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July 8

Angular Momentum

Our earth revolves around its axis, likewise all other planets do the same. All planets and asteroids rotate around the sun which in turn rotates around its axis. Our solar system is a part of the Galaxy which rotates around its center. All other galaxies do likewise. This angular momentum (of our galaxy) could only come from the angular momentum of the primordial hydrogen gas that gave it the mass. Where did this angular momentum come from?

Is it possible to speak of the angular momentum of the whole Universe? If so then the Universe could not be infinite. Correct?

When two galaxies collide, is it possible to assume that they may have vectors of their angular momenta pointing in different directions, perhaps in the opposite directions? Where did this difference come from? How come that after the big bang different parts of the cosmos acquired different angular momenta?

Is there any coherent theory that describes it?

Thanks, - Alex174.52.14.15 (talk) 03:54, 8 July 2013 (UTC)

How do you know the net angular momentum of the universe is not zero? That is, that for every object spinning in one direction at a given speed, there isn't an object spinning the other way? --Jayron32 03:58, 8 July 2013 (UTC)

Absolute rotation and Mach's principle deal with the problems of ascertaining rotation in a large and possibly infinite universe. The other questions - how did the different parts of the universe evolve such that some parts rotate around other parts... well, the universe is not currently homogeneous - mass, energy, and momentum are not uniformly distributed when we consider any relevant scale of length and time. On the scales of galaxies and stellar systems, we can describe how initial conditions are most likely to evolve toward the (almost) steady state we see today, using statistical mechanics, and we see that flattened, coplanar orbits are a low energy configuration that is very likely to evolve, if the initial distribution of matter and energy and momentum started inhomogeneously. Either this distribution was always inhomogeneous (and has evolved to its present state from an initial condition); or the universe started homogeneously and was subjected to some type of spontaneous symmetry breaking in the very early universe. We don't yet know which possibility is more plausible; but high energy research has investigated the nature of symmetry breaking to see if that sort of theory is viable. Nimur (talk) 04:21, 8 July 2013 (UTC)

(ec) This is really a variation on the question of why matter isn't evenly distributed throughout the universe. Once you have clumps of matter, then inevitably those clumps will start to spin as they collapse into smaller, denser clumps. The exact direction they will start to spin depends on the precise distribution of the clumps. StuRat (talk) 04:25, 8 July 2013 (UTC)

To add a fact I learnt recently, which may complicate the issue a litte - rotation around a black hole is (sometimes?) not caused by Newtonian forces, but by spacetime itself curving around the black hole. Aaadddaaammm (talk) 09:50, 8 July 2013 (UTC)

Angular momentum is conserved but that doesn't mean that a non-rotating primordial cloud can't produce spinning planets, suns and galaxies. Suppose you take two objects, each moving toward the other in a straight line with no rotation whatever - then, suppose that they collide off-center. They will both start to spin...and in a frictionless, dragless environment, they'll continue to spin as they move away from each other. Angular momentum is conserved because they each rotate in the opposite direction such that the total angular momentum is still zero. But examine one of these objects when it's drifted thousands of lightyears from the point of collision - and you'll see it spinning all by itself - not noticing that the exact opposite spin is present in some other incredibly distant object.

Hence, it's perfectly reasonable to presume that at the instant of the big bang, nothing whatever was rotating and that the net angular momentum was zero. If that's the case, then despite innumerable collisions and other interactions setting things spinning, the total angular momentum of the entire universe could still be zero. But that's one of those things that we don't yet know. SteveBaker (talk) 13:03, 8 July 2013 (UTC)

Inflation explains why it is zero.Count Iblis (talk) 13:33, 8 July 2013 (UTC)

Where in Wikipedia can I read about rotational anisotropy amongst distant galaxies? Anisotropy#Physics says: "Cosmic anisotropy has also been seen in the alignment of galaxies' rotation axes and polarisation angles of quasars." but doesn't go into any detail. -- 177.121.216.128 (talk) 14:08, 8 July 2013 (UTC)

How about The Observational Approach to Cosmology, by none other than Edwin Hubble, available for free online in its entirety thanks to Caltech and the Mount Wilson Observatory. This was written in 1937 - Hubble relied exclusively on observations in visible light; so there is no mention of radio astronomy in any way; but, from visible light observation alone (including spectrometry), Hubble could deduce the fundamental nature of our expanding universe. There is a few sections in there about inhomogeneous distribution of matter. But for the most part, in visible light, all galaxies are uniformly distributed and randomly aligned. Any anisotropic effect must be very small!

Of course, the cosmic microwave background radiation was not discovered until radio astronomy became commonplace, a few decades later. Often, when cosmologists talk about anisotropy, what they mean is that they are inferring anisotropy from the inhomogeneity of the CMB. In principle, you can infer anisotropy from any non-uniform distribution of stuff in the universe; but the CMB makes the job easier because it is an imprint of such an early stage of the universe.

The only scientists who (attempt to) measure anisotropy directly must do so in laboratory conditions: in particle colliders, or spectrometry experiments, or in applications of material science. The cosmos is too large to see anisotropy (in controlled experimental conditions); it must be inferred by concocting cosmic-scale laws of physics that are consistent with our other observation. Nimur (talk) 16:37, 8 July 2013 (UTC)

Thank you all. It is very interesting. - Alex174.52.14.15 (talk) 23:39, 8 July 2013 (UTC)

clam nectar

Why doesn't lobster nectar or crab nectar exist?Curb Chain (talk) 06:26, 8 July 2013 (UTC)

Nectar comes from plants. Perhaps that's why? (unsigned: 09:25, 8 July 2013‎ User:Zzubnik)

Clam nectar is a thing, but is not nectar in the normal sense. You cook clams, pour off the clam broth, concentrate it by evaporation, and what you have is called clam nectar Read more (barely) at Clam liquor. From looking on Google, it is readily apparent that lobster and crab broth are used in plenty of recipes. No clue why no one concentrates it to nectar. Although I don't know why anyone would want to. Or maybe they do but they just don't call it that. Someguy1221 (talk) 10:26, 8 July 2013 (UTC)

Thanks for the clarification, Someguy12212 Zzubnik (talk) 12:17, 8 July 2013 (UTC)

Clam nectar doesn't come from plants. I imagine that you could easily make lobster of crab nectar, but even clam nectar doesn't seem to be such a popular product, maybe there's not so much demand for other fishy nectars? Aaadddaaammm (talk) 09:48, 8 July 2013 (UTC)

There's clamato juice. Rmhermen (talk) 17:17, 8 July 2013 (UTC)

Fonds made from lobster or crab are a standard ingredient in fine cooking, especially for seafood recipes. In German, this is called Hummerfond or Krustentierfond, but I cannot find the corresponding English term. --Stephan Schulz (talk) 11:15, 8 July 2013 (UTC)

I believe it would be a lobster or crab bisque. --TammyMoet (talk) 18:38, 8 July 2013 (UTC)

What about oyster liquor? It is not cooked; it is the liquid found when the oyster is open live (Am I correct that the oyster is still alive when it is opened?). Do clams have the same sort of liquid?Curb Chain (talk) 00:31, 9 July 2013 (UTC)

They do, when you eat them similarly. --Jayron32 00:09, 10 July 2013 (UTC)

Technical terms for snap-together fastening mechanism?

In many products, two halves of the enclosure are snapped together. In one of the halves, there are tabs with a raised part, sometimes with a profile of half an arrow head if viewed from the side. In matching places in the other half of the enclosure, there are indentations or slots that catch the raised parts of the tabs.

Is there a technical term for this type of fastening mechanism? Are there technical terms for the tabs, the raised part of a tab, and the indentations/slots?

Thanks. --98.114.146.200 (talk) 10:13, 8 July 2013 (UTC)

Sounds like some type of snap fastener. Can you link to an example or illustration?--Shantavira|^{feed me} 10:43, 8 July 2013 (UTC)

I think we're talking about the plastic tabs that would hold together the two halves of the cover of a device like a cellphone or something like that. I guess I'd call it a "self-locking tab", a "clip", a "snap" or just a "captive fastener" - I'm not aware of any more specific term and a search through the long list of articles referenced from fastener didn't turn up anything useful. The tool for opening such fasteners is called a "spudger". A Google search on that term produced lots of pictures of these kinds of fastener - but I didn't see any kind of consensus on the name. So it's possible that there is some obscure technical term - but nothing that seems to be in widespread usage. SteveBaker (talk) 12:50, 8 July 2013 (UTC)

Snap Fit - manya (talk) 05:05, 9 July 2013 (UTC)

Yeah - could be. The two pictures at right are titled that way - but there are no English language Wikipedia pages pointing to either of them. I think we need an article about these things - and a link to it from fastener. SteveBaker (talk) 17:11, 9 July 2013 (UTC)

What is the function of women having longer hairs?

Is this trait present in other primates, too? — Preceding unsigned comment added by 128.237.205.60 (talk • contribs) 13:58, 8 July 2013‎

It's fashion, not biologically determined - humans choose their own hair length. Roger (Dodger67) (talk) 14:06, 8 July 2013 (UTC)

Really? Do women's hair grow faster or there are no difference?

There are no sex-based differences at hair growth, nor have I ever heard of such a claim. Indeed, fashion and personal choice seem to be the rule, e.g. Fabio Lanzoni, pixie cut, etc. SemanticMantis (talk) 14:40, 8 July 2013 (UTC)

I do not believe women's hair grows faster. Anyway, the question should be why men have short hair? If men are warriors, then short hair is an advantage. You don't have to take care of it in the battle field, no one can grab you by the hairs in a fight, any injure can be cleaned more thoroughly. It's not only fashion, but there is also a social role here. OsmanRF34 (talk) 14:42, 8 July 2013 (UTC)

Also gets quite hot, obstructs your view and can cut or choke you in some grappling positions. Even in the milder context of mixed martial arts (with its rules against hair-pulling and a shower after twenty minutes) a (near) bald head or cornrows is the way to go. Benson Henderson is a notable exception, but even he gets distracted by it in his face lately. InedibleHulk (talk) 22:56, 9 July 2013 (UTC)

Speaking from personal experience, it takes 2 to 3 years to grow my hair to my shoulder blades and then it stops. (I'm a man.) An ex girlfriend was a hair factory. She would get her waist length hair cut at the start of the summer (usually usually the week before Christmas) and by the time Autumn arrived, it was waist length again. She used to sell it to wig makers. Short hair is a definite advantage in trench warfare; it's very hard to keep your hair clean in the mud. --TrogWoolley (talk) 15:28, 8 July 2013 (UTC)

My hair (male) will grow to my shoulders in about 6 months (though I haven't let it get that way for quite a while! It goes from about a half inch to enough fringe to enough to get in my eyes in around a month now). It stopped about half way between shoulder and waist (once strightened, it's rather curly). Hair growth varies a lot in both genders! MChesterMC (talk) 15:38, 8 July 2013 (UTC)

Here's a story about a Vietnamese, who died 3 years ago, whose hair was over 18 feet long.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:42, 9 July 2013 (UTC)

Note the Roundheads were a recent misfortune of history - for some reason many ancient warrior cultures didn't find it a problem; not sure if it was a matter of how they wore it or just that given a few minutes before an axe bites into the back of your head there is something better you could be doing with your life than pulling somebody's hair. Wnt (talk) 06:03, 9 July 2013 (UTC)

There are plenty of cultures, even today, where men keep long hair. Sikhs are one example (see [2]), although most modern Sikhs keep their hair short. The Tibetan people are another example: see [3]. In ancient China, hair was seen as a gift from one's parents and therefore never cut; only criminals had their hair cut as punishment. (The Manchu people, after deposing the Ming dynasty, forced all men to adopt the queue (hairstyle) or be beheaded.) See long hair for many more examples of both modern and historical men who had long hair. --Bowlhover (talk) 08:04, 9 July 2013 (UTC)

If long hair was problematic, beards might be worse. It might be that many men go bald as they get older while women generally don't. Ancient Greeks seemed to have beards, Romans less so, St. Paul opposed long hair on men, while Nazarites--like Sampson--didn't cut theirs. Custer seemed to have it long, but by soldiers had it short (very short at times).174.137.237.65 (talk) 19:39, 11 July 2013 (UTC)

Why is pseudoscience so popular?

