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March 9

dust mite covers and bed bugs

Will a special mattress cover designed to keep out dust mites (for those who are allergic) also keep out bed bugs, so that if bed bugs appear in the apartment, the person who lived there wouldn't have to throw out the mattress after eliminating the bed bugs? I guess I want to find out if a dust mite mattress cover could be part of preventative measures. I'm not asking medical advice. Thanks, 74.14.13.241 (talk) 00:02, 9 March 2011 (UTC)

Well it might act as a partial barrier, but bed bugs are particularly resourceful in gaining access to the sleeping body. There are accounts of them climbing up the bedroom wall and jumping off onto the bed, having calculated the appropriate parabolic trajectory! (No, I don't believe that, but I do believe that they will find their way round most obstacles to gain access to their food.) Treatment with insecticide is much more effective, but even that is not guaranteed. Dbfirs 00:11, 9 March 2011 (UTC)

Are you actually asking if the cover will keep them in? i.e. the bed bugs will be locked under the cover and can't reinfect the room? Assuming you kill all the ones in the room? It seems unnecessary to me - killing the bugs in the mattress is pretty easy compared to killing the ones hiding in the room. Also they can live for a year without food, even under that cover. As a general answer, the cover will do nothing, since the bed bugs can live in the room and then walk over to the person on the mattress. (Unlike mites they don't live inside the mattress, they hide on the mattress in seams.) And they can also hide in cracks in the floor or walls, etc. Ariel. (talk) 00:58, 9 March 2011 (UTC)

Antimatter explosion

Is it possible to determine/make an educated guess as to what a (hypothetical) antimatter explosion in air would actually look like? Would it appear similar to a nuclear bomb going off - but larger for the given mass of 'explosive' material? Would there be a mushroom cloud? Would the explosion be the same colour? --Kurt Shaped Box (talk) 00:25, 9 March 2011 (UTC)

It should look more or less like a nuclear explosion, which itself (from a superficial point of view) is just the creation of a gigantic expanding ball of heated air. The mushroom cloud is caused by it being close to the ground, and is not unique to a nuclear explosion (any explosion of a sufficient size will cause one if it is close enough to the ground to suck up dirt). I don't know about the color — nuclear explosions generally just look like the standard black body spectrum (a ball of fire), but you do get weird cloud colors because of the radiation involved, ionization of the air, etc. I don't know what kinds of things you'd get from an antimatter explosion but I'd imagine they would mostly look pretty similar, since the essential thing responsible for the appearance of a nuclear explosion (lots of heat energy all at once) is essentially the same. (I would not expect all of the effects to be the same, mind you. But you can't see neutrons, for example, so the fact that nukes let out gobs of neutrons doesn't really change how they look.) --Mr.98 (talk) 00:31, 9 March 2011 (UTC)

As a point of clarification, while a nuclear mushroom cloud can contain particulate material pulled up (and/or vaporized) from the ground, this is not required to form the cloud. When warm, moisture-laden low-altitude air is rapidly lifted up by the fireball and then cools, fine droplets of water condense out, forming the cap of the mushroom. (Even in the absence of soil and dust from the ground, the vaporized remains of the bomb and its casing rapidly condense to provide a rich supply of condensation nuclei for water droplet formation.) While very-high-altitude bursts won't form explosions, it is because they are unable to draw up enough warm, humid, air from lower altitudes—not because they can't suck up dirt. TenOfAllTrades(talk) 01:12, 9 March 2011 (UTC)

Well, you have to suck up something to get that mushroom stem. If you have an aerial burst (not even high altitude), you get a cloud, but not a "mushroom", like this.--Mr.98 (talk) 12:41, 9 March 2011 (UTC)

If you are reacting exactly equal amounts of the same element (rather than anti-matter in air) it will make almost 100% gamma rays (assuming you can mix the two fast enough, which is NOT easy). That type of explosion will not look like a normal explosion. It will ionize air to a tremendous distance, and will look more like an aurora than a fire. If you just drop anti matter through the air it will look either like a meteor, or a series of explosions (probably depending on how fast it moves through the air). It won't explode all at once, since the initial explosion will push away all the matter, leaving nothing to react with the antimatter. The explosion will then stop, letting matter back in, and it will cycle. If it's moving fast, then the fresh air arriving at the front will constantly provide matter to react with, and it will leave a trail of light. (But because most of the energy is being released in the front, it will rapidly slow down.) I am assuming it will take the form of fire because the two elements being reacted are not the same, so you have residual particles to carry energy as heat. If things match up however (perhaps you pick anti-silicon which has twice the atomic number of nitrogen in air), then you'll get mostly gamma rays and bursts of auroras (aurorae?). Ariel. (talk) 01:08, 9 March 2011 (UTC)

Are you sure it would look like an aurora? What I'm imagining would happen is that said gamma rays would collide with said air and heat them up (e.g. via Compton scattering), making it look like a pretty regular explosion to the naked eye. Similarly the bulk output of energy from a nuke is in the form of neutrons and rapidly moving fission products, which looks, to the naked eye, just like fire when it is done in an atmosphere. The only place you'd notice the difference is if you did it in a vacuum, with a nuke. But I'm not a physicist; this is just my understanding of the visible effects. --Mr.98 (talk) 12:41, 9 March 2011 (UTC)

No, I am not sure (I never got a chance to test the one we built in StuRats lab). But Compton scattering does not heat up air - rather it makes light that looks pretty much like an aurora. And unlike a nuke there aren't any neutrons or other particles left to cause heat effects. It's all neutrinos and photons. Ariel. (talk) 13:15, 9 March 2011 (UTC)

That's completely wrong. Gamma rays don't release their energy by Compton effect. They release it by pair creation that produces a particle shower which efficiently delivers the energy to the medium. I don't think your aurora-like explosion makes any sense whatsoever. The result would be very much like a nuclear explosion. Dauto (talk) 14:33, 9 March 2011 (UTC)

I'm not convinced. Because you have anti-matter (either from the original or the pair production) you can't have a proper particle shower - the shower is annihilated. Maybe some of it heats up the matter, but most will end up as gamma rays again. As further evidence, I heave never read anywhere (and I just checked again) that actual gamma rays from Gamma-ray bursts cause particle showers. If they did then the Compton Gamma Ray Observatory would not need to be in space, they could do it on the ground. Cosmic rays, i.e. protons do. But not gamma rays. Ariel. (talk) 21:51, 9 March 2011 (UTC)

You got it upside down. The observatory must be in space because the gamma rays are effectively blocked by the atmosphere. Read Gamma ray#Matter interaction for more details. notice that pair production becomes the dominant mode of interaction with matter for gamma rays with energy above 10 MeV. A proton-antiproton reaction releases roughly 2000 MeV. The point is moot because most of the energy is released in mesons, not gamma rays, and mesons interact with matter even more promptly than gamma rays do. Dauto (talk) 16:34, 11 March 2011 (UTC)

For further evidence, read Gamma-ray astronomy. Read the caption of the first picture which states "Gamma rays are absorbed by the atmosphere and must be studied from a space telescope.". Dauto (talk) 19:40, 11 March 2011 (UTC)

When I wrote my question, I was thinking something along the lines of an antimatter bomb of comparable physical size to that of a nuke, dropped on an enemy city from a B-52 (or whatever). I suppose that merely allowing the bomb to hit the ground and break open, exposing the antimatter (hitherto contained by a magnetic field in vacuum) to the air would be sufficient for the purposes of mass destruction? That said, what physical effect would a bomb that worked by colliding an equal quantity of elemental matter and anti-matter have on a city and its population - supposing that this massive 'gamma aurora' (and little else) was produced upon detonation? --Kurt Shaped Box (talk) 01:32, 9 March 2011 (UTC)

See Gamma-ray burst. It would sterilize all life. It probably would not do a lot of destruction, because while all those gamma rays eventually end up as heat, they travel quite far and the energy would be spread out. The ground right under the bomb would get hot, but again, the gamma rays would travel deep underground. Note: I'm speaking relatively - it would still be a massive bomb, just not as big as the energy calculations might lead you to expect. If I were designing an anti-matter bomb I would make two types. In both of them I would place the anti-matter in many small containment structures, and place matter right near each structure. The idea it to try to get the two to mix as thoroughly and rapidly as possible. In one type that would be all. I would let them mix, and let the gamma rays sterilize all life. In the second type I would surround the bomb with a tamper designed to absorb as much gamma ray energy as possible. This will turn it into heat and cause a massive physical explosion. This is good for attacking fortifications. StuRat can I join your lab? Ariel. (talk) 02:05, 9 March 2011 (UTC)

Sure, I'm always looking for new henchmen, since they occasional make mistakes and thus must be liquidated. StuRat (talk) 04:15, 9 March 2011 (UTC)

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

I'm not so sure about your speculation here, Ariel. The graph at right suggests gamma rays are absorbed by (transfer their energy to) the atmosphere pretty well. It's hard to say exactly what would happen, but I see no reason to doubt an antimatter weapon would be far more destructive by weight than a thermonuclear weapon no matter where or how you set it off. Please cite a source if you really believe otherwise.WikiDao ☯ 02:44, 9 March 2011 (UTC)

Well by weight no question at all. I was saying by energy. By total energy released, an anti-matter bomb would be less effective than a nuclear one, which in turn is less effective than a chemical bomb. But of course the available energy is far higher so that outweighs it. As far as the graph, that's for the entire depth of the atmosphere. Gamma rays are able to travel in air. Ariel. (talk) 02:58, 9 March 2011 (UTC)

This seems to imply a kilometer for gamma rays, which I guess isn't much. Ariel. (talk) 03:10, 9 March 2011 (UTC)

Your assumption that it's almost 100% gamma rays is incorrect; a significant amount of energy will be carried away by neutrinos. Nucleons and anti-nucleons create pions. While the neutral pions decay largely into gamma rays, the charged pions decay mostly into muons and muon antineutrinos; the muons in turn decay into muon neutrinos, electron antineutrinos and electrons. Icek (talk) 03:29, 9 March 2011 (UTC)

Addendum: And I forgot the positively charged pions, which decay into antimuons and muon neutrinos; the antimuons decay into muon antineutrinos, electron neutrinos and positrons, which can annihilate with the electrons. But the neutrinos will carry away some energy, as they hardly interact with matter. Icek (talk) 03:32, 9 March 2011 (UTC)

Our Antimatter weapon article says: "The effect of a large antimatter bomb would likely be similar to that of a nuclear explosion of similar size." WikiDao ☯ 01:41, 9 March 2011 (UTC)

That is correct. As Icek explained above, the matter-antimatter reaction produces mostly mesons, not gamma rays, and as I explained further above, gamma rays are absorbed by air just fine. Dauto (talk) 14:49, 9 March 2011 (UTC)

As others have said, the explosion should look similar to a nuclear explosion, but if you want a different looking explosion, an impact from a large object like an asteroid should produce a different looking explosion since the fireball would have a tendency to be sucked up into the ionized wake created by the asteroid as it traveled through the atmosphere. See, http://www.stardestroyer.net/Empire/Essays/Planet-Killers.html#Asteroid ScienceApe (talk) 18:29, 9 March 2011 (UTC)

Gamma ray emissions have already been detected at high altitudes in thunderstorms. ~AH1^(TCU) 02:31, 13 March 2011 (UTC)

Aftertaste

Why does chocolate have such an unpleasant aftertaste? Some other sweet foods have similar, but not quite as strong, aftertastes, as well. --75.15.161.185 (talk) 01:07, 9 March 2011 (UTC)

Try a different brand of chocolate. Also, personally, if I eat too much chocolate in a short period of time it starts tasting sour, so perhaps let your tongue rest first. Ariel. (talk) 01:13, 9 March 2011 (UTC)

But it's happened with other foods too, not just chocolate. Most foods with sugar or (to a lesser extent) starch also seem to have a bad aftertaste. Do the carbohydrates break down into acid? --75.15.161.185 (talk) 01:18, 9 March 2011 (UTC)

I find that an aftertaste is usually a sign that they added some nasty chemicals. Read the ingredients. If there are things in the list you can't pronounce, try a different brand without all the nasty added chemicals. StuRat (talk) 03:56, 9 March 2011 (UTC)

I can't rule out that some (thin) person gets an aftertaste from sugar. But U.S. chocolate lovers should beware: believe it or not, there are grinches making chocolate out of castor oil! (See PGPR) I'm talking about the main brands you see in the store aisle - check the ingredients.

Actually, what I really wonder is, what do they do with all the leftover ricin? Where do they farm all those plants? They must have accumulated enough to wipe out a large country by now, if they didn't throw it all out... Wnt (talk) 05:22, 9 March 2011 (UTC)

It really depends what kind of "unpleasant aftertaste" you're talking about. Cacao itself has a complex and bitter flavor, and so high quality chocolates with a high percentage of cocoa mass have a sharp bitterness that is considered part of the complexity of the flavor. Milk chocolate, especially of the Hershey's variety, has a somewhat sour taste which is considered characteristic of its process of production. Some of this is just how chocolate tastes — it is not a simple "sweet" flavor, but a mix of lots and lots of complicated (natural) chemicals that makes cacao such an interesting appeal flavor. --Mr.98 (talk) 17:31, 9 March 2011 (UTC)

I get unpleasant aftertastes and sometimes tongue pain from various foods (chocolate being one of them). But, I have geographic tongue, so it is just a side effect. If I continue to eat bad foods, I get tiny white bumps all over my tongue and it takes many hours for them to go away. -- kainaw™ 17:40, 9 March 2011 (UTC)

The story I heard was that American chocolate has a bad taste because the milk supplied by rail to an early factory would go rancid on its way there. This bitter taste became stuck as the flavour Americans expected in chocolate. European chocolate does not have a bitter taste, although european brands sold in North American have the bitter taste that Americans expect. I remember when out of curiosity I bought a Hershey bar being sold as a novelty here in the UK - I thought it had gone bad. I've never seen any other American chocolate being sold on this side of the Atlantic. 92.28.254.54 (talk) 13:36, 10 March 2011 (UTC)

That sounds plausible (an early processing method introduced a bitter flavour that is now expected by the consumer in modern equivalents). Unlike any other country I've been to, I find it more difficult in the US to find chocolate I like. Hershey's being particularly nasty I agree. M&M's are ok though and seem to taste the same as they do in the UK. Best place for chocolate? Belgium. Even the cheapest most generic chocolate based confectionary I could find (bought in their equivalent of Aldi or Lidl) was absolutely gorgeous! 213.120.209.248 (talk) 14:45, 10 March 2011 (UTC)

The rancid milk sounds like an urban legend, but Hershey is famous for having developed a cheap alternative process. There are many steps involved in making a good chocolate - the kind of cocoa bean, the kind of processing, and the ways in which greedy manufacturers try to replace the cocoa butter; whenever possible, American manufacturers choose the worst possible option. I suppose the real mystery is why Americans haven't learned to import chocolate like we do everything else. Wnt (talk) 21:04, 10 March 2011 (UTC)

I believe cocoa is bitter to start with, then some is "processed with alkali", which can only make it worse. It's only by adding massive quantities of fat and sugar to a tiny amount of cocoa that it becomes good tasting. StuRat (talk) 05:34, 12 March 2011 (UTC)

Activity series

Hey all. I am a first-year chemistry student and right now we are studying single-replacement reactions (example: AgNO₃+Na→Ag+NaNO₃, Na "replaces" Ag) and predicting products. In the reactivity series the teacher gave us, lithium is listed first before all the other metals; this version is also widespread around the internet ([1], [2], [3]). But, why is lithium above sodium and potassium? I thought metals lose electrons more easily as one moves down the table, and thus potassium should be more reactive than sodium should be more reactive than lithiu,m, and a professional chemist concurs with my reasoning. However my teacher insists her table is correct. Who is right? Thanks. 72.128.95.0 (talk) 02:28, 9 March 2011 (UTC)

Reactivity series has a quite different order. It also mentions that there are three different ways to define the order, so perhaps that explains the difference. (The article should really clarify which order the chart at the top uses, and ideally include 3 charts, one for each.) Ariel. (talk) 03:30, 9 March 2011 (UTC)

Equivalence at Inflection

Hello. Why is the equivalence at the point of inflection on a titration curve? Thanks in advance. --Mayfare (talk) 06:42, 9 March 2011 (UTC)

Tagishsimon (talk) 11:37, 9 March 2011 (UTC)

When you have a neutral solution and you start adding 3M base, the solution becomes basic, but no matter how much of the base you add, the solution will never exceed 3M - the more you add, the slower it approaches that concentration. Similarly, you can add a 3M acid and watch the solutions pH lower, but never quite reach that of the original acid. Titration is taking this process in reverse, so the equivalence point is also the point where adding just a bit of acid or base makes the largest change in pH - the change slows down from there - hence the point of inflection. SamuelRiv (talk) 19:45, 10 March 2011 (UTC)

aransremen

aransremen Penulisan lagu untuk menyingkat APA Yang disebut bertujuan Penulisan? —Preceding unsigned comment added by 118.97.15.21 (talk) 10:52, 9 March 2011 (UTC)

Google translate reckons this is Indonesian, and translates it as "aransremen Writing songs to abbreviate the APA The so-called -objective writing?" --Tagishsimon (talk) 11:37, 9 March 2011 (UTC)

There is a Indonesian reference desk. 118.97.15.21 might be better asking there. Or, if he can write in English, ask on the Humanities desk if the question is about music. CS Miller (talk) 12:35, 9 March 2011 (UTC)

Ah. The Indonesian desk appears not to be used often. CS Miller (talk) 12:38, 9 March 2011 (UTC)

It sounds like the question is something like what's the purpose of abbrevating/condensing song arrangements but I'm not really sure. Although I don't speak Indonesian it's not that dissimilar from Malay and while my Malay isn't that great, the grammar and sentence structure seems wrong. It doesn't even seem like the sort of informal language you may expect on the internet, it's almost like half the question is missing. BTW aransremen probably means wiktionary:aransemen and I'm pretty sure the apa is probably just wiktionary:apa i.e. what. I'm not sure why the 'yang' (that/the) and 'penulisan' (writing) are capitalised either. Nil Einne (talk) 14:11, 9 March 2011 (UTC)

Life expectancy according to age

Is the life expectancy is 80 years, what can an 80 years old expect? 80.58.205.34 (talk) 12:56, 9 March 2011 (UTC)

The article on Life expectancy might be reasonably useful for you to look at, but the article on Life table may be even more so (and the pictures and graphs used there-in). If I am reading the table correctly on the 'Life table' article, then it suggests that if you were a 66-67 year old living in the US, you would have a 0.01624% chance of dying before your next birthday, and would be expected to live for a further 17.7 years. I know that you asked specifically about somebody at age 80, but the table only goes to the 66-67 range.

