In reality no. See the article Extra-vehicular activity. In fiction you can make up anything you like including turning off physical laws and having people fall to pieces. Cuddlyable3 (talk) 21:58, 1 August 2011 (UTC)

The above answer is correct, but the reasoning is flawed. There is a significant difference between free fall (which is what astronauts experience, and essentially means that the only significant force acting on a body is gravity) and an absence of the gravitational force. If there were no gravity in Earth orbit, then objects wouldn't stay in orbit—they'd fly off on straight tangents. The attractive gravitational force between an object at 350 km altitude (like the International Space Station) and the Earth is only about 10% weaker than it would be for the same object sitting on the Earth's surface. TenOfAllTrades(talk) 02:55, 2 August 2011 (UTC)

No, not significant. See Gravitational constant, where it says:

The gravitational force is extremely weak compared with other fundamental forces. For example, the gravitational force between an electron and proton 1 meter apart is approximately 10⁻⁶⁷ newtons, while the electromagnetic force between the same two particles is approximately 10⁻²⁸ newtons. Both these forces are weak when compared with the forces we are able to experience directly, but the electromagnetic force in this example is some 39 orders of magnitude (i.e. 10³⁹) greater than the force of gravity — roughly the same ratio as the mass of the Sun compared to a microgram mass.

Comet Tuttle (talk) 22:03, 1 August 2011 (UTC)

I feel the need to clarify: you asked two questions, so the answers are: Yes, the tissues would easily maintain their structural integrity, and no gravity does not have a significant contribution to holding the tissues together. Almost every other force known is more important than gravity at that scale. -RunningOnBrains^(talk) 22:06, 1 August 2011 (UTC)

When you are in free fall you are effectively NOT feeling the effect of gravity form your reference frame. For longer term effects not quite as dramatic as "falling to pieces" there's Weightlessness#Human_health_effects. Vespine (talk) 22:47, 1 August 2011 (UTC)

That's not relevant to his question. Regardless of whether you are in free fall, there is still gravitational attraction between the parts of your body. The OP was essentially asking whether this force was significant, compared to the other binding forces. The answer is "no".--Srleffler (talk) 22:58, 1 August 2011 (UTC)

Assume a spherical astronaut of mass 100kg and a density of 1000kg/m³ (ie. that of water). Those aren't far off the mass and density of a typical person. The gravitational binding energy of that astronaut would then be (by the formula in that article) about 1.4x10^-6 joules, or 1.4 microjoules. According to Orders of magnitude (energy), that's about 10 times the kinetic energy of a flying mosquito. In other words, not much. That's the energy that would be required to break your body completely apart against the force of gravity. Since we don't fly apart whenever a few mosquitos fly into us, we can conclude that there is much more holding our bodies together than gravity. --Tango (talk) 23:21, 1 August 2011 (UTC)

To clarify something even more simple: the force that holds together tissues and other molecular structures is the electromagnetic force (in the form of molecular bonds), not gravity. Gravity holds us on the Earth; it does not hold us together. --Mr.98 (talk) 00:20, 2 August 2011 (UTC)

The body is held together by material in a non-fluid state. If the body were composed entirely of gasses and liquids, it would be far more prone to changing shape and breaking up. To the extent that the body is composed of solids, even if in close combination with liquids, that is the extent to which it can hold itself together. As has been stated above, gravity plays very little role in maintaining structural stability. Bus stop (talk) 02:47, 2 August 2011 (UTC)

A human gets taller after staying long periods in low gravity environments. ~AH1 ^(discuss!) 14:24, 8 August 2011 (UTC)

Geomagnetically Induced Currents

I understand that GICs are a big problem because of long stretches of cables and pipes on a global scale such as telegram/telephone cables, fiber optics, railroad tracks, and oil pipelines across oceans and continents. My question is, in order to stop such a thing why not insert a piece of plastic or some other insulator (maybe every 20 miles or whatever) so that the current won't be conducted through? This can easily be done in oil pipelines for example. So why is't it done? And also does anyone know of any incidents where such a current might have caused an ignition and hence an explosion in a pipeline? Perhaps during a solar storm? Thanks! - Looking for Wisdom and Insight! (talk) 22:34, 1 August 2011 (UTC)

You should read geomagnetically induced current and specifically GIC hazard in pipelines. Dragons flight (talk) 23:14, 1 August 2011 (UTC)

Fiber optics being non-conductive are unaffected by GICs. Cuddlyable3 (talk) 00:36, 2 August 2011 (UTC)

For those conductors which are affected, the questioner's recommendation for a series of zener diodes tied to ground is reasonable, but not optimal. 64.134.228.55 (talk) 00:52, 2 August 2011 (UTC)

I read that article but doesn't really answer any of my questions. Why isn't this optimal? Is this used in practice at all? If not then why not? - Looking for Wisdom and Insight! (talk) 18:20, 2 August 2011 (UTC)

From the article in question:

"The GIC hazard to pipelines is that GIC cause swings in the pipe-to-soil potential, increasing the rate of corrosion during major geomagnetic storms"

Introducing plastic elements into an otherwise all-steel construction is probably more expensive than simply repairing the pipes more often. --Carnildo (talk) 00:52, 4 August 2011 (UTC)

August 2

Identifying YAG crystals

How can I tell a YAG crystal from a diamond ? I tried using a ruby for a scratch test, but couldn't get either to scratch the other. 68.79.93.3 (talk) 01:22, 2 August 2011 (UTC)

Ruby (corundum) should scratch YAG, and should be scratched by diamond. YAG can also be distinguished by its lower refractive index (1.83, versus 2.42 for diamond), higher density (4.56 g/cc, versus 3.52 for diamond), and different cut: [6], [7], [8].

You seem to be stumbling across a inordinately large number of gemstones that need to be identified. (Not a bad problem to have I suppose.) Perhaps you need to start some sort of relationship with a jeweler? APL (talk) 08:11, 2 August 2011 (UTC)

Perhaps the same gemstones, but the OP still hasn't identified whether they are diamonds because of the failure of the scratch test and a lack of trust in any external party to verify they are diamonds Nil Einne (talk) 01:48, 3 August 2011 (UTC)

subatomic particles

Where can I find a list of subatomic particles that result at different energies of proton collision? --DeeperQA (talk) 09:00, 2 August 2011 (UTC)

See list of particles. Dauto (talk) 15:45, 2 August 2011 (UTC)

subatomic shells

Is there a discussion anywhere regarding the possibility of the subatomic particles existing as clouds or in shells within the proton, like the electrons fill shells external to the atom? --DeeperQA (talk) 09:42, 2 August 2011 (UTC)

Usually the internal structure of protons is modeled by form factors. Dauto (talk) 13:48, 2 August 2011 (UTC)

See nuclear shell model. Oops, sorry, misread. Wnt (talk) 14:33, 2 August 2011 (UTC)

The internal structure of nucleons like protons and neutrons is not well understood beyond the "quark and gluon sea" level. We don't have solid, well accepted models for the organization of quarks, with well defined geometries, the same way we do for the electron cloud. There are some models, but none has gained widespread acceptance. See Nucleon#Models. --Jayron32 16:54, 2 August 2011 (UTC)

Wow. That "chiral bag model" sounds very interesting, but the puny weapons of my mind cannot dent its neutronium armor. How does the baryon number, or quark fields, become a matter of topology and how would they cancel each other out? Wnt (talk) 17:02, 2 August 2011 (UTC)

Zinc chloride solution

What is the zinc contend in 65% zinc chloride solution — Preceding unsigned comment added by 41.29.251.155 (talk) 12:03, 2 August 2011 (UTC)

Need more info:

1) What's the solvent ?

2) Is that 65% by mass ?

3) In what form do you want the zinc content ? Also in mass ? 68.79.93.3 (talk) 13:17, 2 August 2011 (UTC)

% by volume, mass or amount? If by mass, then zinc makes up 64.85% the total zinc chloride mass, meaning that of the 65% zinc chloride solution, only 64.85% is zinc. To get the final mass percentage multiply the percentages together: 42.15%. Plasmic Physics (talk) 13:21, 2 August 2011 (UTC)

Which animal in burrow?

In rural south east England recently, I was walking along a broad strip of rough grass adjacent to a field, with some light scrub on the other side. I saw a burrow about an inch in diameter, and a circular bare patch of a few inches diameter around the burrow, which was a little off centre. Does anyone know what animal the burrow may have been made by? 2.97.215.11 (talk) 15:04, 2 August 2011 (UTC)

Do they have chipmunks in England? The article says they are native to N. America and Asia; but perhaps they are an invasive species? --Jayron32 16:48, 2 August 2011 (UTC)

I'm fairly sure (being actively interested in out-of-place animals) that chipmunks have not yet been identified as an invasive species in SE England, though there's no telling if some idiot has released one or more into the wild very recently. However, there are other more likely candidates.

My immediate thought was a weasel, whose burrow entrances, as you will see from that article, are typically this size. Other possibilities are a wood mouse or yellow-necked mouse (aka field mouse), a vole (in the European, not North American, sense), or even a solitary bee or solitary wasp (I'm assuming if it had been the entrance to a communal bee or wasp nest, you'd have seen some of its denizens).

