Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

June 25

Probability distributions in Quantum Mechanics

How do scientists derive probability distributions in quantum mechanics? ? ––115.178.29.142 (talk) 03:09, 25 June 2010 (UTC)

Solve the Schrödinger equation. For one example see Particle in a box or List of quantum-mechanical systems with analytical solutions for others. Graeme Bartlett (talk) 03:57, 25 June 2010 (UTC)

To expand that answer somewhat: solving the Schrödinger equation gives the wavefunction of a system as a function of time, ψ(t). To find the probability distribution of an observable A at a given time t, you express the wavefunction ψ(t) as the sum of eigenstates of A; there will be an eigenstate ψ_a corresponding to each observable value a of A. The "co-ordinate" of ψ(t) along the "dimension" ψ_a will be a complex number φ(a, t) called a probability amplitude. The probability that a measurement of A at time t gives a value a is then the square of the magnitude of the probability amplitude, |φ(a, t)|². Gandalf61 (talk) 08:38, 25 June 2010 (UTC)

A 'perfect solution' is difficult, so sometimes iterative (but approximative) methods like Hartree-Fock are used. John Riemann Soong (talk) 20:38, 25 June 2010 (UTC)

scientific name of the plant( ?or substance?) called "Lapland sesame" in the Wikipedi- article about hand of glory

Please give me to know a botanical name of this thing, if it be a plant; if it be something else, please give me a reas'nably precise definition of that thing. In case past monetary support of {Wikipedia} be of any importance concernin' your-all decision, whether yeah or not to respond unto this query, i mention, that i donated ninety USDollars unto {Wikipedia} in May of this year. —Preceding unsigned comment added by Stig weard (talk • contribs) 04:54, 25 June 2010 (UTC)

Hmmm... Unless there are two Laplands, or some unrelated plant also called sesame, it seems unlikely that there is any sesame native to (or even grown in) Lapland. See sesame and this map which shows where Sesame is cultivated. Sesame is an exclusively tropical plant, while Lapland (northern Norway and Finland) is one of the coldest inhabited places on earth. I did a google search for Lapland Sesame, and turned up almost nothing other than references to the candle recipe already found in Wikipedia. --Jayron32 05:25, 25 June 2010 (UTC)

Agree. It seems that nobody really knows what this is supposed to be, but there is some speculation that it is a bad translation from a French original that meant "sesame and horse dung". Looie496 (talk) 05:28, 25 June 2010 (UTC)

I have corrected the links for you. this is one of those questions that shows just how useless Google can be. There are six hundred-odd links but they are almost circular in source with no answer evident. This seems to have been a 15th century scam but the real identity (if ever there was one) of the plant has been lost. Caesar's Daddy (talk) 15:52, 25 June 2010 (UTC)

I don't know if this is relavent here, but many alchemical/witchcraft recipes usually have ingredients that are either unobtainable, or the name obscured.77.86.123.157 (talk) 15:58, 25 June 2010 (UTC)

Measurment change by interacting

Hi. What's the name of the process, when we measure something, and by measuring we change the properties of this body or thing? 83.31.79.94 (talk) 12:23, 25 June 2010 (UTC)

Heisenberg uncertainty principle.

ALR (talk) 12:35, 25 June 2010 (UTC)

That is incorrect, the Uncertainty principle states that we can't know the exact location and vilocity of a particle at the same time, not that a measurement changes the particles properties, that is a seperate principle. —Preceding unsigned comment added by 74.67.89.61 (talk) 13:03, 25 June 2010 (UTC)

From a pure physics perspective you are indeed correct as it applies to sub-atomic entities. It is, however, used as the basis for a more practical problem in instrumentation and control, measurement impinges on the system and changes the characteristic.

I'd make the observation that I very rarely hear the issue described as observer effect, far more frequently we'll discuss uncertainty, although that does pre-suppose an understanding of the concepts in advance of the discussion.

ALR (talk) 17:42, 25 June 2010 (UTC)

Again, this is incorrect, uncertainty is a concept that limits the information available for two non-commuting observables, whereas the observer effect is merely the much simpler principle that measurement of a single observable forces a wave function to collapse into an eigenstate.

The correct principle is the observer effect. The uncertainty principle's got nothing to do with it. Dauto (talk) 13:37, 25 June 2010 (UTC)

Frequently the Heisenberg uncertainty principle is explained in terms of the observer effect. This is based on Heisenberg's original explanation of the principle (Heisenberg's microscope). However, recent interpretations of the uncertainty principle hold that the principle is a fundamental property of the universe and always valid, and is not simply a result of trying to measure the system. -- 140.142.20.229 (talk) 17:07, 25 June 2010 (UTC)

Yes, we do see that interpretation quite often but it is simply wrong. Dauto (talk) 17:35, 25 June 2010 (UTC)

DIY inspection camera

Is there a way to put together a home-made inspection camera using inexpensive parts? By "inspection camera" I mean something that can feed through a hole no more than an inch in diameter. You can use it to check the plumbing or wiring inside a wall, or to check the condition inside an an air duct. What can you adapt or repurpose for the camera component? --98.114.98.48 (talk) 12:40, 25 June 2010 (UTC)

This is a tiny $13.99 webcam - with LED lighting and infrared capability! All you need is a long enough USB cable and a laptop and you're in business. I'm pretty sure the case is under 1" - but it might be a tight fit. If that's a problem then you might need to remove the pretty plastic casing and make something smaller using electrical tape!

SteveBaker (talk) 13:39, 25 June 2010 (UTC)

Check the articles Borescope and Endoscopy. Cuddlyable3 (talk) 21:17, 25 June 2010 (UTC)

paint and primer in one

does Behr Ultra latex paint and primer in one contain surfactants such as sodium Lauryl sulfate to make the paint mix with the primer ?

the paint im talking about is seen here:

http://www.homedepot.com/Paint-Interior-Paint-Stain/Behr-Ultra/h_d1/N-5yc1vZ1xilZbbbpZ528/R-202182650/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053 —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 14:26, 25 June 2010 (UTC)

It doesn't appear to be just a mixture of paint and primer, so the answer is no. Conventional paint and primer are similar enough to probably not required surfactants to mix (you can try this at home!). However surfactants are widely used in paints anyway.

The lack of requirement for a primer appears to be due to nanoparticles that reduce the porosity of the surface to be painted - I think, the company documentation is not that clear.77.86.123.157 (talk) 14:51, 25 June 2010 (UTC)

I'm guessing that the Aluminium hydroxide and diatomaceous earth are part of the active ingrediantes that make the paint an 'all in one' - mentioned on the MSDS [1], these should be carried by the acrylic (latex) binder just like the pigment. 77.86.123.157 (talk) 15:17, 25 June 2010 (UTC)

i thought oil and water dont mix? primer is oil based and latex paint is water based. does adding surfactants make them mix? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 15:16, 25 June 2010 (UTC)

No, primer can be water or oil based. If you were applying a water based paint you'd 100% certainly use a water based primer. ok maybe not, some people avoid oil based becuase of the solvents, bur water based still stinks, plus oil based paints are gradually being banned. An emulsion of oil/water based paints wouldn't work as planned though - there's no way for the oil component to know to be the undercoat. 77.86.123.157 (talk) 15:20, 25 June 2010 (UTC)

so does it have a water based primer in it ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 18:16, 25 June 2010 (UTC)

Is the product water based or not? It depends what you mean by primer - a primer is just something that treats a surface before painting - this is a primer and paint in one: A primer is a product not an ingredient.77.86.123.157 (talk) 19:26, 25 June 2010 (UTC)

Is it possible to clean a pool with just Baking Soda and Bleach?

I heard a rumor about this. Anyone know anything about it? 148.168.127.10 (talk) 14:46, 25 June 2010 (UTC)

What sort of cleaning do you mean? (algae maybe?) - eg I can clean a pool with a scrubby, some cif and a bucket of water..77.86.123.157 (talk) 14:52, 25 June 2010 (UTC)

oh you must mean this http://wetheadmedia.com/how-to-clean-a-green-pool/ I thought you meant clean the sides.. Both chemicals are replacements for commercial formulations, but you need to know what you are doing, andwill probably still need test kits.77.86.123.157 (talk) 15:46, 25 June 2010 (UTC)

query regarding B.TECH

what does mechanical & electronic-communication{EC} engineering mean? —Preceding unsigned comment added by Spooky92 (talk • contribs) 16:45, 25 June 2010 (UTC)

Can you give more details, it might mean nothing. It might mean a combined course of two disciplines. Which BTECH? 77.86.123.157 (talk) 17:56, 25 June 2010 (UTC)

Big cases of correct theories largely ignored because they came from amateurs

What are some of the big cases where someone without status/credentials/contacts in the scientific community puts out a paper, the paper is largely ignored, and later it is discovered that the paper was right in what it stated? 20.137.18.50 (talk) 16:47, 25 June 2010 (UTC)

Marjorie Rice might qualify, though I don't know if she published her findings. --Sean 17:00, 25 June 2010 (UTC)

I don't think that one counts. Her discoveries were accepted by the main stream mathematitians as soon as they came to their knowlege. Dauto (talk) 17:06, 25 June 2010 (UTC)

I notice that Gregor Mendel wrote a paper describing what he is now known for that was ignored for 35 years. 20.137.18.50 (talk) 17:13, 25 June 2010 (UTC)

One of the best-known cases is John Garcia, who discovered the so-called Garcia Effect, also known as conditioned taste aversion. He had a Ph.D. and worked as a postdoc at Berkeley, but he didn't have any reputation, and his discovery, which now is considered a major part of the history of psychology, was at the time considered so bizarre that he was unable to publish it in any reputable journal. Looie496 (talk) 18:18, 25 June 2010 (UTC)

I have trouble imagining that the theory could be considered "bizarre" — it seems almost obvious. Is there anyone to whom this sort of taste aversion has not happened? Wouldn't you just say, "oh, yes, of course I know that; that happened to me when I was eight years old, even if I don't know why"? --Trovatore (talk) 01:25, 26 June 2010 (UTC)

Can someone with a PhD be considered an amateur? Dauto (talk) 21:28, 25 June 2010 (UTC)

Yes, sure (just having a PhD by itself does not actually make you a member of any particular academic community, much less the one you are innovating in), but probably not somebody working at a postdoc at a major research university. --Mr.98 (talk) 22:27, 25 June 2010 (UTC)

A similar case is Alfred Wegener, whose theory of continental drift was rejected by orthodox science for many years, but is now accepted as the basis of plate tectonics. Ghmyrtle (talk) 21:45, 25 June 2010 (UTC)

Wegener's theory was rejected because it was impossible. It is not the "the basis of plate tectonics"; it posited a different and impossible cause (mechanism) producing the same effects at the surface of the earth. (Cite: Asimov's New Guide to Science, p.174) It is true that scientists wrongly disbelieved that those effects existed, but that was because no possible mechanism was known. If Aristotle had encountered a radioactive substance and theorized that it was warm because it contained the element fire, that would not mean that his theories were "the basis of nuclear physics". Credit is due to Wegener for being partly right, but only for that. --Anonymous, 00:17 UTC, June 26, 2010.