Also, I believe that in the context of your question, the life expectency of 80 years is the life expectency at birth, not at the point when somebody is 80 years old. Hope that helps to a certain extent. Darigan (talk) 13:07, 9 March 2011 (UTC)

Yes, I supposed that the life expectancy is at birth, not when you turn 80. 80.58.205.34 (talk) 13:26, 9 March 2011 (UTC)

Hi again, as a further reference - There is a complete table here http://www.ssa.gov/oact/STATS/table4c6.html (goes up to 119 years old) that gives the expected life expectency for US males and females from ages 0-119. So, a direct answer to your query - In the US, 80 year-old-males have a life expectency of 87.78 years (At birth it is 75.1), and females of 89.33 (at birth, 80.21). Those tables are quite interesting, thanks for asking that question (I wouldn't have come across them if you hadn't). Darigan (talk) 13:44, 9 March 2011 (UTC)

I doubt if many 80-year old males would expect to live for a further 87.78 years. Perhaps a further 7.78. Ghmyrtle (talk) 14:09, 9 March 2011 (UTC)

I believe the meaning was understood, I wasn't aware that by saying that an 80 year old US male had a life expectancy of 87.78 years meant that I was suggesting that he would live to counts fingers... not enough, shoes and socks come off.... be 167.78 years old - But happy to be corrected if that was the case. Darigan (talk) 14:20, 9 March 2011 (UTC)

According to life expectancy (as linked above) it does mean that, the source you used does also apparently use it with the same meaning. Nil Einne (talk) 18:21, 9 March 2011 (UTC)

Yes, I think the term is widely mis-used to mean "expected age at death". I was interested to see that the life expectancy of a US 80-year-old male was almost exactly the same (at just under six years) in 1950 as it was in 1850, and has subsequently risen by less than three years, so the answer to the OP's question is "less than nine years" for a male, and "about ten years" for a female American. Dbfirs 22:16, 9 March 2011 (UTC)

Ants that like sweat or human sweat?

This problem has bugged me for months: ants swarming my hands and feet for my sweat. Just today my laptop keyboard was intruded for that reason (I'm aware there's something like a keyboard sheet/protector but I like to touch the keyboard directly, and this isn't the main point), and I've tried doing Google search and searched archive here for an answer but no avail (unrelated: found sweat bee though, what an interesting world). A friend suggested it could be termite since the table-cupboard is made of wood, but I don't think they look like termites, and I've tried Googling termite sweat but no relevant results as well.

Situation: My campus hostel had a renovation and I moved in after, we got a new table-cupboard (err table + cupboard above, 2-in-1) and I'm using it. On the first few days I noticed ants were swarming the floor even after we cleaned the room. Sometimes they swarmed my feet when they're on the floor, and you know, you'd kill the ants without a second thought - that's when I realised they smell bad. The odour resembles one that's secreted by some other insects perhaps, I'm not sure. You'd definitely get the strong odour if you try killing like 5+ at once, and killing a swarm will definitely make you go "uuuuuuurghh".

These ants are black, with whitish yellow abdomen. They're quite aggressive towards me, but I'm sure it's because of my sweat that they bite me all the time.

How do I find out they're after my sweat is a long story... but an interesting point to note: while trying to find out, I purposely left my cup unwashed after drinking Milo (Nestle product, chocolate drink). After a week, only 2 ordinary black ants came, 1 of which I left it there for hours to see if it'd call its friends, but it looked like it just kept it to itself lol.

I've also tasted my sweat to make sure it doesn't taste sweet, and yes it's very salty as expected (fortunately!).

Now actually I'm just curious if they're an undiscovered species or if there's a new discovery for ants' behaviour.

Any thought is welcomed, thanks. — Yurei-eggtart 15:32, 9 March 2011 (UTC)

Assuming you are in Malaysia, this may be helpful. Malaysian ghost ants stink and are heavily attracted to water sources. -- kainaw™ 16:27, 9 March 2011 (UTC)

Yes I am from Malaysia. Thanks a lot for the link, I think this is the one, except the fact that I'm not used to seeing them up close. The ones I have here seem to be darker (oh my, does that mean they're more experienced?). I'm just a little bit disappointed they're already discovered and even known as pest. — Yurei-eggtart 16:55, 9 March 2011 (UTC)

Yes, they're very likely to be Tapinoma melanocephalum. A keyboard sheet/protector won't help. Your best bet is to do what other ant species do and use chemical interference. Since they rely on a hydrocarbon based trail system a giant wet soapy cloth washing away their lines of communication causes havoc. Sean.hoyland - talk 09:31, 10 March 2011 (UTC)

How many human species coexisted with eachother?

How many different human species lived during the same time period. I know the Homo Neanderthalis and the Homa sapien sapien were around at the same time. Except I am wondering if there are any others. Matthew Goldsmith 19:07, 9 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs) 19:06, 9 March 2011 (UTC)

Our homo article covers this thoroughly. The picture I've attaching shows the most important species but leaves out a lot of minor ones. Looie496 (talk) 19:28, 9 March 2011 (UTC)

The nice graph at Human evolution says it's just the Neanderthals. Comet Tuttle (talk) 19:30, 9 March 2011 (UTC)

The graph leaves out both homo floresiensis and the Denisova hominin, though. Looie496 (talk) 19:36, 9 March 2011 (UTC)

(Edit Conflict) I don't think that that nice graph is meant to be comprehensive, Comet Tuttle. From the figure attached by Looie496, plus generally available information, it seems likely that Homo neanderthalensis in Europe and early Homo sapiens in Africa and beyond coexisted in time with late Homo erectus in Asia, and perhaps Homo rhodesiensis in Africa. To these we can add the disputed Homo floresiensis and the recently discovered Homo denisovan, if they prove valid taxons. It seems quite possible that further new human species also coexisting in time with H sapiens will be discovered in the future. Bear in mind, Lightyearlight, that since various of these species emerged from various others and there are no agreed on sharp boundaries between some of them, there may be valid disagreement over which ones certain coexisting individuals belong to. {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 19:50, 9 March 2011 (UTC)

If we include Australopithecines in the definition of "human" then there were several species sharing the plains of Eastern and Southern Africa too. Roger (talk) 20:05, 9 March 2011 (UTC)

Couldn't various of these different "species" likely have interbred and had fertile offspring, such as modern humans and neanderthals, if not for geographical isolation from each other? Edison (talk) 19:32, 10 March 2011 (UTC)

I don't think that's known - and might never be. Matt Deres (talk) 14:38, 11 March 2011 (UTC)

Premature babies

Why isn't it yet possible to set up artificial transfer of oxygen and nutrients to a premature baby through its umbilical chord? Or even by setting up transfer through the placenta? Since they stick breathing tubes in and try to get the babies breathing with their under-developed lungs, I assume it's completely impossible at the moment. But, on the face of it, it would seem quite feasible given current technology, even if the complete artificial womb is a long way away.

So, what is specifically so difficult about this? 86.163.4.134 (talk) 21:20, 9 March 2011 (UTC)

I've wondered this too. The umbilical cord would not be possible (it closes), nor the placenta. But you can set things up just like in dialysis except with oxygenation instead of filtering. After some searching I found: Extracorporeal membrane oxygenation, which says: "Newborns cannot be placed on ECMO if they are under 4.5 pounds (2 kg), because they have extremely small vessels for cannulation, thus hindering adequate flow because of limitations from cannula size and subsequent higher resistance to blood flow". Seems to me this should be solvable, but I guess it isn't possible now. Ariel. (talk) 22:36, 9 March 2011 (UTC)

Why would they fool with tiny blood vessels when a premie is dying? Why not put in a PIC line like they do for an adult when the peripheral lines aren't adequate? Edison (talk) 19:29, 10 March 2011 (UTC)

N.B. We have an article PIC line. Wnt (talk) 20:59, 10 March 2011 (UTC)

I recently came acrros a documentary series called Baby ER on Zone Reality. Among other things medical personell was collecting blood for testing from a baby and explained that as the blood vessels are small their needles get cloged pretty fast, so they may need to take blood for testing from several sites. I guess drawing blood dosen`t take much time, so it might be yet another reason why they prefer ventilation and feeding tubes over trying to enrich blood with something ~~Xil (talk) 01:37, 11 March 2011 (UTC)

Seems there is another problem: "In infants aged less than 34 weeks of gestation several physiologic systems are not well-developed, specially the cerebral vasculature and germinal matrix, resulting in high sensitivity to slight changes in pH, PaO₂, and intracranial pressure. Preterm infants are at unacceptably high risk for intraventricular hemorrhage (IVH) if administered ECMO at a gestational age less than 32 weeks." Ariel. (talk) 08:09, 11 March 2011 (UTC)

Airbus 321, air speed

Resolved

 – thanks to Dolphin

When I was flying an A321 I observed a sharp shift in the refractive index of the air around the plane on two occasions.

1. In normal flight in a vertical line above the wing near the leading edge.
2. Outside the front of the engine when in glide flight before landing.

I assume that this is a shock waves indicating that the flow on one side is supersonic relative to the air plain. Is the flow supersonic before or after the shock wave?--Gr8xoz (talk) 23:18, 9 March 2011 (UTC)

Why do you assume it's supersonic? I don't know what caused it, but two other possibilities come to mind: The air is being compression heated, or the air is being compressed (or both). Either of those would cause a change in the refractive index. Ariel. (talk) 02:16, 10 March 2011 (UTC)

Gr8xoz is correct. This phenomenon is readily visible when travelling on any of the swept-wing jet airliners, providing you are sitting in a position that allows you to look along the wing, parallel to the leading edge. These aircraft are not supersonic but when flying at their cruising altitude they are transonic. This means the aircraft itself is not supersonic but as the air flows over the top surface of the wing at high speed, for a short distance it is supersonic relative to the wing. The air accelerates progressively as it passes the leading edge of the wing but it does not decelerate progressively. A shock forms, and as the air flows through the shock its speed (relative to the wing and the shock) suddenly decelerates to subsonic. Any gas, including air, approaches a shock at supersonic speed but the instant it emerges from the other side of the shock it is moving at a slower speed. The flow downstream of a normal shock is subsonic. (The flow downstream of an oblique shock is still supersonic but it has changed direction and is slower than the speed at which it approached the shock.) On either side of the shock there are different speeds, pressures, temperatures and densities. The difference in density on either side of the shock explains why the shock is sometimes visible, looking like a crack in a pane of glass. Dolphin (t) 02:35, 10 March 2011 (UTC)

OK so the speed is supersonic in front of the shock wave.(Relative to the wing) Thanks.--Gr8xoz (talk) 16:33, 10 March 2011 (UTC)

March 10

Cyclohexane smell

Why does cyclohexane smell like acetone? --70.244.234.128 (talk) 00:49, 10 March 2011 (UTC)

I don't think that they do. Cyclohexane has a sweet smell like benzene while acetone has a harsh smell. 75.41.110.200 (talk) 02:34, 10 March 2011 (UTC)

It has the same sort of "chemical" smell as acetone (and many other synthetic organic compounds, like paint, paint thinner, etc.). --70.244.234.128 (talk) 00:06, 11 March 2011 (UTC)

A "fuel savings device" question

I've read the articals here on fuel saving devices and understand that there is limited to no evidence of the value of the devices or the claims made by manufacturers. It appears that virtually all fuel saving devices are either additive based or impact the air flow and fuel mixture. However, I came across this (http://www.gfchips.com/fordf150.aspx) device that uses a computer chip to improve fuel economy, etc. Is there any validity to this company's approach (especially given the old adadage: if it sounds too good to be true, it probably is . . .")? 99.250.117.26 (talk) 01:14, 10 March 2011 (UTC)

I think if that chip really worked Ford would have done it already. Especially 60 more horsepower? They would love that. Even if this company thought of something Ford didn't, Ford has to be aware of it and would reverse engineer it. But one thing that really stood out is that they have a chip for every car in existence, and I'm sorry but there is no way in the world that is possible. Ariel. (talk) 02:14, 10 March 2011 (UTC)

It's a scam. See reviews here. --Stephan Schulz (talk) 10:21, 10 March 2011 (UTC)

I won't speak to this specific chip-model, which may be a scam. But electronic engine control is a real thing, and does improve fuel efficiency. Ford calls this EDIS and VCT; Honda calls it VTEC; and so on; these are special cases of an Engine Control Unit, a sophisticated computer/electronic box that "makes the engine go." The auto manufacturer usually "tunes" the car's ECU software, hardware, and the engine's mechanical systems for the best average performance. However, after-market "engine-chipping" is also a real thing - especially on the performance auto-enthusiast circuit (amateur racers and the like). You can tune for best performance for certain driving conditions. Here's a brief article Chip the engine which should give you an overview of the subject.