Despite the fact that we're in the Information age and it's so easy for one to lookup what actual scientists have to say about the latest pseudoscientific theory, people are still easily fooled into Pseudoscience. 163.202.48.125 (talk) 14:20, 8 July 2013 (UTC)

Because people want easy explanations, not difficult science? WegianWarrior (talk) 14:24, 8 July 2013 (UTC)

coming up with hypotheses is easy. coming up with hypotheses which are correct is hard. coming up with hypotheses which are correct, and proving them, is hard and involves actual work. thus, reduction in popularity from one to the next. Gzuckier (talk) 15:12, 8 July 2013 (UTC)

It's because the educational system focusses much more on subjects like language, history, art than on science. We insist that our children learn about history, even if they don't need to know anything about this subject for their future jobs. We can't bear the idea that the future generation would know little about, say, the US war of independence. However, we have accepted the fact that a large fraction fo the population doesn't know anything about Newton's laws of classical mechanics, that they don't know much about mathematics that even people in ancient Greece knew about. Modern science is then not something people can readily understand, it has to be explained in a dumbed down way to them, it can then be difficult for people to see the difference between real science and pseudoscience. Count Iblis (talk) 15:27, 8 July 2013 (UTC)

We would like our children to know about other languages, other cultures, history, philiosophy, music, literature and art as well as science, logic, mathematics and how to rewire a plug and unblock a drain so that they grow up to be well rounded individuals with a variety of resources to draw on in whatever life situations they find themselves. The more knowledge you have in any and all fields, the more ability you have to critically assess the claims of others and, in the end, to reach your own reasoned and reasonable conclusions. Gandalf61 (talk) 16:08, 8 July 2013 (UTC)

Yes, but the criticism of many physicists has been that physics as is it taught in school, is totally misleading. It gives children a wrong view of what the subject is about, most of what is known about how the Universe works is not taught at all. For most other subjects this is not the case, e.g. you do learn in biology class about modern biology. Critical thinking alone is not sufficient, you have to have some minimum amount of basic knowledge. E.g. children in school are not told about the very strong limits on any new forces and how these limits are obtained. There is no reason why you first have to master quantum field theory at university before you can be even told about the basics of the argument. This means that a huge fraction of the population will be unaware fo this, which leaves a lot of room to promote all sorts of pseudoscientific nonsense. Count Iblis (talk) 17:39, 8 July 2013 (UTC)

I don't think it's just physics that has that issue. If you take high school chemistry at face value, you'd think all chemists do is unit conversions. Are moles important? sure, but so are lots of other concepts that don't get mentioned at all. (+)H₃N-Protein\Chemist-CO₂(-) 18:45, 8 July 2013 (UTC)

Right, because teaching children who lack the proper training in the basics things like advanced quantum theory and general relativity is likely to generate positive results. One thing experts forget is that children are not experts, and need to receive basic instruction before they receive advanced instruction. You don't start learning French by reading Molière on the first day, and you don't learn physics and chemistry by starting with the most advanced subjects. You start with the language of chemistry and the language of physics, and build up to the more advanced subjects. --Jayron32 23:12, 8 July 2013 (UTC)

It also doesn't help that the reporting of actual science isn't anything to write home about either. I had a paper published earlier in the year that got a fair amount of mention in the press here in the UK. The BBC website and the broadsheets did a decent job, but the tabloids just ran with it until I even barely recognised it as something I did..... If actual science is not always reported accurately, how the hell is the lay public supposed to know what's genuine and what's not? Fgf10 (talk) 18:54, 8 July 2013 (UTC)

One problem is the lack of critical thinking skills in the general population - these are not taught in schools or even at college level most of the time. It's not even necessary to have much of a science training to get the benefit from that skill set. Just a willingness to stop and think about whether the claims that are being made are likely to be true or not.

Today I read a UFO-nut claiming that Roswell is at 33 latitude, 104 longitude and that the aliens landed there because it's the only dry-land place in the northern hemisphere for which latitude multiplied by pi equals longitude. Math and science let's me know that there must be an infinite number of points on a path for which this is true...but critical thinking makes you ask "Why would the aliens measure latitude from Greenwich?"...and "They rounded to the nearest degree? That's like 60 miles!"

Another problem is that too many people seem to adopt the attitude that if they wish that something were true, then it must be true. "I wish that I could live forever...so there must be an after-life." - that kind of thing.

These problems don't just affect pseudo-science belief - it runs through everything from gambling to buying an extended warranty on your new DVD player to purchasing junk advertised for $19.99 on TV. None of these activities withstands the test of critical thinking.

SteveBaker (talk) 19:54, 8 July 2013 (UTC)

Indeed, some people can reject something that has a huge amount of supportive evidence, like AIDS, intelligent design, or evolution, but embrace any topic in the List of topics characterized as pseudoscience. Hint: just believing in scientist won't make you avoid pseudoscience, you'll still have to check evidence by yourself. Obviously, you won't be able to dedicate much time at each topic, so, you are left with the alternative of trusting other people. No one can avoid being wrong at the end of the day. Time will prove this right. OsmanRF34 (talk) 23:15, 8 July 2013 (UTC)

Did you make a slight error with "has a huge amount of supportive evidence, like AIDS, intelligent design, or evolution, but embrace any topic in the List of topics characterized as pseudoscience" because as I suspected intelligent design is listed as pseudoscience. CambridgeBayWeather (talk) 06:50, 9 July 2013 (UTC)

Sure, thanks for pointing that out. The evidence if for evolution (vs. intelligent design with little evidence, besides look at how complex we are). OsmanRF34 (talk) 07:27, 9 July 2013 (UTC)

The media is generally useless in properly covering scientific matters. Ever known a sciency, nerdy kid at school choose to be a journalist? Too many leading politicians are scientific ignoramuses. Those who support those politicians' parties are psychology pressured to go along with their positions. That's a lot of people. (But I still find it hard to believe that all Republicans in the US were as bad at science as their most recent President. How COULD they accpet that?) HiLo48 (talk) 23:38, 8 July 2013 (UTC)

This being what's called the "Reference Desk", are there any references we could give the OP (rather than our own personal theories)? -- Jack of Oz ^[Talk] 23:55, 8 July 2013 (UTC)

Maybe the OP could first give us a reference for why he said what he said. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:31, 9 July 2013 (UTC)

People tend to believe things that are pleasant to believe, rather than things that are supported by careful evidence. See appeal to consequences, wishful thinking, valence effect and optimism bias. Red Act (talk) 01:46, 9 July 2013 (UTC)

It wasn't that long ago that continental drift would have been considered pseudoscience. Also, I'm not sure why conspiracy theories would be considered "pleasant", although maybe it is pleasant for the believers, as it gives them a false sense of empowerment. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 9 July 2013 (UTC)

And it's funny the OP would bring this up on a day that Google marks as the 66th anniversary of the alleged incident at Roswell. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:49, 9 July 2013 (UTC)

There is fundamental challenge in educating people about science and critical thinking i.e. there is limit to knowledge but there is no limit to ignorance. - manya (talk) 04:51, 9 July 2013 (UTC)

That is exactly wrong. μηδείς (talk)

What do you mean by 'exactly'? There is no limit to knowledge? Or, limit (gaps in knowledge) is not a fundamental issue? Ignorance is not a reason at all or it it not the root cause? - manya (talk) 04:48, 10 July 2013 (UTC)

Medis is correct - there is a definite limit to ignorance and no limit whatever to knowledge. The limit to ignorance is knowing nothing whatever. Someone with literally no knowledge at all is at "absolute zero" on that scale. On the other hand, there are an infinite number of facts you can potentially learn - for example, you may know that (2^57,885,161−1) is a prime number - but there are an infinite number of primes that you can still learn about. Of course in practical terms, there is a limit to how much one human can learn - there are only so many neurones in your skull with which to store that information - but there isn't a limit on the number of things that are out there to be learned. SteveBaker (talk) 19:27, 10 July 2013 (UTC)

Yes, Steve has explained my meaning. A dead dog and a log are both equally ignorant, at a coefficient of zero. Of course, infinite ignorance is a good turn of words when it is called for! μηδείς (talk) 01:39, 11 July 2013 (UTC)

Alright, let me try to explain what I meant to say. We are talking with reference to OP's question as to why people are fooled and why don't they look up available information. This is not about fortunate people who get right guidance from scientists or from educated people with scientific views. Modern science theories and knowledge associated with it was just not there few hundred years back. Few decades from now there will be more knowledge/information. There is limit to such knowledge. (Knowing what prime is knowledge, knowing how to find prime is knowledge, but knowing millions of primes is not the knowledge in this context). And pseudoscience begins where science ends. For example, when knowledge about lightning was not there, it was obviously act of God/daemon. Don't look at ignorance as a measure of lack of knowledge. It is an attitude that one has developed due to which one refuses or denies factual knowledge. For many, it is simpler and easier to believe that 'God made big bang' and life has been "created". - manya (talk) 09:11, 11 July 2013 (UTC)

For something to read other than just our opinions, you could try pseudoscience#explanations. You could also read How Mumbo Jumbo Conquered the World by Francis Wheen. This last one doesn't really explain a lot, but it goes into a lot of information about how these things take off, historically speaking. IBE (talk) 09:36, 10 July 2013 (UTC)

One factor is entertainment. For example, the "Bermuda Triangle" has been thoroughly debunked, but for some folks it's more fun to believe in it (on some level) than to not believe in it (on any level). ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:28, 10 July 2013 (UTC)

I'm going to be brave and mention religion. It's obvious that some people get their facts from their preachers. If you choose to trust them, and lots of people do, you choose to accept everything they say. That can be very misleading. HiLo48 (talk) 11:31, 10 July 2013 (UTC)

Religion is not a pseudoscience, it's a cultural phenomenon, like language and clothing style and so on. I've known religious folks who were also totally accepting of the scientific method. And I've known atheists who thoroughly believe in the Bermuda Triangle, flying saucers, and that we didn't really go to the moon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:36, 10 July 2013 (UTC)

Religion isn't considered a pseudoscience because it's not falsifiable - not because it's a cultural phenomenon. Religious belief is on the decline worldwide (See Demographics of atheism) while, in Pseudoscience#Demographics, we hear that "The National Science Foundation stated that pseudoscientific beliefs in the U.S. became more widespread during the 1990s, peaked near 2001, and declined slightly since with pseudoscientific beliefs remaining common.". If the numbers in Demographics of atheism are to be believed, the number of religious believers peaked sometime around 2008 and is now also in decline. This is a weak correlation - but it's plausible that many people lose their belief in various pseudosciences, then realize that their religious belief is more of the same kind of thing and give that up too. But the conclusion that belief in religion and belief in pseudoscience are related is not an insubstantial one.