The ever reliable Sun says that chipmunks are already here[9]. Alansplodge (talk) 22:23, 2 August 2011 (UTC)

Doh! How could I have missed an announcement in such a scholarly and reputable scientific journal :-) ? {The poster formerly known as 87.81.230.195} 90.197.66.143 (talk) 22:32, 2 August 2011 (UTC)

[Later] Ok, a perhaps more reliable report from a Dr Toni Bunnell of the University of Hull via The Independent, though I note that Dr Bunnell is also a practitioner of Reiki and has investigated healing by laying-on of hands, which suggests a less-than-complete focus on wildlife studies. {The poster formerly known as 87.81.230.195} 90.197.66.143 (talk) 23:04, 2 August 2011 (UTC)

More knowledgeable UK naturalists may have further suggestions, but probably more clues are needed for a definitive identification - any chance of making some follow-up observations? {The poster formerly known as 87.81.230.195} 90.197.66.143 (talk) 19:57, 2 August 2011 (UTC)

What follow-up observations would you like? 2.97.215.11 (talk) 22:57, 2 August 2011 (UTC)

Finding droppings or other perhaps-related debris in the burrow's vicinity; traces of fur around or near its edges; prints in the earth and trackways in vegetation; observations to eliminate insect candidates (taking due regard to appropriate times of year)? You might also consult staff at a nearby town museum for local information and advice about local wildlife, or seek out local naturalist societies: in the latter cases, photographs would be useful, as they can show relevant details of micro-topography that we (given the wide possibilities) have not thought to ask and you might not have noticed or be easily able to describe, but that would be meaningful to experts (of which, let me stress, I am not one). {The poster formerly known as 87.81.230.195} 90.197.66.143 (talk) 23:19, 2 August 2011 (UTC)

Here is a picture of a common vole (Microtus arvalis) burrow, which would be one possibility. Ghmyrtle (talk) 09:44, 3 August 2011 (UTC)

Although the photo of the common vole's burrow does not have the ring of bare earth around it like the one I saw, thae article says it does mostly eat grass, so it could be what I saw. (If it lives off grass, then since grass is so abundant, why are there not millions of them swarming everywhere?) 92.29.116.165 (talk) 11:13, 3 August 2011 (UTC)

Because they are heavily predated, notably by owls. In the absence of external interference (such as unusual weather patterns, human interference with habitats, or outright killing for vermin control or hunting), the complex interactional web of predators and prey tends to remain fairly balanced, though there are sometimes cyclical variations resulting in temporary gluts of prey, followed by gluts of predators, followed by successive population crashes of prey and predators, which in the end average out. {The poster formerly known as 87.81.230.195} 90.197.66.52 (talk) 13:44, 3 August 2011 (UTC)

The significant thing is the bare ground around the burrow entrance. The grass must have been removed somehow. The inhabitant of the burrow has either eaten it, or removed it for making a nest underground. It rather suggests that the inhabitant is timid, only venturing out of the burrow the shortest distance required to get a blade of grass. So probably not a carnivore, and not a giant bee either. 92.29.116.165 (talk) 10:32, 3 August 2011 (UTC)

I vaguely recall that some solitary bees or similar insects do deliberately tidy up the soil around their nest entrances (beyond merely depositing excavated earth), but I can't offhand think of a reference to link to. In general, animals (in the widest sense) do a lot of apparently odd things for reasons that would not immediately occur to you or I, so I would caution against jumping to conclusions prematurely. This, by the way, is a weasel burrow, though unfortunately it's in bare ground (probably in the USA) rather than the more grassy situation you describe. {The poster formerly known as 87.81.230.195} 90.197.66.52 (talk) 13:56, 3 August 2011 (UTC)

I don't think any bees are big enough to need a one inch diasmeter hole. The entrances to bee hives are smaller than that. I think I recall that bees keep the entrance small to keep predators out.

The picture of the weasel burrow has given me the idea that the bare patch might have been due to excavated material, but the soil I saw looked compacted and I would have expected grass to have grown through it. 2.97.219.104 (talk) 11:39, 4 August 2011 (UTC)

Chipmunks don't denude the area surrounding their holes, but the holes are indeed only about an inch wide. The are often long enough to accommodate a good part of a broom handle. I am surprised chipmunks haven't been intentionally introduced to Britain, they would liven up the place. μηδείς (talk) 01:40, 5 August 2011 (UTC)

Tips to identify a Bird of prey in southern england?

In rural south-east england I have had brief glimses of large brown birds that I thought could be birds of prey. One was sitting on a fence post as I sped past, another passed me skimming over the heathland vegetation as if hunting.

For future reference are there any ways of identifying or making a good guess about which species they are, for when I have another brief glimse of similar birds in the future? 2.97.215.11 (talk) 15:12, 2 August 2011 (UTC)

A Red Kite perhaps? They are on the increase in southern England. Try the RSPB bird identifier page.--Shantavira|^{feed me} 15:16, 2 August 2011 (UTC)

The best guess for the first one is buzzard. But I'm more interested in being able to quickly identify birds of prey that I see in the future. 2.97.215.11 (talk) 15:39, 2 August 2011 (UTC)

After looking through the Wikipedia articles, am I correct in thinking that the birds of prey I am likely to see in south eastern Britain would be, using their common local names: falcons, kestrels, harriers, goshawks, buzzards, and sparrowhawks? Owls and the extremely rare eagles would be easy to differentiate. 2.97.215.11 (talk) 15:29, 2 August 2011 (UTC)

Buzzards are a lot bigger than one might think, and usually seen high overhead rather than flying around or perching low down. Really, just as some young prince was once told "there is no royal road to mathematics," for bird identification there is really no substitute for obtaining and studying a good field guide (those published by Collins are held in high regard, but there are others), watching appropriate nature programmes, and above all spending time outside (with the aforesaid guide) actually watching birds (or whatever - the same applies to butterflies, dragonflies, etc). {The poster formerly known as 87.81.230.195} 90.197.66.143 (talk) 20:04, 2 August 2011 (UTC)

Put simply, a large brown bird of prey sitting on a fence post in southern England is far more likely to be a common buzzard (Buteo buteo) than anything else. They are widespread - "common", in fact. Ghmyrtle (talk) 09:37, 3 August 2011 (UTC)

From the RSPB site linked to above, the frequency of British birds of prey is Sparrowhawk 40100 pairs, Buzzard 31100-44000 territories, Kestrel 36800 pairs, Hobby 2200 pairs, Peregrine 1402 pairs, Merlin 1330 pairs, Hen harrier 749 pairs, Goshawk 410 pairs, Marsh harrier 360 females. I have left out owls and eagles. So anything you see is much more likely to be a sparrowhawk, buzzard, or kestrel than anything else. 92.29.116.165 (talk) 10:47, 3 August 2011 (UTC)

Sparrowhawks and kestrels are much smaller and don't often perch on fence posts. Ghmyrtle (talk) 11:42, 4 August 2011 (UTC)

August 3

Snowing right now

Where in the world is it snowing right now? Barbaricslav (talk) 01:35, 3 August 2011 (UTC)

It's winter in the southern hemisphere so it may well be snowing in the ski resorts in the mountains of Chile, for example, or perhaps in the Snowy Mountains of Australia. Antarctica is likely to have a storm or two. I have known it to snow in some of the northern hemisphere mountains in August -specifically in the Canadian Rockies. Bielle (talk) 01:58, 3 August 2011 (UTC)

Perhaps also Alert, Nunavut:

"Alert has a polar climate. The weather is very cold, and there is snow cover for 10 months of the year on average. The warmest month, July, has an average temperature of 3.3 °C (37.9 °F). Alert is also very dry, averaging only 153.8 mm (6.06 in) of precipitation per year. Most of the precipitation occurs during the months of July, August and September, mostly in the form of snow. On average there is 16.1 mm (0.63 in) of rain which occurs between June and September. Alert sees very little snowfall during the rest of the year. September is usually the month with the heaviest snowfall. February is the coldest month of the year. Snowfall can occur during any month of the year, although there might be about 20 frost free days in an average summer.[7]" Count Iblis (talk) 02:09, 3 August 2011 (UTC)

New Zealand's South Island received a heavy snow dump a week or two ago. Plasmic Physics (talk) 04:36, 3 August 2011 (UTC)

It seems that there is no current snowfall in southern Chile, Australia or New Zealand. According to BBC News there should be light snowfall in Punta Arenas on Friday. But Weather Underground reports ongoing snowfall in several locations on Antarctica: Amundsen-Scott, Base Orcadas, Dumont d'Urville Station, and Vostok Station. 130.188.8.11 (talk) 09:30, 3 August 2011 (UTC)

As someone who does a bit of skiing, I can report that, sadly, although it is snow season here in SE Australia, it was 10 degrees C in the nearby mountains today (approx 50 degrees F). But apparently snow is forecast for Sunday. HiLo48 (talk) 10:31, 3 August 2011 (UTC)

hammerhead sharks

can hammerhead bite head on or do they have to turn there heads to one side to stike — Preceding unsigned comment added by Jteuscher (talk • contribs) 01:42, 3 August 2011 (UTC)

Our Hammerhead shark article (which could do with a few more sources I think) suggests that hammerheads are mostly bottom feeders, and states that they may sometimes pin down rays with the 'hammer' to eat them. I'm not entirely convinced by this, but they certainly look better adapted to taking bites out of things underneath than in front. Given that some species have been known to attack humans though, I think it is safe to assume that they are flexible enough to attack in other ways. AndyTheGrump (talk) 02:10, 3 August 2011 (UTC)

For a specific example, see also Great_hammerhead#Feeding mentioning examples where the shark "disables" the prey (stingray) with its first bite, then pins it with its head, and finally "takes the ray in its jaws head-first". This section does cite five references. ---Sluzzelin talk 02:17, 3 August 2011 (UTC)

Torque and power

why the maximum power and torque of an engine specified at different RPM's ?