Will engine chipping give you 60 extra horsepower? Unlikely. Your engine has peak performance numbers; you can mechanically alter the engine to improve those specs, but not by a whole lot; and playing with your valve-timing isn't going to give you 50% more gas-mileage or horsepower. Custom engine-chipping will do things like moving your torque curve around so you get the car's peak performance at a different engine RPM; and it definitely can change your fuel efficiency (for better or for worse)! And as always, mucking with your car's ECU can be risky - if you screw up, you can permanently damage your car's mechanical systems, requiring costly repairs. Nimur (talk) 16:21, 10 March 2011 (UTC)

cdma2000

Hi there. Not really a _science_ question, but does anyone happen to know the theoretical ratio between the channel power (1.23 MHz bandwidth) and the RMS power for a cdma2000 SR1 signal? 80.254.147.84 (talk) 02:11, 10 March 2011 (UTC)

CDMA-2000 is pretty spectrum-filling, so I would "assume" for theoretical purposes that the spectrum is "flat" across the entire channel, and has a specified 3-dB frequency (or specified frequency rolloff rate). Since the signal is a digital QAM constellation with ~64 elements, it is actually pretty nasty when viewed as a pure frequency-spectrum; "theoretically" you should have 64 perfect frequency spikes; but as you of course know, the practical reality is that you have a fuzzy signal whose frequency-spread is determined by your QAM circuit's phase-noise specification. I doubt there's any use to construct a "thorough" theoretical model of the channel power - can you measure it? Otherwise, I'd report the channel power in watts per hertz (or mW/MHz, or other convenient unit), by "assuming" total RMS signal power divided by bandwidth; and spend some time spec`ing the out-of-band frequency rolloff to clean up my estimate. Two app-notes I found on the web search: Linear's AN99 LT5528 WCDMA ACPR, AltCPR and Noise Measurements discussing practical details for measurement; and Tektronix Digital Modulation technical series, Measuring ACPR of W-CDMA Signals with a Spectrum Analyzer. Don't underestimate the power of vendor app-notes - no matter how specific your need, you can probably search the major spectrum-analyzer manufacturers' public libraries, and if you've bought their equipment, you may be able to phone one of their engineers to discuss horrible engineering details with an experienced person. Nimur (talk) 16:46, 10 March 2011 (UTC)

Thanks for the info. The problem is not so much measuring the signal parameters - I have a waveform that purports to be cdma2000, but which has a 99% OBW of 1.275 MHz (as against the CHP bandwidth of 1.23 MHz). I was wondering if that was correct, and, if not, how incorrect it is. You're probably right that a more specialist arena is a better place for this sort of question, though. 80.254.147.84 (talk) 16:45, 11 March 2011 (UTC)

entanglement

would entanglement support the conclusion that given two entangled particles at some large distance apart, if one of the particles were to somehow cease to exist that the other would simultaneously cease to exist? —Preceding unsigned comment added by 98.221.254.154 (talk) 05:03, 10 March 2011 (UTC)

No. Ariel. (talk) 08:09, 10 March 2011 (UTC)

Presumably you want a longer answer, and to start with particles can't just cease to exist - they always turn into something else. And even if they did it does not mean the other one will too. If anything it would be the reverse - one particles ceases to exist, the other ones doubles. (That doesn't actually happen, but it's more realistic than the reverse.) Ariel. (talk) 08:09, 10 March 2011 (UTC)

It's fairly misleading to comment on what physics would do if you forced it to violate itself. —Preceding unsigned comment added by 129.67.37.227 (talk) 14:12, 10 March 2011 (UTC)

I agree - Ariel's first response, while ultra-brief, was probably the appropriate one! Trying to trace out the consequences of a physical contradiction only leads to more bizarre contradictions. Particles can not cease to exist. If you come up with a realistic physical scenario, we can apply some established rules of quantum-mechanics to model what would happen. For example, if a particle decays, then we can model the trajectories of the decay products, and see how the quantum wave-functions would propagate to (and affect) the entangled partner particle. But when you ask a "what if...", all we can meaningfully say is "then our rules don't apply, so we can't answer that." Nimur (talk) 16:55, 10 March 2011 (UTC)

I thought one of them could be annihilated with antiparticle?? —Preceding unsigned comment added by 165.212.189.187 (talk) 18:32, 10 March 2011 (UTC)

You appear to misunderstand what annihilation means. Please see Annihilation - at least the introduction. -- kainaw™ 18:36, 10 March 2011 (UTC)

Perhaps the OP is thinking of one particle falling into a black hole? I have a meagre understanding of QM but wouldn't then the entanglement be destroyed but not the particle? Blakk and ekka 18:46, 10 March 2011 (UTC)

No effect of entanglement is detectable with measurements on only one particle. So if you "throw the other particle away" in the sense that you never measure anything about it again, entanglement ceases to matter, though it's theoretically still there. Throwing a particle into a black hole is one way of getting rid of it, but there are easier ways. -- BenRG (talk) 00:52, 11 March 2011 (UTC)

"Since energy and momentum must be conserved, the particles are not actually made into nothing, but rather into new particles. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all quantum numbers of the original pair are zero." OK, So one particle could be made into new particles while the other might not be? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:06, 10 March 2011 (UTC)

If the two particles are entangled, then any operator that acts on the wavefunction of Particle 1 can cause the wavefunction of Particle 2 to change. That is not synonymous with "the decay of Particle 1 forces the decay of Particle 2." It means that the operator must modify both wave-functions. Tragically, in efforts to "simplify" descriptions of quantum-mechanical treatments, pop-science books do not emphasize the precise nature of this statement: both wave-functions may be affected is not the same as information was transferred, nor the particles are linked together, nor the action on particle 1 caused an action on particle 2. Two entangled particles form a composite quantum-mechanical system. Certain operators must act on the composite system. The composite system's final result will depend on the operator and the composite system's prior quantum state. The state of either particle is a subset of the composite system. Nimur (talk) 20:46, 10 March 2011 (UTC)

"Any operator that acts on the wavefunction of Particle 1 can cause the wavefunction of Particle 2 to change" is incorrect. There's only one wavefunction, which describes the entire system. If the particles aren't entangled then you can factor the wavefunction into a product of separate wave functions for each particle, but if they are entangled then you can't. That's one way of defining entanglement. -- BenRG (talk) 00:52, 11 March 2011 (UTC)

Yes or no, can one decay and not the other? —Preceding unsigned comment added by 98.221.254.154 (talk) 00:41, 11 March 2011 (UTC)

Yes, one can decay and not the other. For example, one could be an electron (stable) and the other a neutron (unstable). They don't have to be particles of the same type. But "decay" doesn't mean "cease to exist". Decaying doesn't destroy entanglement. -- BenRG (talk) 00:54, 11 March 2011 (UTC)

Sorry, so there could be more than one "particle" in an entangled "pair"?98.221.254.154 (talk) 01:47, 11 March 2011 (UTC)

Yes, any number of particles can be entangled. -- BenRG (talk) 03:26, 11 March 2011 (UTC)

Is every particle in our galaxy entangled with every other one? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:41, 11 March 2011 (UTC)

Yes, I suppose so. (Slightly.) -- BenRG (talk) 09:02, 13 March 2011 (UTC)

Myasthenia Gravis

What is the right way of presentation "Myasthenic crisis" or "Myasthenia Crisis"? aniketnik 10:06, 10 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

To describe the occurrence of symptoms in a person with myasthenia gravis, you would call it a "myasthenic crisis." --- Medical geneticist (talk) 11:01, 10 March 2011 (UTC)

Feeling cold in the morning and body weight

Hello. When I wake up in the morning, I have a cold sensation that usually lasts an hour or more. When I mentioned about this to a friend, he said he has experienced the same, and it's related to having a metabolism that effieciently converts extra energy into heat, and that this is probably why we're both thin while we eat a lot and don't get much exercise. Could this be the case? 212.68.15.66 (talk) 10:09, 10 March 2011 (UTC)

If I were you I'd see a doctor. We're not allowed to give medical advice. --TammyMoet (talk) 20:02, 10 March 2011 (UTC)

I'm not ill, why would I? I've always felt chilly in the morning, but in fact I've been very healthy, I hardly ever catch any disease. What I'm asking is whether the "super metabolism" could explain the chilly feeling and my apparent "immunity" of gaining too much weight. 212.68.15.66 (talk) 07:50, 11 March 2011 (UTC)

OP it is quite possible for you to be quite ill without being aware of it! My original advice still stands. --TammyMoet (talk) 13:56, 11 March 2011 (UTC)

In my opinion you're overreacting, as there is nothing that suggest that the OP is ill in any way. I've always felt a bit cold when I wake up, and I too have been very healthy. Time for some LOGIC: The OP mentions his/her friend has experienced the same, and I also feel cold in the mornings usually for half an hour. Therefore, it's probably rather common, and if feeling cold in the mornings was related to a common medical condition, we would probably know about. On the other hand, it might be a symptom of a very slowly advancing terminal disease... but my money's on Looie496's suggestion on reluctance to leave the warm bed behind. Zakhalesh (talk) 20:46, 11 March 2011 (UTC)

I can think of two conditions which match the symptoms described by the OP, but our prohibition on diagnosing mean I can't even mention them. Both conditions are common in the Western world, and can remain undiagnosed for many years, silently causing many problems which, if diagnosis had been made earlier, would not have occured. --TammyMoet (talk) 21:23, 11 March 2011 (UTC)

Since interpreting everything as a sign of a disease is itself a disease, you'd better get yourself to a doctor right away, Tammy. :-) StuRat (talk) 00:45, 12 March 2011 (UTC)

_{I'm actually speaking to mine on Monday because I suffer from one of the conditions I was writing of... --TammyMoet (talk) 10:04, 12 March 2011 (UTC)}

I don't know what "a cold sensation" means. Nearly everybody experiences a circadian rhythm of body temperature in which the temperature drops during the night and rises around daybreak. Whether there is anything unusual about your sensations is unclear without a better description. Lots of people are averse to getting out from under warm covers on a chilly morning. (I don't consider this medical advice.) Looie496 (talk) 23:02, 10 March 2011 (UTC)

A few points:

1) If you turn the temperature down at night (or have an automatic thermostat that does so), it may actually be colder. Even if the temp is turned back up by the time you get out of bed, it still may take some time for the house to get up to the new temperature.

2) Activity warms you up, and a bit of exercise in the morning might do the trick.

3) It might be warmer in your bedroom, particularly under the covers, due to your body heat overnight, and walking into another room may cool you down. This seems to especially be a problem with bare feet on uncarpeted floors, as in the bathroom or kitchen. A cold toilet seat will also wake you right up. StuRat (talk) 00:50, 12 March 2011 (UTC)

It may just be a side-effect of wearing light clothing. I like to keep my bedroom cool. When I get up in the morning at this time of year, from under the warm bedclothes, I feel cold until I put on some warm clothing. You may just be not wearing warm enough clothing. Your body has to use extra energy to keep itself warm, hence you do not get fat. Feeling cold in the morning is a small price to pay for being perpetually slim - lucky you. 92.15.11.100 (talk) 13:23, 14 March 2011 (UTC)

Will Global Warming cause the Moon recede faster or slower from the Earth?

Global Warming will cause sea level rise. This will have some effect on the tidal friction the Moon experiences, causing the rate at which it recedes from the Earth to change a bit. Will this rate increase or decrease? Count Iblis (talk) 15:02, 10 March 2011 (UTC)

It will recede faster. With more liquid water instead of solid, the tidal friction will increase, so the moon's recession will occur faster. For partial support of that statement, see the second paragraph of Tidal acceleration#Angular momentum and energy. Red Act (talk) 15:24, 10 March 2011 (UTC)

On the other hand, by melting ice into water some of the mass that is now near the poles will move closer to the equator changing earth's Moment of inertia slowing down its rotation and therefore increasing the time between a high tide and the following low tide reducing the rate of the motion of the tides around the planet and decreasing the pace with which the moon is moving away from the earth :). Dauto (talk) 01:45, 11 March 2011 (UTC)

And note that any effect would be so slight it would be difficult or impossible to even measure. StuRat (talk) 00:39, 12 March 2011 (UTC)

Hmmm, wouldn't the change in total lengths of coast lines be a factor here, as this ultimately provides for the friction that moves the tidal bulge ahead of the Moon? It seems to me that this could change quite dramatically if e.g. all the ice on Antarctica were to melt, but I'm still not sure if this woild increase or decrease the recession rate.Count Iblis (talk) 15:28, 12 March 2011 (UTC)

Chemical catalog

In a chemical catalog item description, what is the meaning of something like (N/10)? For example, "Hydrocholric acid solution, 0.1N (N/10)". I am looking specifically at Cole Parmer and I've been unable to find any explanation in their information. ike9898 (talk) 16:56, 10 March 2011 (UTC)

N means 'normality'; it's a way to express concentration. See Concentration#Normality for details. TenOfAllTrades(talk) 17:53, 10 March 2011 (UTC)

Well, I understand that, but is "0.1N (N/10)" any but just completely redundant? ike9898 (talk) 19:30, 10 March 2011 (UTC)

Why would redundancy be bad? The catalog wants to sell to people who use different methods of expressing concentration, and it's in their interest to make the concentration instantly understandable to both sets of people. - Nunh-huh 20:42, 12 March 2011 (UTC)

Solution of NaOH at 40% m/m

I need to prepare a 100ml solution of NaOH at 40% m/m (in water). As NaOH absorbs the humidity in air, I have consulted an old Handbook, section sodium hydroxyde, concentration properties of, in varying concentrations but I am still unsure as to how much NaOH (in grams) I need. Please help.

Thank you very much. --192.197.51.41 (talk) 18:06, 10 March 2011 (UTC)

First, the preparation of weight/weight solutions is tackled by our RefDesk's foremost competitor here.

I should add that I'm a bit surprised to see "m/m" or "mass/mass" coming up. It seems from searches that this is in vogue for recent homework problems. On the one hand, yes, the number on the balance is in grams of mass; on the other, what the balance measures is weight.

Now the real question you have is what the purity of the NaOH is. You could run various tests on it, or try to purify it e.g. by baking it at high temperature to drive out the water, but the traditional chem lab way to handle the problem is to titrate the sodium hydroxide solution after you've made it, against a known standard. In this way you can adjust the molarity to be exactly right, and therefore the m/m value. (Though usually people titrate to get an exact molarity rather than an m/m value) Wnt (talk) 20:53, 10 March 2011 (UTC)

Thanks, I got it figured out. --192.197.51.41 (talk) 22:20, 10 March 2011 (UTC)

Does copier or printer ink contain metal?

I was wondering whether photocopier ink or laser-printer ink contains any metallic substances or metal compounds?

Thanks. 71.252.113.85 (talk) 20:37, 10 March 2011 (UTC)

It depends on the ink. Our article toner may help. Most toner is pure carbon (say, graphite powder), or something similar (like carbon black), but may also include a plasticizer, a binder, one or more liquid solvents, and so on. In general, these are synthetic polymers. Colored ink may contain pigment, which may include synthetic polymers, or metallic pigments. Nimur (talk) 20:51, 10 March 2011 (UTC)

Is it possible for the polymers in black copier or printer ink to be magnetic? 71.252.113.85 (talk) 03:03, 11 March 2011 (UTC)

Definitely possible to formulate a magnetic ink--see MICR. DMacks (talk) 18:37, 12 March 2011 (UTC)

But is ordinary ink magnetic? 71.252.113.85 (talk) 19:56, 14 March 2011 (UTC)

Xerography in photocopiers often use the metalloid selenium, which is not likely found in the ink. ~AH1^(TCU) 02:28, 13 March 2011 (UTC)

Some ink has metal in it by design. It's so magnetic character readers can read them. The line of numbers on the bottom of checks is one example of this. One such technology is called MICR - Magnetic Ink Character Recognition. thx1138 (talk) 22:50, 15 March 2011 (UTC)

http://en.wikipedia.org/wiki/MICR

Probability cloud of a free electron?

Would the probability cloud of a free electron look the same as an electron in the ground state bound to a hydrogen atom? ScienceApe (talk) 20:40, 10 March 2011 (UTC)

No, not as far as I can tell. Until you get a better answer, consider these related questions: why would you think that the electron_cloud would look the same in both cases? Compared to a 'free electron' (presumably with no other particles around), an electron bound in hydrogen has at least a few additional forces acting on it, especially the electric field generated by the proton. Shouldn't this difference in forces change the shape of the probability cloud (and perhaps radically so)? SemanticMantis (talk) 22:40, 10 March 2011 (UTC)

No --Gr8xoz (talk) 22:31, 10 March 2011 (UTC)

Without a nucleus to bind the cloud, the autorepulsion will cause the cloud formation to disolve. Plasmic Physics (talk) 22:41, 10 March 2011 (UTC)

Here's the problem. You can't formulate a wavefunction for an electron in free space. Let's trace out how we do it for a simplified quantum mechanical treatment of an electron in an Hydrogen atom: (see our article on Hydrogen atom, particularly the solution of the wave function.

• First, define a coordinate system by assuming the proton to be heavy and therefore immobile. (The hydrogen proton is located at the origin).
• Now, define the Coulomb potential - for practical purposes, this is $1/r$, where r is the radius from the origin. (How can you define the coordinate-system of the free electron, if there's no reference origin? You have to pick an origin at random, which isn't a problem, but then there's zero potential energy gradient, and so the electron has a probability of being anywhere relative to your undefined origin).
• Solve the Schrodinger equation using the Coulomb potential and normalize using physical constraints (probability that the electron exists somewhere must equal 1).