Note, A. Wegener: The hypothesis of continental drift (ca. 1915), evolved to seafloor spreading (ca. 1962), and more recently to the theory of plate tectonics (ca. 1967). He based his publications on cartography, paleontology, glacial striations and old orogenic uplifts. But paleomagnetism, reflection seismology, sonar survey and gravity anomaly survey were needed to etablish the hypothesis. There was a lack of sound data... --Chris.urs-o (talk) 07:03, 26 June 2010 (UTC)

Keep in mind—as has been pointed out by the likes of Carl Sagan and others—that the cases of "amateurs who were totally wrong or actually just cranks" vastly overweighs the extremely limited number of times that an amateur was judged a crank and turned out to be brilliant. Quoth Sagan: "They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown."

Two really famous cases (depending on how you define "amateur") are Wegener and Albert Einstein (came up with the special theory of relativity while working at the Swiss patent office). If you go back historically, of course, the line between professional and amateur is quite blurry until the strong professionalization of science in the 19th century, and even then some fields (like astronomy) still often have a strong history of contributions from amateurs. (Even today, many astronomical discoveries—e.g. comet Hale-Bopp—are done by amateurs pointing telescopes at the sky.) --Mr.98 (talk) 22:27, 25 June 2010 (UTC)

It's worth noting that in Einstein's case his Annus Mirabilis papers were accepted for publication in a prestigious journal (Annalen der Physik), and that his work – particularly the special theory of relativity – were generally widely and rapidly accepted by the scientific community. TenOfAllTrades(talk) 22:43, 25 June 2010 (UTC)

Well, it's worth noting that the papers were accepted for publication largely through the influence of a single person (Max Planck), who acted as his sponsor, more or less. It was nothing like the expectations of modern peer review and there is little doubt that Einstein's papers would have been rejected had the standards been a bit higher. If you read his classic SR papers through the lens of what "physics in his time" was considered to be, they are extremely unusual, very amateurish in many ways (they read more like an exercise in logic than a work of physics, even theoretical physics, and have horrible citation practices). As an experiment give "On the Electrodynamics of Moving Bodies" a read without considering that the author is Einstein and obviously correct and you'll see what I mean—it's a very odd paper and if it had the name "Joe B. Crank" attached to the top of it you'd probably dismiss it as nonsense.

And to say that SR was rapidly accepted is an exaggeration. Most physicists did not regard it as "physics" at all in the traditional sense (they considered it philosophy or simply irrelevant), with the exception of the photoelectric effect, which they did find to be a rather convenient explanation. By the time Einstein put together GR it was considered something that needed to be known about but not at all unambiguously true. After the GR experiment of Eddington, relativity as a whole got a lot of attention but was still considered extremely scientifically controversial. Even after Einstein was generally recognized as a great scientist (say, in the 1920s and 1930s) by many (i.e. the newest physicists) it was still a pretty controversial theory. It was not until the 1940s and 1950s that it really became considered one of the gold standards of physics. Now one can say that many of the physicists we now consider to be the "winners" in history (e.g. Bohr and Eddington and even Planck) thought Einstein was pretty brilliant from the start. But they are not actually representative of the larger scientific community as a whole in Einstein's time, and depending on what one defines as your community, the up-take was really quite different (e.g. the physics communities in Germany, France, England, USA, Russia, and Japan all received relativity pretty differently). I'm not saying this to be pedantic, but studies on the reception of relativity are sort of a "canonical" topic amongst historians of physics and it was anything other than straightforward. (For a nice overview, Helge Kragh's Quantum Generations is great, and has an excellent graph of the early distribution of scientific publications on relativity and a great section discussing it, which you can see in Google Books. You'll notice it takes about 5 years for even the Germans to really start to get interested in the subject.) --Mr.98 (talk) 23:57, 25 June 2010 (UTC)

My aim here was mostly to respond to the original poster's question — specifically, to note that Einstein doesn't really qualify under the terms given. The fact that his work was supported and endorsed by Planck by itself suggests that he was not without academic contacts. And whatever else may be said about his papers, they certainly weren't 'largely ignored'. (To be fair, Einstein was far from the only scientist to benefit from the much laxer variety of peer review practiced a century ago.) I'll grant that his work wasn't universally and completely accepted for years (sometimes decades) and that there were geopolitical factors which hampered its acceptance in some countries (particularly France), but that's not unusual even for non-crank science published by well-known scientists. Consider the Higgs boson. It was first postulated in 1964, it's part of the Standard Model, but it's still not totally accepted — and it's still possible to have a career as a respectable scientist developing Higgs-less models. (One of those models might even be correct!)

The graph you've linked to is interesting. The figure legend observes that (on the subject of relativity) there is a "...decrease in the total number of publications between 1910 and 1915..." and notes that this feature "...probably reflects that, by 1911, the special theory of relativity was widely accepted among physicists and was no longer considered to be at the cutting edge of physics." I would tend to argue that five years is actually not a long time for a major new theory to gain prominence (if not predominance) in physics, particularly one for which experimental tests are difficult — and in an era when publications had to be distributed on paper and interpersonal communications tended to travel by snail mail. TenOfAllTrades(talk) 02:27, 26 June 2010 (UTC)

I think Einstein qualifies, even though he was shepherded in by someone "inside" the institution. I don't think "amateur" is meant to mean "totally ostracized". Einstein was an outsider. The only reason he got taken seriously at all is because an insider decided he wasn't a crackpot.

The graph and the accompanying chapter make it a bit more clear what is going on, especially if you recall that Einstein wasn't the first (or only) person talking about relativity theories (he was entering into a field already populated by the likes of Poincaré, Lorentz, etc.). Einstein's own specific take on things—that there is no such thing as universal time, for example—was really not accepted as true for quite a long time. By the time Einstein started work on GR, the idea of relativity and Einstein's contributions (again, because of Planck's sponsorship, in part) was enough of a topic that it warranted some attention from other theorists, but it was still a very, very minor part of how physics was thought of at the time, and considered irrelevant by most. It was not until 1919—for both scientific and political reasons—that it really became something that people had to grapple with (because of the immense attention given to it, and the huge implications saddled on it), and even then it was certainly still considered extremely controversial, often incorrect, by most "established" physicists.

Anyway, in the end, I don't think Einstein is a bad case study for this kind of question, even if he is obviously a rather singular historical figure. He's definitely an outsider, and he definitely had a struggle in getting his work accepted, in part because he was not in synch with the priorities or methods of the predominant physical community, and because the conclusions he proposed were seen as very out of step with how contemporary physics was developing. (Today we always refer to aether theory as the "classical" view, but this is quite ahistorical—it was considered a radical, unifying theory for the late-19th century and early-20th century, a real vanguard composed of really quite sophisticated mathematics. It was wrong, of course, but it was as "revolutionary" as what replaced it.) He also illustrates the way an outsider can get a "shortcut" into the mainstream discussions: get a major sponsor who can't be dismissed, weasel your way into mainstream journals, follow up some rather vague theories with really quite striking experimental reports. (And while you're at it, become a major international icon. ;-) --Mr.98 (talk) 12:12, 26 June 2010 (UTC)

As a chemist, my own favorites are John Dalton and Amadeo Avogadro. The former was excluded from university because of his religious beliefs; he wasn't exactly an "amateur", but he described atomic theory while earning his money as a schoolteacher and his theory would not be fully accepted for many decades. Avogadro is a more flamboyant character, an ecclesiastical lawyer but part-time revolutionary... still, he found the time to imagine Avogadro's Law, for which he never received credit during his lifetime: now, it is considered one of the bases of modern chemistry, hence the Avogadro constant named in his honour. Physchim62 (talk) 23:29, 25 June 2010 (UTC)

See http://www.environmentalgraffiti.com/sciencetech/the-5-most-important-amateur-scientists/940. I do not know how quickly their discoveries were accepted.—Wavelength (talk) 00:31, 26 June 2010 (UTC)

It's an interesting stab at a list, for something that gets caught up in real definitional issues, anyway. Faraday, for example, was certainly an outsider when he started, but he apprenticed under Davy before doing his really fundamental work. Does that make him an amateur? (Or just of low class in a highly stratified society? Is there a difference in 18th century British science?) Mendel was not so much an "amateur" as in a parallel profession, one that did value agricultural research and had cross-overs to mainstream academic biology (though Mendel himself was pretty much at the fringes). He wasn't denounced as a quack or anything, but he was ignored, mostly because his work just didn't have much exposure and even Mendel didn't think it was a general theory of heredity. His work was "rediscovered" many years later and translated into a somewhat different framework. Edison pushes that nice boundary between "inventor" and "scientist," wherever we want to try and draw that line. Evans and Leavitt I don't know enough about to comment, except that again there is a long, rich tradition of amateur astronomy, one that continues to this day. --Mr.98 (talk) 01:18, 26 June 2010 (UTC)

SeeHistory of radio. Discovery of the ability to transmit and detect high frequency electromagnetic radiation which Thomas Edison called "etheric force" in 1875, and which separately was discovered in 1878 by David Hughes, were rejected as "mere electromagnetic induction" by leading scientists of the day. When Hertz in 1886-1888 did similar experiments more mathematically based on Maxwell's theory the results were accepted. Hertz was better credentialled, and had a systematic mathematical and theoretical basis for the observations. Edison similarly discovered and wrote up Thermionic emission, the basis for diode vacuum tubes, but scientists of the 1880s rejected it as merely charged bits of carbon coming off the filament, and decades later Fleming used the same tubes with improvements to invent the diode valve or vacuum tube, with a better physical explanation, after the discovery of the electron by others circa 1897. Scientists of the era considered Thomas Edison and Hughes to some extent to be mere amateurs/tinkerers/inventors. Edison (talk) 04:23, 26 June 2010 (UTC)

In the 18th century, Kant realized that some of the "stars" are actually galaxies. In the 19th Century, a lot of bad science "discredited" this brilliant conclusion. Not till the 1920s was it established beyond doubt. 63.17.62.100 (talk) 06:53, 26 June 2010 (UTC)

Ants in my vacuum cleaner

If I use my vacuum cleaner to suck up an ant trail, will they survive the journey up the tube to the filter bag, or do I have to empty it to prevent further infestation? Hemoroid Agastordoff (talk) 17:04, 25 June 2010 (UTC)