Torque is essentially force, power is essentially force multiplied by velocity. They are different things. You can have a large torque when the engine is not moving, but the power in that case is zero. Looie496 (talk) 02:44, 3 August 2011 (UTC)

Effect of star Jupiter on Earth

In his series of books beginning with "2001 A Space Odyssey", Arthur Clarke has a race of super advanced aliens cause Jupiter to turn into a star. If such were to happen, would we be likely to see the new Jupiter with the naked eye, and would the light be bright enough to disrupt life on Earth? — Preceding unsigned comment added by GuadalupePeak (talk • contribs) 02:39, 3 August 2011 (UTC)

I guess you didn't read the book. (2010: Odyssey Two, that is.) In the book, he has the aliens turn it into a very dim star, just bright enough to warm up Uupiter's moon Europa. Looie496 (talk) 02:50, 3 August 2011 (UTC)

As far as the visibility is concerned, you can already spot Jupiter with the naked eye during daytime, see here. If Jupiter were to turn into a star, it would be much easier to spot, of course. Count Iblis (talk) 02:56, 3 August 2011 (UTC)

Jupiter's Moons Ganymede and Callisto can also be seen using the naked eye, see here. Count Iblis (talk) 03:13, 3 August 2011 (UTC)

I think we used to have a page on the Lucifer Project which is a conspiracy theory that NASA (or the illuminati or NWO or whatever malevolent power you want to believe in) were going to try to ignite Jupiter.. Looks like the page is gone, but you can still find info about it if you google the term. Vespine (talk) 03:51, 3 August 2011 (UTC)

I think the main concern with this would be whether the new star would be bright enough to damage the retina, like an arc welder. Jupiter is about 1/10 the radius of the Sun, thus 1/100 the area - but it's also 4-6 times further away, making it 1/16 to 1/36 smaller in apparent size than that. But if it had the same color temperature as the sun, that 1/1600 bit of area would be just as bright as the sun itself. In total eclipses even fairly small areas of exposed sun are dangerous - actually much more dangerous than looking at the sun because the iris opens up, not being designed for extreme brightness in an overall dark scene. Especially at night this would be dangerous. Humans might learn to avoid looking at it before going blind (though I think something like that would be harder to learn than you'd think) but certainly nothing else would. These risks would be much reduced if it turned out to be a brown dwarf or something, much cooler on its exposed surface. Wnt (talk) 04:46, 3 August 2011 (UTC)

It's a pretty pointless question, it's like asking: if Jupiter gives off light, how much light would it give. The answer is pretty much up to you. Alternatively, if this lead sinker floats in water, how dense is it. Lead doesn't float in water, so the answer is: it is as dense as you want it to be, although less than water. So, if Jupiter was a star, it is as bright as you want it to b, as long as it is brighter than it's natural reflection. Plasmic Physics (talk) 05:26, 3 August 2011 (UTC)

Not to get too picky, but Jupiter is technically "brighter" than its natural reflection, it emits more energy than it gets from the sun, per the Kelvin–Helmholtz mechanism. What makes Jupiter not a star is that it doesn't undergo nuclear fusion; according to our article on Jupiter, it would need to be 75 times more massive in order to support nuclear fusion. In order to make it a star, Arthur C. Clarke had to invoke his own third law by introducing a little bit of "magic" in the form of the monolith. As Plasmic Physics notes, there is no conceivable way Jupiter could actually be a star, so discussing how it would become one is a purely fictional venture. --Jayron32 05:44, 3 August 2011 (UTC)

Well, in the 2010 film it was shown about the same color temperature as the Sun, and I think then my comments would hold. People would look up in awe and wonder, and end up tapping around with the white cane. Wnt (talk) 16:54, 3 August 2011 (UTC)

Meh. There's no evidence the filmmakers were terribly interested in making a scientifically accurate depiction of such a star anyways. Like anything else in the film, the effect is for dramatic purposes and isn't supposed to be scientifically accurate. I mean, you've completely accepted that a giant magic rectangle is capable of turning Jupiter into a star and yet have a problem with the spectral class of the star so created as represented in the film? If physics already doesn't work as it is supposed to in said film, what's the point of picking and choosing which wrong physics to complain about? The new star doesn't blind the people in the film because film physics works different than real physics. There's almost no point in playing the "how many ways is this film wrong" game unless you want to go all the way, and really what's the point. Films, like nearly all fiction, depend on suspension of disbelief to work; if you're so unwilling to accept such a suspension of disbelief to enjoy the film on its own terms, I don't see where this is a productive line of thought anyways. --Jayron32 18:00, 3 August 2011 (UTC)

Well, you don't neccesarily have to go all the way, as long as you are willing to make exceptions, and not to base an argument on those exceptions, to avoid circular reasoning. Plasmic Physics (talk) 19:31, 3 August 2011 (UTC)

The article was Lucifer Project I change the link supplied by User:Vespine and restored the page for those that want to read it. Graeme Bartlett (talk) 13:15, 4 August 2011 (UTC)

Beyond the standard model and low temperature physics experiments

Hi, is it possible that one could find standard model discrepancies at very low temperatures (like someday 10^{-50} kelvin?) as well as at the very high energies in particle accelarators? Thanks, Rich Peterson24.7.28.186 (talk) 03:54, 3 August 2011 (UTC)

• Like maybe dark energy doesn't "work" except at low temps?24.7.28.186 (talk) 03:56, 3 August 2011 (UTC)

• • The reason why high temperature testing of the Standard Model is done in the first place is generally to try to understand what the universe was like arbitrarily close to the Big Bang. The deal with low-temperature physics is, we have lots of examples around us (i.e. most of the universe is pretty cold) and most of the really exotic stuff happens when particles are energized enough to start to break down. You can get essentially infinitely hot (pre-empting the objections: yeah, I know there are limits here too, but not the same way as at the other end), but you've got a limit to how cold you can get. We've gotten very close to that cold limit, so we've got a pretty good handle on what happens there, but we've come nowhere near recreating the conditions at Big Bang time, which is why that is where the bulk of research is driven. --Jayron32 04:22, 3 August 2011 (UTC)

I feel like the "limit to how cold you can get" is illusion. The universe goes through different regimes of physics according to the log of its age, and the log of its temperature. There may be no limit to how old or how low temperature it can get, and I'm also suspicious that over very long time scales at very low temperatures and very low masses, some new physics could emerge when ours is too hot to be of much importance, just as has happened so many times before in history. Wnt (talk) 04:56, 3 August 2011 (UTC)

Could you please explain to me how one can go a slower speed than "stopped". Because I am not smart enough to understand how one may get colder than absolute zero. --Jayron32 05:35, 3 August 2011 (UTC)

Seconded. --Stephan Schulz (talk) 07:07, 3 August 2011 (UTC)

As I said, a logarithmic scale. People have proposed all sorts of bizarre physics for the first second after the Big Bang. What happens when you look at the interactions of matter at 10^-30 Kelvin over a period of 10^50 years? Maybe we're living now in another one of those periods of strange high-energy physics in the "moment" after the Big Bang, from that perspective? In other words - suppose there's proton decay. Suppose there's electron decay.^[10] Suppose you have a sea of neutrinos and nothing else, whizzing around over unimaginable time spans until they somehow come to rest with respect to one another. Do they start forming chemical-ish interactions? (No, I don't know, but I think it's a fair question) Wnt (talk) 08:09, 3 August 2011 (UTC)

I suppose it's possible, but it may also be outside of the range of human observability. Imagine a world where stuff happens on a timescale where one second of our time is expanded into 1 million years of real time (that's basically the logarithmic scale you are talking about here). Effects on THAT scale may well be unobservable within the limits of our methods to detect them. If humans lived one billion years rather than 70 years, and were able to observe the universe at such a time scale who knows what we may see. But, Wnt, you're delving into the realm of pure speculation; and while we may hold that technology may allow us, in the future, to delve into such realms scientifically, there is no indication that we may now or even within our lifetimes, so there's really no point in making it a big deal, right now. We can only say that, based on our current observations we have no reason to suppose anything terribly interesting happens at such low temperatures. It might, but there is nothing to say that it will. --Jayron32 11:37, 3 August 2011 (UTC)

I recognize this - though I wouldn't rule out that physicists might do a fair job of describing what a particle mediating a neutrino-neutrino bond would look like if there were one. The main reason why I think about this is that so often I have seen "the end of the universe" (and the "beginning of the universe" for that matter) described in such definite terms, when I feel like there is no real evidence that any era of time and temperature is truly the first or the last. Wnt (talk) 13:29, 3 August 2011 (UTC)

Except that the end of the universe may not even be at absolute zero, it could be considerably warmer than that. See Ultimate fate of the universe. While the physics of what might happen at some (currently impossible to achieve) arbitrarily tiny temperature close to absolute zero may be interesting, there is no wide spread agreement that the universe is asymptotically approaching that temperature. It is but one model of the end of the universe, and there's not yet a whole lot of evidence that it is far-and-away the best model. --Jayron32 13:52, 3 August 2011 (UTC)