So, in free space - you don't have anything to define your wave-function, and the electron can be anywhere. The only thing you can do is measure an electron - determine its current state (its momentum and its position, subject to the uncertainty principle), and then you can predict where it will be next (which is, of course, anywhere, since it is unbound). When you measure it again, at some other position/momentum, the principle of indistinguishability means you can not know whether you've measured the same or a different electron! So, there's no way to predict the position of an electron in an unbound system (no defined coulomb potential). It has an equal probability of being anywhere; and anything you measure has a likelihood of being a different electron. Nimur (talk) 23:29, 10 March 2011 (UTC)

This is completely wrong. See Wave packet. Truthforitsownsake (talk) 02:17, 11 March 2011 (UTC)

Well, in actuality, I never apply quantum-mechanics when I'm describing free electrons. Most of the time, I can treat my plasmas as a superposition of an electron gas and an ion gas, and solve using classical or relativistic electrodynamics. By the very nature of the involved length, time, and energy scales, quantum-mechanical properties are less relevant to free electron clouds, in practice. I'm not surprised that my attempt to describe a quantum mechanical system for an electron gas sounds awkward. I respectfully disagree that my explanation is "completely wrong" - I think it's completely correct, although it's surely "stretching the limits of the conventional application of quantum mechanics." Nimur (talk) 14:54, 11 March 2011 (UTC)

The hydrogen atom orbitals are a complete basis for smooth electron wave functions that approach zero at infinity, so they don't tell you anything about the electron by themselves. An electron that's nowhere near the nucleus can still be described by a sum of these solutions. The only thing that's special about them is that they're energy eigenstates. If you remove the nucleus, leaving the background potential zero everywhere, then it's no longer possible to write down a basis of energy eigenstates, but I think that's just a pathological corner case. You can still work in some other basis like a wave-packet basis, or you can write down energy eigenstates if you add, say, a single nucleus a billion light years away. -- BenRG (talk) 02:35, 11 March 2011 (UTC)

magnetic earth

will we ever know for sure what is inside of the earth or if it is hollow will we ever know for sure what causes the earth's magnetic field — Preceding unsigned comment added by Lufc88 (talk • contribs) 21:41, 10 March 2011 (UTC)

I think we're pretty sure about the structure of the Earth. Is there any reason you don't believe the scientific explanations presented in that article? Geology and geophysics are evidence-based sciences, and there is a lot of evidence to back up the current theories. Have a read at those articles for details on the experimental toolkits available to help scientists gather evidence about Earth's interior. Nimur (talk) 21:46, 10 March 2011 (UTC)

We will never know anything about the world for sure, we could just be hallucinating or in a computer simulation. We have a rather good model for the structure of the earth, we may never know some finer details but as long as we can trust the measurements the overall structure are known, it is not hollow and could not be hollow since no known material would be strong enough to keep it from collapsing. --Gr8xoz (talk) 22:41, 10 March 2011 (UTC)

For why we know the Earth isn't hollow, see Hollow Earth#Contrary evidence. Also, the interior of the Earth has been mapped in detail using seismic tomography, without any evidence of any hollow space; see Seismology#Seismic waves.

As per Earth's magnetic field#Field characteristics, the currently accepted theory is that the Earth's magnetic field is primarily due to electric currents in the (liquid) outer core, similar to an electromagnet. This is called the dynamo theory, although a numeric model of the Earth's magnetic field consistent with the dynamo theory has not yet been achieved. Red Act (talk) 22:45, 10 March 2011 (UTC)

how can we prove that it is the dynamo effect any ideas — Preceding unsigned comment added by Lufc88 (talk • contribs) 22:49, 11 March 2011 (UTC)

The main way is by comparing Earth with other (terrestrial) planets and moons which lack a magnetic field. Venus doesn't appear to have one, and Mars appears to have a relatively weak one, as does our Moon. So, if these lack the molten iron outer core of the Earth, that's fairly good evidence that this is the reason. The Moon shows little evidence of recent volcanism, so that supports it being solid, not liquid. Mars shows signs of massive ancient volcanoes, but less activity more recently. More study is needed there. Venus is difficult to study, due to it's thick cloud cover and corrosive atmosphere. StuRat (talk) 00:31, 12 March 2011 (UTC)

March 11

18 year Lunar Perigee effects on tides?

I saw an article yesterday that said in mid-March the moon will be as close to the earth as it ever gets ("lunar perigee"), and that this is an 18 year cycle. Sadly, nothing of the sort is mentioned in Orbit of the Moon. I have two questions: 1) is this true and where on Wikipedia can I read more about it? 2) will this cause record high tides? if yes, what would the tidal variation be between the moon at its closest and furthest orbital positions? The Masked Booby (talk) 00:50, 11 March 2011 (UTC)

The mentioned 18 year cycle is probably a Saros cycle, which governs eclipses. The moon reaches perigee about once a lunar month, but the exact timing with respect to the phase of the moon changes. The Full moon cycle of about a year-and-a-bit would be the closest connection between lunar perigees and the size of tides -- we get the largest tides when the moon is close to us just at a spring tide. The Saros cycle arises from the interference between the full moon cycle and the moon's periodic movement north and south of the ecliptic (which also happens about once a month but again only roughly, due to the precession of the lunar orbit). –Henning Makholm (talk) 02:11, 11 March 2011 (UTC)

Henning has given an excellent response. On a general level do you remember (assuming you are old enough) any 'record' tides 18 years ago when the same circumstances pertained. I don't, and I've experienced more lunar phases than I care to mention ;-) Richard Avery (talk) 07:26, 11 March 2011 (UTC)

Diet theory

As far as I remember body stores excess energy in fat. If I have lost weight by eating less, does it follow that my body has used my fat instead of food, and since there is no fat available I should eat more now and I won`t get fat again? 89.235.211.162 (talk) 01:18, 11 March 2011 (UTC)

As our dieting article states, weight loss usually means that one has lost both fat mass and muscle mass. Could you rephrase your last sentence? It didn't make logical sense to me. I must mention that your questions about this may be deleted, or go unanswered, if you ask questions about your body, because that touches on our no-medical-advice policy — I would recommend asking questions about a hypothetical generic human instead. Comet Tuttle (talk) 01:43, 11 March 2011 (UTC)

Eating is not a medical issue and it is a biology question. I don`t see what is there not to understand. A person eats less. He or she loses weight. Assumption is that weight loss is result of body being forced to use fat to get necessary energy. Would it be healthier if person wouls start eating more, given that there is no more fat reserves to dig in? Will increasing food consumtion result in weight gain or will the body convert all food into energy stright away? 89.235.211.162 (talk) 02:46, 11 March 2011 (UTC)

If a person takes in more calories than they expend, the body will have a net positive amount of "energy" and will store it as fat. If a person takes in fewer calories than they expend, the body will have a net negative amount of "energy" and will respond by breaking down fat stores, then muscle if insufficient fat stores remain. If a person's caloric intake and expenditures are roughly equal, they will remain the same. One of Comet Tuttle's points was that what you (the OP) "should" do is dependent on a whole variety of factors and isn't really in the domain of the reference desk. It is doubtful that you have completely eliminated all of your fat stores, and we don't have any way of knowing whether you have altered your basal metabolic rate in the course of your weight loss (by increasing lean muscle mass, for example), or if your daily activity level has significantly increased (thus requiring higher caloric intake simply to break even). So, whether or not you can "eat more" without gaining the weight back is impossible to answer. The bottom line is that you can simply use a scale to weigh yourself (pick one time of the day and try to be consistent). This will answer your question. --- Medical geneticist (talk) 03:08, 11 March 2011 (UTC)

No, I moved to diffrent town for my studies, the only thing I altered was how much I eat, because I don`t like to cook and was hardly ever hungry. I like the result. However lately I am feeling hungry more often, although I eat as much as usually. Hence I wonder. 89.235.211.162 (talk) 04:21, 11 March 2011 (UTC)

Beware of yoyo dieting: losing weight, then gaining more back. It is the usual result of dramatic dieting and weightloss, because your body adapts to the lack of calories and starts to lay fat down more easily. If you find, in a few months time, you are heavy than you were before the weightloss, the only way to definitely break the cycle of steady weightgain is to not diet. 86.163.4.134 (talk) 09:42, 11 March 2011 (UTC)

I think I understand the logic behind your question. Let me state what I think you meant to ask, then answer that:

"Since we have fixed number of fat cells, if I eliminate all of them by dieting, will it then be impossible for me to gain weight since I no longer have any fat cells in which to store additional fat ?"

OK, the biggest flaw with that theory is that fat cells just shrink when you lose body fat, they don't disappear entirely. They can be removed, via surgery, but not all of them. This leads to the remaining fat cells getting even larger, and having many small fat cells provides for a smoother looking body than a few huge ones. But, if we could theoretically eliminate all of our fat cells, what would happen ? I suspect that you would die, or at least get diabetes, as burning fat is important to bridging long gaps between meals. And, on the other extreme, when you ate a big meal, if it couldn't be stored as fat, would your blood sugar skyrocket ? StuRat (talk) 00:07, 12 March 2011 (UTC)

Incidentally, one reason why you may be hungrier now is that you aren't getting all the nutrients you need. If you had an unhealthy diet, but ate 10x as much as you should have, then you might have managed to get all the vital nutrients just by volume, whereas now, if you continue to have an unhealthy diet, but just eat less, you may have deficiencies, leading you to crave more food. Make sure you have a healthy diet, and this problem should go away. StuRat (talk) 00:13, 12 March 2011 (UTC)

No, I wasn`t aware that number of cells is fixed, I thought body generates new cells and eliminates old cells (to extent, at least). I am acctualy concerned of the effect anonymous poster before you mentioned. So let me rephrase. I believe I am hungry because my body has depleted its fat reserves and wants to get more energy from food now. Up until now I ate as much as I craved, but I am worried that because of whole yo-yo dieting deal my body wants me to eat more than I acctualy need. So should I eat as much as I crave or only a little bit more? 84.52.32.137 (talk) 00:30, 12 March 2011 (UTC)

If eating as much as you craved made you overweight before, I suspect that it would do so, again. But, as I said, the answer to cravings isn't to eat more junk, it's to eat the proper amounts of the right things. StuRat (talk) 01:02, 12 March 2011 (UTC)

I ate what my parents served, not junk, though possibly too much bread, matter of fact I`ve been eating more junk food while losing weight than ever before. I currently eat stuff from all major food groups, mostly salad. So I see your point as valid, but I doubt it applies here (besides I guess lacking specific nutrients would cause cravings for a particular product, which contains them) 84.52.32.137 (talk) 01:26, 12 March 2011 (UTC)

Cravings aren't necessarily that specific. And if you've been eating more junk food while losing weight, that supports the idea that you may be malnourished. Salad is a good component of a healthy diet (although the common iceberg lettuce is almost devoid of nutrients), but you might not be getting enough protein. For that you need meat, dairy, beans, or nuts. StuRat (talk) 06:08, 12 March 2011 (UTC)

But all salad normaly contain dairy products, meat and vegetables. Just because I eat fast food once in two weeks dosen`t mean I am malnorished. I learned what is healthy diet in elementary school, no need to educate me on that. I said it is a theoretical question - assume that there are no other factors than quantity and tell me, if it is wiser to increase food consumtion as much as I feel or increase it by little less 89.235.214.143 (talk) 17:10, 12 March 2011 (UTC)

Increase the quantity a small amount at a time, until you start to gain weight, then pull back a bit, to keep your weight steady. As for your statement that "all salads normally contain dairy products, meat and vegetables", that's not true, many have no meat or dairy products. I suspect that you are getting things like a Cobb Salad, which has all sorts of things in addition to a standard garden salad. Such "salads" may actually be quite unhealthy. Try a garden salad, on occasion, too, and skip the rich bleu cheese dressings in favor of a simply vinaigrette. StuRat (talk) 21:59, 12 March 2011 (UTC)

Any fluctuations and reductions in your weight will probably fluctuate around your normal body weight. ~AH1^(TCU) 02:21, 13 March 2011 (UTC)

In the place where I live it is the traditional understanding of what `salad` means, I buy them ready made at grocery store (as I said I don`t like to cook) and they haven`t gotten down the method of producing tasty salad with any other dressing. But anyway thanks, I don`t know why, but idea of letting it fluctuate around slightly and ajusting as needed hadn`t occured to me. 89.235.214.143 (talk) 02:56, 13 March 2011 (UTC)

I don't like to cook much either, but making a salad isn't cooking. With raw ingredients like "baby cut" carrots, cherry tomatoes, and a bag of spinach, you can assembly a salad quite quickly (I just had one for dinner). I like to rinse the ingredients, then just drain, mix and eat. The only problem I've had is they sell huge bags of spinach which tend to rot before I finish them. Still, I bet a do-it-yourself salad will be both cheaper and healthier than a pre-made salad. StuRat (talk) 09:04, 13 March 2011 (UTC)

monopole

what would happen if you took a bunch of magnets shaped like a pyramid (with one pole at the top point and the other pole at the wide base) and then glued them together with all the top points facing in? —Preceding unsigned comment added by 98.221.254.154 (talk) 02:00, 11 March 2011 (UTC)

Your description of a magnetic "pole" as a point is unfortunately oversimplified. The simplest magnetic moment is inherently described as a dipole. A magnetic "pole" doesn't exist at one specific position in the magnet: it is an effective orientation - a preferred direction - that is built into the magnet. Complex ferromagnets have an effective average dipole moment, and so it's fun to draw this as a "north" pole region and a "south" pole region, but in truth, what you have is an net average orientation of all the individual microscopic orientations that make up the magnet. As such, the "north pole" doesn't exist "at the point" of the pyramid, nor the "south pole" at the "wide base." The entire magnet is polarized. Nimur (talk) 02:14, 11 March 2011 (UTC)

(ec) Their magnetic fields would cancel each other out, and only leave a slight inwards-pointing field in the middle of the faces of the resulting polyhedron, and a slight outwards-pointing field at the corners, or vice versa. Some distance from the compound object (say, two radii from the center) there would be practically no net field. –Henning Makholm (talk) 02:18, 11 March 2011 (UTC)

Ah yes, I didn't actually answer the original question! So, to directly answer what would happen: I can't quite follow the geometry the OP is envisioning, but it sounds like you've got a bunch of magnets oriented so that they want to repel each other. Well, if you squish them together, and maybe glue them in place, the result will be that from far away, you'll have an effectively larger, but weaker, magnet. And if you get really close near any of the individual pyramid-shaped magnets, you will find that your magnetic field is best described as a superposition of several individually-oriented dipole fields. (You might even find a way to mathematically re-represent that as one single higher-order moment, if you're pretty slick with math). Nimur (talk) 02:19, 11 March 2011 (UTC)

It could also be modelled as a superposition of two perpendicular linear quadrupoles, so I suppose it is an octopole. —Preceding unsigned comment added by 129.67.37.227 (talk) 02:41, 11 March 2011 (UTC)

Is it correct to compare a magnetic monopole to a one sided coin? Plasmic Physics (talk) 09:29, 11 March 2011 (UTC)

I don't mean a trick coin where both sides are either heads or tails, I mean a coin with literally only one side. Plasmic Physics (talk) 09:32, 11 March 2011 (UTC)

No. An electron is a "monopole" for charge after all. We have never found one for magnetism, but that doesn't mean it's illogical in the way a one sided coin (in a 3D world) is. Ariel. (talk) 10:00, 11 March 2011 (UTC)

I get the concept of a charge monopole, what would be a correct analogy then? Plasmic Physics (talk) 10:07, 11 March 2011 (UTC)

An electric charge monopole is totally described by its position and its charge magnitude. A magnetic dipole must include, at the minimum, its position, magnitude, and orientation. If you want to try and stretch this analogy, you could say a "magnetic monopole would be sort of like an arrow that doesn't point in any direction." In a sense, a magnetic dipole must be oriented - it's built in to the definition of a dipole to have a vector orientation; and our theory of magnetism requires the elementary magnetic unit to be a dipole. In the same way, if you had an arrow and it didn't point in any direction, ... well, you wouldn't have an arrow anymore. Nimur (talk) 14:47, 11 March 2011 (UTC)

I don't agree with all of the above. There sure is room in our current theory of magnetism for magnetic monopoles. Read 't Hooft–Polyakov monopole. That's why the search for a magnetic monopole is not considered a fool's errand. But they have never been observed and it is possible that they simply do not exist. A better analogy for the meaning of a monopole would be a rug that has been combed down away from a central position. Dauto (talk) 16:03, 11 March 2011 (UTC)

Insofar as you mean magnetic field lines would emanate from a monopole, yielding the hypothetical Gauss's law for magnetism, $\nabla \cdot \mathbf {B} =q_{m}$ - yes, that is how we would mathematically describe as a magnetic monopole, if it exists. And we would draw it on paper the way Dauto describes it. Is there room in our theory for it? Sure, with minor modification of Maxwell's equations, we could trivially add a magnetic monopole term; but to make those modified equations fit with experimental observation of physical reality will be a much more subtle and challenging problem. My tendency is to believe that the magnetic monopole does not exist, and is a contradiction against everything we physically observe about magnets, even if we could write equations to describe what it would hypothetically look like. Future experiment may disprove my belief - you're right that it's not futile (and indeed, is a worthwhile avenue for experimental physicists to pursue); so I'm open to the unlikely possibility of discovery of a magnetic charge. Nimur (talk) 16:35, 11 March 2011 (UTC)

The modified equation's fit just fine with experimental observations. I would like to clarify the point that 't Hooft–Polyakov monopoles are predicted to exist by the standard model of particles, so they are not as fringe as one might think. Dauto (talk) 16:48, 11 March 2011 (UTC)

Drugs

What affects do drugs have on the mitochondria in humans? How are other organelles affected? Albacore (talk) 02:20, 11 March 2011 (UTC)

Which drugs? We can't even begin to answer the question without specifics. --- Medical geneticist (talk) 02:55, 11 March 2011 (UTC)

Well, uncoupling agents are defined by their ability to (essentially) break down the electrical resistance of the mitochondrial membrane e.g. by acting as proton ionophores, discharging its energy unproductively. Oh, and rotenone works a different way, jamming the electron transfer apparatus. Wnt (talk) 04:42, 11 March 2011 (UTC)

Big rip or Big crunch?