The ants will survive (at least a good majority will). I remember reading that if you want to kill the ants, you could vacuum up some kind of dust right after you get the ants, but I can't remember what it was. Talc maybe? Or diatomaceous earth? Googlemeister (talk) 18:19, 25 June 2010 (UTC)

I think diatomaceous earth will work -- it has a dehydrating effect on insects (including ants). FWiW 67.170.215.166 (talk) 02:36, 26 June 2010 (UTC)

Disposing of the bag promptly is a good idea. Edison (talk) 04:07, 26 June 2010 (UTC)

Ant dust. Mitch Ames (talk) 13:17, 26 June 2010 (UTC)

Urologists

How many urologist are there in new jersey68.236.210.120 (talk) 17:19, 25 June 2010 (UTC)

I've added a section header for this question. Comet Tuttle (talk) 17:31, 25 June 2010 (UTC)

428 [2] 77.86.123.157 (talk) 17:51, 25 June 2010 (UTC)

How many urologists does it take to change a lamp bulb? Cuddlyable3 (talk) 14:17, 26 June 2010 (UTC)

Dunno. Tell us/--RampantHomo (talk) 20:15, 27 June 2010 (UTC)

One. S/he holds up the light bulb and the world revolves around them. (Works for any kind of medical doctor.) -Atmoz (talk) 20:29, 28 June 2010 (UTC)

Memory

I have heard there is one memory condition where one is unable to forget out anything and everything you experience is remembered forever. The advantages are obvious: One would never forget one's in-laws' birthdays for example ;). But What Would be some disadvatages to having such a permanent memory? Would it be harder to recall things? 76.229.149.7 (talk) 17:59, 25 June 2010 (UTC)

I think you're looking for hyperthymesia. An interview with the first identified case suggests that she doesn't find it harder to recall things; rather, things are recalled whether or not she wants to. She certainly expresses disadvantages to the condition in the interview. In particular, the inability to forget (and moreover, the inability to avoid remembering) tragedy is pretty lousy. Having a merely eidetic memory has a lot more practical upside. — Lomn 18:06, 25 June 2010 (UTC)

There is no such condition. There are people with extraordinary memory for events, but not perfect. There is however a well-known work of fiction by Jorge Luis Borges describing such a person, called Funes the Memorious. The most common problem for people with extraordinary event memory is difficulty in seeing patterns -- when somebody remembers every detail of every event, they have trouble seeing what the events have in common. The Russian psychologist Alexander Luria wrote a wonderful book called The Mind of a Mnemonist] about such a person. Looie496 (talk) 18:10, 25 June 2010 (UTC)

I've heard of people with such a "condition"...while not a medical condition, persay, the phenomenon does exist...I remember it being mentioned in a National Geographic article. [3] Ks0stm ^(T•C•G) 21:42, 25 June 2010 (UTC)

Perhaps not that relevant, but Gene Wolfe's The Book of the New Sun has a protagonist with an Eidetic Memory. The condition is a prevalent theme in the book, and is explored in several ways. Zigorney (talk) 19:14, 25 June 2010 (UTC)

You may want to read this book (http://www.amazon.co.uk/Delete-Virtue-Forgetting-Digital-Age/dp/0691138613) it is all about the virtue of forgetting and how useful it is (for society as well as individuals). It's an interesting area but whilst I have this book I must admit it's not the best read (a bit repetitive and a bit woolly in terms of their proposed solutions) but it has a lot about the disadvantages of never forgetting (that you wouldn't be able to escape ones past being a major issue). ny156uk (talk) 20:32, 25 June 2010 (UTC)

Some neurobiologists and cognitive psychologists think that once something makes it from short term memory into longterm memory (via attention being paid to it, through analysis and study, through rote rehearsal), it doesn't really go away, but we just lose the ability to access it. If I've forgotten someone's name, recognition is far better than recall. Same for "forgotten" addresses or phone numbers. The right prompt can cause it to be right there. But memory can be reconstructive, and we can be fooled into "remembering" things that never happened, by the right instruction [4]. An electrical stimulus in the temporal lobes of the brain during brain surgery, as reported by Wilder Penfield, can supposedly cause random forgotten incidents from the distant past to be relived in vivid detail in some individuals. Or maybe the "memories" are created out of fragments like dream experiences. Alexander Luria wrote "The Mind of the Mnemonist" about Solomon Shereshevsky, who could remember amazing amounts of detailed information. He sounds much like the mnemonist in The 39 Steps (1935 film). Some of us can probably recall a lifetime of factual information, but fail to recognize someone they were introduced to 5 minutes ago. Edison (talk) 23:15, 25 June 2010 (UTC)

since we're onto novels, try Black Milk by Robert Reed. interesting view on the topic.

The problems with excessively high retention are mostly social: (1) being able to remember accurately events which others have revised is uncomfortable (most people's memories are inaccurate and revised in various self-serving ways, and do not like being reminded that things were not as fun and noble as they remember them to be). (2) if the retention includes emotional states as well as simple factual recall, one may be left re-experiencing a lot of unpleasantness. consider being forced to remember how you felt (in full detail) whenever you think about high school. --Ludwigs2 03:56, 26 June 2010 (UTC)

It would be so easy to win at Trivial Pursuit and similar trivia games that either such a person would have to throw games by "not knowing the answer" or people would hate them. Edison (talk) 04:06, 26 June 2010 (UTC)

I think that it may be hard to focus on a task at hand if you are continually bombarded with vidid memories of yesteryear. Vranak (talk) 18:02, 26 June 2010 (UTC)

When you consider the numbers involved, remembering literally everything is quite impossible. Consider your eyes: Suppose we imagine that they take ten snapshots of the world per second - and at (let's be generous) 1000x1000 pixels of resolution and with (again, being generous) just 8 bits of color fidelity. 10 megabytes per second of data flows into the brain the entire you're awake - if you stay awake 10 hours a day then that's 130 terabytes of data per year...add in audio, touch, taste, smell, body positioning, pain, emotion, ideas we think up ourselves...we could probably double that number. Over a 70 year lifespan, that's 18 petabytes. We have about 33 billion neurons with about 10,000 synaptic connections each. It's hard to turn that into bits and bytes - but for sure, there isn't any possibility of storing more than around a terabyte. My home computer has more memory than that - but there aren't many places in the world where you can store 18 petabytes...WalMart's data storage center (which stores every credit card transaction ever made at one of their stores) has less than that. Google have more - but not a lot more!

The literal impossibility of storing that much information in a brain that's about 6" across means that we're simply incapable of storing that much data. Hence the brain has to do aggressively lossy data compression - and why it is vital to our ability to continue to function that we're able to forget unimportant things - or to simplify and 'soften' memories of more distant events. I can remember the day my son was born and the day I got married pretty well - but I have zero memory whatever of the 23rd of January 1964. The reason why we forget things is to make room for the new things we need to have memory of. Memories that you refer to a lot are strengthened - memories you don't use fade away. This isn't a flaw in the system, it's a very clever part of how evolution has 'designed' our brains to cope with vast data input and horribly limited data retention ability.

SteveBaker (talk) 13:08, 28 June 2010 (UTC)

Silicone solvent?

I'm trying to remove some 3-year old 100% silicone caulk from a textured glass panel. The textured glass prevents me from using razor blades. When I try to peel or rub the silicone off, it just comes off in bits. Is there any chemical method to removing silicone? —Preceding unsigned comment added by 70.167.58.6 (talk) 18:11, 25 June 2010 (UTC)

In short, no. There is no simple way to chemically remove silicones from glass. You can sometimes remove them physically, if you're lucky, but it's usually not worth the bother (as you seem to be discovering). What do you want to do with the glass afterwards? Physchim62 (talk) 18:26, 25 June 2010 (UTC)

It's glass from the 40's in an old office. The previous occupants thought it would be neat to affix acoustic foam to the windows using silicone glue. The foam was easy to tear down. But all these islands of silicone remain on the glass. Would a heat gun help to peel it off? Or would it just make a gooey mess? --70.167.58.6 (talk) 18:33, 25 June 2010 (UTC)

A heat gun might crack the glass, be careful.

My local DIY store sells silicone remover. Just Google it. --Heron (talk) 18:38, 25 June 2010 (UTC)

The problem with "silicone remover" is that it sticks to the glass itself, making it very difficult to get anything else to stick there. You can't see it, but it's there to prevent any other putty from sticking. If you must keep the glass plates, the best bet is patience and a judicious use of sandpaper (the cheapest works best, just don't scratch any visible bits of the glass) Otherwise, replace the glass. Physchim62 (talk) 18:58, 25 June 2010 (UTC)

Potentially, depending on how aged the sealant is you could used wd40/diesel/other oil (also consider nitromors or equiv) to try to soften it - it wont' remove it but it might make your job easier.

Disposable plastic knives (or even bluntish metal knives), as well as rotary brass brushes may be helpful tools in getting it off.77.86.123.157 (talk) 19:39, 25 June 2010 (UTC)

There's a technical paper here [5] it suggests

• tetramethylammonium hydroxide (TMAH) in alcohol - you probably can't get this
• solvents such as CH2Cl2 and DMF (again "nitromors" is a CH2Cl2/MeOH mixture - it might work)

as well as fluorides

A home grown version might be caustic soda in methanol, or isopropanol - but this also is very dangerous to work with in terms of burning your hands or face off.77.86.123.157 (talk) 19:50, 25 June 2010 (UTC)

You could also try DMSO. I had a professor that used to say "If it doesn't dissolve in DMSO, it wasn't meant to dissolve". Accodring to our article, it is safer than DMF and other similar compounds. --Jayron32 17:08, 26 June 2010 (UTC)

Silicones tend to form chemical bonds with glass (the tubes of silicon contain chemicals that polymerise) - that's why hydroxide or fluoride is needed to debond it. DMSO could make a good solvent for these, but probably won't work on its own. —Preceding unsigned comment added by 77.86.115.159 (talk) 17:19, 26 June 2010 (UTC)

A word of warning here: Fluoride in DMSO will enter the body via skin contact, and will have toxic effects similar to those of concentrated hydrofluoric acid (deep burns, etc.) So if this is what you plan on using, make ABSOLUTELY sure that you wear nitrile gloves and clothing (these are impervious to DMSO). Clear skies to you 67.170.215.166 (talk) 05:38, 27 June 2010 (UTC)

Why nitrile gloves? They will just dissolve. See Dimethyl_sulfoxide#Safety. --Chemicalinterest (talk) 18:23, 27 June 2010 (UTC)

Right, I meant neoprene, not nitrile. I stand corrected. 67.170.215.166 (talk) 01:29, 28 June 2010 (UTC)

June 26

Cobalt (III) oxide

What is the oxidation state of cobalt in Co₃O₄? --478jjjz (talk) 03:04, 26 June 2010 (UTC)