Also agreed. But an open universe is still the leading contender. I think that any glimmer of evidence in this direction would do much to dispel the pall of fatalism that pervades modern pop physics. If people realize there's even a chance that the universe goes on and on and on, with new kinds of physics at each new time scale, it would fire up their imaginations. Wnt (talk) 16:52, 3 August 2011 (UTC)

Yes, it is possible that one will find that the Standard Model is false by studying physics at very low temperatures. That could happen if quantum mechanics (on which the Stanard Model is based) is not fundamental. If quantum mechanics is only approxmately true, then that would give rise to an effective theory in which decoherence would happen eve if there are no nteractions with the environment. This would then become visible only at extremely low temperatures at which the decoherence rate due to the environment becomes very small. Count Iblis (talk) 14:52, 3 August 2011 (UTC)

Thanks199.33.32.40 (talk) 18:46, 3 August 2011 (UTC)

That of course implies that any human created model of the universe could even be fundemental. I'm not entirely convinced that any model could exist at infinite precision; The Standard Model exists because it works, not because it is (or even should be expected to be) infinitely true under an arbitrarily high level of precision. If the Standard Model is shown to not apply at certain conditions (be it very high or very low temperarures, or any other set of extremes) then science would supplant it with a more precise model which includes the new data and the new paradigm. It wouldn't make the Standard Model substantially more wrong however; the existance of quantum mechanics doesn't make the Newtonian models invalid, for say, calculating ballistic trajectories or figuring out the stresses on bridge supports. Models are always going to be an approximation on reality, and we choose which models we use by the specific application where they work not because they are expected to be right for all applications. It isn't a question of being "fundementally" correct, just in finding the correct paradigm to give you the best solutions for your particular problem... --Jayron32 15:06, 3 August 2011 (UTC)

Getting sulfur from Gypsum.

Gypsum is Calcium Sulfate and has the formula CaSO4·2H2O, which seems to indicate it has a lot of sulfur in it. Let's say I wanted to get pure sulfur out of gypsum, what would I need to do? — Preceding unsigned comment added by 24.72.218.111 (talk) 06:41, 3 August 2011 (UTC)

You could use a strong reducing agent to obtain the sulfur - though the reducing agent would be worth more than the sulfur. Or you could use microorganisms that extract oxygen from the gypsum under anaerobic conditions - I'm not sure if this has been done on a large scale for synthetic purposes, but it happens accidentally with drywall, which can thus emit hydrogen sulfide which can more readily be used to make elemental sulfur.^[11] Google knows no hits for "fermenting gypsum" - somebody ought to fix that. ;) Wnt (talk) 08:04, 3 August 2011 (UTC)

To what temperature in Kelvin or degrees Celsius does Gypsium have to be heated to decompose it into vitriolic aire and calx? Is it easier to reduce vitriolic aire to sulfur? Plasmic Physics (talk) 08:44, 3 August 2011 (UTC)

"Vitriolic aire" is not a common term for me, but as sulfuric acid is called "oil of vitriol" I'll assume that it is SO3. Usually people are interested in doing this reaction the other way, in Flue-gas desulfurization. From a few scraps I just read it sounds like the decomposition of gypsum isn't very pretty, with decomposition starting around 900 C but peaking at 1200-1300 C.^[12][13] Decomposition is into lime (CaO, calx?) and SO3, but at that temperature SO3 is more or less in equilibrium with SO2. At much cooler temperatures, 500-800 C, SO2 (and I assume SO3) can react with carbon to produce elemental sulfur.^[14] Wnt (talk) 13:50, 3 August 2011 (UTC)

Evolution

Apart from Index to Creationist Claims, what other major, long, detailed or comprehensive list of arguments defending evolution or responses to arguments against evolution are there on Internet websites? Is that list the only such list in talk.origins?

I am asking this because there is a list of responses to Index to Creationists claims in Creationwiki. — Preceding unsigned comment added by 110.174.63.234 (talk) 08:34, 3 August 2011 (UTC)

There is no need for a list since the validity of scientific theories is not decided by a list contest. Dauto (talk) 14:29, 3 August 2011 (UTC)

That really doesn't answer the poster's question at all. I can think of plenty of reasons why a list would be useful, besides a "list contest". —Akrabbim^talk 14:50, 3 August 2011 (UTC)

Don't know if you'll think it counts but there are several YouTube channels with lots of evolution videos that give evidence for evolution and also rebut creationist claims. I can't search YouTube at work but the main one I can think of off the top of my head is thunderf00t, if you find his channel you should be able to go through related videos from there. His most recent videos have him debating banana man, I recommend you don't start with those videos since his debating is not nearly as polished as his self produced videos. Vespine (talk) 22:27, 3 August 2011 (UTC)

EM waves traveling through a vacuum

What's the physical difference between a volume of space in a vacuum with no EM wave propagating through it and another volume of space in a vacuum with an EM wave propagating through it? 20.137.18.50 (talk) 18:18, 3 August 2011 (UTC)

The physical difference is that one has an EM wave propagating through it and the other does not. Sorry, but that is a physical difference, and there's no simpler way of stating it. I could say that one of them contains photons and the other doesn't, but that really isn't any simpler. Looie496 (talk) 18:24, 3 August 2011 (UTC)

"I could say that one of them contains photons and the other doesn't, but that really isn't any simpler." If that's true, then the presence or absence of wave/particles is something I can begin to get my head around. 20.137.18.50 (talk) 18:27, 3 August 2011 (UTC)

It may be easier to take your thinking back one step, classification wise, to understand how EM radiation works. Think of EM radiation as a physical thing itself. That thing can be modeled as or observed as a wave, or it can be modeled as, or observed as, a particle, depending on which context you want to work with it. It's kinda like asking "am I a father or am I a son". I am actually both, but it depends on what context (in relation to my own father, or in relation to my own child) you are asking the question. Likewise, "electromagnetic radiation" is a thing like me. Asking whether or not EM is a wave or a particle depends purely on the context of the question. Just as I am both a father and a son at the same time, and I can say that without contradiction, you should also be able to accept that EM is both a wave and a particle at the same time. When you ask "what is the difference between the a vacuum with EM radiation and one without", the simple answer, as Looie496 stated, is the radiation itself. --Jayron32 18:37, 3 August 2011 (UTC)

And from the experimental point of view, the presence of a EM wave can be detected with, for instance, an antenna. Associated with the wave there are oscillating electric and magnetic fields (That's what's waving) which influence the behavior of the electrons in the antenna creating a measurable signal. Dauto (talk) 18:43, 3 August 2011 (UTC)

However you want to slice it: electric fields, and magnetic fields, are fundamental properties of the universe. They exist. We can measure their values. We can write equations that precisely model their observed behaviors. You can choose a variety of different approaches to write accurate equations that work well for particular scenarios.

(Classical electrodynamics): If you want to model the universe as a coordinate-space, you must define a vector-field for the electric (E) and magnetic (B) fields. An electromagnetic wave exists when this vector-field takes on certain specific values, and can propagate. We explicitly define those values by solving the wave equation for Maxwell's equations, which define the relationship between the position and value of E- and B- fields.

(Relativistic electrodynamics): Special relativity explains the coordinate-transform that relates electric field and magnetic field. Using the mathematical framework provided by relativity, it becomes trivial to translate your coordinates into a different frame; physically, this means that magnetic field and electric field represent the same phenomenon. For example, one observer at one position at some instant may see a static magnetic field; while relatively-moving observer (moving at a specific velocity) may see no magnetic field, and a time-varying electric-field. These observations are equivalent and consistent with a coordinate transform. Maxwell's equations, which work in classical situations, work equally well for relativistic treatments.

(Quantum electrodynamics): If you want to model the universe using particles, you must specify the position and value of the photons, which is equivalent to defining the wavefields as above. If you consider incredibly small time- and length- scales, or very high energies, you must consider other fundamental interactions, in addition to electric and magnetic interactions.

(Electroweak unification): Furthermore, electric field and magnetic field are special cases of electroweak interaction, observed at low energy scales. Electroweak unification is the rigorous mathematical formulation that explains how electric field, magnetic field, and the weak interaction can all be represented in a single equation.