Is it more likely for the universe to end in the concept "big rip" or "big crunch"? — Preceding unsigned comment added by Lightylight (talk • contribs) 04:29, 11 March 2011 (UTC)

Our article on the ultimate fate of the universe notes that current scientific data supports an open universe. That viewpoint is incompatible with a "big crunch", but does not necessarily support a "big rip" scenario. — Lomn 04:38, 11 March 2011 (UTC)

That article also says that the Big Freeze is "currently the most commonly accepted theory within the scientific community". There are a couple of variants of that scenario, depending on whether protons can or cannot ever decay. Gandalf61 (talk) 14:58, 11 March 2011 (UTC)

Zoologist specialising in Lepidoptera, "Busck", active beginning to mid C20?

Hi all,
The usual question: any clues about entomologist with either abbreviation "Busck." or full family name "Busck"? Binomial authority for Ypsolopha querciella amongst a whole lotta others. Google is not being friendly. Sounds Scandinavian, and first name initial may be "A".
Thank you! --Shirt58 (talk) 09:52, 11 March 2011 (UTC)

The "A" would appear to be "August" and his publications are listed at WorldCat. SpinningSpark 11:05, 11 March 2011 (UTC)

A F Braun, Lepidoptera, active mid C20

Hi all - same again. Binomial authority for Parectopa geraniella inter alia. Apologies for being such a bother. --Shirt58 (talk) 10:09, 11 March 2011 (UTC)

Annette F Braun [4], [5]. SpinningSpark 11:34, 11 March 2011 (UTC)

Japanese and Chinese earthquakes

Could there be any connection between the two earthquakes, or are they just coincidence? Thanks. 92.24.186.163 (talk) 14:06, 11 March 2011 (UTC)

As a first-order answer, "no, these are just coincidences." To explain in more detail, scientists have been studying earthquakes for a long time, and there are many theories about triggering earthquakes. There's a certain plausibility about massive geological events (like a powerful earthquake) affecting a geographically distant fault and triggering another earthquake; but unfortunately the data record is not clean enough to make a solid, scientific conclusion. Scientists have also investigated more indirect triggers for earthquakes, such as magnetic interactions between large sections of the Earth's interior; glacier, sediment, ocean/tidal, and other "variable" geological overburden loads, and so on. If you're interested, here are a few historically notable research papers: Earthquakes Cannot Be Predicted (1996); and my personal favorite work on earthquake prediction, Scientists debate new evidence for electromagnetic earthquake predictors (1991). (This paper triggered much heated debate). As you can see, most scientists do not believe there is any geological, seismic/teleseismic, electromagnetic, nor any pattern of animal behavior, nor any "telepsychic" method, that can predict earthquake incidence. But, reputable scientists continue to seek any sort of signals that might indicate earthquake precursors, or solidly indicate that one earthquake triggered a second one. Nimur (talk) 15:16, 11 March 2011 (UTC)

Thanks, interesting papers which I shall read, although the question is if there could be any connection between them, which is a different from asking about predicting them. 2.97.212.204 (talk) 16:22, 11 March 2011 (UTC)

Valid consideration: it's really two sides of the same coin. If Earthquake A causes Earthquake B, then there must be some physical mechanism (like a propagating seismic wave from A that disrupts the rock material strength along the fault-line for B). If there is such a connection, we should be able to observe it - or at least, identify what hypothetical "perfect, noiseless measurement instrument" would be required to observe it. And if we can observe A and measure its effects, we should be able to predict Event B. So the distinction between "A triggers B" and "A allows seismologists to predict B" is fairly moot. This is conceptually described with more rigorous scientific precision in the literature I linked. Nimur (talk) 16:45, 11 March 2011 (UTC)

Not really. Prediction is about things in the future, this is asking about things happening at the same time. In economics or finance, for example, there are series which are random and unpredictable yet which have a relationship with each other - in other words they may show Cointegration or Correlation. You've also forgotten that A and B may both be caused by some other factor. 92.15.24.90 (talk) 19:41, 11 March 2011 (UTC)

Earthquakes mostly are the result of movement of tectonic plates. Japan happens to lay on thee diffrent plates and there have been two previous earthquakes in the same region of China in recent years. If you take a look at maps in articles on both quakes and the ones on earthquake, you`ll see that they appear to be on different edges of Eurasian plate, close to diffrent fault lines and are moving in diffrent directions. It can be a coincidence. Though of course it could be that Eurasian plate has become particulary active. ~~Xil (talk) 21:37, 11 March 2011 (UTC)

To add to the list, there have been a number of large earthquakes in New Zealand lately, including the most recent one in Christchurch, and increased volcanic and seismic activity in Hawaii. One theory I've heard is that the Moon may cause this, by being closer than it has for the last 18 years (I'm not sure if this is true, the question posed a few above this should hopefully provide and answer). Since the Moon causes tides (along with the Sun), in water, and also causes hidden tides in the solid portion of the Earth (in the form of both stress and strain), it's not impossible that the Moon's gravitational effect could trigger quakes. Now, if so, the question would come up as to why it's all in the Western Pacific. Perhaps that region was "ready to blow" for other reasons, and the Moon just provided the spark. StuRat (talk) 23:54, 11 March 2011 (UTC)

The whole region is nutorious for seismic activity. See Pacific Ring of Fire for some statistics ~~Xil (talk) 00:54, 12 March 2011 (UTC)

Yes, but it appears to have increased recently. And I congratulate you on your "nutorious" spelling. :-) StuRat (talk) 00:59, 12 March 2011 (UTC)

There is no evidence of any increase in seismic activity that I'm aware of. Rates of earthquake occurrence appear to be constant since seismograph recordings began at about 1900[6]. Mikenorton (talk) 12:26, 12 March 2011 (UTC)

I mean quite recent quakes, like in the past month. There definitely seem to be more big ones in this time-frame, than for the average month. However, as noted below, some clustering of big quakes is to be expected, even if they are random. StuRat (talk) 21:48, 12 March 2011 (UTC)

I heard on tv two scientists say that earthquakes did tend to cluster together in time, even though they are in different places. 92.15.2.144 (talk) 00:57, 12 March 2011 (UTC)

If they're truly random, then they will show clustering. Mikenorton (talk) 12:26, 12 March 2011 (UTC)

This claim was made on CNN by a geology Prof., and he was referring to the really big quakes of magnitude 8.7 or larger. Such quakes are quite rare, they happen on average every few decades. However, there is a strong clustering that contradicts them being random. So, around 1960 there were 3 such huge quakes witin a period of a few years and we now have two or 3 of them (depending on whether you count the predicted magnitude 8.7 2005 Sumatra earthquake ). Count Iblis (talk) 15:24, 12 March 2011 (UTC)

I heard some reports stating that the 2011 Christchurch earthquake triggered more shocks all across the Pacific Ring of Fire to places as far as Alaska, but it's likely impossible to ascertain the connection. Propagation of quakes along the fault line occurred following the 2010 Chile earthquake. However, the 2011 Yunnan earthquake was likely not tied to the Japan shock, even if it is connected to the aftershock sequence from the 2008 Sichuan earthquake. ~AH1^(TCU) 02:17, 13 March 2011 (UTC)

Changing # of chromosomes in evolution

How do new species arrive that have a different number of chromosomes from their antecedents? I can see how the number could go down, actually, in theory, at least, but increasing-- where'd the DNA come from? Unless one of the already existent chromosomes split in the new species (seems like extremely high odds against that happening while not causing serious problems, let alone fitness) And yet many species of life have differing amounts of chromosomes, so it must happen. 20.137.18.50 (talk) 16:18, 11 March 2011 (UTC)

Polyploid plants can be formed from two monoploid parents, so the number of chromosomes can double in a single generation. Often, rather than suffering decreased fitness, many polyploid plants are quite hardy and robust, and specifically have characteristics desirable for agriculture. Many of our primary crop plants today are polyploid. See this section of our page for examples. There are other ways chromosome number can change, but this is a good place to start. SemanticMantis (talk) 16:32, 11 March 2011 (UTC)

You answered your own question. "It must happen". Which means that your intuition about the odds of that happening is simply incorrect. Dauto (talk) 16:42, 11 March 2011 (UTC)

That doesn't answer the how though, Dauto. 90.195.179.167 (talk) 16:44, 11 March 2011 (UTC)

Thanks, SemanticMantis, paleopolyploidy covers exactly what I was wondering about. Dauto, I didn't mean to doubt that it happens, I only meant to express my desire to understand how it happens, noting my perspective at the time given how easily bad things happen when genes get messed with. 20.137.18.50 (talk) 16:48, 11 March 2011 (UTC)

What makes you think that the splitting would have to mess up any genes? The splitting could happen between genes. There is a lot of non-coding DNA between genes in most Eukaryotes. Dauto (talk) 16:55, 11 March 2011 (UTC)

I don't have any specialized knowledge on the subject, and am glad to have any wrongheaded assumption I have made replaced by fact. 20.137.18.50 (talk) 17:10, 11 March 2011 (UTC)

One thing to bear in mind is that increasing the chromosome number by splitting one, or decreasing it by merging two, chromosomes (see Chromosome 2 (human) for an interesting example of the latter) does not involve creating or destroying any DNA, because differently-numbered chromosomes are not all the same size - indeed, they are conventionally numbered according to size order. When such merges and splits occur, individuals with them may initially still be able to reproduce with "unmodified" individuals because the two sets can still line up well enough: over time, the modification may multiply until modified individuals are regularly mating, and then the modification may, through some advantage, take over through Natural Selection.

Also, genes can migrate from one chromosome to another over generations, and smaller chromosomes may have shrunk by some of their genes having moved to larger ones: in time a chromosome could eventually dwindle away to nothing by this mechanism, again reducing the chromosome number. Some mitochondrial genes have over the aeons transferred from the mitocondria's single circular chromosome (I oversimplify) to nuclear DNA chromosomes, which is one reason why mitochondria can no longer operate as independent living organisms, and it has been suggested that the human Y chromosome (already our tiniest) will eventually disappear in this way (several human male-sex-determining genes are already on other chromosomes).

As others above have mentioned, sometimes the Chromosome complement can double "in one go" through polyploidy (I believe it's happened about 4 times in our own deep ancestry). When this happens the organism has a complete operating genome plus a "spare", and genes in the latter are then available to evolve new genes without losing the functions of the "originals". This could also happen if a single chromosome pair was doubled, or increased from 2 to 3, but sometimes such increases can cause deleterious effects, as in Trisomy 21.

Just as you say, such occurrances are rare, and non-deleterious ones rarer, but the deleterious ones are eliminated by Natural Selection, and there is so much time available over the millions of years over which evolution operates that the rare advantageous ones have time to accumulate. {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 21:30, 11 March 2011 (UTC)

Is there an example of a species with a variable number of chromosomes, where at least two of the variations could be described as "healthy" ? StuRat (talk) 23:44, 11 March 2011 (UTC)

Yes, Homo sapiens! This link refers to an individual from China with 44 chromosomes (22 pairs) as opposed to the usual 46, and I am sure I have recently read of a family in Scandinavia with the same count (though not necessarily due to the exact same variation), that I am momentarily unable to find references for. The latter family displays somewhat reduced but by no means destroyed interfertility with 46-chromosome individuals, because, as in my description of the Chromosome 2 merge above, the 2 unmerged chromosomes from a "normal" partner can still align well enough with their corresponding end-linked "double" chromosome to achieve homologous pairing. The individuals with 44 chromosomes are entirely healthy; they merely have the same genes packaged in a slightly different way. I suspect that this sort of variation is more common than hitherto realised (because who has been looking?), and I believe some other species more commonly show variable counts, but can't bring any to mind just now because it's past 5 in the morning! {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 05:24, 12 March 2011 (UTC)

Interesting, thanks. StuRat (talk) 05:59, 12 March 2011 (UTC)

That is a great link. Note that the man was actually the offspring of two people who both carried the translocation! So there's already some population out there (though probably very small) carrying this new chromosomal configuration.

What is interesting to consider is that if there are even just a few people like this man, it quickly reaches the point where outsiders are the ones with the "funny" chromosome pattern, in the sense that they'll be less capable of producing offspring with members of the group than they are with one another. Should it happen that group members are sitting on some good genes for some situation, this means that their group might spread out and start to dominate an area, and in this way start to look like a "new species" (though further barriers obviously would need to evolve) Wnt (talk) 07:16, 12 March 2011 (UTC)

There's also Przewalski's Horse which has 66 chromosomes and other horses have 64. It's debated whether it's a species or a subscpecies, partly because it can produce fertile offspring with other horse (sub)species. There's a discussion at the talk page that you might find interesting. I also recall reading about some small animal in the Middle East which had varying number of chromosomes in the same species. It might have been some kind of mongoose or rodent. I'll se what I can find.Sjö (talk) 08:09, 12 March 2011 (UTC)

Not exactly what I was looking for but http://www.talkorigins.org/indexcc/CB/CB141.html mentions the common house mouse and the plant genus Clarkia.Sjö (talk) 08:17, 12 March 2011 (UTC)

There was a similar discussion here two weeks ago, see (refdesk 2011-Feb-28) Chromosome numbers and speciation. Populations with interbreeding members having different numbers of chromosomes display chromosomal polymorphism. This is also discussed in Karyotype#Chromosomal_polymorphism. --NorwegianBlue ^talk 20:37, 12 March 2011 (UTC)

See also viral fossil and insertional mutagenesis. ~AH1^(TCU) 02:09, 13 March 2011 (UTC)

After looking at the link provided by the very knowledgeable anonymous editor, http://www.thetech.org/genetics/news.php?id=124, I am wondering why the 6×6 table is not symmetric. The last column, third last row, should be the same as the last row, third last column, shouldn't it? The contents do indeed look the same to me, but one is crossed out, the other isn't. Why would that be? — Sebastian 19:13, 13 March 2011 (UTC)

Strange breakers on Japanese Tsunami

There is a strange looking video of the tsunami coming onshore on CNN [7] (I can't figure out how to link to the video directly, you need to click on "Witness deals with quake terror" in the video gallery"). The wavefront is showing breakers only over a narrow and very well defined front. It does not seem to be due to the wave passing over an undersea obstruction as the breakers are long lasting and continue to show all the way in. What is the explanation for this? SpinningSpark 16:47, 11 March 2011 (UTC)

I also saw it. My impression is that the ground surface along that "strip" was different from the ground on either side of it - turbulent flow over a rougher surface flanked by less turbulence where the substrate is smoother. It also looked like the depth of the water in that area was only a metre or two so even relatively minor "texture" differences could cause a substantially different amount of visible turbulence on the water surface. Roger (talk) 19:41, 11 March 2011 (UTC)

It may be due to a sand bar. The shallower the water, the closer the waves and the more likely they are to break. In WW2, the spacing of the waves measured from aerial photographs was used to estimate the depth and slope of the D-day beaches using a mathematical formula. I have been unable to find an article about this formula: the nearest I could get is this Waves and shallow water but there may be a better article hiding somewhere. 92.15.24.90 (talk) 20:15, 11 March 2011 (UTC)

(edit conflict, replying to Roger) Yes, that's the obvious conclusion but I remain unconvinced for a couple of reasons. Firstly, the wake behind the breakers is ruler straight and constant width as if it was following a road, yet the effect continues up the beach where there is no sign of any lateral change in colour or texture of the substrate - I am sure that a change from sand to shingle, for instance, would be visible in the picture and such natural features are rarely so unnaturally straight. Secondly, I believe tubulence and/or friction caused by the substrate would cause a reduction in the wave velocity, but this is not borne out by the perfect straightness of the wavefront through the turbulent and non-turbulent sections. SpinningSpark 20:21, 11 March 2011 (UTC)

The type of wave may be a spilling breaker which explains why it keeps frothing for a long time. The second issue is why the white breaking part of the wave seems to keep a constant width for so long. This might be an illusion. The wave may be breaking as the instability in the crest and the resulting turbulence is spreading sideways at some fixed speed. Observed at a beach, such a domino-effect may seem rapid, but the same velocity observed from a helicopter seems small. Especially as we visually measure it not in metres per second but in percentages of the already wide breaking crest. It must also be taken into account that waves with a longer wavelength travels faster, so again our beach-aquired intuition about the forward speed of a wave versus the sideways spread of a collapse may not be correct. EverGreg (talk) 22:24, 11 March 2011 (UTC)

Looking at these videos, what seems striking is that the waves are actually able to move water upward in a given spot for a long period of time. In other words, there's a vast long hump of water with a strong horizontal momentum, so that it can wash right up over an obstacle. So I think we're seeing water that not merely is passing over a submerged obstacle, but which is actually striking an object that projects above the point where its surface was. Even so, it just vaults up over it and moves on. Wnt (talk) 07:10, 12 March 2011 (UTC)