Both +2 and +3 as the article title suggests ie Co₃O₄ links to Cobalt(II,III) oxide , the II and III are roman numerals - it's Stock nomenclature. 77.86.115.159 (talk) 03:26, 26 June 2010 (UTC)

If cobalt's oxidation number is +2, then Co₃⁺² O₄^-2; so the net charge is 6-8 = -2. However, this can't be because the net charge is supposed to be 0.--478jjjz (talk) 03:37, 26 June 2010 (UTC)

--- For cobalt (III) oxide

If cobalt's oxidation number is +3, then Co₃⁺³ O₄^-2; so the net charge is 9-8 = +1.--478jjjz (talk) 03:46, 26 June 2010 (UTC)

Seriously, read the article - Cobalt's charge is 2 and 3 - that is one third have charge 2, and two thirds have charge 3 - ie it's Co²⁺(Co³⁺)₂ (O^2-)₄ . It has the spinel structure, the spinel article has more information.77.86.115.159 (talk) 03:52, 26 June 2010 (UTC)

I didn't know that one element could have 2 different oxidation states in one compound. Thank you. "Co²⁺(Co³⁺)₂ (O^2-)₄" was extremely helpful.--478jjjz (talk) 04:06, 26 June 2010 (UTC)

N₂H₄O₃ or NH₄NO₃ might be an example for nitrogen.--Stone (talk) 07:58, 26 June 2010 (UTC)

Other well known examples are magnetite, Fe²⁺(Fe³⁺)₂ (O^2-)₄, and Prussian blue, (Fe³⁺)₄([Fe^II(CN)₆]⁴⁻)₃. Prussian blue, or iron(III) hexacyanoferrate(II) is particularly interesting because there is another compound, traditionally called Turnbull's blue, which is iron(II) hexacyanoferrate(III), (Fe²⁺)₄([Fe^III(CN)₆]⁴⁻)₃. It turns out that the two compounds are the same: you cannot tell which iron atoms are iron(II) and which are iron(III) in the compound. Physchim62 (talk) 10:50, 26 June 2010 (UTC)

That Turnbull formula looks weird: hexacyanoferrate(III) would be a 3− not 4− anion? Iron(II) hexacyanoferrate(III) would be (Fe²⁺)₃([Fe^III(CN)₆]³⁻)₂ The prussian blue#Composition section is an interesting example of how important it is to document the experimental method:) But it also does state not that so-called Turnbull's blue (the preparative method) is iron(III) hexacyanoferrate(II), but instead that it rapidly converts by electron exchange to become it (from the other oxidation-state form). And that there is good evidence which iron oxidation state is in the cyanide complex and which is the counter-cation. DMacks (talk) 16:57, 26 June 2010 (UTC)

Alpha Centauri at 1 G acceleration

How long would it take to reach Alpha Centauri on a ship that accelerated at one G (about 9.8 meters per second per second) for half the trip then spent the last half decelerating at that same rate. Would it even be possible to maintain that rate of acceleration for that long without crossing the speed of light?

I ask this because this would be a convenient way to make "artificial gravity" during the transit. Seems like it would make life a lot easier for the passengers.

63.245.168.34 (talk) 03:25, 26 June 2010 (UTC)

The speeds and distances associated with continuous 1G acceleration in space have been frequent topics on the Science Reference Desk. At [6], for instance, I linked to a site with a relativistic calculator. It sems to be defunct. but the Internet Archive Wayback Machine lets us regress in time (so to speak) to a version from May 2008 which lets you input variables and derive the info you seek.Alpha Centauri is 4.365 light years away (per the Wikipedia article. The webpage says 4.3 light years). The calculator says the trip would take just under 6 years to an observer left behind on Earth, but only 3.58 years as experienced by a traveller on the ship, which would reach a max speed of .952C. Sure the artificial gravity would make life easy for those on board, but figuring out how to build an engine to provide 1G acceleration for 3.58 years would make life a living hell for the engineers assigned the task of designing it and the persons required to pay for building it. Edison (talk) 04:02, 26 June 2010 (UTC)

As far as "crossing the speed of light", it would take an infinite amount of energy for any particle to reach the speed of light. See Speed of light#Upper limit on speeds. Comet Tuttle (talk) 05:30, 26 June 2010 (UTC)

Okay, this leads to a point I've been confused about for a while. When you think of a normal "constant acceleration", you think of an acceleration due to a constant force. At low speeds, a constant force will yield a constant acceleration as expected. However, when you approach relativistic speeds (as you do in this case), it requires a larger and larger force, and eventually becomes impossible, to maintain a constant acceleration. So the question of "constant 1g acceleration" is not really all that simple. I don't understand how the calculator that Edison linked to accounts for this; can anyone shed some light on this?-RunningOnBrains^(talk) 06:40, 26 June 2010 (UTC)

I presume it doesn't. It isn't a 'practical relativistic calculator' just a 'relativistic calculator'. It presumes you are capable of building a ship capable of reaching '.952C' (or whatever maximum speed for your distance), in other words capable of accelerating at a constant 1G for your travel distance, and surviving that travel. Whether it's likely to be possible is besides the point of the calculator Nil Einne (talk) 07:11, 26 June 2010 (UTC)

Edit: In fact as I somewhat expected it says "Note how the kinetic energy becomes extremely large. Besides this, there are many other practical problems in realizing a star ship (such as hitting small dust particles while moving at relativistic velocities)" and the site does in fact show the maximum kinetic energy as one of the results which in this case is 202430223928 megajoules per kilogram. Nil Einne (talk) 07:14, 26 June 2010 (UTC)

Actually, it doesn't require a larger and larger force (if you deplete fuel, it actually takes less force). What you're thinking of is what's required to maintain a constant 1g acceleration in the original frame of reference. But that isn't possible; that would eventually put you over the speed of light.

In this context, when we talk about a "constant 1g acceleration", we mean in the ship's frame of reference. Assuming the ship's (rest) mass remains constant, that requires only constant force (again, force as measured in the ship's frame).

So if you had some magical source of constant force, you could indeed do this, ignoring as Nil says the hazards of your environment.

But no one knows of any such source. If you carry fuel with you, you'll run out. The Bussard ramjet is an idea for getting fuel from surrounding space, but apparently the current consensus is that it probably won't work (though I tend to be skeptical of that sort of prediction when the limitations all appear to be "engineering difficulties" rather than genuine physical limits). Even with the Bussard ramjet, though, you eventually hit some sort of limit, because the fuel keeps coming at you faster and faster, and eventually the force you have to apply to it to keep it in the reaction chamber is going to equal the outgoing thrust. --Trovatore (talk) 07:28, 26 June 2010 (UTC)

How much matter would have to be converted to energy to produce the calculated 202430223928 megajoules per kilogram of kinetic energy? It should be E/C² but units can be a stumbling block. Dividing 2.02 E17 joules by (3E8 m/sec²)², I get 2.24 kilograms. Then double that, because you have to decelerate, so 4.48 kg of mass would have to be converted to energy to accelerate a 1 kg payload over the specified voyage. How long would it take the Sun to produce enough energy to accelerate that one kg if all the Sun's output were used to drive the spacecraft? Sun says it converts 4.26 E6 metric tons of mass to energy per second. A tiny fraction of the Sun's output from departure to midpoint would produce the specified acceleration over that timespan. It looks like .024 kg per second of matter converted to energy would power the voyage of a million kilogram spacecraft. (Maybe the folks at Alpha Centauri would power the deceleration after the midpoint turnaround). (Note:All calculations are subject to large and careless errors and should be checked). Edison (talk) 20:04, 26 June 2010 (UTC)

Ballistics calculations done with energy are usually misleading. You usually can't get anything but a tiny tiny fraction of the energy you use as kinetic energy of the craft, because almost all the energy is carried away in the other direction by the reaction mass. If you use a solar sail, the "reaction mass" is the photons bouncing off the sail (note that it doesn't help to absorb them instead; you get worse results that way). Solar sails do get better from this perspective as you approach the speed of light away from the light source, because the reflected photons are red-shifted and therefore don't carry away as much of the energy. --Trovatore (talk) 20:30, 26 June 2010 (UTC)

But, if you're relying on the last effect to bail you out once you get near the speed of light, keep in mind that this is giving you improved increase in kinetic energy per unit time in the Sun's frame of reference, not the ship's. From the perspective of the ship, the light from the Sun is red-shifted, and is therefore providing less thrust. --Trovatore (talk) 20:35, 26 June 2010 (UTC)

You could also consider using a laser-driven solar sail. With no reaction mass having to be stored on-board, you don't have any of those nasty restrictions. You can use just one solar sail for the first half of the journey - then when you are halfway there, you release the connections between craft and sail and deploy a second solar sail behind you. The laser light from back home must then hit the original (now disconnected) sail - uselessly accelerating it towards your destination at ever increasing speeds. However, if the first sail is mirrored, the light can bounce off of that and back towards your craft and its second solar sail. That allows you to decelerate throughout the second half of your trip...and perhaps even return home again. Additionally - instead of using a true laser - you could build a gigantic lens system and focus sunlight directly onto your craft. The lens would have to continually and microscopically adjust its focal length as the vehicle gets further away. There are undoubtedly vast problems with building large enough lasers, lenses or mirrors, but those are not issues of fundamental science - they are engineering and financial issues that could probably be overcome given the willpower to do so. However, it's hard to imagine anyone funding such a crazy effort. SteveBaker (talk) 05:57, 27 June 2010 (UTC)

There are some similar questions here, question 7.5 on page 13 is actually about a mirror propelled by a laser. I'm wondering though about how to deal with the fact that a laser beam will always diverge. If the initial beam of the photons appearing out of the laser is L, then the uncertainty in the momentum of the photons perpedicular to the beam direction will be of order hbar/(2L) at best. Dividing this by the momentum in the direction of the beam of h/lambda, gives an angle of divergence of lambda/(4 pi L). You can think of this as giving the width of the peak of the inteference pattern if you were to shine the laserlight on a far away screen. I don't see how one can make this angle arbitrarily small. Count Iblis (talk) 15:01, 27 June 2010 (UTC)

You don't necessarily have to deal with the divergence - after all, the only problem with that divergence is that a lesser percentage of the energy you put into laser ends up propelling the spacecraft rather than shooting off uselessly into space. But since the laser can stay back here in our solar system, we can make it larger to compensate for the wastage due to divergence without making the spacecraft bigger or heavier. If we can build one big solar-powered laser, then we can (in principle) build 100 of them...or 1000 or whatever it takes to deliver enough energy on target. That's why it's only an engineering/economic problem - not a matter of fundamental physics. Similarly, we can make the solar sail larger - if one square kilometer isn't enough - why not make one 10 times bigger and have 1000 square kilometers? Again, it's an engineering issue - not a matter of fundamental physics. SteveBaker (talk) 01:49, 28 June 2010 (UTC)

There has been some distinction between "physical impossibility" and "engineering limitation" - this is a valid distinction to draw. However, we need to make clear that we do not know about some physical possibilities and impossibilities until our engineering capabilities bring us into the regime where those physical laws will start to manifest, so that we can do controlled experiments. For example, it would not have been possible to know that the speed of light was finite until we were able to build machinery precise enough to measure it. So, our ability to develop correct physical theories (and deduce physical impossibilities) was limited by our engineering capability. After we started measuring that the universe behaved in certain bizarre ways, we developed consistent equations and physics to describe those behaviors. I think it is fair to say that there may be as-yet-undiscovered limitations (and possibilities) related to interstellar travel that we currently have no physics to describe. Once we start building giant lasers and spacecraft, we may learn new details about relativistic phenomena. Material properties, fundamentals of energy transfer, and so on, all plausibly might need to be rethought and re-understood in this new regime. Nimur (talk) 20:49, 27 June 2010 (UTC)

Production of Mn oxide

What is the chemical equation if you heat Manganese oxalate hydrate in a crucible in the presence of oxygen?