Whether you want to model this universe by representing it with quantized state (including inherent uncertainties in those quantized states); or if you prefer to model it as a set of continuous fields for all coordinate-points; or as a lorentz-contracted, general-relativity-compensated space-time coordinate system; it is just this simple: electric field, and magnetic field, are fundamental properties of the universe, along with the value of mass and charge, and a few other physical quantities. We take their existence in the equations as axioms, because that matches our observations of the universe. Despite their apparent mathematical simplicity, the equations we use to define field or particle interactions are based entirely on experiment. Nimur (talk) 19:05, 3 August 2011 (UTC)

Gravitational waves and frame of reference

I was just reading the article on gravitational waves, and from what I gathered, any moving object produces gravitational waves, like a boat on a lake. Would this mean that there is an absolute frame of reference? --Melab±1 ☎ 19:38, 3 August 2011 (UTC)

Never mind, I saw the part talking about acceleration. But, does anyone still care to comment? --Melab±1 ☎ 19:38, 3 August 2011 (UTC)

You said "any object", but I suspect that all massless particles should be excluded from this list, so make that "any object with mass". StuRat (talk) 20:15, 3 August 2011 (UTC)

Your suspicions are unfounded. Massless particles also contribute to gravity, since they do carry energy. Beware that only the rest mass of a massless particle is zero. Dauto (talk) 20:47, 3 August 2011 (UTC)

Well, I'll comment on the original question. My understanding is that gravitational waves are thought to transform in the same way as light waves -- a way that does not yield an absolute frame of reference. Looie496 (talk) 15:42, 4 August 2011 (UTC)

Destroying the Popemobile

Could the Popemobile be destroyed by an anti-tank weapon? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:54, 3 August 2011 (UTC)

Simply glancing at both articles that you linked make it clear that the Popemobile has bullet-proof glass around the Pope's seat and anti-tank weapons easily cut through bullet-proof glass. -- kainaw™ 19:58, 3 August 2011 (UTC)

If the Popemobile was impervious to anti-tank weapons, wouldn't they make tanks out of the same material? AndyTheGrump (talk) 20:52, 3 August 2011 (UTC)

I thought maybe the Popemobile had something besides bulletproof glass protecting the Pope. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:50, 3 August 2011 (UTC)

"Sir, It's impervious to our anti-tank weapons!" "Then it's time to break out the big guns. Prepare the anti-popemobile weapons." APL (talk) 22:03, 3 August 2011 (UTC)

Many of the Popemobiles don't even have glass. They are completely open. Did you even attempt to scan the article? -- kainaw™ 15:04, 4 August 2011 (UTC)

Yes hes also protected by God . No weapon forged against his Holy Father shall prosper! (Isaiah 54:17) FeydHuxtable (talk) 15:58, 4 August 2011 (UTC)

[[Except for all of those Popes who were, in the end, assassinated. --Mr.98 (talk) 16:17, 4 August 2011 (UTC)

No. There are several Popemobiles so one anti-tank weapon would be insufficient. Also permission to do the experiment might be refused. Cuddlyable3 (talk) 22:20, 3 August 2011 (UTC)

Answering Kainaw: It says that Popemobiles have been required to have bulletproof glass ever since the Pope John Paul II assassination attempt. Answering FeydHuxtable: Listen to Mr.98. Answring Cuddlyable3: There may be several Popemobiles, but there is only one Pope. All an assassin would have to do is figure out which one is carrying the Pope and then fire off his anti-tank round. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:37, 4 August 2011 (UTC)

the moon should have an atmosphere

because take ONE lonely molecule of whatever "air" you want...as it wonders around the moon, it would rather go inside (due to the moons gravity however small) than wander off, and once it is around the surface, that small gravity will always be enough to make it go 'Id rather stick around here" than just wander off again, as though the moons gravity was literally 0. so by this reasoning, either there is no moon, its mass is really 0, mass does not correlate with gravity, or the moon actually does have an atmosphere contrary to popular opinion. is this? p.s. excuse lithuanian. — Preceding unsigned comment added by 84.0.197.58 (talk) 22:07, 3 August 2011 (UTC)

Does the article Atmosphere of the Moon answer your questions? --Jayron32 22:13, 3 August 2011 (UTC)

I'm sorry, but that article seems to be gobbledegook to me, and more a coverup than anything else. It's very short, for one thing, and introduces a word word "sputtering' for how sunlight supposedly pushes off the atmosphere from the moon, and also 'outgassing' and 'meteorites' all to push the atmosphere off of the moon. Sunlight obviously has a negligible ability to move anything, as opposed to enough gravity for the astro-men to make just tall bounds, but fall back to the moon. Think about it: the astro-men jumped and fell back down, but we are to assume that sun somehow with light alone makes the atmosphere careen off? Also outgassing is likewise ridiculous suppogestion - it might explain why some things from INSIDE the moon go volcanoing off outside the moon, but that does not explain why atmosphere already hanging around would not fall in, just like astro-men. The only reasonable explanation from reading that article (which does not address any of my specific questions posed above) is that it is a cover-up, invented after a fact, perhaps to match imagery or prevously published astro conjecture. There is nothing in the article which makes sense to me, and the whole thing is fishing. Can you address my points in this paragraph, if I am after all mistaken (which is not without unprecdent). Also with micrometeorites, what is the article suggestion: that for every molecule of gas, a micro-meteorite comes at just the right trajectory to careen off with it like two billiard balls? Or, what is the mechanism supposabled?--84.0.197.58 (talk) 22:23, 3 August 2011 (UTC)

You have misunderstood the article that Jayron32 referred you to; it actually explains how the Moon does have a thin but lingering atmosphere. The article Sputtering explains what that word means. Congratulations on your mastery of English as a Lithuanian apparently located near Budapest, and on exposing yet another of Wikipedia's cunning coverups. Cuddlyable3 (talk) 22:46, 3 August 2011 (UTC)

Despite your disbelief solar radiation and solar wind do exert enough pressure to remove most of the moon's atmosphere. Why on earth would anybody want to cover up the existence of a lunar atmosphere?

(WP:EC)As I understand it, you're technically correct; there are a few gas molecules hanging around. See Atmosphere_of_the_Moon, which describes how this 'atmosphere' is so low-density as to be negligible, for all but the most pedantic or specifically detailed purposes. SemanticMantis (talk) 22:16, 3 August 2011 (UTC)

Atmospheric escape has better detail than Atmosphere of the moon, for some reason. Comet Tuttle (talk) 22:34, 3 August 2011 (UTC)

The language desk will be green with envy of "suppogestion". Wanderer57 (talk) 00:59, 4 August 2011 (UTC)

Acutally the reason why earth enjoys such a healthy and thick atmosphere is due to the Magnetosphere, without it the sun would blow most of our atmosphere away too, which is precisely what happened on Mars and is the reason why Mars only has a thin atmosphere. Secondly, comparing astraunaughts to gas molecules is pretty silly. Astraunaughts are huge and slow and gas molecules are tiny and fast, they only need a tiny push in just the right direction to send them flying. Vespine (talk) 01:21, 4 August 2011 (UTC)

I think OP asks a valid, interesting and intelligent question, and the ones who "answered" him perform the usual wp bizzo of setting up a straw man, and bashing that, or just ignoring the question. There are gas molecules that come in from outer space, and ones that are radiated from within the moon. Is it not the case, OP wants to know, that ALL of these molecules will be bound permanently to the moon, and so the atomosphere can only grow, and never be diminished?

I think the answer is that as the sun warms the gas, some of the gas molecules will be bounced up high and come near to the escape gravity zone. There, if they hit again in the right direction, they will leave orbit and escape the moon. The more molecules there are, the more likely it is that such collisions will occur, and the more gas molecules will leave the moon. That means that as the atmosphere is depleted, the gas becomes colder and less active. That it turn means that there will always be a thin gas around such bodies, but the less massive they are, the more likely it is that gas will escape the planet. There is probably some mathematical correlation whereby we could predict how thin the atmosphere of a planet would be, if we know how massive it is. Myles325a (talk) 07:31, 4 August 2011 (UTC)

Nobody is bashing strawmen here. we gave him a straight answer and he disdained it as being ridiculous. There's nothing we can do if someone refuses to read an article with an open mind. By your answer it seems to me that you should read Atmospheric escape as well to get a more thorough understanding of that subject. Dauto (talk) 14:18, 4 August 2011 (UTC)

This is a fair question, not answered in the article, and the language gibes are uncalled for. Now let's get started. From a quick Web search:

Lunar escape velocity = 2.4 km/s

Mars escape velocity = 5 km/s

Venus escape velocity = 10 km/s

Earth escape velocity = 11 km/s

Jupiter escape velocity = 60 km/s

As we see, that's a difference, but not nearly so qualitative a difference as there is between the atmospheres of these planets. Atmospheric escape explains that Mars and Venus have both lost a fair amount of atmosphere due to their lower mass. Specifically it explains (Atmospheric_escape#Thermal_escape_mechanisms that escape happens because some individual molecules of air reach escape velocity, at the level in the atmosphere where the mean free path is comparable to the scale height. That last bit means the bigger a planet's atmosphere, the higher a platform the air has to jump from in order to reach orbit; but even on Earth that isn't really much of a difference. For Jupiter and Saturn it probably matters! But the key here is that there's someplace where you're looking at the Maxwell distribution and asking how many individual air molecules, just because of their temperature, can make the jump all the way out beyond the planet's gravitational pull, never to return.

Now if you think the article about the lunar atmosphere is gobbledygook, you're not going to like that article on the Maxwell distribution, but reading through it carefully it looks like the drop-off for high velocities is proportional to e^(-v^2), which provides a pretty sharp cutoff. (I've tried before to make mathematical articles clearer to the reader, but their incomprehensibility is pretty strongly defended, and I'm not good enough with the topic to accomplish much) Note that the difference between Earth and the Moon is comparable to the difference between Jupiter and Earth - as a result Jupiter swims in a vast sea of hydrogen, whereas the Earth is stripped of hydrogen and helium, and the Moon is stripped of everything. (Temperature also has to do with this, but I think it would only affect velocity according to its square root, which isn't that huge of a difference) Though I suspect that if there were enough xenon it could hold onto that - I see some forum postings and such agreeing but didn't pursue a good source. Wnt (talk) 17:17, 5 August 2011 (UTC)

August 4

Spotting nocturnal animals at night

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 full...an 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)

Response to Creationwiki

What is talk.origins's response to Creationwiki's refutations of Index to Creationist Claims? What are its people's response? — Preceding unsigned comment added by 110.174.63.234 (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 talk.origins 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 talk.origins responses, look in the web archives and some usenet archives of talk.origins 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 talk.origins, 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 talk.origins, they shouldn't be giving a response like they would on talk.origins. Bear in mind talk.origins is just a usenet group, and the talk.origins archive is primarily someone's archive of selected posts to the usenet group. There is no such thing as an 'official' talk.origins 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 [15] 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 [16] (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 talk.origins 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

i got my medical check-up result,and was curious about the medical terminology.ABO :O — Preceding unsigned comment added by 173.2.212.31 (talk) 05:32, 4 August 2011 (UTC)

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

International space station

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 (talk • contribs) 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 McWalter ☻ Talk 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

actually universe is huge...we born on earth .which is in milkyway galaxy and our star sun..how about the evidence of the aliens or living creatures on other galaxies ? they too have huge stars and some dwarf galaxies too...is there any evidence or any reports those things? — Preceding unsigned comment added by Pebel vsrk (talk • contribs) 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 $10^{10^{1000000000000000000000000000}}$ 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)

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)

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

I would like to know what companies made periscopes and TDC's for US submarines of WW II, please 24.89.36.162 (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

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.199.33.32.40 (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

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. 82.43.90.27 (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

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 27.97.208.211 (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)

Freeview signal, UK

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? 92.24.140.101 (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 McWalter ☻ Talk 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 McWalter ☻ Talk 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 McWalter ☻ Talk 21:09, 4 August 2011 (UTC)

Brownian ratchet

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?