SteveBaker (talk) 19:27, 10 July 2013 (UTC)

Bugs and Steve - you both missed my point. Maybe I didn't express it well. I wasn't suggesting that religion itself is a pseudo-science. Even in my country there are people so hooked on their religion that they trust their pastor for all knowledge. That means they believe in Creationism (a pseudo-science in my book), and all its associated nonsense, such as an earth that was created in 4000 and something BC. That means they can't believe what their science teachers tell them on evolution. Once that seed is sown, they have less trust in what their science teachers are telling them about anything. HiLo48 (talk) 22:17, 10 July 2013 (UTC)

Yes, I think that's a definite issue here. Creationism is basically a totally debunked pseudoscience - although it's possible to formulate a statement of it that's unfalsifiable - for example, if you maintained that the creator created everything 4,000 years ago - you might claim that he/she/it deliberately included things like fossils and long stretches of identical DNA in wildly disparate lifeforms and strong indicators of evolution such as the recurrent laryngeal nerve in the giraffe. If the creator does a perfect job of creating a universe that looks EXACTLY like one that began with the big bang and included Darwinian evolution - then indeed the world could be 4,000 years old. However, creationists that I've spoken to don't seem to believe that - they prefer to believe that dinosaurs had bones made from solid rock and that they died and sank deeply into the mud during the Noah's flood because they were so heavy. (sigh!) SteveBaker (talk) 14:29, 11 July 2013 (UTC)

Secondary cells/rechargeable batteries

I am doing a science project on batteries, how it works, the effects on the environment as well as rechargeable batteries. I've searched the web and took out all 4 chemistry books at our local library, but I can't find any useful info on rechargeable batteries. All I could find was the discharge rates, history and so forth.
I am doing a few experiments: building normal batteries with combinations of

• Zink,Zinc sulphate
• Iron, Iron Sulphate
• Copper, Copper Sulphate
• Magnesium, Magnesium Sulphate
  

,meaning that I could build a total of six batteries. I did these already and it worked fine, but now I want to build a rechargeable cell. Can I use one of these combinations to recharge with a DC current? (And then how large must the current be?)
Can someone please help me, I really did my best to do it on my own?
Thanks!
--Romeo Kilo (talk) 15:48, 8 July 2013 (UTC)

It sounds as if you are wanting to build a Nickel–iron battery and a Lead–acid battery. Please note that both contain corrosive electrolytes, so great care should be taken with these. Dbfirs 15:55, 8 July 2013 (UTC)

Part of (some would say the main) goal of a science fair is to develop and test your own ideas, not just reproduce what someone else has already done. You wonder "what if?" or "would this work?", based on "well, it goes one way, can I push it backwards?" or "why aren't the same ones used for rechargeables?", and then you actually do the test. It's rare that students actually do that (instead just doing the "known" experiments over and over again), and it's refreshing to see that when I judge them. Maybe it will work! Maybe it won't! Maybe it won't work well but it will work "well enough" to prove that the idea is valid (and then the "extensions/future work" part of your conclusions is to improve them by varying electrode shapes, electrolyte concentrations, etc.; or to apply this really simple idea as a low-cost or chemically safer alternative for situations where that is a critical detail). DMacks (talk) 16:28, 8 July 2013 (UTC)

I agree with that, but there's a lot to be said for replicating previous results before trying to do something new. It's always a useful learning experience, and people who skip that step often end up regretting it. Looie496 (talk) 17:19, 8 July 2013 (UTC)

It is nice to have an opinion from a experienced judge! My teacher also prefers new and creative topics. The problem is, I am, according to a psychologist totally left-brained, so it is very difficult for me to think up my own ideas. I like science projects where there is a given topic, but when it comes to choosing your own topic...

Romeo Kilo (talk) 19:22, 8 July 2013 (UTC)

Another thing that I worry about is the fact that the reading on the voltmeter jumps around when the battery is connected. Is this normal? Should I take an average of the readings?Romeo Kilo (talk) 19:27, 8 July 2013 (UTC)

Investigating this would actually be a useful part of your project. How does the reading "jump around" (ie, how does it vary with time, approximately)? What factors do you think might cause this? How many of these factors can you eliminate or hold constant? Can you vary any of them, and see what influence they have on the voltmeter reading? Tevildo (talk) 01:28, 9 July 2013 (UTC)

I did this experiment myself in high school. My results were that none of what you have can make a rechargeable battery. But lead plates were rechargeable, and you did not have to use corrosive sulfuric acid for this to work either. Using exotic electrolytes like mercuric chloride had no useful effect. My highest current was with an aluminium pie plate in sodium carbonate solution, which could make one amp (with a carbon rod other electrode). There were amazing results with two aluminium electrodes and a carbon rod, it ended up working like a transistor. Graeme Bartlett (talk) 11:52, 9 July 2013 (UTC)

Wow, these are nice answers! – b_jonas 22:51, 10 July 2013 (UTC)

I got a new idea: I'm going to test if the concentrations of the salts used in the battery makes a difference to the volts. I'm sure it had been done before, but I could get no facts, so I am going to try myself. One concept I am struggling to understand is mol. Does anybody have a website, link or perhaps their own explanation of what mol is and how to use it? Thanks! (and sorry for my bad English)
Romeo Kilo (talk) 18:48, 11 July 2013 (UTC)

Is it true that fasting "programs" your body to store fat?

Topic says it all. ScienceApe (talk) 15:51, 8 July 2013 (UTC)

What? Could you please explain what you mean?Rich (talk) 05:36, 10 July 2013 (UTC)

This article from the Guardian discusses possible benefits of fasting, including weight loss, and less hospital time (according to several linked scientific studies) [4]. There was also a recent piece on NPR about the possible benefits of fasting, here [5]. Also, don't confuse planned, regulated fasting with so-called Yo-yo_effect which describes how certain "feast or famine" approaches to diet are linked to promoting fat storage (see article for refs). In short, fasting and yo-yo effect are rather different things. SemanticMantis (talk) 16:34, 8 July 2013 (UTC)

Fasting has been discussed here ad nauseam, you might want to search the archives at the top of the page. μηδείς (talk) 17:11, 8 July 2013 (UTC)

Also check Starvation response. Your body doesn't know if it's not getting any food due to your spiritual practices or a famine. It has learned to deal as well as it can with the latter, but it's badly programmed in the case of the former. OsmanRF34 (talk) 22:47, 8 July 2013 (UTC)

Hmmmm. I'm not sure your body doesn't know. Problem is, I can't think of a way to do an ethical controlled experiment to test that, so I'm not sure how to look up the result. It is certainly plausible that the body could have actual access to the knowledge of whether a fast was intentional or not. Wnt (talk) 21:45, 10 July 2013 (UTC)

July 9

Can an echo be reborn?

If the history books I read as a child tell it true, King Midas once grew donkey ears and some gossipy fellow couldn't resist at least telling the reeds. The reeds carried his words and wouldn't let them go, and eventually they got back to the king (or one of his crew).

Now, I know there is considerable evidence to suggest all fables are bullshit, and none showing that reeds (or any crop) do this. But could even one word's worth of sound, after being reflected, absorbed and distorted throughout the world, ever be bounced back together, just by chance? Or are the waves lost forever (like scrambled eggs) if they don't reach a microphone?

If it makes it simpler, could it happen if Earth was encased in a bubble, and nothing reached space?

I'm not asking if it is likely (it's not). And I realize that if it could happen, it would be far too quiet to hear with ears (human or donkey) and in a far away place and time from the speaker or the king. But is it theoretically possible?

Also, where's the "echoiest" place on Earth, in fidelity and/or number of echoes? InedibleHulk (talk) 07:19, 9 July 2013 (UTC)

Nevermind. I was thinking of a sound wave as actual particles. Not the case. Stupid question.

The second one's still open, though. Google's not helping, but maybe I just can't guess the phrase. InedibleHulk (talk) 09:13, 9 July 2013 (UTC)

You may wish to read Whispering gallery, and Hair cell in which things a bit like reeds amplify sound (but much smaller in scale). With modern recording technology this can be done with your phone. Graeme Bartlett (talk) 11:43, 9 July 2013 (UTC)

Hadn't thought about the similarities in reeds and hairs. Thanks. Wasn't aware of whispering galleries. Pretty spiffy! InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

If you wait long enough, this is how it would happen. Count Iblis (talk) 14:56, 9 July 2013 (UTC)

Might be a long wait before I finish that paper, too. A bit over my head. But from what I did understand in skimming, seems like it might be interesting. InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

The problem with the OP's question - and with Count Iblis' piano-in-a-box thought-experiment, is that nobody has specified how similar a newly-created sound (or a piano) need be before we consider it identical to the original. Without a measure of similarity, we can't estimate the probabilities with any confidence, except in the extreme case (exactly-identical thermodynamic state, like in the paper Count Iblis linked). In the case of a sound wave, an exact waveform match is less probable than a perceptually similar sound wave. In the case of a piano, there are huge swathes - disjoint and unconnected - scattered throughout the total space of available thermodynamic states, in which we would say "a piano is present," but they are unlike the original piano.

My point is, we can't be quantitative about the probabilities unless we constrain the problem better. Nimur (talk) 15:18, 9 July 2013 (UTC)

Similar enough that a person could (when amplified) recognize the word (say "swordfish"), but not necessarilly recognize the voice, I guess? InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

This strays into the... "science"... of EVPs, that ever-popular hallucination game of popular ghost hunting films. Since you can hear, by random chance, voice-like phenomena in white noise every now and then, it stands to reason that eventually words will "echo back" in a very, very loose sense. The catch being that they will echo back with no more likelihood than if they had not been spoken the first time.