--478jjjz (talk) 04:11, 26 June 2010 (UTC)

• I have done this experiment. The product is Mn (II) Mn (III) oxide = Mn Mn₂ O₄ I just need to use mass % to figure out the coefficients.--478jjjz (talk) 05:33, 26 June 2010 (UTC)

Manganese(II) oxalate hydrate is Mn(C₂O₄).2H₂O (or sometimes Mn(C₂O₄).3H₂O)

The first step is dehydration:

Mn(C₂O₄).2H₂O → Mn(C₂O₄) + 2H₂O

The decomposition in air gives Mn₂O₃ without any carbon monoxide (see [7])

Mn(C₂O₄) +¾O₂ → ½Mn₂O₃ + 2CO₂ (equation 1)

Manganese(II,III) oxide is formed when Mn₂O₃ is heated, some oxygen is lost:

3Mn₂O₃ → 2Mn₃O₄ + ½O₂ (equation 2)

Combining equations 1 and 2 gives:

3Mn(C₂O₄) + 2O₂ → 6CO₂ + Mn₃O₄

So the overall reaction is

3Mn(C₂O₄).2H₂O + 2O₂ → 6CO₂ + Mn₃O₄ + 2H₂O

77.86.115.159 (talk) 14:18, 26 June 2010 (UTC)

I kowtow before thee. Your response was thorough and simply phenomenal. Thank you.--478jjjz (talk) 02:53, 27 June 2010 (UTC)

No need, we are here to serve .. 77.86.115.159 (talk) 03:05, 27 June 2010 (UTC)

In a vacuum it will form manganese(II) oxide. --Chemicalinterest (talk) 18:25, 27 June 2010 (UTC)

Ion nomenclature

In Manganate#Permanganate, manganate, hypomanganite, and manganite, shouldn't hypomanganite and manganite be switched? Because it should go hypo-ite, -ite, -ate then per-ate, like the chlorine oxoanions.--Mikespedia is on Wikipedia! 07:26, 26 June 2010 (UTC)

This is most likely a typo in the article! Thanks! I will change it.--Stone (talk) 08:06, 26 June 2010 (UTC)

Wait...then is potassium manganite a typo?--Mikespedia is on Wikipedia! 09:59, 26 June 2010 (UTC)

Manganate(V) is hypomanganate, not hypomanganite. The potassium manganite article is just plain wrong, I'll try to fix it in a moment. Physchim62 (talk) 11:08, 26 June 2010 (UTC)

Actually, it was only one sentence which was obviously wrong in potassium manganite, removed now. Physchim62 (talk) 11:32, 26 June 2010 (UTC)

Manganites can also refer to mixed oxides of manganese and other metals (eg [8]). The mineral manganite is MnO(OH), a slightly hydrated form of Mn₂O₃. Physchim62 (talk) 11:32, 26 June 2010 (UTC)

So now what are the correct names?--Mikespedia is on Wikipedia! 12:36, 26 June 2010 (UTC)

IUPAC proposes permanganate, manganate(VI) and manganate(V), along with the systematic names tetraoxidomanganate(1−), tetraoxidomanganate(2−) and tetraoxidomanganate(3−). Physchim62 (talk) 12:58, 26 June 2010 (UTC)

So how about the trivial name?--Mikespedia is on Wikipedia! 13:26, 26 June 2010 (UTC)

Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1222. ISBN 978-0-08-022057-4. give "hypomanganate" as a trivial name for managanate(V), as does Cotton, F. Albert; Wilkinson, Geoffrey (1980), Advanced Inorganic Chemistry (4th ed.), New York: Wiley, p. 746, ISBN 0-471-02775-8. The latter reference (which I've only just looked up) also refutes the potassium manganite article: apparently, the compound formed by the dissolution of manganese dioxide in concentrated potassium hydroxide is K₃Mn^VO₄ (by disporportionation), ie potassium hypomanganate. Physchim62 (talk) 13:35, 26 June 2010 (UTC)

I've corrected potassium manganite, which now redirects to potassium hypomanganate. Physchim62 (talk) 15:29, 26 June 2010 (UTC)

... manganite is a IV species, I've put Potassium manganite up for speedy deletion. Potassium hypomanganate seems fine.77.86.115.159 (talk) 16:17, 26 June 2010 (UTC)

Mixed metal oxide manganites do exist - I've created a temporary hat note from manganite.

These are quite notable eg [9] - if anyone wants to create an article about these compounds please do. They appear to be of interest due to their magnetic properties ie Computer hard disk=$$$ eg [10] There really should be an article on these...Sf5xeplus (talk) 17:03, 26 June 2010 (UTC)

Lanthanum strontium manganite already exists, although it's not in wonderful shape. Physchim62 (talk) 18:28, 26 June 2010 (UTC)

Mixed-valence is currently a redirect to inner sphere electron transfer, an article that does talk about mixed-valence compounds. Seems the relevant section or two could split out into its own article and extended on this topic. DMacks (talk) 17:17, 26 June 2010 (UTC)

(edit conflict) Yes, indeed. Those mixed valence manganites seem to be based on manganese(III) compounds which are doped to give some manganese(IV). Interesting, there is a potassium compound, K₆Mn₂O₆, which contains discrete Mn₂O⁶⁻
₆ anions [11]: I would call that compound potassium dimanganite. The lithium and sodium manganites, MMnO₂, are mixed oxides with a distorted NaCl structure. Physchim62 (talk) 17:19, 26 June 2010 (UTC)

So now they go permanganate, manganate, hypomanganate and hypomanganite?--Mikespedia is on Wikipedia! 02:47, 27 June 2010 (UTC)

And how about manganate(IV)?--Mikespedia is on Wikipedia! 02:50, 27 June 2010 (UTC)

Not quite:

+7 permangante

+6 manganate

+5 hypomanganate

+4 would be manganite - if we had a good example..

+3 would be hypomanganite ... These are for oxo-anions - for metal oxides in general people call them manganates or manganites irrespective of oxidation state.. (sometimes they get it right, and call Mn3+ a hypomanganite, but not often..)

Or just use manganate(n)

It's all described here [12]

77.86.115.159 (talk) 03:08, 27 June 2010 (UTC)

Eating late leads to weight gain?

I know it's repeated a lot by non-scientific sources (cover of magazines) but can anyone point me towards some scientific sources, or something similar, that discuss if eating before going to sleep increases weight gain (than eating the same diet, but only at a different time)? Shadowjams (talk) 07:39, 26 June 2010 (UTC)

I don't know of any such sources, but I'm butting in just to point out that this is not, in my opinion, really the right question. The right question is, if you schedule your evening meal early vs late, will that make a difference in your weight? You can't assume that your dietary intake will be the same in the two scenarios. It's possible that one of them will make you overall hungrier than the other. --Trovatore (talk) 07:43, 26 June 2010 (UTC)

I understand the distinction you're making, and my question is the original one. I'm interested in the nutritional / metabolic question rather than the public health considerations. You bring up a good point though: that though may be the reason for so much popular culture repetition of that statement. From a public health perspective the causation is less important than the correlative effect. Shadowjams (talk) 08:34, 26 June 2010 (UTC)

Oh, no, it's still causation. Just with an extra link in the causal chain. Correlation could be an indication of causation in the other direction, or a common cause for the two effects; that's not what I'm talking about. --Trovatore (talk) 09:16, 26 June 2010 (UTC)

Here's a BBC article [13] which is about breakfast size. It makes it sound like a behavioral thing, as you say. But wait! Here's a more recent one [14] about eating late at night, which makes it sound metabolic (and highly speculative). 213.122.29.174 (talk) 11:16, 26 June 2010 (UTC)

I remember hearing that there was a study that claimed people who ate more at night were fatter than people who didn't, but then subsequent investigation showed that the study hadn't properly looked at how much people were eating the rest of the time, so really all the study showed was that people who ate more tended to be fatter. I can't find this story, however. 86.164.57.20 (talk) 14:32, 26 June 2010 (UTC)

Well, a lot of bodybuilders will have a late night shake since they believe it'll prevent muscle breakdown. TheGoodLocust (talk) 17:38, 26 June 2010 (UTC)

Thank you all. That BBC link seems to sum up my instinct, "At this stage, the results could still be interpreted as controversial when applied to humans." Maybe I need to spend some quality time on pubmed. Shadowjams (talk) 09:18, 27 June 2010 (UTC)

Sensing colours

What causes the difference between sensing colours in a coloured material and in coloured light? For example, to me, a reddish violet colour reflected from some material looks delightful, but exactly the same colour being displayed by a computer screen looks very different, even some disgusting. Is that a matter of a colour system or does the brain perceive the information differently? --87.95.51.116 (talk) 13:22, 26 June 2010 (UTC)

By "exactly the same" colour you mean that you perceive the same colour whereas colours can have very different spectra but seem the same. The colours on a computer screen have to be made from the 3 available primary colours and they limit the range of possible colours. In the case of a material one's perception is affected by knowing that the surface has a texture that can be touched. Cuddlyable3 (talk) 14:05, 26 June 2010 (UTC)

Other factors that may explain the difference you perceive are that the screen image flickers, and the material is lit by ambient light of a certain colour for which you unconsciously compensate. Cuddlyable3 (talk) 14:11, 26 June 2010 (UTC)

See gamut for the technical details of how our eyes respond to colour, and the limited range most monitors have. CS Miller (talk) 16:05, 26 June 2010 (UTC)

When you look at a colored material, the light reaching your eye is determined by a combination of the color of the material and the color of the illumination, but your visual system automatically subtracts the color of the illumination, to such a high degree of perfection that we are generally not even aware of the process. When you look at a colored monitor, the visual system again attempts to compensate for illumination, but the result is very different. Thus you really aren't seeing the same thing at all in the two cases. In fact it isn't ever correct to say that a material has the same color as a light unless the lighting conditions have been precisely calibrated, and even then a small change in lighting will cause the appearances of the two to diverge. Looie496 (talk) 04:18, 27 June 2010 (UTC)

Some considerations are:

• The aesthetic effect of a slight texture.
• Shiny reflections (particularly highlights). On hard, rough surfaces such reflections will be fragmented, but still present.
• The reflection of light (which may be strongly coloured) from other nearby objects. 3D artists know this as radiosity, and it is important to realism and prettiness.
• Related to this is that parts of the object further away from other objects (or walls) will be more brightly lit. This has an effect even when the object is viewed close-up. Outside of computer screens, we rarely encounter objects which present areas of flat colour of a single tone (and just as well, because it would be confusing.) We don't tend to be conscious of this, though, and I think it might be the effect most important to your question - surfaces which appear to be a single tone really aren't. You can verify this by taking photographs and inspecting them digitally.
• In artificial light, the parts nearer the light source are more brightly lit (because of the spread of the light).
• Internal illumination of a surface can make the whole thing glow (this would tend to make it more similar to a flat colour on a computer screen, though). Transparency and refraction may matter.
• Oddities of various materials which cause tone and hue variations depending on the angle of the surface (or a local part of it) to the eye. The pile of velvet produces an effect similar to lenticular printing. Some materials are iridescent.