86.181.170.252 (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? 86.181.170.252 (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. 86.181.170.252 (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? 86.181.170.252 (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

$\langle E\rangle ={\frac {1}{2}}I\langle \omega ^{2}\rangle ={\frac {1}{2}}k_{B}T$

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?) 86.181.170.252 (talk) 02:34, 5 August 2011 (UTC)

Living liquid

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?

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." [17] 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. 86.161.210.242 (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)

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)

August 5

Question (acetone)

I used Acetone to clean my car windows. The fumes and vapors from the Acetone got so bad that it irritated my eyes and body. What can I do to get rid of the fumes and vapors? Thanks and hope to hear from you soon. Thanks for the answers, is there any more suggestions. — Preceding unsigned comment added by 174.111.55.161 (talk) 01:30, 5 August 2011 (UTC)

If that question still requires an answer, let us know. μηδείς (talk) 01:48, 5 August 2011 (UTC)

Roll down the windows and drive for an hour with the air blasting through the car. You might wish to read our acetone article. Looie496 (talk) 01:50, 5 August 2011 (UTC)

If the vapour saturation is high enough, duck and light a match. Plasmic Physics (talk) 02:02, 5 August 2011 (UTC)

Watch out, some idiot will try that and sue... but seriously, acetone is a small, highly volatile molecule which easily diffuses into the air and blows away. Also, in small amounts acetone is a normal metabolite in the human body - though in diabetics it can build up to acetone breath and become part of a pathology. So as long as you let the car air out enough that you don't smell it (assuming a normal sense of smell) it should not be a hazard at trace levels. Wnt (talk) 05:24, 5 August 2011 (UTC)

Can hardly sue Wikipedia for misinformation, it is a wikia afterall. Plasmic Physics (talk) 08:04, 5 August 2011 (UTC)

No, but they can get a court order to force Wikipedia to reveal your identity, and then they can sue you. --Jayron32 16:16, 5 August 2011 (UTC)

Is using acetone to clean car windows a good idea? Seems like a great way to ruin the rubber seals and allow leaking later, or to damage the paint on the car. Googlemeister (talk) 12:49, 5 August 2011 (UTC)

Agreed, bad idea. Use the blue window washer solution made for cars. But, now that the deed is done, I suggest rinsing it thoroughly, rolling all the windows down, and letting is sit for a while. StuRat (talk) 21:51, 5 August 2011 (UTC)

Thomisida

White and pink crab spider

. Good morning everybody. This spider is surely a member of the Thomisidae family. But I'd like to know the exact species. I photographed it in July, in my garden, lower St-Lawrence region, Prov. of Quebec, Canada. Dhatier (talk • contribs) 03:21, 5 August 2011 (UTC)

Good morning. That is a very fine photograph. Cuddlyable3 (talk) 12:40, 5 August 2011 (UTC)

WHAT PERCENT OF THE PLANETS IN THE GALAXY HAVE LIFE

i know it is hard to say for sure, so your best guess is fine. also, do most planets with life have aliens (sentient) or just trees and bugs and single cell organisms?--Fran Cranley (talk) 03:42, 5 August 2011 (UTC)

The short answer is that nobody knows. The long answer is to look at the Drake equation, fill in the necessary fields with whatever value you consider appropriate, and then admit that you don't know either. All we know is that this planet has life, and that it took a long time to evolve to its present state - so a modicum of care over the health of the planet might not be misplaced. AndyTheGrump (talk) 03:50, 5 August 2011 (UTC)

From what we have observed, it seems there could be 1,235 planets outside the solar system that we can detect (as of Feb 2011). There are also 8 planets in this solar system. As far as we know only 1 of them has life (but we could be wrong). So if you want to calculate a percentage based exclusively on what we have observed of the Galazy so far, it is 0.0805%. Obvioulsy there is a vast amount of unobseverd planets, so that percentage doesn't mean anything at all. --Lgriot (talk) 11:21, 5 August 2011 (UTC)

We don't know if any of the "observed" extrasolar planets have life ("observed" in quotes because we mostly just deduce their existence indirectly from spectrographic and brightness variations when observing their parent stars). We have found no blindingly obvious signs of life on other planets in the solar system, but we have extremely rarely even looked for signs of life at any of the known or suspected extrasolar planets. Our tools for doing that are wholly inadequate at the moment. Indeed, our inadequate observation equipment very much limits the type of planets we can detect to implausible candidates for life. Life on Earth evolved essentially as soon as the surface cooled down. This suggests that primitive life may be very frequent. On the other hand, complex life seems to have taken ~3 billion years to evolve from single-celled ancestors, and wether Earth has evolved intelligent life yet is debatable ;-). --Stephan Schulz (talk) 11:44, 5 August 2011 (UTC)

Where do we find anyone intelligent enough to debate that? Cuddlyable3 (talk) 12:38, 5 August 2011 (UTC)

I believe life must be far more prevalent than intelligent life. As noted above, life on Earth seemed to start as soon as the proper conditions existed, so I would assume this would also happen elsewhere. However, if there were many planets with advanced technology, then we'd expect to have heard from some by now. Perhaps there's a middle ground, with many planets containing whales and such, which are somewhat intelligent, but either not quite intelligent enough for extra-planetary communication, or simply lacking the hands, tentacles, etc., needed to do so. StuRat (talk) 21:46, 5 August 2011 (UTC)

What I'm a bit scared about is that the reason for the Fermi paradox may well be that technological civilisations destroy their habitat (and thus themselves) before they learn to leave it... --Stephan Schulz (talk) 23:46, 5 August 2011 (UTC)

Water flowing on Mars???

NASA is saying they see evidence of briny water flowing on present-day Mars, perhaps under the surface. How on, erm, Mars is it possible for water to be liquid when it should freeze or evaporate in the cold and thin atmosphere? Wnt (talk) 05:01, 5 August 2011 (UTC)

The simple answer is that the conditions under the surface must be different enough from those at the surface to circumvent the problem you describe. Dauto (talk) 06:14, 5 August 2011 (UTC)

Do planetary geologists predict higher pressures underground on Mars sufficient for liquid water to exist? -- 203.82.81.40 (talk) 07:39, 5 August 2011 (UTC)

The key is "briny". Pure water would definitely not be in a stable liquid state at the temperatures that they observe at these sites (250 to 300 K). Salt decreases the melting point of water (by up to 70K, they say) and makes it more stable. --Wrongfilter (talk) 11:28, 5 August 2011 (UTC)

I see someone has started a pretty nice article on seasonal flows on warm Martian slopes, which clarifies that even though the water may be only as salty as Earth's oceans, the slopes are 250 to 300 K. I hadn't realized that anywhere on Mars ever got up to such balmy temperatures! But what still confuses me is why it doesn't evaporate instantly. Is there some way that a relatively thin layer of soil could maintain a partial atm of pressure? Wnt (talk) 16:18, 5 August 2011 (UTC)

Yes, that is what I am wondering. From a Terran point of view, the atmosphere of Mars seems rather vacuous (MSL pressure of ~ 0.6% earth atmosphere. Also, where can I read abou the physical properties of brine? Wrongfilter suggests a 70K freezing-point depression, but our brine article gives 21.1 K (delta temp). Can the boiling point be elevated over this at such low pressures? -- 203.82.93.106 (talk) 20:23, 5 August 2011 (UTC)

I recall reading that Mars was at 20 degC when one of the probes landed on it, but I don't recall which probe it was and if that value turned out to be a measurement error or anomaly. Googlemeister (talk) 20:26, 5 August 2011 (UTC)

Per Climate of Mars the orbitally observed range is -143 to +27 C with a mean temperature of -55 C. The upper part of that range would allow liquid water even without solutes, but it would still turn to vapor under the very low pressures present at the surface. Dragons flight (talk) 00:09, 6 August 2011 (UTC)

Some thoughts:

1) Mars may have had a thicker atmosphere in the past. The magnetic field of a planet seem important here, as it deflects the solar wind, which would otherwise blow the atmosphere away. Early Mars likely had a strong magnetic field, like Earth, due to a molten iron core.