Of course, if the NSA has planted listening devices in the reeds, all bets are off - which points out that we're making some assumptions about the landscape. They're probably very reasonable assumptions, but it would be interesting to hear a physicsey way of expressing what they are. Wnt (talk) 20:42, 9 July 2013 (UTC)

Yeah, I suppose that's true. Could sound like the original word, but be made by entirely different vibrations. Sort of how (speaking of ghosts) people can look just like old portraits without containing the exact elements, or what came out of the end of a teleporter (theoretically) wouldn't be you, just an exact copy.

And yeah, the US has certainly made reeds and echoes obsolete. The joke about cornfields having ears is creepier than funny now (though it never was exactly funny). InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

Imported Fizzy drink tastes

I've always wondered, can the taste of fizzy drinks change if they're imported by airplane? Can the altitude some how affect the taste? Clover345 (talk) 15:25, 9 July 2013 (UTC)

Remember, most of the name brand soft drinks are produced locally with only the concentrate being imported in. So the ingredients used in the final product may not be identical in two different countries. I know this isn't what you asked but I thought it might be relevant. StewieCartman (talk) 15:51, 9 July 2013 (UTC)

Carbonated drinks do taste different (as do many other foods and drinks) if you consume them while your at high altitude. However, taking the can up to 40,000 feet, then bringing it back down again can't affect the taste because the can is pressurized by the CO2 inside and the pressure of the contents won't change by any significant amount at altitude.

I agree with User:StewieCartman that any taste differences are due to the difference between canning plants and minerals and other impurities in the water that they use. It's also well-known that both Pepsi and Coke change their formulations from one country to the next to cater to local tastes.

SteveBaker (talk) 16:54, 9 July 2013 (UTC)

Coca-cola#Franchised_production_model points out that "Independent bottlers are allowed to sweeten the drink according to local tastes.". SteveBaker (talk) 17:02, 9 July 2013 (UTC)

Yeah, somewhat famously the sweetener used in soft drinks varies by country of production. Such as one place may use corn-based sugar, another sugar cane - some say the latter is quite a bit better. 88.112.41.6 (talk) 19:17, 9 July 2013 (UTC)

So, I think we agree: Imported drinks taste different from locally produced versions of the exact same brand - but that's not because they've been imported by plane - they'd taste just as different if brought in by ship or truck or whatever. SteveBaker (talk) 15:11, 10 July 2013 (UTC)

Crustaceans

Do coast-dwelling crustaceans prefer course grained sediments over fine grained sediments?99.146.124.35 (talk) 23:19, 9 July 2013 (UTC)

In particular, I want to know about other crustaceans besides crabs. I have already learned a lot about crabs grain size preferences.--99.146.124.35 (talk) 23:21, 9 July 2013 (UTC)

Metal-free

Over the past 15 years or so, a fringe group has developed that desires things to be "metal-free" to avoid the effects of metal on the human body. Without getting into politics about whether these groups consist of left-wing kooks or holistic visionaries, I'd just like to ask a question about ceramics, which seem to be fine according to such thinking.

For example, while the dental implant has historically been made of titanium, there are now ceramic implants available for those who'd like to avoid metal for one reason or another (holistics, esthetics, etc.). I understand how having a white or pink implant might be beneficial from an esthetic perspective (because zirconia can be colored), but if the point is to avoid metal, isn't ceramic just a metal oxide? I mean, zirconia is zirconium oxide (ZrO₂), and zirconium is a metallic element. Conceptually (or, perhaps actually), does the oxide prevent it from leaching out elemental metal into the body? I remember reading about toxic waste being stored in the ground in the Yucca Mountain in ceramic casks because metal casks can rust (oxidize) and allow for leakage, while ceramic (metal oxides) take that many more hundreds of thousands of years to break down because it can't oxidize, already being a metal oxide.

Thanks! DRosenbach ^{(Talk | Contribs)} 23:39, 9 July 2013 (UTC)

Ceramics are not just "metal oxides". See ceramic for more details. --Jayron32 00:07, 10 July 2013 (UTC)

If you wanted to avoid corrosive gasses, would you have to avoid table salt because it contains chlorine? μηδείς (talk) 01:41, 10 July 2013 (UTC)

Please tell me, Medeis, you are being facetious, because it is hard to tell, and if I'm going to give a chemistry lesson, I'd hate to waste my time if you really don't need it. --Jayron32 02:32, 10 July 2013 (UTC)

I think it's clear that Medeis was being facetious. The basic point, which Jayron of course understands perfectly, is that compounds that contain metallic elements generally don't have metallic properties. For example granite contains substantial amounts of aluminum, but isn't the least bit metallic. Looie496 (talk) 02:38, 10 July 2013 (UTC)

I was not being facetious. Metallic oxides and other compounds with metals are not necessarily metallic in their behavior, while certain organic films are, I believe, metallic in their behavior. Of course the burden of explanation lies on the anti-mettalite. Do the abjure Iron and Magnesium and Zinc? If so, they die or live as hypocrites. If all they abjure are metallic substances they have a liimited life available. μηδείς (talk) 03:15, 10 July 2013 (UTC)

You really believe that table salt contains corrosive chlorine gas? --Jayron32 03:23, 10 July 2013 (UTC)

Without knowing the nature of the original poster's friend's objection, we can't take this chlorine analogy in a relevant direction. Obviously salt doesn't contain chlorine as a "corrosive gas", but it does contain chlorine. Unless we have some idea what is really meant by "metal", we can't tell if salt is a good "look how ridiculous it sounds" demonstration or is off-topic because the concern is really "the presence of the atoms in any form" (and without knowing why that might matter...). Metal-containing compounds without "metallic" properties still could each metal atoms, and pieces of metal can leach metal atoms...once the atoms are out, maybe it doesn't matter what their former form was ("chemicals have no memory"). Or maybe the original forms are so different that they do not leach the same types of ions (or don't leach at all), in which case the salt analogy is relevant. DMacks (talk) 05:30, 10 July 2013 (UTC)

Note also that table salt is more direct analogue, since Sodium is a metal. I, for one, found μηδείς response quite appropriate. Putting on my whacko-head, I assume that a "metal" is anything that is highly refined and looks silvery/shiny. Salt is not a metal, but a "crystal", and crystals are, of course, good. But (science head back on), some ceramics are very resistant to both wear and chemical attacks, and even if some material is lost, it tends to be in a highly reduced, stable, inert form. So the premise is whacko, but the method makes some sense if one buys the premise. --Stephan Schulz (talk) 06:30, 10 July 2013 (UTC)

Per Stephan, the OP's fringe acquaintances might be "right" – sort of, in a manner of speaking – albeit by an entirely specious ("wrong") chain of reasoning. The bioavailability and potential toxicity of metals in the body certainly and unquestionably often depends on their oxidation state and the presence and/or type of complexing ligands. For instance, metallic chromium (Cr(0), as chrome plating, say) is pretty harmless. Cr(III) may be an essential dietary element in trace amounts. Cr(VI) is a potent carcinogen. Organometallic compounds of lead or mercury are often dramatically more toxic than the corresponding pure metals. On the other hand, while many barium compounds are highly toxic, the barium sulfate suspension used as a radiological contrast agent is largely harmless, because the sulfate salt is so poorly water soluble.

It is possible that the solubility (and/or reactivity, and/or bioavailability) of oxidized/complexed metals in the ceramic or polymeric preparations used in medical implants is generally lower than it would be if those same metals were in their native, reduced, metallic form. But at best this might represent a 'rule of thumb' guesstimate, rather than an absolute etched-in-stone "shiny metal is worse for you" principle—I would be inclined to check against actual published data and known properties of the metals and compounds in question. And of course the metal used in the metallic implant is seldom the same metal that is used in the ceramic implant (in DRosenbach's example, a zirconium compound is substituted for titanium) so it's very much an apples to oranges comparison. TenOfAllTrades(talk) 14:44, 10 July 2013 (UTC)

As usual, these crazy fringe ideas don't hold muster. Avoiding compounds containing metal is utterly impossible. Your brain works by maintaining sodium and potassium ions in various states of disequilibrium - and if you eliminate those two metals from your diet, you'll die. Technically, hydrogen is also a metal - so you'd have to stop drinking water, which would erase these crazies from the gene pool fast enough to warrant a well-deserved Darwin award!

So we have to assume that they're really trying to eliminate atomic metals - not compounded with other elements - and thats much more practical. Non-compounded metals would have been pretty rare during early human evolution - and not really necessary to survival...so I suppose that a sufficiently determined bunch of loonies could get together some kind of an off-the-grid society that espousedeschewed un-compounded metals.

This is a slightly strange set of beliefs though. There are some pure metals (mercury for example) that are quite toxic and should justifiably be avoided at all costs - and others (such as titanium) which the body not only tolerates but seems to seek to actively join with that are very useful in medicine (artificial joint implants, for example). Certainly we haven't evolved any particular tolerance or intolerance for pure metals as a whole because such things were not present in our environment through most of our evolution. What effects pure metal have on us is largely a matter of luck.

But to focus on pure metals is weird. Take, for example silver...it's a mild antimicrobial agent, which makes it useful - it's biologically inactive - and even if consumed in huge enough quantities, it only causes argyria (which is an embarrassing, but not dangerous, medical condition that irreversibly turns your skin blue). On the other hand, many simple compounds of silver are nasty poisons. On the other hand, look at sodium - which as a pure metal would instantly lethal - but compounded with chlorine (another nasty poison) produces table salt, without which we would die.

As a practical matter though, our bodies need metal compounds - our blood contains iron in the haemoglobin that carries oxygen through our tissues - we need to eat iron-containing compounds or we'll die, but swallowing a handful of steel ball-bearings doesn't have a whole lot of effect, except that you'll be shitting ball-bearings for a while afterwards. (WARNING: Don't do this!)

So whether you choose elemental metals or compounded metals as a fundamental rule of life just doesn't make sense. Why eliminate the benefits of silver just because mercury is so nasty?