213.122.13.154 (talk) 11:02, 27 June 2010 (UTC)

toxic to fish ?

There was an NPR story[6] this morning about the use of Dawn dish detergent in the BP oil spill.

arent soaps toxic to fish ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 17:49, 26 June 2010 (UTC)

This does not directly address your question, but presumably the soap is used to clean aquatic birds, like pelicans, and aquatic mammals, rather than fish. --Jayron32 17:56, 26 June 2010 (UTC)

Yes. Conventional soaps (soap bar) are harmful because they reduce the level of oxygen in the water. Liquid detergents are similarly harmful; they also damage the fishes gills, as well as they eggs, and make the absorption of toxic chemicals more likely.

Old fashioned detergents, and laundry detergents are also toxic to fish for other reasons - lowering pH and presence of phosphate causing algae blooms. (not all algae blooms are harmful, but some are)

It's summarised here [15] in the third section. that's about freshwater, but it's similar for marine as well

Also see http://www.sciencedaily.com/releases/2009/03/090316101430.htm 77.86.115.159 (talk) 18:13, 26 June 2010 (UTC)

If you are refering to this NPR story, Dawn dish detergent is used more on birds and turtles and such, an example being the Pelican pictured here.

"Dawn spokeswoman Susan Baba says [[...]] the reason Dawn is so good at cleaning birds without hurting them is that it was designed to erase grease from dishes without harming hands. The exact formula is a secret, but she says the key is balancing the surfactants — the chemicals that cut the grease." Dunno if that helps clarify anything. :) ^Avicenna_sis @ 18:49, 26 June 2010 (UTC)

It's important to note that there are 2 types of detergent being used here:

• Dawn : used to clean birds etc - this is being used (I assume) on land, and may not come into contact with fish
• 'Oil dispersants': these are the 'detergents' that are used at sea to disperse the oil slick, they are toxic to fish (as is the oil, fundamentally)

'Dawn' isn't being poured directly into the Gulf of Mexico as such.77.86.115.159 (talk) 19:16, 26 June 2010 (UTC)

Life expectancy in the UK

A newspaper says "He [UK politician] pointed out that in 1940, when the retirement age was set at 60 for women and 65 for men, life expectancy was 72. Today it has soared to 89 for men and 90 for women". Is there any truth in the latter claim in particular? Thanks 92.15.5.103 (talk) 19:56, 26 June 2010 (UTC)

Seems No. See http://www.statistics.gov.uk/cci/nugget.asp?id=168, there is more detailed data in the links on that page.77.86.115.159 (talk) 20:03, 26 June 2010 (UTC)

It's possible that this is a statistical balls up (where did you read it)?

eg http://www.independent.co.uk/news/uk/politics/mens-pension-age-up-to-66-from-2016-2009087.html appears to be confusing percentage expectancies of reaching 65 years and life span - ie 90% of women live to be 65? Is that what you got? 77.86.115.159 (talk) 20:09, 26 June 2010 (UTC)

City AM, 25th. June 2010, page 9. 92.15.5.103 (talk) 21:40, 26 June 2010 (UTC)

Doesn't look like misreporting - the govermental site gives the same words.77.86.115.159 (talk) 22:19, 26 June 2010 (UTC)

http://www.dwp.gov.uk/newsroom/ministers-speeches/2010/24-06-10.shtml repeats similar - looks like the minister's speech contains an error if the goverment statistics are to be believed - I'm fairly certain someones balls up their table.77.86.115.159 (talk) 20:13, 26 June 2010 (UTC)

Having had a quick look at the data it definately seems that ~90% of people can expect to live to 65 in the UK .. this appears to be the truth (though the male female difference appears to be ~5% not 1% ..as of 2006-8 see interim life tables). 77.86.115.159 (talk) 21:04, 26 June 2010 (UTC)

On BBC World the figure of 89/90 years was also mentioned, but it was said that some who is 20 years old now can expect to live that long. Count Iblis (talk) 00:12, 27 June 2010 (UTC)

That seems rather optimistic and assumes the UK's economy and technology will progress at the same rate - much less regress.TheGoodLocust (talk) 01:11, 27 June 2010 (UTC)

Actually, it probably assumes no progress at all. Any attempt to factor in future progress involves lots of guesswork, so it usually isn't done. They calculate these probabilities by assuming that the chance of the person in question dying during the year when they are X years old is the same as the proportion of people that were aged X a year ago that died during the last year (actually they usually average over 3 years or so, but that isn't important). So, it's how long you could expect to live if stuck in a time loop living the last year again and again. The figure is wrong, though. The Office of National Statistics (see the interim life tables linked to above) says a man aged 20 can expect to live to 78 and a woman to 82 (that's less than a year older than expectancy at birth, since we've all but eliminated infant mortality in the UK - the chance of a child dying before turning 20 is tiny). I don't know what BBC World was talking about. --Tango (talk) 13:38, 27 June 2010 (UTC)

Perhaps for this purpose (finding a good argument for increasing the pension age), the government asked the people doing to calculations to be less conservative and make some reasonable assumptions about progress in medicine? Count Iblis (talk) 14:32, 27 June 2010 (UTC)

It's possible, but if it were possible to make such reasonable assumptions why wouldn't they always be used? Life tables are mostly used for determining fair values for pension schemes and life insurance policies, and people doing such calculations would have exactly the same requirements from their data as people wanting to work out a fair retirement age. --Tango (talk) 16:20, 27 June 2010 (UTC)

Calcium Hypochlorite

I have about 10 kg left of dry powder bought as Calcium Hypochlorite three years ago. It is in a non air-tight (but child proof) plastic container and seems to have lost its zing. So does this slowly decompose to CaO in air? The WP article only lists reacting with CO2 and I cannot believe enough of that has got through the container lid. Roughly how long can I keep it if I get some more (so how much should I buy)? The large compact tablets of presumably the same thing were airtight sealed and seem to have lasted better. --BozMo talk 21:13, 26 June 2010 (UTC)

This book [16] page 523 mentions that the stabilily is reduced by absorbed water content, and that typical compositions loose about 3-5% effectiveness per year. This [17] states that it 'rapidly decomposes on exposure to air' and 'liberates chlorine with water' - so a non air tight container, especially in a damp enviroment will go off eventually.

It seems unlikely that 10kg has gone off.. I recommend removing some from the top of the container, and seeing if it's better lower down.77.86.115.159 (talk) 21:48, 26 June 2010 (UTC)

The decomposition in air at room temperature is not totally straightforward, some chlorine will be evolved, but not all - roughly Ca(OH)Cl 'basic chloride' is roughly what is left over from:

4Ca(OCl)₂ + 2H₂O >> 4Ca(OH)Cl + 3O₂ + 2Cl₂

though a variety of reactions can occur including a slow reaction which increases the acidity, which in turn increases the above decomposition

3Ca(OCl)₂ >> 2CaCl₂ + Ca(ClO₃)₂

So once the stuff starts to go off, it tends to go off faster and faster.. The best bet is to keep it in a dry place, out of light and heat, and keep it dry.77.86.115.159 (talk) 22:07, 26 June 2010 (UTC)

Relatively high incidence of lactose tolerance in Spaniards

Why do Spaniards have relatively high lactose tolerance in comparison to their neighbors? --Belchman (talk) 21:50, 26 June 2010 (UTC)

I wasn't aware that they do. In various group studies I've seen, the southern French and Portuguese populations have had higher percentages of lactose intolerance. [18] [19] [20]. As with most things generically related, I suspect fluctuations in prevalence is a result of how often those genes are used. In populations where lactose intolerance is higher, it's reasonable to assume that either lactose was less available to them, or they didn't have it quite as much. Regards, --—Cyclonenim | Chat  21:58, 26 June 2010 (UTC)

The article Lactose intolerance describes what is known about its cause and distribution. Cuddlyable3 (talk) 22:01, 26 June 2010 (UTC)

automotive question

What is minimum PSI cylinder compression pressure for 1275cc engine in a MG Midget?