The effect of the water piling up is due to the wave entering shallow water and is a "normal" effect of tsunamis. Unlike normal waves which are only on the surface, tsunami waves occupy the full depth of water. The foot of the wave is slowed by the substrate and the rest of the water piles up on top of it. SpinningSpark 09:07, 12 March 2011 (UTC)

Anyway, my gut feeling from watching the video is that there was an obstacle over a long region, which had slightly different elevations (relative to the tsunami, at least) in different areas; and that only where it extended above some critical threshold did it cause the flow to become turbulent. But that's not an expert opinion. Wnt (talk) 16:34, 12 March 2011 (UTC)

That's what it looked like to me, too. WikiDao ☯ 17:43, 12 March 2011 (UTC)

30 seconds into the video you can see the frothing edge being at an angle with the rest of the wavefront. This would be a sign of refraction caused by different parts of the wave being at different depths. So elevations probably factored into this. EverGreg (talk) 19:03, 12 March 2011 (UTC)

In a way, you can say that elevation not just factors in this, but is the main deciding factor. What complicates the matter is that it's not so much the elevation at the place you're observing, but the whole topography of the ocean floor (at least up to a certain depth) over which the wave has passed before. Shallower waters slow down waves, which bundles them much as an optical (convex) lens does. (In the eighties, there have actually been successful experiments in Norway, where they constructed submerged lenses to focus oceanic water waves into one location, where they could be harnessed. Not sure what became of that.) So the streak you're seeing is basically the same as a light beam. The same happens on a global scale, as you can see in this NOAAH height map (the same we linked to from our article). — Sebastian 19:37, 13 March 2011 (UTC)

Air circulation

What is the name for a large body of rotating air, something like an ocean gyre but in the air? --T H F S W (T · C · E) 19:38, 11 March 2011 (UTC)

A cyclone or anticyclone, depending on which way it is rotating. Looie496 (talk) 19:45, 11 March 2011 (UTC)

Note that the direction of rotation is different either side of the equator. Cyclones rotate counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere and anticyclones do the opposite. The distinction that is not location dependent is that the pressure in a cyclone decreases towards the middle and in an anticyclone it increases towards the middle. Cyclones are also called low pressure cells and anticyclones are high pressure cells. Roger (talk) 19:55, 11 March 2011 (UTC)

Note that an ocean gyre is a more or less "permanent" pattern of circulation, though, lasting many thousands of years, at least, while a cyclone or anticyclone only lasts a small portion of a year. StuRat (talk) 23:25, 11 March 2011 (UTC)

The gyres are propelled by the winds. Specifically, they are propeled by the westerlies and the trade winds. The presence of the oceans forces the ocean motion into the gyre patterns. Dauto (talk) 00:56, 12 March 2011 (UTC)

See Hadley cell and Rossby wave. Roger (talk) 19:23, 12 March 2011 (UTC)

From a meteorological point of view, jet streams are probably a closer equivalent of gyres than synoptic atmopsheric systems. They're more "permanent", so to speak, and encompass a much larger area than lows and highs. They don't rotate, per se, but they do circulate. Juliancolton (talk) 23:25, 12 March 2011 (UTC)

"Quasi-stationary" systems in the atmosphere include the Azores High, Siberian High (winter), Icelandic Low (not year-round) and others. ~AH1^(TCU) 02:07, 13 March 2011 (UTC)

This should be a synch...

There was recently a case where a baby was delivered at the side of the road, by the (non-medical) father, with paramedics on the phone. One thing the paramedics advised baffled me. After the baby was delivered, they said it was important to synch off the (uncut) umbilical cord, to prevent continuing blood flow between the mother and baby. Since no other string was available, the paramedics advised him to use the shoelaces from the shoes he was currently wearing. I can't imagine a less sterile item than those laces, and cringed when I heard that advise. So, my Q is, why is it so important to stop the blood flow immediately, rather than just wait for the ambulance to arrive ? StuRat (talk) 20:26, 11 March 2011 (UTC)

Just by the way, I think you mean cinch. --Trovatore (talk) 20:28, 11 March 2011 (UTC)

Thanks, I wasn't sure how to spell that, as it's not a word I normally use, at least in writing. StuRat (talk) 23:16, 11 March 2011 (UTC)

Why does the shoelace or whatever is used to tie the umbilical have to be sterile? The cord and placenta will be discarded soon anyway and the cord will be cut and properly clamped with a clean clamp when the ambulance arrives. The cord must be shut off asap because if it isn't nothing would prevent the baby's blood draining out through the placenta after it detatches from the uterus, which can happen very soon after the baby is born. Not shutting off the umbilical cord will result in a dead baby within minutes wheras a dirty shoelace might have a slight chance of making the baby ill hours or even days later - the choice is a no-brainer. Sterility is in any case massively overrated as a requirement for people who have normal functioning immune systems. We survived for millions of years without even having the concept of germs or sterility. Roger (talk) 20:43, 11 March 2011 (UTC)

We also survived for millions of years without the thumbs necisary to tie a knot or build a clamp, so shutting off the cord must not be manditory (although it might lower the death rate of baby and mother). —Preceding unsigned comment added by 205.193.96.10 (talk) 21:23, 11 March 2011 (UTC)

Animals bite off the umbilical cord, probably not a method that would be prefered by human fathers. Wouldn`t squeezing the cord shut and waiting for the ambulance work too, though, without creating risk for infection? ~~Xil (talk) 22:18, 11 March 2011 (UTC)

I'm not sure how biting the cord off would help prevent bleeding - it would increase it, surely? You'll probably need your hands for other things. Taking care of the mother and baby, delivering the placenta, etc.. Using a shoelace is the standard advice. --Tango (talk) 22:28, 11 March 2011 (UTC)

Yes, I would think biting off the cord would both cause bleeding and infection, due to all the germs in saliva, and the presumably undeveloped immune system in the offspring. What prevents these things from happening ? StuRat (talk) 23:19, 11 March 2011 (UTC)

I`m just saying that the argument about no thumbs might be invalid, I am not sure how the said animals don`t bleed to death. I believe in olden days they would cut the cord and tie a knot in it, not sure, if it is right, though, couldn`t find any quick information ~~Xil (talk) 00:38, 12 March 2011 (UTC)

As long as the unbilical cord is intact and not bleeding, then there is no route for infection to get it so you don't need to worry about sterility. Anyway, worst case scenario: you have to give the baby a shot of antibiotics. Not a big deal. We do (of course) have an article: Umbilical cord#Clamping and cutting. It doesn't discuss infection, but does discuss the pros and cons of clamping quickly, slowing and not at all (there doesn't seem to be a lot of difference). --Tango (talk) 22:28, 11 March 2011 (UTC)

March 12

Starvation and blindness

I have read that starvation can lead to temporary vision loss (and when the patient is returned to his or her regulat diet, the vision problems go away), is this true, and how?—Preceding unsigned comment added by 142.1.253.163 (talk) 21:08, 11 March 2011

If you have a vitamin A deficiency, you can go blind. Clarityfiend (talk) 01:29, 12 March 2011 (UTC)

Yes, people who willingly under go starvaion can and do experiance blindness. Hunger_strike#Animal_rights--Aspro (talk) 23:33, 12 March 2011 (UTC)

how does a vacant space,hole( in electronis) have a mass?

in electronics mass of hole is considered . Hole is a vacant space created when electron is migrated to conduction band from the valance band. how can this free space have a mass? —Preceding unsigned comment added by 117.197.192.72 (talk) 01:24, 12 March 2011 (UTC)

It is not a real mass. It is an effective mass which basically mean that the hole moves around displaying a behavior which can be interpreted as if it was a particle with mass. Think about it. The hole moves about by having electrons jump from neighbor regions and filling the hole and living a vacancy behind. This motion is not instantaneous and respond to external forces (such as an external electric field) in such a way that we can interpret the whole thing as if a particle with positive charge and some non-zero mass was there. That's the hole. Dauto (talk) 02:19, 12 March 2011 (UTC)

Beyaz and Natazia

Where is the page for Beyaz so short at the moment? At the same time where is the page on Natazia as well? Basically, I would like to learn more about these birth control options. — Preceding unsigned comment added by Mybodymyself (talk • contribs) 03:57, 12 March 2011 (UTC)

WP does not have information on everything - yet. The article on Beyaz is short because no-one, including you, has added more information to it. The article on Natazia does not exist for very similar reasons. If you put 'Natazia' into google you will receive about 84,000 hits, some of these contain excellent information about Natazia. Richard Avery (talk) 08:23, 12 March 2011 (UTC)

Why is blood typing routine in Mexico, but not in the United States?

Question: Why is blood typing routine in Mexico, but not in the United States (outside of the contexts of blood-donation or surgery)?

Context: I'm in my mid 30s, was raised in the United States, now living in Mexico. I've never donated blood (shame on me!) or had surgery (knock on wood). Therefore I've never had any occasion to have ABO or Rh(D) blood-typing done. Neither I nor my parents know my blood type. (Father is A, mother is B, so I gather I could be anything, depending on their relative zygosity; no, I'm not asking you to determine paternity!).

It seems I'm not that unusual for someone from the USA; according to this website, 60% of Americans don't know (warning: this site also advocates the blood-type personality/diet quackery). More anecdotal confirmation: 1402 people on a US website professing blood-type ignorance.

Arriving in Mexico City, it appears that everybody here knows their blood type. It is requested on the driver license application, as well a myriad other government documents; it appears on taxi-driver medallions posted in every (legal) taxicab's rear passenger-side window. If the subject comes up, without fail every Chilango is incredulous that I don't know what to them is as basic a piece of personal information as one's birthdate or second (maternal) family name (whoops, I fail there, too!).

One Mexican friend has gone so far as to call my mother negligent and my doctor an idiot. "You need to know in case you're in an accident and need a blood transfusion!", she says. I reply, "My US doctor told me, 'You only get tested at the moment it becomes necessary, in the ER or blood donation van'." "But there's no time in an emergency! You could die while they're testing you!" Cue hysterical screaming.

More anecdotes: One of the poorest municipal governments in Mexico offers free blood-typing analysis

A Mexico State legislator proclaims obligatory blood type testing to be an unnecessary and irrelevant requisite for registering schoolchildren, implying that the practice is currently standard.

So what accounts for this difference? I accept my facts are all very anecdotal (perhaps there's a MEDLINE article somewhere beyond my search-fu), but what, if anything, could this say about respective medical practices/bureaucratic zeal of each society? Or other countries? Sorry for being long-winded!

--189.227.64.126 (talk) 04:03, 12 March 2011 (UTC) Gringo seudoanónimo

Knowing your blood type is useful for you and, really, only you. If you don't want to take the time to get a test (free from many places), then it is all on you. Once you decide to try and have children, then your blood type is important for the child also because there are possible complications based on the compatibility of the mother's and father's blood type. Chances are the mother's doctor will have both the mother and father checked. When my wife was first pregnant, her doctor had by blood type checked even though I already knew what it was - just to be sure. Beyond that, anything that may happen in which your blood type is important to others will include a blood type check. -- kainaw™ 04:20, 12 March 2011 (UTC)

I should have answered about the need for blood transfusion. It is safe to use O- blood while your blood type is checked (which takes minutes in an emergency, but 20-30 minutes under normal circumstances). By the time you finish some O- blood, your blood type will be known and you will likely be given your specific blood type. If, for some reason, there is no O- blood, O+ is usually safe to start with (with very rare complications). From what I've seen, O+ is usually in higher stock levels than O-, but I don't think that is because there is simply more O+ blood donated. I think it is because O- is used more. But, I never checked donation/usage statistics on that. I spend my time at the Red Cross doing experiments on how donating blood affects hypertension, diabetes, and hypercholesterolemia. I've only been surprised once: donating blood increases blood pressure for a few hours. Then, it is lowered for a couple days. I assumed it would be lowered for a few hours and then return to normal. But, it is late and I'm drifting quickly off topic. -- kainaw™ 04:27, 12 March 2011 (UTC)

In an emergency, Rh-negative type O blood can be transfused about as safely as type-matched blood that has not been cross-matched. Thus, it's arguably more efficient to maintain a stock of type O blood than it is to depend on typing everyone and assuming that the blood type document they carry is accurate (many people carry identification that belongs to someone else, for a variety of reasons, and might not be in condition to explain during an emergency). As our Rh article I just linked points out, Rh negativity is much less common than Rh positivity, hence O^- donors are significantly less common than O⁺ donors. -- Scray (talk) 04:42, 12 March 2011 (UTC)

In addition to the above, there is also a risk of mistakes, either a mistake in transferring data from the test to the ID-card or whatever, or because the ID-card belongs to a different person. The consequences of giving a transfusion with the wrong blood type can be disastrous, but there's usually no serious consequence if you take the time to check the blood type and give O-blood or other fluids in the meantime. Also, blood typing everybody will take resources that might be better used elsewhere. Source: Opinion from the Swedish Riksdag's comittee on social services (Swedish).Sjö (talk) 10:53, 12 March 2011 (UTC)

I heard from someone at the ASBBC that the US military routinely retypes soldiers before sending them overseas because so many of the dogtags they get in basic end up being wrong. Other than the possibility for errors, you also have to find the card/ask the person/etc... in order to find the blood type, and honestly that might take longer than just a stat ABO type. I'd guess that the difference between the US and Mexico is probably that the US has a much better blood bank infrastructure and at least a couple of units of type O blood are routinely available at any hospital (most hospitals I've seen have two or four units reserved precisely for this purpose). Either that or living in Mexico is more dangerous and you're far more likely to need a transfusion... SDY (talk) 12:46, 12 March 2011 (UTC)

Thanks for your responses. Paraphrasing somewhat polemically:

Kainaw: Blood typing is useful to individuals, but not to a society at-large. Implication: the US has made a rational choice, and Mexico has not, for some unexplained reason.

Scray: A blood bank infrastructure which maintains a stock of O+ O^- blood is arguably more efficient. Implication: The US has this stock, Mexico does not and therefore inefficiently relies on individuals to carry accurate records. (BTW, most Mexicans are type O)

Sjö: Resources are more efficiently spent testing at the moment of need rather than beforehand. Implication: Mexico wastes its resources. Why?

SDY: The US has a better blood bank infrastructure than Mexico. Implication: Consequently, the individual burden to track blood type is eliminated. I'll ignore the joke about Mexico being more dangerous to live in... though its 2000 traffic accident death rate was 168% greater than the US (and 714% greater than Sweden's!)

The unspoken judgment in all of your responses is that Mexico has backward medical practices compared to the US, ie. economic factors rather than cultural explain the difference. Let me tell you that this view is not generally well received here in Mexico, and would likely be termed mamón, or "stuck up." The woman I mentioned above countered that Mexico, being a country with strong indigenous roots, has a longstanding pro-active, self-medicating tradition, where one must literally bring one's own medical records to each doctor visit. The US, by contrast, being an immigrant society, has discarded whatever traditional health participatory patterns and instead defers to its medical system to know what's best. Which is better might depend on one's values (or you could measure by life-expectancy, incidence of diabetes, etc.)

So, returning to the question; if it's just a question of economic development, aren't there counter-examples of wealthy/highly-developed societies where every person is expected to know one's blood type? Japan comes to mind, (I only know about it from reading about the popular belief in blood-to-personality typology, which Mexico incidentally does not share). --189.227.64.126 (talk) 04:33, 13 March 2011 (UTC) Gringo seudoanónimo

Every nation/culture has its superstitions. I don't think anyone who replied in this thread judged Mexico as less rational "on average" than, say, the U.S., just as less rational on this one particular point. If you want to talk about ways in which the U.S. wastes its resources, well, don't get me started. -- BenRG (talk) 08:57, 13 March 2011 (UTC)

IP189.227...'s summary of my comment is inaccurate though I do agree with their self-characterization of that summary as "somewhat polemical". I did not suggest a stock of "O+ blood" (I specifically suggested O^-). More importantly, each government must make their own decisions regarding how best to manage emergency supplies. I simply stated that it is "arguably" more efficient to transfuse O^- blood when transfusion cannot wait, and type & crossmatch in the meantime. -- Scray (talk) 13:49, 13 March 2011 (UTC)

Corrected my arguable argumentative summary. Thank you, Scray. 189.227.64.126 (talk) 14:54, 13 March 2011 (UTC)

I agree that it's somewhat polemical, though maybe not wholly inaccurate. GSWs and MVAs aside, I'm actually looking at medical records in the Dominican Republic right now, and "self-medicating tradition" has left me a little... nonplussed. People taking cipro for toothaches makes me want to modify the appearance of the nearest wall with my forehead. SDY (talk) 15:45, 13 March 2011 (UTC)

There is plenty of self-medicating tradition in the United States also. I work in hypertension, diabetes, and hypercholesterolemia research. It is amazing how people who freely blow thousands of dollars every year on beer, cigarettes, and lottery tickets will penny-pinch over a $10/month medication bill. Further, there are cultural superstitions that border on insanity (in my opinion, they step clearly over the line). For example, there is a black culture superstition that hypertension is not real. It doesn't exist. It is a white supremacist trick to get black men to take hypertension medication that actually makes them sterile. So, black men (who are known to be at the highest risk for hypertension) tend to avoid hypertension medication out of fear that it will make them sterile. You cannot reason with self-medicating traditions because you cannot reason a person out of an opinion that he or she reached without reason. You just have to hope they don't pass it on their children. -- kainaw™ 18:17, 13 March 2011 (UTC)

Tokyo's earthquake

2011 Sendai earthquake and tsunami: Most news sources claim that this earthquake is the biggest one ever recorded in Japan's modern history. However, Tokyo only experienced a seismic scale 5+ quake this time (thanks to the distance). This is big but not as big as the city-devastating quake the scientists warned about. So far most damages were caused by tsunami rather than the quake. Much of the city survived the quakes.