SteveBaker (talk) 15:05, 10 July 2013 (UTC)

Eschewed, not espoused. But an excellent post, as always. Tevildo (talk) 20:59, 10 July 2013 (UTC)

Ooopsie! I corrected it - thanks! SteveBaker (talk) 14:16, 11 July 2013 (UTC)

Note that argyria specifies that the silver is converted to the sulfide and other compounds when brought into the body, and converted back to the metal by UV irradiation of the skin. (Though until I see a picture of a modest subject with unpigmented regions where he traditionally wears clothing, I'm not sure I believe it) The invasion of large particles of metal through the body and their orderly dissemination throughout the skin seems hard to picture, though. Wnt (talk) 21:40, 10 July 2013 (UTC)

Yep. But since the silver is in the skin for keeps - eventually, enough UV light arrives to turn the victim blue - although it might take years for the condition to...erm...develop (photography joke!). So while there may initially be unpigmented regions under clothing, they will eventually turn blue. It's weird that something so seemingly dramatic and obviously not right could be essentially medicaly harmless and yet completely irreversible. However, we're getting a bit off-topic here! SteveBaker (talk) 14:16, 11 July 2013 (UTC)

something so seemingly dramatic and obviously not right could be essentially medicaly harmless and yet completely irreversible...see also tattoo. The ability to trap and retain insoluble pigments in certain layers of the skin is well-known. TenOfAllTrades(talk) 15:00, 11 July 2013 (UTC)

July 10

Why can't I run an electric heater in reverse to cool a room?

Headphones convert electricity into sound. Plug headphones into a mic jack, and they can be run in reverse, that is, convert sound to electricity, and work as a crude microphone.

An electric heater converts electricity to heat. So why can't it be run in reverse, converting heat to electricity and cooling the room?

Is there any way to lower the temperature in a closed room (i.e. without venting heat to the outside)? (Assuming there is electrical power available in the room, raising the temperature is easy: electric heater.) --Lph (talk) 00:40, 10 July 2013 (UTC)

Because heat is a statistical representation of kinetic energy; and if you make something hotter than its surroundings, the probabilities are higher that energy will transfer out of the object: in other words, heat flows from high-temperature objects into lower-temperature objects. This is a direct requirement of statistics that define the probability of one air-molecule bouncing in to another one.

We quantify the average behavior using Newton's law of cooling, or the Stefan-Boltzmann law, or the Maxwell distribution; but they are all derivable using similar mathematical analysis. Nimur (talk) 00:57, 10 July 2013 (UTC)

No, there's no way to lower the temperature of a closed system, such as a sealed room, see the laws of thermodynamics. Intuitively, try to imagine unburning something to see why this won't work. μηδείς (talk) 01:15, 10 July 2013 (UTC)

No, you can sometimes lower the temperature, just not the entropy. We have a very brief stub on the instant cold pack. --Trovatore (talk) 01:42, 10 July 2013 (UTC)

Now that I think about it, I'm not sure, but Medeis did specify a closed system. Does an endothermic reaction in an idealized "box universe" lower the temperature of the whole system, or just transfer some kinetic energy from one part (cold pack) to another (surrounding air in the box)? SemanticMantis (talk) 02:28, 10 July 2013 (UTC)

It lowers the temperature of the whole system. --Trovatore (talk) 22:12, 10 July 2013 (UTC)

Right, and if you drop a rock from a few meters, it releases energy as heat (sound and vibrations) -- yet adding that heat to a rock on the ground will not cause it to jump a few meters in the air. The OP may also be interested in reading about the arrow of time, which some scientists and philosophers have interpreted in terms of entropy. SemanticMantis (talk) 01:23, 10 July 2013 (UTC)

Also an electric heater does not form a closed system with the room. If you check behind the device that converts electricity into heat you will usually find a wire that then connects through a series of transformers to a device that converts heat into electricity. Hcobb (talk) 02:33, 10 July 2013 (UTC)

Along the same line of reasoning: supposing we have a very warm room; and we connect it to the (colder) outside world using a copper wire. The thermoelectric effect is a real thing - a voltage could be produced, and the hot air in the room that impinges on the copper inside the room can excite some valence electrons, creating a voltage relative to the copper wire outside the room. Current could flow.

However - we know this doesn't happen in practice. Why? It's statistics, again. Hot air impinging on a copper wire is more likely to transfer its energy as a phonon than to thermoelectrically-excite a valence electron - in other words, the heat transfer is more likely to occur through thermal conduction - so the copper wire will be a heat pipe conducting heat energy out of the room through thermal conduction. For every electron that gets knocked into a conduction band by a thermal process, millions of thermal phonons (ordinary thermal vibrations within the atomic lattice) are created. The magnitude of this effect dwarfs any thermoelectric effect, which is so far below the noise-floor as to be un-measurable.

A few very special materials do exhibit the thermoelectric effect in a way that is measurable, (but copper is not one of those materials). In principle, if you had a huge chunk of thermoelectric material, and you had a very warm room, and a very cold outside, you could hook up a wire and generate a non-negligible amount of electric current. The current would carry energy out of the room. The key point is, there is a cold reservoir - the outside world - where the heat-energy is getting dumped out. Through the thermoelectric effect, electricity is just a mechanism by which that energy is getting transferred from hot to cold. And this method would be very inefficient, compared to using a conductive material, or allowing regular air convection to run its course and transfer the heat by more conventional means. Nimur (talk) 02:59, 10 July 2013 (UTC)

The OP specified: "in a closed room (i.e. without venting heat to the outside)". μηδείς (talk) 03:05, 10 July 2013 (UTC)

Exactly. Thermoelectric conversion involves moving heat from a hot junction to a cold junction in order to generate electricity (the Seebeck Effect) and the cold junction would have to be outside the room.

Yes, as noted above, it is possible to lower the temperature of a room without dumping heat outside: just use a cold pack. The endothermic chemical reaction doesn't actually change the internal energy of the room--it just arranges the atoms so that some of the energy that used to be heat is now trapped as potential energy in the structure of the cold pack's molecules. If this seems surprising, it shouldn't be. Consider that you can turn the room into a 1000-degree inferno just by lighting a fire, and that definitely doesn't absorb heat from the outside!

These kinds of chemical reactions are irreversible, so once the cold pack is used, it can't return to its original state without releasing heat (and dumping it into the room). If you want a purely physical process, that would involve taking thermal energy out of the room, and that energy has to go somewhere. You could maintain a temperature differential, where a tiny portion of the room is extremely hot and everywhere else is cold, but that differential requires additional energy to maintain--and the whole room will eventually heat up. You could cheat by dumping the energy outside in a different form--for example, using a laser beam to shoot it into outer space, where it doesn't heat up the Earth. You could convert the energy to another form of potential energy, for example by using it to lift up a heavy object.

EDIT: here's a very specific example of a physical process that cools a room. Suppose you have a giant cylinder with an airtight, and initially immobile, partition in the middle. On one side of the partition is a vacuum, and a spring that attaches the partition to the top of the cylinder. On the other side is a highly pressurized gas. Now, you release the latch holding the partition in place. The pressurized gas pushes on the spring and compresses it. The gas cools due to adiabatic expansion, and some of the gas's thermal energy turns into the potential energy of the spring. When the room reaches thermal equilibrium with the cylinder, it will be cooler than before. --Bowlhover (talk) 06:24, 10 July 2013 (UTC)

Certainly there are on-off things (such as instant-cool ice packs) that will convert heat into chemical bonds and thereby cool the room. However, they are one-off things. Once the ice pack has done it's thing, the room returns to an equilibrium temperature - and no further cooling is possible without buying more of them. With an electric fire, you can make the room hotter only by bringing in energy from the outside and keeping it there. Air-conditioners aren't like reverse-electric-fires. They don't suck heat out of the room and produce electricity as a by-product (which would be VERY handy here in Texas right now!) - instead, they consume electricity, suck heat from one place and generate even more heat in another place...a typical household A/C unit dumps the excess heat outdoors - and the heat it produces out in my back yard is considerably more than the heat it removed from the room, which explains my soaring electricity bill!

A reverse-electric fire (ie a device that turns heat into electricity) would be a violation of the second law of thermodynamics. There are devices that can turn a heat-gradient into electricity (a "peltier-effect" device, for example) - but in order to pass muster with the second law, they have to heat up something else in the process. Using a peltier device to cool a room will only work if it's colder outside than inside...and you can achieve that effect just by opening a window!

In the end, we're running into the problem of entropy. The tendency of the universe to move from a more ordered state into a more disorderly one. Electrical flow is very organized - heat is pretty much the ultimate in disorder (at the molecular level)...so the universe lets us convert electricity into heat (order-to-disorder) - but not the other way around. Thermoelectric devices like peltier-effect gizmos work by increasing the orderlyness of one place at the price of increasing the disorder in some other place to an even greater degree. The total amount of disorder in the universe is thereby increased and the laws of physics are happy!

SteveBaker (talk) 14:06, 10 July 2013 (UTC)

The OP could sit for a while with the heater blowing in his face. When he turns it off, it should feel cooler in the room. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:25, 10 July 2013 (UTC)

Of course if you were using an air source heat pump to heat your room, rather than an electric heater, you could run it in reverse as an air conditioning unit. Mikenorton (talk) 18:10, 10 July 2013 (UTC)

Thanks, everyone, for the very interesting and informative replies! --Lph (talk) 22:43, 10 July 2013 (UTC)

Angular momentum II

This is a continuation of the discussion I initiated a few days ago and which is still posted on this page. Although a few interesting ideas transpired the overall result left me dissatisfied. The most interesting comment was that by SteveBaker that two non rotating balls after collision may acquire angular momenta. That's fine but I don't think this can be applied to the early Universe. There were no balls there of any size. There was plasma there until 370,000 years of age, that's it. Was there any verticity? I cannot answer this question but I wish someone could.

I have two hypotheses, one is sort of crazy. At the very earlier stage, really before the inflation, the system was subject to quantum fluctuations which later generated sound waves and clumps of matter. One of those "fluctuations" could have been a lateral jolt that gave the system a rotation, but one can ask: a rotation in respect to what? Still another difficulty arises: how this rotation of the whole Universe translated into verticity of the local matter? The fact that we cannot detect this universal rotation now may be one of the results of inflation although I have hard time visualizing how this could happen. If I am not mistaken rotation of superfluid like liquid helium can generate local vertexes although I may be wrong on that.

My second hypothesis assumes that up to the age of about 100 million years or so there were no rotating parts in the whole Universe. At that time massive stars were formed (which had no angular momenta) and after about 1 million years of burning collapsed into supernovas or neutron stars. What are the stars made from? Plasma. Plasma supports sound waves. There were sound waves on the surfaces of earlier stars. So, when the stars exploded they threw much of their mass into the surrounding space but those jets were not symmetrical, they were once-sided perhaps or more complex. They must have given the remnants of the stars an angular momentum because of the reactive force. Perhaps strong magnetic fields also contributed to this irregularity. I hope I use correct terminology.

Once the star begins to rotate, the surrounding medium must rotate in the opposite direction.

How does it sound? Are there non-rotating stars in the sky?

Thanks, - Alex174.52.14.15 (talk) 03:30, 10 July 2013 (UTC)

I think you mean to say vortex and vorticity; a vertex is something else altogether.

Symmetry breaking in the very early universe is a complicated topic. I found a nice website, on the topic, part of an elementary course on Cosmology from the University of Oregon. All 26 lectures are available at no cost. I skimmed several of them, and read a couple in more depth - they meet with my approval, for what that's worth).