2) Modern Mars is rather desert-like, and deserts have extremes of temperatures. So, while the average temperature may be much lower on Mars, those portions in direct sunlight may warm up considerably, with little atmosphere and no oceans to support cooling and redistribution of that heat by convection. StuRat (talk) 21:38, 5 August 2011 (UTC)

Claims of Scientific Evidence Against Evolution

I have heard some people claim that there is scientific evidence against evolution. Is that true? If so, then what they? Are they really scientific evidences against it? — Preceding unsigned comment added by 110.174.63.234 (talk) 08:22, 5 August 2011 (UTC)

No they are not real scientific evidence against it. Real evidence agaisnt it would be for example fossils of rabbits in the precambrian. Nothing like has ever been observed. It is just people making it up, because they don't want to accept the massive biological evidence AND DNA evidence, AND fossil evidence that are all pointing to the same obvious conclusion: Evolution is a fact.--Lgriot (talk) 11:30, 5 August 2011 (UTC)

FYI, we have articles directly relating to Lgriot's claims: Precambrian rabbit & Evolution as theory and fact. — Scientizzle 15:29, 5 August 2011 (UTC)

The Talk.origins website has a taxonomically organised list of claims by creationists. Notice "claims", not "scientific evidence". The list is here. --Stephan Schulz (talk) 11:48, 5 August 2011 (UTC)

Fossil rabbits in the Precambrian layer wouldn't disprove evolution. Even I you could prove they were definitely from that time period, and weren't just some later insertion, it would only disprove our current models of common descent and maybe our current taxonomical theories. To disprove biological evolution itself would require something much more basic, like disproving that traits are physically inherited, or proving that each species can only vary within certain narrow parameters and that they therefore cannot drift more than a certain genetic distance from a somehow hardcoded 'typical' version of the species, or that no mutations ever produce viable offspring. Of course, we have such a wealth of data showing the opposite that you would also have to show how all this data could be wrong, while proving this unlikely scenario. It would have to be a proof on such a basic level, because biological evolution is a mathematical inevitability once you have inherited traits, variation in traits, and variable reproductive success. Even if the inherited traits had no impact on reproductie success, you would have genetic drift which is sufficient to establish new species if populations are isolated. This is, of course, why even many of those pushing for a creationist interpretation start introducing things like 'Intelligent Design' and 'microevolution': because any halfway intelligent person who looks at the evidence can see that evolution simply has to happen, unless our most basic assumptions about inheritability, or even cause and effect, are fundamentally broken. 212.183.128.47 (talk) 12:03, 5 August 2011 (UTC)

it would only disprove [...] maybe our current taxonomical theories. Maybe??? Come on, mamals during the precambrian era!? it would maybe disprove our current taxonomy? It would be earth-shatering. We'd have to review everything end-to-end. I'd personnaly start wondering if something is playing a little game with us. And I'd be very interested in those theories that try to reconcile these rabbits with the taxonomy we now have. That would be a very interesting debate. --Lgriot (talk) 13:29, 5 August 2011 (UTC)

I can't help it: I read too much scifi. Time machine? Aliens? Separate descent of animals up to rabbits on Atlantis, spreading to the rest of the world when it sank? Rabbit-shaped plant roots? Rabbits turn out not to be mammals? Given that any theory has to explain why all the other evidence suggests our current theories as well as explaining the rabbit, I wouldn't like to say with certainty that it would actually suggest our underlying theories of how taxonomy works would necessarily be wrong, since it would be so unlikely anyway that an explanation that looks unlikely now might look more likely in the event. But even if we had to rework all of that from the bottom, it still wouldn't disprove evolution. 86.161.210.242 (talk) 15:23, 5 August 2011 (UTC)

Perhaps rabbits evolved intelligence and made an attempt at paleontology, with some casualties. ;) But seriously, there is a point there that if we can think of excuses for such a gaping hole in the theory, there's some doubt as to the falsifiability of the theory. I don't think this is a problem limited to evolution though - any theory which is extremely fundamental to a science becomes difficult to falsify because there are so many lines of proof favoring it and so many ways to explain away one experimental observation (the Voyager data questioning whether gravity is really inverse square, for example). There may indeed be some risk that a society could be "blinded with science" this way, but I doubt evolution (or gravity) is the example. Wnt (talk) 16:26, 5 August 2011 (UTC)

And, while we are on the subject, "What, if anything, is a rabbit?" [18] AndyTheGrump (talk) 16:36, 5 August 2011 (UTC)

Maybe finding the Precambrian fossils of this rabbit would convince me, or at least convince me to run away... very, very fast. --Modocc (talk) 21:20, 5 August 2011 (UTC)

You mean Pioneer, not Voyager. The Voyagers weren't spin-stabilized, instead achieving attitude control through the frequent firing of thrusters. The resulting unpredictable little accelerations are much too big for it to be possible to determine if the Voyagers have also experienced the Pioneer anomaly. Red Act (talk) 17:35, 5 August 2011 (UTC)

Good catch! No wonder I didn't find the link. ;) Wnt (talk) 18:11, 5 August 2011 (UTC)

The honest answer is, of course there's scientific evidence against evolution. There's scientific evidence both for and against practically any proposition you care to name. The problem is to weigh the evidence, and figure out, on balance, which side does it support more than the other. --Trovatore (talk) 22:35, 5 August 2011 (UTC)

Come on then. Give us the answer to the OP's question. What IS that evidence? I can't think of any. HiLo48 (talk) 22:47, 5 August 2011 (UTC)

I'll answer, but before I do let me clarify that I'm a biologist myself and pretty much totally convinced of the validity of evolution. The strongest evidence against it, in my view, would be cases where biological systems seem to show very sophisticated engineering, in ways whose natural origins we don't yet understand. One very basic example is the genetic code, using triplets of DNA to code for amino acids; a less basic one that particularly strikes me is the modular structure of the cerebellum. Looie496 (talk) 23:28, 5 August 2011 (UTC)

I wasn't even necessarily going that deep. My point is more that evidence comes in chunks of all sizes; sometimes you put together a lot of little pieces of evidence, none of them very strong in themselves, to reach a scientific conclusion. And there are certainly various small pieces of evidence against evolution. For example, whenever we think that species B evolved from species A, but there must have been an intermediate type C, then if evolution is true, it is more likely to find C in the fossil record than if evolution is not true. If, then, we have not found C in the fossil record, then in the sense of Bayesian inference, that is a small, scientific, data point against evolution. It is not convincing in itself, but it is the sort of thing that could be added to a scientific case against evolution, and is therefore evidence. --Trovatore (talk) 23:58, 5 August 2011 (UTC)

Radio frequencies

I recently noticed my local FM station at 107.9 can also be heard at 86.5. Why is this? I know that the Intermediate frequency is 10.7 MHz, and 107.9 - 10.7 -10.7 is 86.5, though I have no idea how this plays into effect. ^Avic_ennasis @ 13:31, 5 Av 5771 / 5 August 2011 (UTC)

If you look at the station's website, you might find that it has a main transmitter and a relay situated somewhere else, in order to get better coverage. Hence, they'll be on separate frequencies.--Aspro (talk) 13:49, 5 August 2011 (UTC)

(ec)Broadcasters want everyone in a large area (say all of Belgium or all of Arkansas) to hear a station. But a single tower broadcasting will not reach the whole territory (for reasons of power use and topography). So they (or usually mast operating companies like Arquiva) built multiple towers (usually on top of hills) to "tile" the whole territory. In order to service people in remote valleys and people with rubbish antennas, these transmitters are a bit overpowered (than they'd need to be if everyone had a big antenna on their roof). So if you live roughly between two towers, you can see both. In #Freeview signal, UK, above, we talk about the same scenario for TV reception. But whereas TV antennas are (kinda) directional, you'd usually receive FM with an omnidirectional antenna, so you can receive signals from both towers on the same radio receiver, without having to do anything to the antenna. To prevent the two towers from interfering with one another, they transmit on different frequencies. For you, between the two, you're getting a reasonably strong signal from both. You've not said what country you live in (and where) which would help us know precisely what's up, but the scheme is much the same the world over. You can search the website of whatever authority controls broadcast in your country (e.g. in the US it's the FCC) and find the locations of all the regional radio and tv broadcast towers (and their boosters), which usually also lists the channel assignment (the frequencies) each station is broadcast on from that tower. Armed with that you can figure out the physical location from which you receive every signal. TL;DR - you're getting signal from different towers. -- Finlay McWalter ☻ Talk 13:50, 5 August 2011 (UTC)

I understand the use of multiple towers/frequencies to reach a larger audience. However, unless I'm mistaken, most FM radios in the US don't go below 87.5, which is why I'm surprised to hear content on 86.5. Also, if it matters, the callsign of the station heard on 86.5 is "Y108", the same as 107.9. If they were intentionally broadcasting on 86.5, wouldn't they have to identify that in some way? ^Avic_ennasis @ 14:04, 5 Av 5771 / 5 August 2011 (UTC)

The original signal at the intermediate frequency (IF) has to be mixed with another frequency to be converted to the carrier frequency. Mixing is kind of like adding and subtracting frequencies, so to get 107.9 MHz from 10.7 MHz, you need to mix it with 97.2 MHz (97.2 + 10.7 = 107.9). However, on the output of the mixer there will also be an identical signal at 97.2 minus 10.7, or 86.5 MHz. There is meant to be some filtering to remove the 86.5 MHz signal, but in this case some energy managed to get through to you, since none of the components are ideal. —Akrabbim^talk 13:55, 5 August 2011 (UTC)