Thanks . . . Joe

<removed email address>

I removed your email address so you don't get spammed. Ariel. (talk) 04:10, 27 June 2010 (UTC)

Opal vs clear in old incandescent bulbs

What difference did 'opal' or 'clear' finish make to the light in old incandescent bulbs? Was one more white than the other? --78.148.142.76 (talk) 22:25, 26 June 2010 (UTC)

clear was more efficient, but a pain to look at so you would want it in a light fitting. Whereas the opal did not blind eyes seeing it, so it is more suitable for the bare globe. Strangely Incandescent light bulb does not mention it. Graeme Bartlett (talk) 22:30, 26 June 2010 (UTC)

Yes, the 'opal' is/was just a Diffuser (optics) - didn't really affect the colour.77.86.115.159 (talk) 22:37, 26 June 2010 (UTC)

I never heard of diffuse white bulbs being called "opal". Must be a UK thing. If someone gave me an "opal" bulb I would probably be expecting it to be pink or something. --Trovatore (talk) 23:14, 26 June 2010 (UTC)

I've generally seen it as short for opalescent, rather than a direct reference to opals. If that helps at all... 86.164.57.20 (talk) 01:57, 27 June 2010 (UTC)

The first incandescent light bulbs were clear glass, but were often placed in frosted glass fixtures to decrease the glare. "Ground glass" had a surface which had literally been made rough by sanding or etching. "Frosted" was a term used more commonly than "opal" for early light bulbs which diffused the direct glow of the filament as in this 1904 citation. Here is a 1902 description of "opal glass" as then used in shades for gas lights: [21].Here [22] is a 1913 House and Garden article about opal or frosted glass shades around lights. Here is a 1911 engineering article which discusses frosted, etched and opal glass to diffuse illumination. They likely used a clear bulb in a diffusing globe. They were probably slightly less efficient than clear bulbs. A later term was "soft-white." Modern frosted or soft white bulbs are likely to have a water-soluble white coating inside the bulb, rather than it being actually etched by acid or sandblasting as in early frosted bulbs. The color temperature of the light would have been somewhat independent of the forsted or clear bulb, and would have been related to the design efficiecy and lifetime of the filament. I expect that the frosted or clear light bulb would not have been tinted blue as in modern "full spectrum" bulbs, but would have had a typical somewhat yellowish appearance of incandescent bulbs. Edison (talk) 03:24, 27 June 2010 (UTC)

Probably a UK thing as trovatore says - opal or clear over here .. google shopping.77.86.115.159 (talk) 03:48, 27 June 2010 (UTC)

I don't know where "over here" is to you but in the States, we generally have a choice between clear and "soft white" which I think is what everyone seems to be calling "opal". Dismas|^(talk) 08:51, 27 June 2010 (UTC)

UK, should have been clearer - thought link to google.co.uk would be obvious, but on second thoughts, it's not —Preceding unsigned comment added by 77.86.115.159 (talk) 12:10, 27 June 2010 (UTC)

Tip: If you click on the first link in an IP signature, it takes you to the contributions page for that address. At the bottom of that page there's a link called "Geolocate", which will show you where the post comes from (well, usually and approximately; there are a few gotchas). --Trovatore (talk) 10:14, 27 June 2010 (UTC)

Power supply to the town sewage works

Today I took a stroll down to my local sewage works (life in the fast lane, huh), and the overhead electrical supply to it caught my attention. I've taken a couple of photos of the utility pole outside - photo A and photo B. I have two questions:

• Firstly, what are the characteristics of that electrical supply likely to be (this is in the UK). It's surely three-phase, and of a fairly high voltage (the pole is ~25ft tall, with some serious anti-climb measures and lots of warning signs about carrying high objects nearby). I believe high-users like this in North America get either 13kV or 4kV - what would such a facility typically get in the UK? (It's a pretty big site, with several acres of tanks, serving a town of around 10,000 people).
• Secondly, what that is that little light thing, that's best seen in photo B? It's about ten feet off the ground, it carries the legend P360-alpha, and there's no cable running to it. I'm guessing it's a warning light - that somehow being near the pole with a conducting thing like a ladder causes enough flux for this thing to light up as a warning. Frankly it's not in a place I'd feel happy about visiting in the dark, so I can't discount that it's simply a solar-powered lamp (or somehow powered by the field of the transmission line) so that it illuminates the "danger of death" signs at night.

Any ideas? Thanks. -- Finlay McWalter • Talk 23:14, 26 June 2010 (UTC)

A. Three phase obviously 11 or 33kV are standards [23]

Images from geograph.org 11kv 33kv lloks like yous is 11kv, though that is an uneducated guess - there should be standards for UK power line construction somwhere on the web. Haven't found them yet. (It seems there are some other voltages used 6.6kv as well).

this link has some typical images. [24]

B. why don't you get a lightweight aluminium ladder and have a closer look at the light just kidding. If it's solar powered then you should be able to see the solar cell using a mirror attached to a fishing rod Maybe not. A safe way to see it to attach a video camera to a kite and then fly it above the device No. Sorry can't help myself. Don't know.77.86.115.159 (talk) 23:58, 26 June 2010 (UTC)

The "little light thing" has a wide-angle globe, so it looks like an illumination lamp to illuminate the warning signs and/or light up the area for linesmen to work at night. I can't tell how it's powered, but if we're talking about an 11-kV 50-Hz power line, then there's no way you could get enough flux through the air to power the lamp, not even with a bucket truck nearby for conductance -- so it can't be a warning light like you say, nor can it be powered by the field of the power line. FWiW 67.170.215.166 (talk) 05:50, 27 June 2010 (UTC)

The "P360 Alpha" gadget is lightly built and poorly attached to the pole, with one screw per side. It has no wires going to it. If it were a solar light I would not expect it to put out much of a light overnight, or after a few overcast days. It looks like a plastic cylinder, with a lid to keep rain out (can't rule out a solar collector on the top, but is is not optimally aimed for any latitude but the equator). At the resolution available, the bottom looks like it might be a basket with fine openings, which would keep out birds but let in bugs and air, so I wonder if it might be a non-utility gadget used on the pole with permission of the utility for sampling what bugs are in the area, or for air quality monitoring. They would periodically come along and collect the sticky paper inside or see what wandered into an internal trap, or what passed through filter paper. Edison (talk) 20:45, 27 June 2010 (UTC)

Along those speculative lines - maybe it's designed to trap bugs that might otherwise eat the wooden pole? (I sense this is far from likely)83.100.183.236 (talk) 20:49, 27 June 2010 (UTC)

I doubt that. Poles are usually treated with serious preservatives. If my speculation about a trap for studying what the insect population is (rather than eradication) it might have a solar powered UV led to attract insects at night. Some insect study traps are triangular paper prisms with sticky paper inside, others are plastic cylinders with an attractant inside and a funnel trap to prevent escape. Edison (talk) 20:53, 27 June 2010 (UTC)

Applying Occam's razor, it seems likely that the light was installed but wires were never connected to it (or were removed later) so it is not operational. On the other hand, other photos of the P360 Alpha also lack wires. Maybe the light is battery-operated. Nimur (talk) 21:01, 27 June 2010 (UTC)

As it appears to have a transparent lid, I'd suggest that it is solar-charged darkness-activated light. —Preceding unsigned comment added by Csmiller (talk • contribs) 21:11, 27 June 2010 (UTC)

Thanks to everyone for your observations so far. Some clarifications (which aren't intended to cast aspersions on your inventive ideas, but probably will anyway). Yes, it's just like Nimur's Flickr photo - the underpart is definitely either glass or plastic (it's not a wire mesh). The line runs N-S and the P360 was attached to the south facing surface. As the only approach is from the east, I wouldn't think this was the best location for a warning light. This is in Northern England, which means solar power is pretty unlikely to be effective for a light, particularly in the winter. The UK doesn't have much in the way of serious wood-eating insects (no termites or army ants and relatively few beetles), so I'd be surprised if this was its purpose. I guess it could be for collecting insects for some kind of survey, but it's well above the anti-climb barbed attachments and clearly in the danger zone, so I'd guess that if that is its purpose, it must be there necessarily (that is, it's studying the effect of the power lines on insect behaviour) - there are plenty of fence posts, lamp standards, and telephone poles at which a study unrelated to electricity could be undertaken. The land surrounding its location is the aforementioned sewage plant, some playing fields, and a farm. A stream runs to the west. I still think (without any evidence) that it's to do with safety (given its intrinsically unsafe location). Perhaps if someone does accidentally bridge the overhead lines to ground, this thing flashes or wails, warning the others in that worker's party that they mustn't touch their stricken colleague. -- Finlay McWalter • Talk 21:48, 27 June 2010 (UTC)

But how can it sense that the line has been shorted if it's not connected to it in any way? No, it can't be a sensor -- it's prob'ly there for illumination (e.g. to illuminate the "Danger of Death" warning signs). FWiW 67.170.215.166 (talk) 01:36, 28 June 2010 (UTC)

Putting it on the S side of the in England is consistent with solar cells on the top. Have you noted whether it lights up visibly at night? I liked the idea of plastic mesh at the bottom to exclude birds and collect a sample of collect insects, but if it is plastic with no holes some sort of light or warning device seems like a good explanation. I think it looks really flimsy and lightly built to be permanent utility equipment. It would also get severely in the way of a worker climbing the pole, since he would have a belt going around the pole opposite the side the gaffs in his boots dug in. The top could be a solar collector and the bottom an LED light, but the middle seems rather large just to hold the batteries. I have not been impressed with the usefulness of solar lights, since a few cloudy days greatly decreases their ability to stay lit all night, and a warning light only on for part of the night seems useless. A light which comes on when it senses someone near, or with a motion sensor, might work better, or a light which comes on when it has detected a surge of current in one of the lines overhead might be useful as a fault indicator to help locate where a line fault occurred. It could be triggered by a transmitter in a passing utility truck after a line fault, and light up if it detected the current surge. This would go quicker than present fault indicators, which only have a little indicator which shows red when a fault current has passed it, but which take a slower examination with binoculars. (Or it could be a hanger for a miniature UFO). Edison (talk) 19:07, 28 June 2010 (UTC)

(I am On FIRE these past few weeks at the RefDesk!) I'm in the industry so lucky I have the answers at hand. First answer first: the rule that we use is "11kV per shed, plus one shed extra". The insulators in your photos (those glass discs) have two sheds (discs) and are therefore 11kV (the UK uses 11kV). Second answer: the device is a fault path indicator, Googling that term I found the EXACT device in your photos at the manufacturer's website which also describes the principle of operation. QED :) Zunaid 19:38, 28 June 2010 (UTC)

Splendid, that's plainly it exactly. What a clever idea - I'd imagine that flashing should be visible from a helicopter, making locating a fault on a long countryside line much more tractable (would that such a system had existed to diagnose failures in cheapernet, back in the day). If someone more electrically knowledgeable that myself wants to take a stab at writing a fault path indicator article, I'd be happy to tramp back out to the sewage works (depending on which way the wind blows) with a decent, zoomable camera to take some more worthwhile shots of it. Thanks to Zunaid, and to everyone for your imaginative suggestions. -- Finlay McWalter • Talk 20:25, 28 June 2010 (UTC)

Even better than that is to have it on supervisory i.e. it communicates back to the control centre remotely (via radio, GPRS, power line carrier, fibre optic etc.) so that we can see first time where the fault is and dispatch the operator to only patrol that part of the line. I'll have a stab at creating a stub sometime in the coming days, just a bit busy at the moment. Zunaid 07:54, 29 June 2010 (UTC)

June 27

endocrine disruptors

Are all nitric substances endocrine disruptors or just potassium nitrate? for example, are amyl nitrate and nitric acid endocrine disruptors? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 01:21, 27 June 2010 (UTC)

Nitric acid is too darn corrosive to be an "endocrine disruptor" -- if you get some of it inside your body, it will burn you from the inside out before any endocrine disruption can take place. Don't know about amyl nitrate, though. FWiW 67.170.215.166 (talk) 02:39, 27 June 2010 (UTC)