Before you jump to hypothesizing, it's not a bad idea to educate yourself about all the things that are factually known. Nimur (talk) 03:45, 10 July 2013 (UTC)

It actually should be verticity. Vorticity is a measure, verticity is a quality. Thanks for the references.

Thanks, - Alex174.52.14.15 (talk) 02:01, 11 July 2013 (UTC)

You imply that the acquisition of rotation was not possible because "there were no balls" - but rotation can be induced in any volume of tiny objects if there is some kind of force binding them together - gravitation, for example. To create a rotation, you only need a "couple". Any object of non-zero size can be started in rotation if there are two or more non-parallel forces being applied to it...so in a system of three bodies, each with mass and non-zero size, any two of them are exerting gravitational forces on the third - and unless they are in a perfectly straight line, you'll have a couple - resulting in rotation. SteveBaker (talk) 18:56, 10 July 2013 (UTC)

To clarify, two non-rotating balls have a net angular momentum before an off-center collision. To see this, imagine they just barely miss each other, but catch each other by a little hook - now they don't move on in either direction, but their entire energy remains as the two twirling madly around their common center of gravity. The result is that if you have n particles moving through space, any two of them have some angular momentum around a given axis as determined by the lever arm of their torque, and only if all the net angular momenta happen to add to zero do you have a system with zero angular momentum.

There is, admittedly, something that seems haphazard about all this; just as it seems strange that angular momentum is quantized while the position in space seems not to be. I feel as if, somehow, we are viewing the universe in a fictional mental framework very different from its physical reality. Wnt (talk) 21:33, 10 July 2013 (UTC)

Thanks to everyone who contributed but I am still dissatisfied. For one thing the "references" although cute are too elementary and too familiar to me in topics to be of any help. It was nice to read some of the pages just to enjoy the technical language. SteveBaker continues to argue that the colliding masses do not have to be solid to generate momentum. This might well be true but I cannot visualize it. It simply isn't very intuitive. Let's say a mass of plasma flies through space and meets another cloud of same. The particles should just mix, that's it, if they are electrically neutral. Now, if they are not and also if strong magnetic fields are involved, then a cloud of plasma can act as a solid object, this is true. Perhaps this is the correct path to understanding how galaxies get rotated.

Thanks, - Alex174.52.14.15 (talk) 02:01, 11 July 2013 (UTC)

Taking your two masses of plasma colliding. You seem to agree that if they are charged or magnetic - then rotation can be induced by the electromagnetic force. In fact, the only way those two clouds could pass through each other without any interaction whatever is if there are no forces whatever between the particles that make them up. But why only consider the electromagnetic force? Any pair of forces acting on an object with non-zero size will suffice to make a "couple" - and that includes the strong and weak nuclear forces and gravitation. Since all objects that have mass produce gravitational forces - then rotation of some kind is more or less guaranteed to emerge from any interaction - even at a distance. In the case of two clouds of plasma, the amount of gravitation and other forces may be very tiny indeed - and the resulting rotation will also be tiny - but over an uncountably large number of interactions happening in the universe, sizeable rotations will eventually emerge. SteveBaker (talk) 14:05, 11 July 2013 (UTC)

Thank you but now I clearly see that you are mistaken. Week and strong nuclear forces act on subatomic distances only and I don't think they are applicable here. Imagine a ball at a certain height falling on the surface of earth under the condition that no lateral wind force is applied. Do you expect the ball to start rotating BEFORE it hit the earth? I don't think so. So, gravitation alone cannot do it.

Thanks, - Alex174.52.14.15 (talk) 17:11, 11 July 2013 (UTC)

Tidal Force allows bodies to exchange angular momentum through gravitation. 209.131.76.183 (talk) 17:29, 11 July 2013 (UTC)

Alex - when you ask a question here, you might take the time to actually read what's written rather than triumphantly telling us that you now understand it all and we're wrong. Gravitation can cause rotation in the case when there are THREE or more bodies involved AND when the gravitational vectors are not parallel. When you drop a ball, it pretty much falls DIRECTLY towards the center of the earth - and indeed, if the ball and the earth are the only bodies in consideration, your common experience of gravitation is correct. But when there are multiple sources of gravity (the earth, moon and sun, for example) and the motion of the ball isn't conveniently directly towards or away from any of them - then induced rotation of all of those bodies is inevitable. Your common intuition defeats you here. Similarly, the nuclear forces do indeed operate at very small distances - but if they are inducing rotation in very tiny objects, and if there is enough time for their tiny influences to add up - then that's enough to break that "symmetry" and cause the onset of rotations. But no matter, gravity is plenty powerful enough. SteveBaker (talk) 01:32, 12 July 2013 (UTC)

Well, it might be true (actually it is certainly true) but we are talking about the primordial angular momentum when right after the inflation there was no angular momentum anywhere. At that time there was nothing to exchange. This is the enigma. How did it all start? - Alex174.52.14.15 (talk) 18:15, 11 July 2013 (UTC)

You're simply not understanding what we're telling you - you can get rotation from simple translation in the presence of forces such as gravity. I've shown you that in two previous responses. Admittedly, a clockwise rotation induced in one object will be precisely equalled by anticlockwise rotation in the other - so the NET rotation of the universe is still zero - but multiple swirls and eddies will start to build even in an initially rotation-free universe. SteveBaker (talk) 01:32, 12 July 2013 (UTC)

The structure formation in the early universe happened in a turbulent environment where vortexes easily formed. Do a google scholar search for 'universe "structure formation" vortex' to get a some papers on the topic. here is an interesting example. Dauto (talk) 13:38, 12 July 2013 (UTC)

Go fuck yourself

The phrase "go fuck yourself" is often censored as "instructed to perform an anatomically impossible act". Some time ago I encountered what appeared to be a photograph of a man with the tip of his penis inserted in his anus. Was this a photoshop job, or was he actually managing to have anal sex with himself? --67.160.38.148 (talk) 04:53, 10 July 2013 (UTC)

It is probably technically feasible given the ranges of sizes of various body parts. That is, a man with a particularly long penis could probably make it reach. The Wikipedia article titled Human penis size may lead you to the necessary measurements to determine this on your own. --Jayron32 04:57, 10 July 2013 (UTC)

I can make mine reach and could have probably put the tip in, but didn't want to. Of course, if I really wanted to fuck myself, I'd need an erection, and I am absolutely certain it doesn't bend that way. Mine, anyway. If the guy in your picture looked hard, I'd assume it's fake, but who knows? It could have just been terribly damaged. InedibleHulk (talk) 05:31, July 10, 2013 (UTC)

I've seen pics and videos of such things but, as you say, they were not erect and hence there was no "fucking" going on. -- Jack of Oz ^[Talk] 12:05, 10 July 2013 (UTC)

There are some misguided people who oppose Wikipedia's coverage of autofellatio, but you'll find some folks have kindly donated more proof at Commons:Category:Autofellatio. (I'd look up the other thing but ... I haven't thought of what to call it!) Wnt (talk) 21:23, 10 July 2013 (UTC)

I've seen it called "self-sodomy" (a Google search on that term - NOT AT WORK - will confirm this), but that doesn't meet WP:RS. "Autosodomy" (ditto) is also used. Tevildo (talk) 21:57, 10 July 2013 (UTC)

I thought autosodomy was when you really, really like your Duesenberg. Clarityfiend (talk) 23:33, 10 July 2013 (UTC)

Not a problem as long as you don't stick anything in the tailpipe. DMacks (talk) 01:38, 11 July 2013 (UTC)

You can check your progress on the sodometer. -- Jack of Oz ^[Talk] 07:25, 11 July 2013 (UTC)

No, no, no. You use a sodometer to find the exact amount pf sodness between steering wheel and driver's seat. - ¡Ouch! (^{hurt me} / _{more pain}) 07:01, 12 July 2013 (UTC)

Raw Pork

So how come Mett doesn't cause illness or parasitical infestation, when raw pork is considered unsafe for consumption almost everywhere? Rojomoke (talk) 12:50, 10 July 2013 (UTC)

A quick look finds a WiseGeek article on the safety of Mett [6][7], which states that it is intended to be eaten the same day the pig is killed, which should reduce the risks of a bacterial build-up. As with most foods though, cultural factors are often significant when it comes to issues of what is considered safe, and objective data on safety may be hard to locate. AndyTheGrump (talk) 13:03, 10 July 2013 (UTC)

The main risk of raw pork is trichinosis. At least in Germany (where Mett is popular), this risk has been basically eliminated by strict inspection codes for meat, especially pork, and by particularly strict production codes for all minced meat products. --Stephan Schulz (talk) 13:41, 10 July 2013 (UTC)

You might want to read this[8] before you jump to conclusions about pork safety. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:18, 11 July 2013 (UTC)

I really don't quite see how the sale (or not) of a US pork producer (which will likely export to China) affects the effectiveness of food inspections in Germany. --Stephan Schulz (talk) 11:26, 11 July 2013 (UTC)

Maybe you should change the section header to make it clear this is only about German hogs. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:36, 11 July 2013 (UTC)

There may be some confusion here. In my original comment (the one you, at least according to our standard indentation patterns) replied to, I pointed out that in Germany, where Mett is popular, proper production codes and food inspections mean than pork is quite safe. If you did not intend to reply to my comment, sorry, but then please make it clear what you reply to. I really don't see a strong connection of your comment to any of the preceding posts. Indeed, now I'm not even sure if you warn us that pork may not be safe (because it might be imported from China?), or that pork can indeed be safe (as "several senators" seem to imply for meat meeting American safety standards). --Stephan Schulz (talk) 11:59, 11 July 2013 (UTC)

It's not that it doesn't cause infection. You can be sure that well cooked pork is safe against trichinosis and other bacterial infection. Raw pork can be safe or not, depending on the handling and inspections. In doubt, then, cook it. OsmanRF34 (talk) 16:39, 10 July 2013 (UTC)

In addition to trichinosis being rare in many countries, it's killed by freezing the pork before preparation. --Sean 20:06, 10 July 2013 (UTC)

The genetics of the royals

Have the European royal families been an object of scientific research? It's clear that having children with your relatives is a bad idea, but how bad is it? How many more cases of mental retardation, disabilities, speech disturbances and so on are there? OsmanRF34 (talk) 16:35, 10 July 2013 (UTC)

See Haemophilia in European royalty for one possible issue. AndyTheGrump (talk) 16:37, 10 July 2013 (UTC)

Inbreeding increases the chances of a phenotypic abnormality with autosomal recessive genes, but doesn't really have anything to do with hemophilia, which is inherited as a sex-linked recessive gene. Hemophilia B spread through the royal families after a single mutation, and was inherited in the usual straightforward way, without any couples who *both* bore the mutation. - Nunh-huh 13:17, 11 July 2013 (UTC)

See Prognathism, and this article in Discover magazine [9]. Note that it is a bit simplistic to think "inbreeding causes bad things". In fact, most race horses, prize dogs, etc are highly inbred. But, when it's done intentionally to keep "good" alelles, it's usually called line breeding (unfortunate redlink, just google it). Cleopatra is sometimes mentioned as a human who may have benefited from such a collapsed family tree. Finally, all of the above can be considered as aspects of founder effects. SemanticMantis (talk) 18:03, 10 July 2013 (UTC)

But pedigree dogs are very frequently afflicted with genetic diseases. Surf to almost any of our articles about famous dog breeds and you'll see a list of genetic problems brought about by inbreeding. I looked up Poodle (at random) and found that the breed suffers from: "Addison's disease, gastric dilatation volvulus, thyroid issues (hyperthyroid and hypothyroid), tracheal collapse, epilepsy, sebaceous adenitis, juvenile renal disease, hip dysplasia, and cancer". But pick another breed and you'll get a different list - so these diseases can only have become more prevalent because of the specializations the "poodle-ness" implies - and that's due to inbreeding. In recent years breeders have started to work hard to eliminate these problems - but that degree of gene-pool management would be a brutal thing to impose on humans!