• http://www.jma.go.jp/jp/quake/20110311145349391-111446.html
• http://www.jma.go.jp/jp/quake/20110311150154391-111446.html

東京都　　震度５強　東京千代田区大手町　東京江東区東陽 ...

Tokyo Metropolitan area, seismic scale 5+: Chiyoda Ward, Koto Ward, ...

Does it mean that this earthquake is still not the big one feared by the scientists? -- Toytoy (talk) 04:20, 12 March 2011 (UTC)

The big earthquake that was to destroy Tokyo aka the next Kanto Quake was due in 1995. 139.130.57.34 (talk) 04:36, 12 March 2011 (UTC)

I think this was the big one feared by scientists. It may not have been directly on-target, but an 8.9 earthquake sure does release a lot of energy. I think it will be a while before the next big one. --T H F S W (T · C · E) 05:19, 12 March 2011 (UTC)

I noticed that very few buildings in Tokyo collapsed because of the earthquake. Much of the subway system remains undamaged. The tsunami caused much more damage than earthquake. Japan's buildings survived the seismic scale 5+ quake. Since there are many more faults even closer to Tokyo may cause earthquakes, I doubt that the next big one is still waiting to happen. However, this disaster reminds us the seriousness of tsunamis. They are probably even worse than earthquakes.

This earthquake is MUCH larger than the Great Hanshin earthquake of 1995. However, since the Hanshin earthquake's epicenter was almost under the cities, many highly-developed metropolitan areas experienced seismic scale 6 to 7 rocking and shaking. Buildings collapsed. People were killed or rendered homeless. This time Tokyo's citizens suffer much less. On the other hand, people living in some coastal areas were wiped out completely because of the killing tsunami. -- Toytoy (talk) 08:11, 12 March 2011 (UTC)

The rupture area of the Sendai earthquake does not overlap with the estimated rupture area for the 1923 Great Kantō earthquake, so it's unlikely to have changed the risk for a re-run of that event, it might even trigger it, like the 2005 Sumatra earthquake, which followed close on heels of the 2004 Indian Ocean earthquake, rupturing an adjacent area of the Sunda megathrust. Mikenorton (talk) 12:57, 12 March 2011 (UTC)

The Sendai earthquake may have been close to the maximum strength for a Japanese quake but was certainly not the worst-case scenario. Such a quake would be a magnitude 9+ tremblor occurring near the Tokyo Bay region. Seismologists have not ruled out the possibility of M7+ aftershocks occurring very close to Tokyo Metropolitan Area. ~AH1^(TCU) 02:01, 13 March 2011 (UTC)

INDIA A SUPER POWER

I AM A STUDENT FROM GOA,INDIA. I AM A SCIENCE STUDENT OF 2011 BATCH. I THINK INDIA HAS A MULTIDIMENSIONAL MILITARY FORCE TO SECURE ITS TERRITORY AND ENOUGH MILITARY STRENGTH TO COMBAT ANY A THREAT. — Preceding unsigned comment added by K55WI4DFG (talk • contribs) 09:20, 12 March 2011 (UTC)

How jolly nice for you. Now if you can just clear up some of those shameful slums, you'll be all set to join the 20th Century. (P.S. Printing in full caps is regarded as a style best suited for the uneducated and uncouth. Then again, perhaps you better keep on using it.) Myles325a (talk) 09:53, 12 March 2011 (UTC)

How is this a science question? SDY (talk) 12:47, 12 March 2011 (UTC)

How is this a question? --41.132.13.74 (talk) 18:08, 12 March 2011 (UTC)

Nice one Myles325a, What a prick!! but then you are in Australia! Caesar's Daddy (talk) 14:21, 12 March 2011 (UTC)

I think India needs to test more powerful thermonuclear weapons before such a claim can be made. Count Iblis (talk) 15:14, 12 March 2011 (UTC)

That seems like a rather silly and arbitrary definition. 200 kilotons not good enough for you? Is it going to make you treat them differently than if they had 1 Mt? From a strategic standpoint, what matters less is the size of the boom (even 1kt is enough to be "unacceptable" if it goes off over a city), but where you can put it (if you can't deliver the thing, then it isn't much of a threat). --Mr.98 (talk) 16:21, 12 March 2011 (UTC)

My understanding is that many definitions of true "superpowers" are the ability to project force globally. Both the USA and USSR could have, essentially, put "men on the ground" on any continent. India cannot reasonably do this to my understanding. They do note even have secondary strike capability outside of the subcontinent. Securing your own territory just makes you a power — not a "super"-power. --Mr.98 (talk) 16:21, 12 March 2011 (UTC)

We have an article that discusses the possibility of India becoming a superpower. It doesn't seem particularly likely in the immediate future. Matt Deres (talk) 20:01, 12 March 2011 (UTC)

See veto power and regional power. ~AH1^(TCU) 01:55, 13 March 2011 (UTC)

F.A.G.E?

I HAD SEEN MY DOCTOR'S QUALIFICATION. IT WAS WRITTEN F.A.G.E. I HAD SEARCHED IN THE WEB SEARCH ENGINES AND COULD NOT GET THE ANSWER. COULD SOMEONE HELP ME OUT WHAT DOES F.A.G.E. STAND FORRaavi4321 (talk) 11:12, 12 March 2011 (UTC)

Possibly Fellow of Academy of General Education as offered by Manipal University. I can't identify if this is an actual qualification or a membership though. Nanonic (talk) 14:27, 12 March 2011 (UTC)

Fake Acronym to Gain Employment? Clarityfiend (talk) 20:26, 12 March 2011 (UTC)

Potentiometric Titration

Hello. Will I get a normal titration curve if I titrate, with a potentiometer, KIO₃ in acidic solution against ascorbic acid mixed with starch indicator and KI? Thanks in advance. --Mayfare (talk) 17:26, 12 March 2011 (UTC)

See the Wikipedia articles Titration and Titration curve. Since a titration is a method of quantitative chemical analysis you will have to do the experiment to see the result. Cuddlyable3 (talk) 20:53, 13 March 2011 (UTC)

How did mid-twentieth-century fixists explain the dovetailing opposite coasts of the Atlantic Ocean?

How did recent "fixists" (opponents of the theory of continental drift, including Harold Jeffreys and others) explain the dove-tailing outlines of South America's east coast and Africa's west coast? 82.31.133.165 (talk) 20:32, 12 March 2011 (UTC)

Just coincidence, they could argue. After all, they aren't an exact fit, due to erosion and changing water levels. Then they would point to all the adjacent continents that don't seem to match very well, such as the lack of an Italy-shaped indentation in North Africa. StuRat (talk) 21:36, 12 March 2011 (UTC)

Unless you happen to have been a mid-20th century "fixist", your opinion about it doesn't matter to anyone other than you. Matt Deres (talk) 04:57, 13 March 2011 (UTC)

I don't agree. Studying the reaction of scientists who deny a new science has direct application today, such as those (few) scientist who seem to deny the existence of global warming (usually those with a big grant from somebody who wants them to say that). StuRat (talk) 08:54, 13 March 2011 (UTC)

What has that got to do with anything? The comment was directed at you, not the questioner. The OP wants to know what certain people thought/said/wrote about a particular topic. They're not interested in what StuRat would have said if he'd been there. Matt Deres (talk) 14:00, 13 March 2011 (UTC)

We have a history section in the continental drift article, and an entire article Timeline of the development of tectonophysics. From that article, I found this history book online, Scientific controversies... (by Arthur Caplan, 1987), with an entire chapter on the continental drift debate, and an entire sub-chapter entitled "The fixists' response to Wegener's drift theory" which should give you a pretty solid footing. You could then pursue the original papers published by the involved parties. Caplan lists several specific opponents of the modern theory of plate tectonics and continental drift. Nimur (talk) 22:48, 12 March 2011 (UTC)

Limestone flakes changing color

Detached pieces are lighter in color.

I just noticed a limestone block that has pieces coming off in lighter colors. How/why do the pieces change color? They're definitely part of the original block: the contours of the pieces conform precisely to the contours of the section of the block on which they're sitting, and you can see that the piece in the top left gradually changes; it's only partly detached from the block. Moreover, how do the pieces come off? They've obviously not been moved or broken off by human action; is it simply the result of winter weather? Note that I've uploaded a more comprehensive image. Nyttend (talk) 21:30, 12 March 2011 (UTC)

The usual method is that water gets between the layers, freezes, expands, and breaks the layer off a bit further with each cycle. As for the color, water may be the culprit there, too, if the broken off pieces are able to dry out due to increased surface area and temperature (they would be air temperature, while the attached pieces would be closer to the ground temperature). You might want to wet them down and see if they then look the same. StuRat (talk) 21:35, 12 March 2011 (UTC)

Yep, classic spalling / exfoliation. I also agree with StuRat; the flakes just look dryer to me. SemanticMantis (talk) 21:55, 12 March 2011 (UTC)

Preventing earthquake/Tsunami damage by triggering them?

Can we prematurely trigger e.g., the expected next Cascadia megatrust earthquake, using hundreds of simultaneous underground nuclear explosions along the fault line? Then everyone can be evacuatated well in advance of the event and no one will die. Radiation is contained just as in ordinary nuclear tests, so there isn't a big issue here, it seems to me... Count Iblis (talk) 21:50, 12 March 2011 (UTC)

A priori, I would say: 1. It's not clear that you can trigger an earthquake with nukes. Nukes are big on a human scale but not a geologic scale. 2. In the example you give, the fault line is well under the sea floor. That would present a few logistical difficulties to say the least. 3. Radiation is contained when you know what the seismic and geological characteristics of the ground are. (And even then, sometimes mistakes happen.) In this example, you would be trying to affect the geology rather drastically. That seems problematic for containment. 4. The uncertainties are rather gigantic. 5. Politically infeasible. --Mr.98 (talk) 22:47, 12 March 2011 (UTC)

Also, the nukes would probably only work to trigger a quake if it was just about ready to go, anyway. And, if we are able to predict that, then we really don't need the nukes, just evacuate everyone when it's ready to go. StuRat (talk) 23:30, 12 March 2011 (UTC)

Some years ago I remember seeing or reading something about a situation in the US where water was pumped into or out of the ground, and this had an effect on the rates of minor earthquakes in that area. 92.15.8.206 (talk) 00:27, 13 March 2011 (UTC)

You are referring to the Denver earthquakes, where seismicity was triggered by injecting liquid waste into a deep borehole (3671 m) at the Rocky Mountain Arsenal, see here, this was due to changes in the effective stress on existing fault planes caused by increased pore fluid pressures - basically as rocks are more deeply buried they become harder to fault, but if you reduce the confining pressure by pumping fluids in this allows small adjustments on the existing faults to release some of the stored elastic strain energy in the form of earthquakes. Mikenorton (talk) 09:19, 13 March 2011 (UTC)

The weight of the water might cause the Earth to compress under it, generating tremors. I recall that Hoover Dam had that effect, as Lake Mead filled with water. StuRat (talk) 00:43, 13 March 2011 (UTC)

If you change the load on part of the crust, by filling a large reservoir or by excavating a large mine, you will change the local stress state, potentially triggering an earthquake. Mikenorton (talk) 09:19, 13 March 2011 (UTC)

The combined force of the nuclear explosions would need to be at least as great as the tidal forces of the Moon and Sun to trigger an earthquake.predictably. The bomb blasts are impulses that would have to be synchronised and could cause additional havoc by their shock waves. Just the vision of a following radioactive tsunami makes the OP's idea unsellable. Cuddlyable3 (talk) 20:21, 13 March 2011 (UTC)

Seamounts and faults focus tsunamis?

Simulated wave height of the 2011 Sendai earthquake and tsunami

The map of the calculated wave height for the recent tsunami is intriguing. Obviously, it's a simulation, proceeding from known laws, but is there a shorthand way to understand its prediction?

In particular, there are some general rules that seem to apply to that picture:

• The waves typically travel in nearly straight lines - red areas don't spread much and attenuate very slowly.
• When they hit an obstacle they intensify.
• When they hit a seamount/guyot they intensify in a straight line downrange from it, at least for some hundreds of miles.
• California and Oregon receive some extra-special exception to this rule, where the wave gets intensified at the Koko Guyot, travels along a ridge to the east of it, then follows a transform fault all the way to North America. (There's another transform fault to the south that seems to get the same treatment, but many others that seem unaffected)

Do any of these speculations of mine actually represent scientifically known rules that we should add to the article about tsunamis? Wnt (talk) 22:02, 12 March 2011 (UTC)

Such simulations are not the result of simple applications of physics. They are usually numerical physics models. I suspect this particular plot is created by measuring peak-wave-amplitude in a full 3-D or 2.5-D numerical wave equation modeling exercise. Here's a summary of the MOST numerical wave model used to generate the plot you linked. You can search for prior research-publications on the Pacific Marine Environmental Laboratory tsunami-modeling website, or contact NOAA's researchers for more details of the techniques they use. Waves behave in very complicated ways when they are injected into a nonhomogeneous environment (i.e., variable sea-depth, sea-temperature, salinity, and any other factors that might affect wave propagation characteristics). General ideas about constructive and deconstructive interference might help guide your intuition, but in practice, the complex interactions between the wave and its environment defy "simple" rules. Nimur (talk) 22:55, 12 March 2011 (UTC)

Comparison of model data with tide gage data is interesting (for example, the model was off by about 10 cm for high-point and about 30 cm for low-point for San Diego). See also the March 11, 2011 Honshu event at NOAA. WikiDao ☯ 23:14, 12 March 2011 (UTC)

Interestingly, the main direction of the tsunami plume pointed toward Southern Chile at a location south of the 2010 Chile earthquake epicentre, which in turn produced a tsunami that pointed south of this year's Japan earthquake. Modelling would also likely take the Coriolis force into account, and the path of Japan's tsunami seemed to follow some bathymetric seamounts and ridges toward Chile. Subsea surface heights are known to affect sea level. ~AH1^(TCU) 01:51, 13 March 2011 (UTC)

March 13

Changes in personality test results and IQ when the subject is drunk

It is common knowledge that people change their apparant personality when drunk, but are there any research papers that compare the results obtained on Big Five personality traits personality tests and IQ tests for the same subjects after consuming alcohol and when completely sober? Thanks 92.15.8.206 (talk) 00:24, 13 March 2011 (UTC)

There is a lot more research on the effects of personality on alcohol consumption than on the effects of alcohol consumption on personality. There seems to be a general consensus that drinking increases impulsiveness, but I didn't spot any research that assesses this using standard personality tests. Looie496 (talk) 01:30, 13 March 2011 (UTC)

I suppose the problem with personality tests is that they ask the subject to recall their past behaviour or attitudes, eg "Do you like parties?" which would not be much affected by current intoxication. 92.15.26.29 (talk) 21:35, 13 March 2011 (UTC)

Why do nuclear reactors have batteries for cooling?