I think your math is a little off. :-) If it helps, the local station is WDSY-FM. ^Avic_ennasis @ 14:04, 5 Av 5771 / 5 August 2011 (UTC)

Thanks, typos corrected (87.5 --> 86.5). —Akrabbim^talk 14:11, 5 August 2011 (UTC)

In that case, it might be a pirate re-transmission. Is this the first time you have noticed it; in other words, could it have just popped up during the summer vacation like so many pirate stations. Just looked up the US frequency allocations and this is for television, non government broadcasts; that finishes at 88mhz with FM radio above that. So, off-hand I cant think of any legitimate reason that it should be there. Also, if you can receive it way-down-there on 'your' radio, it suggest to me there might be a slight chance that you also have your rig wired up to a rotatable array of some sort, in which case you could have a go at DXing its location and reporting it.--Aspro (talk) 15:02, 5 August 2011 (UTC)

Akrabbim is correct and the effect is described at Superheterodyne receiver#Image frequency (fimage). The guesses above about multiple transmitters, pirates and a direction-finding rig are all wrong. Cuddlyable3 (talk) 16:09, 5 August 2011 (UTC)

The "Laotian bird" Nock-ten (2011)

I have posted a question here at the language desk asking for a reliable source explaining the nature of the "Laotian bird" for which this storm is named. Comments there by those who might have a clue would be appreciated. μηδείς (talk) 15:57, 5 August 2011 (UTC)

I don't know. But a source that looks like it actually took a moment to do some translation says it's Laotian for "bird" (rather than a kind of bird).[19] True, most of the world's media says that it's a "Laotian bird", but I have a sinking feeling they're all copying each other and a 2004 Wikipedia article. [20] This becomes increasingly a worry - as Wikipedia becomes the only easy source for looking up certain things, we may end up breathing our own exhaust. Wnt (talk) 17:28, 5 August 2011 (UTC)

Maybe we're looking in the wrong place. Tropical Storm Nock-ten (2011) says it was the Japan Meteorological Agency (JMA) which gave the storm that name. Maybe it would be more reasonable to assume that it's a Japanese word, maybe for a Laotian bird. HiLo48 (talk) 22:39, 5 August 2011 (UTC)

When in the history of Astronomy could a planet on the far side of the sun be ruled out?

Hello everyone, bit of a conundrum for you. A common speculation in the old sci-fi genre over the years has been a planet orbiting the sun in the same orbital plane as the jolly old Earth but exactly opposite us, so it was always concealed behind the Sun. I was wondering is any of you fine chaps could tell me when such an idea could be definitively proven to be merely a fancy. Not being too up on the old star-gazing routine I'm a bit stumped! I would imagine it could perhaps either been when our understanding of the solar system and our ability to see the effects of a heavenly body's gravitational field on other heavenly bodies was mastered. Alternatively perhaps when those very clever chaps started launching those space probes and the telemetry showed no such place.

Can any of you fine fellows help an old duffer out here? It's a bit hard on the old noggin don't you know. Chin chin! Quintessential British Gentleman (talk) 18:42, 5 August 2011 (UTC)

Yeah, you basically answered it yourself. We'd see such a planet's gravitational effect on other astronomical bodies (Neptune, for example, was expected to exist before we actually observed it...sort of). You might be interested in 2010 TK7, an asteroid that shares Earth's orbit. --Goodbye Galaxy (talk) 19:24, 5 August 2011 (UTC)

Right... but that wasn't your question! Whoops. If I had to guess, I'd say around late 1700s to mid 1800s, but I'm not entirely sure. --Goodbye Galaxy (talk) 19:27, 5 August 2011 (UTC)

If it was a small planet, like Mercury or smaller, it could hide longer then another earth sized planet could, but at some point, the IAU would take away the planet status. Googlemeister (talk) 20:23, 5 August 2011 (UTC)

A so-called counter-Earth would have been known since antiquity, since it would periodically be visible from Earth. First, Earth's orbit is elliptical and not circular, so a planet that was following the same path about the Sun would 'gain' on us when it was close to the Sun, and fall behind when Earth was close to the Sun. (This problem could be avoided if the counter-Earth were in a symmetrical orbit.) The second problem is that the Sun's position is perturbed by the other planets (especially Jupiter) and so wiggles back and forth; depending on where the counter-Earth was in its orbit, it would periodically peek out from behind the displaced Sun.

Leaving aside those issues, a planet of Earth's mass sharing our orbit wouldn't be dynamically stable. (Or, alternatively, our orbit wouldn't be stable.) Small perturbations (caused, for example, by the other planets) would lead to exponentially growing imbalances in the forces on the counter-Earth, relatively rapidly dragging it out from behind the Sun. The mathematics governing Lagrange points (a counter-Earth would be at L₃) showed up in the eighteenth century; presumably a capable astrophysicist of that era would have been able to determine that no stable counter-Earth orbit could exist. TenOfAllTrades(talk) 20:51, 5 August 2011 (UTC)

If it was small enough and dark enough, we might not know about it even now. Of course, as noted previously, something that small can't really be called a planet. However, the definition of a planet includes it clearing it's orbital path of debris, which is difficult to determine if the path was cleared, but presumably mainly by the Earth. StuRat (talk) 21:28, 5 August 2011 (UTC)

Is Wikipedia auditioning for the part of Colonel Blimp? Cuddlyable3 (talk) 21:45, 5 August 2011 (UTC)

Hmmm, it's true that the center of mass of the Sun and Jupiter is outside the Sun. But wouldn't the Earth and Counter-Earth, being bodies orbiting the sun, follow it on its orbit around its center of mass with Jupiter, thus remaining in line with one another and the Sun? Wnt (talk) 22:54, 5 August 2011 (UTC)

move the world

One of the ancient philosophers, maybe Archimedes, stated that with a large enough lever and a place to stand he could move the world. I have my doubts on that. Given known materials, would it be possible to construct a lever capable of moving the earth a distance of 1 cm if we could assume that a 180 lb Archimedes had a place to stand, and a fixed point where he could use his lever, (we should probably assume that he needs to be capable of moving his lever as well)? My guess would be that even if his lever was a Titanium alloy, the lever would need to be so long that poor Archimedes would just have his lever flex on him rather then lifting the earth, but I am only assuming here. Googlemeister (talk) 20:46, 5 August 2011 (UTC)

Agreed, no real-world material would work. Also note that such a lever would be quite massive, so it's gravitational effect on the Earth might well outweigh any use as a lever. StuRat (talk) 21:30, 5 August 2011 (UTC)

(ec)We can't assume what you ask so it's not our problem. Cuddlyable3 (talk) 21:34, 5 August 2011 (UTC)

It should be noted that you don't need a lever to move the world. Any amount of force will do, for example just jumping up and down. Granted it won't move the Earth by 1 cm. But if you're allowed to start not on the Earth ("a place to stand") then you could theoretically shoot yourself at the Earth with enough energy to change it's orbit by 1 cm, or any amount that you like. Rckrone (talk) 22:39, 5 August 2011 (UTC)

According to my rough calculations, if you can find a material workable enough to shape and rigid enough so as not to bend too much, you can nudge the earth over a bit. The trick is to get enough of the material to create a lever with a length something in the range of 100 to 1000 times the diameter of the observable universe. (Less if you weigh more than 200 kilos and are quite strong.)

As noted these are "rough calculations" so please get input from another person at this desk before starting fabrication. CBHA (talk) 23:46, 5 August 2011 (UTC)

A problem here is that like any object, the Earth's doesn't have a precisely defined momentum and position. The uncertainty in the momentum is actually quite large, it's of order sqrt(M k T) with T the temperature at its surface. This means that it becomes a problem to say that a small amount of momentum, say, of order 10 kg m/s added to the Earth actually changed its orbit. The probability that nothing changed at all will be significant. Count Iblis (talk) 00:35, 6 August 2011 (UTC)

August 6

I've read that children dislike vegetables because they're bitter?

I don't see it in the vegetable article though. I'm also wondering if cooking vegetables change their bitterness, if any. Thanks. Imagine Reason (talk) 00:14, 6 August 2011 (UTC)

Most vegetables don't have much bitterness. The most widely eaten exception is spinach; chard and other greens are even more bitter. In Asian cuisine bitter melon is commonly used, and it's a lot more bitter. There are many more bitter spices than vegetables. Looie496 (talk) 00:37, 6 August 2011 (UTC)

Possibly relevant: slow acetylator. --Trovatore (talk) 00:44, 6 August 2011 (UTC)

... except it's a redlink; WADHAAOE. I'm shocked. --Trovatore (talk) 00:45, 6 August 2011 (UTC)

Children dislike vegetables because vegetables don't taste as well as sweets, cookies, icecream, cake etc. Count Iblis (talk) 01:06, 6 August 2011 (UTC)

There are other reasons not to like veggies. Some are tough, and cooking can help there. Adding fat, like butter, can also make them "go down easier". Some people also have a genetic tendency to dislike cruciferous vegetables, like broccoli. And, perhaps by bitter you meant "not sweet". In that case, they may like some of the sweeter veggies, like carrots and beets, or adding a sweet salad dressing to the rest. StuRat (talk) 01:08, 6 August 2011 (UTC)

Or just follow Amy Chua's advice. :) .Count Iblis (talk) 01:50, 6 August 2011 (UTC)

cosmic strings

what are cosmic strings?