One or two generations of in-breeding may not do too much harm - but when you do it for dozens of generations (as european royalty did) - you effectively cut off these people from the rest of the species and (in effect) you have a new sub-species with a gene-pool of maybe 100 individuals. A gene pool that small is just too small to avoid genetic problems from accumulating. There does seem to have been research on the effects of all this. Type "inbreeding european monarchy" into Google scholar and you find a TON of papers that have been written on the topic.

SteveBaker (talk) 18:48, 10 July 2013 (UTC)

I take your point, certain dog breeds are plagued with genetic disorders. But I wasn't referring to just any poodle. I mean the show winners, who may have several generations pedigree of ancestors that did not have e.g. juvenile renal disease. Very bad things have happened to breeds when they were obsessively bred to meet bizarre standards, and in those breeds, a pedigree with documentation of lack of a disease is a very valuable thing indeed. The fact that people in the past didn't breed their poodles with genetic disease in mind doesn't mean that selective line breeding can't be used to improve individual traits and performance, or that such practice must necessarily bring deformity and disease. For instance, this breeding project is very focused on dog health and longevity (and dire wolves) [10]. Here's another example that illustrates a "positive" founder effect: all modern Thoroughbred racehorses are thought to descend from a single, very large-hearted 17th century mare! [11]. Finally, I must confess I find all this artificial selection a bit creepy. I don't mean to defend inbreeding in general, but I do think "inbreeding=bad" is an overly simplistic message. Clearly, the sad state of poodles and Hapsburgs tells us that it can cause problems when taken to extremes, but cousin marriage doesn't really have many risks. You seem to understand the subtleties here, so I'm mainly pointing out to others that there are also potential benefits to inbreeding. SemanticMantis (talk) 19:25, 10 July 2013 (UTC)

"doesn't really have many risks" is not how I would interpret statistic that show a 50% to 500% increase in risk. Some drugs are sold with far less effects. Rmhermen (talk) 20:06, 10 July 2013 (UTC)

500% increase in risk of what? I'm no expert, I was basing my claim on my reading of our article, which says "The children of first-cousin marriages have an increased risk of genetic disorders, though the incremental risk enhancement is relatively small, according to many researchers." Cousin_marriage#Genetics says, with citation: "In April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40" -- so my understanding of our article is that cousin procreation poses a low-level risk to offspring, which is not very different from other "risky" procreation. SemanticMantis (talk) 21:47, 10 July 2013 (UTC)

2.8+3=5.8 or almost 6 which is nearly 100% increase. Later in the article you will even higher increase in spontaneous abortion rate and infant mortality in various arrangements of cousin, second cousin and double cousin marriages. Rmhermen (talk) 21:19, 11 July 2013 (UTC)

There is a fairly detailed exposition on the subject of inbreeding in Robert Heinlein's Time enough for love, where Lazarus Long tries to figure out if it would be okay for twins to make babies together (the subject is relevant in other portions on the book, but lets pass on the details dreamed up by Heinlein's perverted mind), and the conclusion was that it was basically okay. I also remember reading something about an island where a goat couple was introduced, and then the island was pretty much left alone for a long time, and then when humans came back there was a large population of goats with a pretty good genetic diversity - and if I'm not mistaken, the explanation was that the island actually had predators for the goats which culled the (probably numerous early on) genetically defective individuals. The problem with the Rois faineants is that they were probably not under considerable evolutionary pressure, letting shortcomings accumulate (most people in the middle ages probably had a much lower of chance of surviving hemophilia than the average king). I'd love to provide references but my internet access is limited at work. I think the island in question may have been Arapawa Island? 64.201.173.145 (talk) 20:42, 10 July 2013 (UTC)

Yes, Arapawa mentions the relevant solution: culling. If you are willing to have a large number of children or animals die, so long as you have enough to carry on the line, inbreeding's problems can be tolerated. But as the quoted Discover article mentions, part of that culling is also effective sterility. (Sterility in this case being culling at the level of gametes or early embryos. The same with the goats, obviously. As long as they produce enough kids fast enough they will survive. Sexual reproduction also weeds out the harmful mutants. Imagine two carriers of a gene that's lethal when homozygous have four offspring. One will be homozygous and die, two will be heterozygous and live, one will be mutation free. That is a change from 1/2 to 1/3 rate of the gene in one generation. As for a %500 increase in risk, if the original risk is 1/10,000, a 500% increase means a risk of 1/2,000. Again, tolerable. μηδείς (talk) 01:34, 11 July 2013 (UTC)

For most of human history in most societies, marriage of cousins (not always necessarily first cousins) has been the norm (since nearly everyone within walking distance was related). We've survived, though often at the cost of high infant mortality in the past. Dbfirs 06:10, 11 July 2013 (UTC)

...but with very much of that infant mortality not being the result of genetic defects, but of bad nutrition and infectious diseases. Marriage between close relatives is primarily a problem in the case of recessive gene defects, it does not magically create monsters. --Stephan Schulz (talk) 07:12, 11 July 2013 (UTC)

(Anecdotal evidence:) No, cousin marriage certainly is not an instant recipe for mutants. I am the product of many generations of cousin marriages (including an avunculate marriage or two), and none of my close relatives on any side are monsters—or particularly unhealthy in any way. הסרפד (call me Hasirpad) 23:05, 11 July 2013 (UTC)

I have found the relevant passage from Time enough for love on Google Books: [12] - however, some parts are missing and the page numbers are not indicated. Searching for "Unfavorable gene reinforcement" should lead to the proper page if you can find a complete electronic edition. 64.201.173.145 (talk) 12:54, 11 July 2013 (UTC)

It's one of Heinlein's best books if not best. One should read the whole work. μηδείς (talk) 18:03, 11 July 2013 (UTC)

Royal intermarriage has a (rather disappointingly) short section on inbreeding.

For those interested in inbreeding in general ;-), we have an article on Patrick Stübing who had four children with his sister, one of them healthy, one with a heart condition and two with severe disabilities (could be case specific, maybe neither of them should have children, period.) Ssscienccce (talk) 13:56, 12 July 2013 (UTC)

The "Runaway Train" Lever

According to [13], "Local firefighters were later called to put out a fire on the train. While tackling that blaze, they shut down a locomotive that an engineer had left running to keep the brakes engaged." -- and the train went off and killed 60 people!

The article Lac-Mégantic derailment gives a similar opinion, though saying there were supplemental brakes that should have been set.

In forum discussions [14] some people say what I would have expected, namely that the brakes are like on trucks where a failure of air pressure makes them engage. Meanwhile, others say that there is an emergency lever somewhere on the outside of the train that can shut off the engine automatically!

Does this mean that someone can go wherever local news reports have quoted residents complaining about idling trains, find one, pull the lever, and (with some probability, depending on if hand brakes were set) sit back and watch the fireworks? Wnt (talk) 17:09, 10 July 2013 (UTC)

I hope you realize Barack Obama now knows you said that. μηδείς (talk) 17:45, 10 July 2013 (UTC)

Well, if I'd seriously been planning to derail trains I'd have kept it to myself! Thing is, maybe the spooks ought to notice this because lots of people must have thought of this after reading today's news. Wnt (talk) 17:58, 10 July 2013 (UTC)

It's evidently not a simple matter. There are two completely separate braking systems - the air brakes require positive air pressure to engage the brake, but there is a separate hand-brake system - which has to be applied separately to each car. Evidently the hand brakes are activated by external levers - but in this case, they didn't set the hand brakes on all of the cars...certainly there were insufficient to stop the train from running downhill without help from the air brakes. Our article Railway air brake explains the rather complex system which prevents the air brakes from failing when the locomotive ceases to supply air or if either of two redundant sets of hoses breaks. As far as I can tell, that "fail-safe" system works by filling up a pressurized reservoir on each car which holds the brakes on in case of problems. In this case, the air supply from the locomotive ceased - the brakes on the cars duly engaged - which is why it didn't immediately run away when the engine was stopped. But the brakes would only stay engaged as long as their air reservoirs held out. When that air finally ran out, the cars would start to un-brake, and eventually there were eventually insufficient cars with either reservoir air remaining or hand-brakes applied to keep the whole thing from running away.

I think it's a bit simplistic to take the view that the entire system is ridiculously flawed and that a trivial modification would make it all safe. The engineers who design these things aren't stupid - and there is enough history of runaway trains for them to know the importance of getting this right. But it's clear that despite multiple backup systems, a sufficiently complicated set of human procedural screwups and mechanical failures can still result in a runaway train.