They could obtain all the energy they wanted from the heat of the rector. —Preceding unsigned comment added by 212.169.190.126 (talk) 03:12, 13 March 2011 (UTC)

As far as I understand, normally that's exactly what they do - they need to power the pumps that take the water in, but when the tsunami hit they shut down the reactor and went to diesel to continue cooling. The diesel then failed and they had to go to battery to power the pumps. Again, as far as I know, that's the main power need - pumping, venting, etc. SamuelRiv (talk) 03:52, 13 March 2011 (UTC)

The first backup, before they had to go their diesel generators, is to take power from the grid. This was impossible because the earthquake had caused all the power stations along the coast to go into auto-shutdown, including their own one. This left them on tneir own with only their own diesels and batteries, which worked fine until the subsequent tsunami flooded them. SpinningSpark 11:29, 13 March 2011 (UTC)

You only get power from the reactor when everything is working correctly. Hence the need for backup systems. --Mr.98 (talk) 11:58, 13 March 2011 (UTC)

Also note that according to (most of) the news stories, the batteries were for instruments and controls, and were not for running the cooling pumps. -- 119.31.126.69 (talk) 12:06, 13 March 2011 (UTC)

Yes, I get the idea that a shut-down generator won't generate electricity directly. However, a shut-down reactor still generates heat (right?), so you could connect a Stirling engine with a cooler to generate all the electricity that you want. A part of the cooling would be passive, through the cooler of the Stirling engine, and the rest would be through the power generated through this process. 212.169.183.128 (talk) 12:53, 13 March 2011 (UTC)

Whether you could even do that in theory would really depend on how you had the plant set up. Have you actually been inside a nuclear power plant? They are not like those idealized reactor diagrams you see that explain how they work. They are massive industrial facilities, the size of many factories put together, with miles of pipe, concrete, and so forth. The turbines themselves fill gigantic rooms, deafeningly whirring away. They are quite a spectacle and I do recommend trying to visit one at least once in one's life, just to get a sense of the scale of the things and the work that goes into running them. I went on a tour of one awhile back and was bowled over by the complexity — you're not just going to rush in and tinker with them, especially not in an emergency situation. It sounds to me like you are either proposing that they'd have such a system already in place (which is probably not economical, considering the specific situation in which it would be useful, which would be quite rare) or adding one on the fly, which seems totally impractical, and not as easy as just using batteries. --Mr.98 (talk) 15:41, 13 March 2011 (UTC)

No, I was not thinking about an on-the-fly solution after an accident and also not an add-on solution to an already built nuclear power plant, but as an ideal solution. You need a backup cooling anyway, and this cooling system needs to be connected to the reactor somehow, so generating power shouldn't be a problem for it. You are right at pointing out that the nucleus quite rarely melts out (even if it might be happening right now). But, if it does, then the harm is apocalyptic (at least on a local scala). 212.169.183.128 (talk) 15:59, 13 March 2011 (UTC)

What happened in Japan (earthquake + Tsunami) is probably rare enough, so no one was prepared for this specific case. Once again, accidents happen, when people think they are prepared for something.Quest09 (talk) 16:58, 13 March 2011 (UTC)

If I understand things correctly, tsunamis are highly correlated with earthquakes; an earthquake that moves the seafloor is highly likely to create a tsunami. Why should one expect the combination to be rare? –Henning Makholm (talk) 20:50, 13 March 2011 (UTC)

production of hydrogen from cooling water in nuclear accident -- was it a thermal decomposition?

It couldn't have been alpha particles or free protons finding electrons, right?

I know how to find the equilibrium reversal temperature to be 2300K. But obviously the pressure conditions are higher inside the nuclear reactor, and both temperature and pressure are increasing at the same time. How do I find the temperature where the equilibrium constant is 1?

Suppose I did start at some reactor pressure T1 -- perhaps I could draw a pressure-temperature curve as the reaction proceeds to T2? How do I calculate the total heat capacity of this reaction? (Is the heat capacity constant within this range, or do I have to account for this too?)

Also, does the presence of thermal decomposition provide a natural sort of "superboiling point" for water? That is, if I were superheating steam initially at 2300K at 1 atm, and suppose pressure were constant (the rxn is taking place in a large bladder or a balloon), would the steam basically stay at this temperature until all of it had converted to 2300K? John Riemann Soong (talk) 03:50, 13 March 2011 (UTC)

Is it accurate to model water as an ideal gas at 2300K and 600 kPa? John Riemann Soong (talk) 03:59, 13 March 2011 (UTC)

Fukushima I Nuclear Power Plant mentions caesium-137 as a fission product. It is radioactive, but as long as it hasn't decayed yet, it reacts chemically as an alkali metal -- like sodium except more so -- dissociating the cooling water into H₂ and OH^-. My understanding is that the systems that ordinarily disposes of the released hydrogen safely failed due to the loss of power. –Henning Makholm (talk) 04:45, 13 March 2011 (UTC)

A nuclear scientist on BBC News last night (sorry, don't remember his name) speculated that the hydrogen was produced, after the cooling pumps had failed, by the oxidation of the zirconium cases drawing oxygen out of the water leaving hydrogen as a by-product. SpinningSpark 09:10, 13 March 2011 (UTC)

Right. The zirconium is a not very reactive at low temperatures, but at higher temperatures it readily converts with water to the oxide leaving the hydrogen. This is a known problem in nuclear reactors.--Stone (talk) 20:01, 13 March 2011 (UTC)

say me what are you thinking about this subject

about formation of planets in solar system--78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

Akbar Mohammadzade wrote:

According to recent 30 years observations and increasing knowledge of man about the earth and planets in solar system , some astronomers are trying to give suitable theory about the formation of planetary system . My study has one difference with those theorems , for my goal of finding any solution for several paradoxes that i had list in my last article . from the angle of sun pole with planetary system quarter to existing of heavy elements in our system and the inner heat of earth ,..... Noticing to the recent studies about the origin of heavy elements in first solar nebula I focused on the properties of super novas , if there was this complex of element in thus nebula , that might be huge part of them in sun , but it has made of helium and hydrogen in general , this fact together with defragments of matter in terrestrial planets and giant planets says us some new rules about planetary system . I found out an approach for solving this problem , that it might be this system had created in two or three steps , first the sun and gas giant planets , second the creation of terrestrial planets with matter sent by neighborhood exploded supernova (in place where that conjunct with sun and solar system )and final creation of satellites and moons . In this sent article I say that supernova was send matter toward sun by 17degree angle(orbit of Pluto) and that reached here molten and changed sun quarter angle 7 degrees . akbar mohammadzade Iran university of science and technology --78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

That would appear to be an attempt to explain why the Sun and gas giants have fewer heavy elements than the terrestrial planets, moons, and smaller objects. However, that is already explained with a simpler theory, in that small planets, having insufficient gravity, lose their lighter elements, like hydrogen and helium, and thus become proportionally enriched in heavy elements. So, to propose an alternate theory (and expect it to be accepted) you would need to find a way to discredit the existing theory and prove your own. StuRat (talk) 08:46, 13 March 2011 (UTC)

(after edit conflict with StuRat) It is difficult to give a proper view on the works of Mr Mohammadzade without seeing the full paper, but I presume that it is not available in English as you appear to have translated an abstract yourself. The standard theory of planet formation is explained at nebular hypothesis, and we also have an article on star formation. A few comments on specific points:

• It is quite correct that the universe is 90% hydrogen and 10% helium with very little else. It is not true that this is not the make-up of our own solar system. Most of the mass is in the sun and jupiter which are both mostly hydrogen. The reason that on earth there is little hydrogen (other than in compounds such as water) and virtually no helium is that these elements are too light to be bound by the earth's gravity and 'evaporate' into space.
• It is correct that the heavier elements originate from supernovae. Elements up to iron in the periodic table are produced by nuclear fusion in large stars. These are later spread around by supernovae explosions. Heavier elements are produced by nuclear fission in the actual supernovae explosions themselves. The standard theory would have these heavier elements in place at the time of formation of the solar system, not arriving later as seems to be suggested by Mr Mohammadzade.
• It is quite unlikely that the curreent position of Pluto is where it originated (see Pluto#Origins and cannot therefore be taken as evidence of early solar system events as Mr Mohammadzade suggests.

SpinningSpark 09:01, 13 March 2011 (UTC)

notice this discussion :

The mater is separated such as spectrum from mercury to Neptune ,the question is this :suppose one element or particle at any place of first nebula , how did it found that’s same particle from distance which light spends in 22 hours to produce core of earth from nickel and iron?--78.38.28.3 (talk) 09:49, 13 March 2011 (UTC)

I'm not sure what that is saying, I can't quite parse the sentence. First of all, in a nebula material is drawn inwards and may eventually form stars and planets; material does not travel outwards from the centre. If the question is concerning the differing structures of the planets, there is general principle that the innermost planets have the largest nickel-iron cores (Mercury's core is particularly large in proportion to its size) and the outer planets have the smallest. This is simply because metal is more dense than rock or ice. Likewise rocky structures give way to ices in the outer reaches of the solar system. SpinningSpark 11:51, 13 March 2011 (UTC)

Hypertension and Asthma

How important are the blood pressure readings for a person who is suferring from hypertension and asthma? What is the significance of blood pressure in a person suffering from hypertension and asthma ? aniketnik 08:22, 13 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

I'm not sure if high blood pressure itself causes or triggers asthma. However, stress may cause both, so there could be a linkage between BP and asthma that way. StuRat (talk) 08:39, 13 March 2011 (UTC)

In case you don't already know, "hypertension" means high blood pressure. thx1138 (talk) 12:32, 13 March 2011 (UTC)

Regardless of asthma, hypertension must be controlled because it leads to other comorbidities, primarily diabetes and high cholesterol. Therefore, it is important to get a hypertensive patient's blood pressure below 140/90 (the current standard) or 130/80 (for patients who are diabetic or have chronic kidney disease). Many studies have shown that controlling blood pressure limits progression to other comorbidities and greatly reduces cardiovascular disease risk (see Framingham Risk Score for information on how blood pressure is used to calculate CVD risk). So, knowing blood pressure is very important for hypertensives. -- kainaw™ 18:25, 13 March 2011 (UTC)

Why so cloudy on Venus ?

That is, why hasn't the thick atmosphere been lost to space, since Venus has no substantial magnetic field to deflect the solar wind ? StuRat (talk) 09:08, 13 March 2011 (UTC)

Our solar wind article says "...planets with a weak or non-existent magnetosphere are subject to atmospheric stripping by the solar wind. Venus, the nearest and most similar planet to Earth in our solar system, has an atmosphere 100 times denser than our own. Modern space probes have discovered a comet-like tail that extends to the orbit of the Earth." Which implies that it is being stripped but presumably will take a long time because the atmosphere is so dense. SpinningSpark 09:27, 13 March 2011 (UTC)

If it's been blowing off for billions of years, shouldn't it all be gone by now ? Or is it being resupplied in some way ? StuRat (talk) 10:04, 13 March 2011 (UTC)

Multiple sources confirm that it is being stripped, but I could not find anything to give a timescale (other than it is a lot slower than at Mars). Closest I could find was

"The precise evolution of Venus' atmosphere is not known. Nevertheless, it seems that there is an agreement among specialists that the terrestrial planets' atmospheres result from an evolutionary process which takes several hundred million years (Walker, 1975, Hart, 1978, Melton and Giardini, 1982, Zahnle et al, 1988, Hunten, 1993, Pepin, 1991, 1994). The present atmosphere of Venus is then a secondary atmosphere that acquired its major properties about 1 Gyr after the formation of the Solar System (eg. Hunten, 1993, Kasting, 1993)." [8].

SpinningSpark 10:58, 13 March 2011 (UTC)

Note that Venus is believed to be still geologically active. Count Iblis (talk) 14:35, 13 March 2011 (UTC)

Video

I'm trying to watch one of my video tapes, but every time I play it, it just grinds to a halt. How can I fix this? jc iindyysgvxc (my contributions) 11:24, 13 March 2011 (UTC)

Sounds like there is something wrong with the tape itself. I used to work at a video rental store (back when they used to rent videos!!), and it is relatively easy to take them apart and check if everything is spooled correctly. This post explains how to do it. If it were me, I would take it apart, see if everything looks right (nothing is jammed or twisted). I'd also try playing another VHS in the player, just to make sure it isn't the player that is broken. --Mr.98 (talk) 11:53, 13 March 2011 (UTC)

(ec) Take it to a TV repair shop? Sometimes this is due to the tape becoming loosley wound. If your player will fast forward it without sticking, try winding it fully to the end and then fully rewinding before attempting to play it again. If your player won't do this you could try manually tightening it, but this can be quite tedious. Have you checked if your other tapes play ok? If they don't there is probably something wrong with your player so it needs repairing; if the others do play ok you could also look for dirt or obstructions fouling the tape cassette mechanism. SpinningSpark 11:59, 13 March 2011 (UTC)

To boldly go, though dead, where no man has gone before...

Suppose I wanted my ashes, or to make this quite silly - my brain - to leave the solar system and voyage between the stars like the Voyager probes. Is it within the realm of private citizens to create a rocket that could escape the Sun's gravity? Can I fling my remains out of our solar system? The Masked Booby (talk) 11:58, 13 March 2011 (UTC)

Not sure about out of the solar system for the price of $995 you can have them sent into space.--NortyNort (Holla) 12:51, 13 March 2011 (UTC)

For current state of play see space burial (we really do have an article on everything !). The only person whose remains are currently en route out of the solar system is Clyde Tombaugh - approximately one ounce of his ashes have hitched a lift on the New Horizons spacecraft, which crosses the orbit of Uranus in a few days time. To escape the Sun's gravity you either need a dumb payload and a *very* big rocket, or you need a smaller rocket and a mission plan that include one or more gravity assists, which in turn assumes a capability for deep-space tracking and in-flight manoeuvres. Or you could develop a very efficient but highly sophisticated inter-planetary propulsion system, such as an ion thruster. Any of these routes is beyond the reach of any private citizen. Your most affordable option is to pay NASA to put a small portion of your remains on their next flight out of the solar system - I imagine that would cost you around $10 million (the going rate for a space tourism trip on the ISS is $15-$20 million). However, in the current economic climate, you might have a long wait for the next bus. Gandalf61 (talk) 13:17, 13 March 2011 (UTC)

Well, to expand on the OP's idea, why does it have to be ashes? Why couldn't an uncremated human body make the trip? --KägeTorä - (影虎) (TALK) 13:22, 13 March 2011 (UTC)

It could, but it might be significantly more expensive, as long as the commercial price tags for lifting stuff into space (even just geostationary orbit) lie at tens of dollars per gram. Of course if you can't find an existing interplanetary probe to hitch a ride on, the cost lifting the payload into Earth orbit might not even dominate. –Henning Makholm (talk) 15:50, 13 March 2011 (UTC)

I hope the moon is not being contaminated by people's ashes, as the first link claims. 92.24.186.239 (talk) 13:28, 13 March 2011 (UTC)

The Moon is already "contaminated" by 6 Apollo Lunar Module descent stages, 3 Lunar Roving Vehicles, 2 Lunokhod rovers and umpteen other lunar probes. Compared to the hardware already left on the Moon, a few grammes of sterile human ashes will have little impact. I would be more concerned about the waste of resources involved in a dedicated lunar burial flight (as opposed to hitching a lift on a pre-existing science mission) - it is the complete opposite of a green burial. Gandalf61 (talk) 13:49, 13 March 2011 (UTC)

See List of man-made objects on the Moon. 75.41.110.200 (talk) 19:16, 13 March 2011 (UTC)

Why bother? The Earth is, sort of, a giant spaceship... Count Iblis (talk) 17:10, 13 March 2011 (UTC)

With so many power plants out of commission, how will Japan import the needed power in the shorter term?

In the longer term, they replace or repair the damaged plants. Right now, nearly all(?) of Japan has rolling blackouts 3 hours a day. (Hopefully from 2-5 AM, but probably not.) That can't keep happening until the power plants are fixed/replaced.

Couldn't they use undersea cables to import power from other nations? What are some other power solutions in the meantime? --70.179.169.115 (talk) 14:57, 13 March 2011 (UTC)

I imagine that a more efficient model that undersea cables would be to just import big generators and fuel for them. You can move a lot of coal very cheaply and very efficiently on big boats, more cheaply than building undersea power cables, I imagine. But this is just a guess — I haven't run the numbers. --Mr.98 (talk) 15:32, 13 March 2011 (UTC)

Rolling blackouts have to happen all through the day. Different places get power at different times - that's what "rolling" about them. They could use underpower cables, but only if they are already there - it takes a long time to lay such cables. We have an article, Electricity sector in Japan, but it doesn't cover this question. Since it doesn't mention electricity imports (just fuel imports), I guess there aren't many, which means they won't be able to increase them quickly.

They will have to reduce demand instead. That usually means cutting off the supply to big factories. They've probably already done that (if any big factories are even able to operate at the moment), but this disaster is on a scale much greater than anything they are prepared for, so it's still not enough. They'll probably get things sorted out over the next few days in terms of supply. What will take longer is fixing the distribution network - there are downed power lines all over the place.

--Tango (talk) 16:45, 13 March 2011 (UTC)

Perhaps they won't have to cut the power, or maybe have. Grandiose (me, talk, contribs) 20:55, 13 March 2011 (UTC)

Form work of Plinth Beam or Shuttering of Plinth Beam

How to Calculate Form work of plinth beam in Running Feet. —Preceding unsigned comment added by 182.178.71.47 (talk) 20:11, 13 March 2011 (UTC)

Note: this question was also asked on the math desk. I don't understand it well enough to figure out which desk is the proper one, but whomever can offer an answer, please add a pointer to the other copy. –Henning Makholm (talk) 20:46, 13 March 2011 (UTC)

I suggest you consult a professional engineer on how to build formwork for a plinth beam. I suspect there are too many variables involved for us to be able to provide a useful (and safe) answer here.--Shantavira|^{feed me} 21:26, 13 March 2011 (UTC)