SteveBaker (talk) 18:30, 10 July 2013 (UTC)

See Chester General Rail Crash for a virtually identical accident (with less serious consequences) in the UK. The train involved in that accident wasn't fully-fitted, but did have sufficient continuous brakes to prevent the runaway - _if_ they'd been connected correctly. Not that we should speculate about Saturday's accident beyond the officially-published investigations. Tevildo (talk) 19:57, 10 July 2013 (UTC)

And this incident report from 2007 contains a detailed description of the failure mechanism that Steve describes. Tevildo (talk) 20:00, 10 July 2013 (UTC)

Hmmm, the Chester General Rail Crash article talks about vacuum brakes not being connected properly to work while in motion. Seems about as different as it could be - is that the wrong link? And to make an off-topic editorial response -- what's "ridiculously flawed", that's not the engineering but the design. Leaving trains idling unattended is, first and foremost, a serious noise nuisance to the local community - the biological instinct that finds it to be a nuisance is dead-on, namely that large heavy objects moving continually lead, eventually, to disasters; that's the instinctive dread that low-frequency noise makes people feel. The design of the train should have taken deliberate and accidental terrorism into account, so that if a well meaning fireman pulls a lever it isn't going to cause a catastrophe. Whatever engineering it takes to implement such common-sense priorities simply needs to be done, rather than not done; the quality of the engineering is not really at issue. Wnt (talk) 21:16, 10 July 2013 (UTC)

What is ridiculously flawed is not the engineering or the design, but the railroad's operations procedures! Had they followed proper safety procedures by parking the train on the siding (rather than the mainline like they did), and then not just screwing down the handbrakes but also blocking the wheels and/or applying the derail, the whole disaster wouldn't have happened even if all the air brakes failed! No amount of safety engineering can prevent disasters if people ignore the safety procedures, as they did here! (I believe the technical word for blocking the wheels is "scotching", and the blocks used for this are known as "sprags" -- or is that only in British English?) 24.23.196.85 (talk) 02:27, 11 July 2013 (UTC)

Scotch says you're right about scotching (and notes chock as a similar concept...that's the more general term I've heard in the US for many different types of wheeled vehicles). Sprag sounds like a different approach. DMacks (talk) 04:25, 11 July 2013 (UTC)

Given that they were actually blaming the fire company, are these established as universal safety procedures? And from a counterterror perspective, how much extra protection does setting handbrakes and/or chocks actually provide? I'd feel a lot more comfortable if they followed the rules of the rest of the world and parked their train (true, in a proper parking space, not the middle of the road) with the ignition off, the brake set in some permanent way, and preferably, with the turn of a key required before it can be started moving again. Why are they so insistent on having their engines idling uselessly and bothering the neighbors? Wnt (talk) 05:01, 11 July 2013 (UTC)

Note that on most sidings, both the switch and the derail (if equipped) are secured in position with padlocks to deter tampering. As for leaving the engine running, the reason why they do that is because starting a diesel locomotive is not as easy as starting your car -- the procedure for doing this is more involved (more like starting a plane engine), and can take several minutes. Plus, after starting, the engine must warm up for 10 minutes or more before the train can safely be moved. 24.23.196.85 (talk) 01:43, 12 July 2013 (UTC)

The parallel plane and train disasters of this past weekend, both potentially due to (whose?) negligence, remind me of Sean Connery's comment in Rising Sun: "In Japan, they fix the problem. In America, they fix the blame." ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:11, 11 July 2013 (UTC)

Coke didn't freeze

I forgot a bottle of coke in the freezer but it didn't freeze. When I opened it the coke started to, so I quickly closed it again and now it's a viscous liquid. What is the physical explanation to that? Thanks, 84.109.248.221 (talk) 19:01, 10 July 2013 (UTC)

See Supercooling. 209.131.76.183 (talk) 19:07, 10 July 2013 (UTC)

I don't think that's what is happening here -- or at least not all that is happening. The CO2 coming out of solution plays an important role, I believe. Looie496 (talk) 21:33, 10 July 2013 (UTC)

Adiabatic cooling? Dismas|^(talk) 23:34, 10 July 2013 (UTC)

I konw this works much better when the coke is shaken up before putting it in the freezer, though not sure why this lowers the freezing point/ removes nucleation sites (I think the lack of nucleation sites is what is stopping it from freezing.). When you open it the CO2 is released and bubbles provide nucleation sites for ice to form. The viscous fluid you have is just a slush of ice and coke. 80.254.147.164 (talk) 12:31, 11 July 2013 (UTC)

Unsourced speculation - is it possible that the freezing point is just below the freezer temperature when under pressure? Looking at our graph of the melting point of water vs pressure, I doubt that the pressure of the carbonation (<1 MPa, I think) would lower the point enough to make it work reliably, but if the freezer (or the part of the freezer the bottle is in) is only slightly below freezing, it could be what does it. 209.131.76.183 (talk) 19:44, 11 July 2013 (UTC)

July 11

Post-operative fever : another Five Ws  ?

Hello Learned Ones ! I was inopportunately dozing at the end of Grey's Anatomy (of which I am a late-coming fan) , season I, episode 3, & did'nt catch clearly the five causes for post-op. fever as enumerated by Meredith : "wind (splint, ...), water, etc...". Could some of you recall them to me ? , this mnemotechnic line seems quite interesting. As for the term "splint", I infer it means that patient must learn to gently hold his abdomen while coughing ? Thanks beforehand for your answers , t.y. Arapaima (talk) 17:39, 11 July 2013 (UTC)

Look at our article on postoperative fever -- hey, presto!, it's right there. Looie496 (talk) 17:50, 11 July 2013 (UTC)

Aw, I'm so ashamed : it was just there (& even with the ref. to "Grey's Anatomy" ! ) , & I didn't find it !. I swear I looked for it, but I typed "post-operative" , continental way, & it gave me a useless page ([ http://en.wikipedia.org/w/index.php?title=Special%3ASearch&search=post-operative+fever&fulltext=1]

. Thanks Looie for you time & kindness, have a good summer day. T.y. PS : I thought WP could correct a (slight) mispelling in a search statement ? ... And how come Five Ws didn't mention it ? Arapaima (talk) 07:08, 12 July 2013 (UTC)

Cricket Revometer

In their coverage of the The Ashes, Sky are showing off a new gadget called the "revometer". It measures the number of revolutions per minute that spin bowlers put onto the cricket ball, which is an indication of the amount of drift and turn they should extract. There's no gadget inside the ball and I don't think the data comes as part of the Hawk-Eye system, although I suspect a specialist (presumably high-speed) camera is involved. Does anyone know how it works? ManyQuestionsFewAnswers (talk) 18:09, 11 July 2013 (UTC)

The cricket ball doesn't have a uniform surface. I suspect what it's doing is using computer vision to identify the portion of a ball-tracking camera's image that contains the ball, then checking for a periodic variation in brightness. The length of that period is determined by the speed the ball is spinning. --Carnildo (talk) 22:48, 11 July 2013 (UTC)

That would be kinda tricky because the balls' axis of rotation isn't necessarily perpendicular to the camera - if it were spinning end-on, then there wouldn't be any overall flicker at all. So I suspect it's grabbing two very high resolution photographs close enough together in time and tracking where the seam is moving...that's not *so* difficult and would result in a reasonably accurate spin rate measurement regardless of the axis of spin...providing that the camera has a sufficiently large image of the ball at two consecutive moments in time and a sufficiently short capture time (ie shutter speed) to end up with a reasonably sharp image. SteveBaker (talk) 01:09, 12 July 2013 (UTC)

Ashton Agar in particular has been bowling with some atypical axes of rotation for a spinner - with unusual amounts of topspin or with a scrambled seam. I'm not sure what difference that makes technically. ManyQuestionsFewAnswers (talk) 12:05, 12 July 2013 (UTC)

Gastritis

The gastritis article claims that sometimes it can occur after infections but surely this should say during infection? Doesn't the bacterial infection cause the inflammation or gastritis in the first place and after the infection is gone, the inflammation will also go, unless there's another cause? Clover345 (talk) 21:45, 11 July 2013 (UTC)

Boiling water with vending machines... in SECONDS! A miracle!

How do vending machines boil water so quickly to make instant coffee cups or instant noodle cups? I suspect they have some sort of high pressure thingy inside there. Sneazy (talk) 22:17, 11 July 2013 (UTC)

Maybe they have a Instant hot water dispenser inside? Vespine (talk) 22:42, 11 July 2013 (UTC)

(ec) There are two approaches that can be used, depending on the required flow rate and available electric supply. Some machines maintain a small well-insulated hot water reservoir at close-to-boiling temperatures; this hot water can be dispensed on demand for hot beverages and instant noodle cups. Having a hot reservoir means that the manufacturer can get by with a smaller heating element, since the heating cycle can last a lot longer than the few seconds that the cup is being filled. Here's a surprisingly detailed schematic of a hot band cold instant beverage vending machine, featuring a six-liter holding tank with a 900-watt heating element: [15].

It's also possible to heat water on demand, however the electricity requirements are steeper. To heat 1 mL of water from room temperature to boiling takes about 300 joules; to heat a cup (eight ounces or about 250 mL) of water from room temperature requires 75 kJ. If dispensed over twenty seconds, that's just shy of 4 kilowatts of on-demand heating. (That is a fairly hefty load, but not impossible to supply if the vending machine location is designed with this type of use in mind; it's comparable to the power drawn by an electric clothes dryer.) TenOfAllTrades(talk) 23:10, 11 July 2013 (UTC)

Is that energy source green? Is there a particular company or set of companies that sells these types of products? Do they use greener energy, or do they just don't care about where the energy source come from? Sneazy (talk) 00:52, 12 July 2013 (UTC)

I doubt it's anything other than whatever wall socket is handy nearby...so no more or less green than the lights in the area where the machines is situated - or other vending machines at that location. What is "green" is minimising the amount of water that has to be kept hot. The instant heaters - while they use a lot of power, only do so for a short amount of time. The total energy they use is less than the type that keep a small tank of hot water because no matter how well insulated that tank is, it's going to be losing some energy over time. SteveBaker (talk) 01:01, 12 July 2013 (UTC)

As Steve says, the source is the wall plug of course, so it entirely depends where you are. If you are in Canada or in Sweden, it is likely to be mostly from hydroelectric powerplants. If you are in France, it is 77% nuclear power. If you are in Dubai, it is most likely from burning some sort of fossile fuel like gas. --Lgriot (talk) 08:58, 12 July 2013 (UTC)

Well to make this instant heater work anywhere, why they don't just put like a supercapacitor to store the electrical energy so it can distribute the load over a longer time? Modern SMPS have 80+ efficiency so... everyone is happy 140.0.229.26 (talk) 13:51, 12 July 2013 (UTC)

A 75kJ supercapacitor isn't cheap, and the existing technology works well and service people are familiar with it. Keeping water warm in a well-insulated tank won't waste that much power, and the machine can be scheduled to shut off at hours it won't be used. Also, many machines are operated by vending services, and they aren't concerned about the amount of power being used unless the owner of the site starts complaining. 209.131.76.183 (talk) 14:53, 12 July 2013 (UTC)

July 12

Heads of State who were also Medical Doctors?

Hi, does anyone know of any Heads of State (current or former) who were medical doctors? The only one I've been able to find is Ram Baran Yadav, President of Nepal. Thank you for your help. LastPolarBear (talk) 11:24, 12 July 2013 (UTC)

François Duvalier -- Finlay McWalterჷTalk 11:37, 12 July 2013 (UTC)

Mohammad Najibullah (he article says he graduated as a doctor; it doesn't say whether or not he practised as one). -- Finlay McWalterჷTalk 11:49, 12 July 2013 (UTC)

Sun Yat-sen. {The poster formerly known as 87.81.230.195}212.95.237.92 (talk) 12:57, 12 July 2013 (UTC)