To the OP: can you please cite the sources of the statement that potassium nitrate is an endocrine disruptor? I'm not being negative, I'm just curious. Potassium nitrate is routinely used as a food additive, and has LD50 of several g/kg weight, comparable to that of the table salt. How does it affect the human endocrine system? --Dr Dima (talk) 06:34, 27 June 2010 (UTC)

to dr. dima: http://pubs.acs.org/doi/abs/10.1021/es032437n —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 08:25, 27 June 2010 (UTC)

It says that nitrates are suspected, not proven, to be endocrine disruptors. 67.170.215.166 (talk) 09:04, 27 June 2010 (UTC)

For a direct reference, one could look at this article which finds no evidence that nitrates have an endocrine disrupting effect during male rat embryogenesis. It's a pretty limited scope of investigation, but you could track down any references they cite that have shown evidence for nitrates as endocrine disruptors. --- Medical geneticist (talk) 11:57, 27 June 2010 (UTC)

This ref, for example, shows in vitro endocrine disruption by inorganic nitrate (with all due caveats, what happens to mouse tumour cells in a Petri dish might not necessarily happen in the human body). But to answer the question posed, all the studies we're citing are looking at inorganic nitrate, so sodium nitrate would be equivalent to potassium nitrate. The hypothesis is that endocrine disruption comes from production of nitric oxide in inconvenient places, so that would imply that you'd get similar results from amyl nitrite (or amyl nitrate, but fewer people sniff amyl nitrate!). The big difference is the exposure profile: if you're going around sniffing enough amyl nitrite to cause serious endocrine disruption (assuming the hypotheses are correct), you would have many, many other health problems first! Inorganic nitrate, on the other hand, is a well known contaminent in drinking water around the world, and people exposed literally from the day their born until the day they die. As such, it's potentially a much bigger problem, and several groups have looked for effects on human reproduction, without much success from the studies I've seen. Physchim62 (talk) 16:17, 27 June 2010 (UTC)

what about Nitric acid in water ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:09, 27 June 2010 (UTC)

Nitric acid in water is a source of inorganic nitrate, in that sense it is no different from potassium nitrate; however, it is not a major source of human nitrate intake. Physchim62 (talk) 00:18, 28 June 2010 (UTC)

Or, to put it another way, cyanide is a very potent disruptor of your endocrine system (among other bodily functions), but it is not helpful to label potassium cyanide as an "endocrine disruptor". Physchim62 (talk) 00:20, 28 June 2010 (UTC)

Fan curve derivation

How is the fan curve - pressure vs volume flow rate - derived? In other words how is it related to the specifics of the fan (no of blades, blade angle, blade length etc)? Also how is the efficicency curve of the fan derived (if it can be derived - Im not talking about the friction loss in bearings etc but the hydraulic losses which depend on geometry)? If the answers to the above are not available, can someone tell me how the efficiency varies with fan rpm? Im not talking about ways to calculate/measure the above but get an equation for it. Thanks—Preceding unsigned comment added by 125.17.148.2 (talk) 08:11, 27 June 2010

You may get some information from this designer of industrial fans or through the Fan Manufacturers Association. Cuddlyable3 (talk) 23:44, 27 June 2010 (UTC)

The Navier-Stokes equations are used with numerical methods, usually either differential equation solvers or similar forms of simulation (including, in some cases, Boltzman particle simulation by Monte Carlo methods) to design fluid dynamic shapes, including fans and propellers. Why Other (talk) 00:54, 28 June 2010 (UTC)

So what is basically the equation for the fan curve - and the fan efficiency? I know most things ultimately trace their origins through Navier Stokes but it is far too complicated for me to derive it from there. Does anyone have the equation(s)? Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 10:38, 28 June 2010

you will need to ask this question on the math reference desk because in its simplest case it's a 3-D PDE solution. You should also specify bthe fluid (air) material (steel, plastic) and its tensile strength, density, and smoothness, which influences the transitions between laminar and turbulent flow. 208.54.14.90 (talk) 16:21, 28 June 2010 (UTC)

'Metallic conduction' in non metals

Hi. Any examples of metallic conduction (and hence metallic appearance) in non-metals other than poly(sulphurnitride) eg eg, excluding heavily doped polymers such as poly-enes? (ie from a pure compound). Not semiconductors please. ie conductivity better than 100 Ω^-1cm^-1 or thereabouts. 83.100.183.236 (talk) 14:27, 27 June 2010 (UTC)

Carbon nanotubes are good thermal conductors. --The High Fin Sperm Whale 16:59, 27 June 2010 (UTC)

Graphite is a pretty decent electrical conductor, it's even used in old-fashioned voltage regulators and such as a variable resistance element. (Note that diamond is non-conductive.) Clear skies to you 67.170.215.166 (talk) 01:40, 28 June 2010 (UTC)

According to our Molecular electronics article, various charge transfer complexes can easily give you "resistivities as low as 8 ohms-cm", and can go down to the metallic region. General research tip: once you have a read ref, try to search for other articles that cite it or later publications from its authors. Any good followup or later major discovery on a topic will cite precedent/previous work, and few PIs do not publish "just one article" on a breakthrough topic. DMacks (talk) 16:00, 28 June 2010 (UTC)

Metallic appearance

Similar to above question, excluding metal (and metal based powders) are there any pigments or other compounds that have a metallic appearance (specifically - any used as a metallic pigment) ? Thanks. 83.100.183.236 (talk) 14:30, 27 June 2010 (UTC)

Some phthalocyanate dyes (what, no article?) can have a metallic appearance. FWiW 67.170.215.166 (talk) 01:44, 28 June 2010 (UTC)

Did you mean Category:Phthalocyanines - as far as I know - they don't..87.102.11.74 (talk) 02:14, 28 June 2010 (UTC)

Well, maybe it's a different kind of dye (something other than phthalocyanines), but I'm pretty sure that there are organic dyes that have a metallic appearance. FWiW 67.170.215.166 (talk) 01:07, 29 June 2010 (UTC)

Can woodlice breath underwater?

82.43.90.93 (talk) 14:51, 27 June 2010 (UTC)

Certain types can as they live in water! But regarding the more common land species, I'm not sure. Regards, --—Cyclonenim | Chat  15:45, 27 June 2010 (UTC)

No, terrestial types can't. They will drown if put in the water. --The High Fin Sperm Whale 16:57, 27 June 2010 (UTC)

Their oxygen requirement must be tiny. They have spiracles rather than lungs. Wouldnt they be able to absorb enough oxygen from water? 92.29.119.46 (talk) 19:20, 29 June 2010 (UTC)

oysters

af2ter opening some oysters from the delaware bay I have found what appears to be some sort of a crab living inside the shell.Can someone identify the creature & provide some info (does it spend its entire life there,how does it get there etc...) ? —Preceding unsigned comment added by Dvp56 (talk • contribs) 15:57, 27 June 2010 (UTC)

Oysters do snap shut if disturbed. The crab could have crawled into the oyster, and the oyster would have closed its shell, trapping the crab. --The High Fin Sperm Whale 16:53, 27 June 2010 (UTC)

Is the crab living inside the shell with a live oyster, or is it living in an empty shell? Hermit crabs will live in discarded or empty shells of other critters... I've not seen one use a bivalve shell in this way, but the world is a diverse place, and I don't see why there wouldn't be some variety or species that has that behavior. --Jayron32 22:19, 27 June 2010 (UTC)

See oyster crab. I've seen these crabs many times when eating oysters from North Carolina. I eat them right along with their delicious hosts! --Sean 14:42, 28 June 2010 (UTC)

Is the oyster crab a parasite, or is it living in the oyster shell a benefit to the oyster somehow? Googlemeister (talk) 16:21, 28 June 2010 (UTC)

Switching mobile phones while flying.

Is it really necessary to turn our mobile phones off while flying in airplanes, as instructed? Or it is just a fear of new technology like putting off our shoes from the room where computers were used.I myself have never turned off my mobile phone while travelling in airplanes, but just put it in silence mode.This is just to check what will happen and nothing has happened.I am a very frequent flyer. —Preceding unsigned comment added by 113.199.218.23 (talk) 16:06, 27 June 2010 (UTC)

A relative who is a pilot tells me that mobile phone signals can mess with the navigational equipment — if I remember rightly, the VOR, among other things. While flying light aircraft, he is permitted to send text messages (there are plenty of times when he has a minute to type the message), because the text is just a quick burst of signals, while talking on the phone involves several minutes of constant signals. The point of turning your phone off is to ensure that you don't talk on it: having the phone on isn't by itself a problem. Nyttend (talk) 16:12, 27 June 2010 (UTC)

In addition to interfering with the plane's equipment (which isn't really a problem on modern passenger jets - they all have appropriate shielding), it can cause problems with the phone network due to you being a similar distance from lots of cell towers (since the distance between the cell towers is small compared to your height above them). Two non-neighbouring towers will assume that no phone will be communicating with both of them, so they will often use the same channels. Your phone will realise there is a low signal and boost power (flattening your battery quite quickly) and at that higher power will be able to communicate with both towers, causing lots of confusion. --Tango (talk) 16:26, 27 June 2010 (UTC)

We have a pretty lengthy article on this: Mobile phones on aircraft. Comet Tuttle (talk) 17:45, 27 June 2010 (UTC)

I hope never to share an airplane with someone who disobeys the safety instructions (every time and frequently!) just to check what will happen because whatever happens happens to everyone on board. Cuddlyable3 (talk) 23:37, 27 June 2010 (UTC)

If mobile phones were really that dangerous to the aircraft, they wouldn't let you take them on board! Physchim62 (talk) 23:40, 27 June 2010 (UTC)

What a nonsensical statement, Physchim, you should know better than that! 67.170.215.166 (talk) 01:48, 28 June 2010 (UTC)

Recently I have seen a larger number of people agreeing that the ban on mobile phones on planes doesn't make sense technically. However, the airlines and others don't object because no one wants to be stuck next to someone yelling into their phone the entire flight. It would make flying worse than it already is. After reading some extremely technical discussions of this on Slashdot I am of this persuasion. --mboverload@ 23:45, 27 June 2010 (UTC)

The fact that there's an agreement among "large numbers of people" that the ban doesn't make sense is irrelevant, since most of these people are not experts on the subject. As for the technical issues involved, I can tell y'all with certainty (having a private pilot's license with an instrument rating) that the VOR, ILS and comm radios installed on all aircraft as per FAA regulations all operate in the VHF band, which is the very same band used by cell phone networks. This raises the possibility of electromagnetic interference with the plane's radios and navigation systems, and while the likelihood of this happening is pretty low (because there's only a slight possibility of any particular cell phone being on the same channel as the plane's radios), if it does happen it can be very dangerous because the pilot would then have a hard time communicating with ATC and/or wouldn't be able to follow the VOR radial/ILS beam. It's ESPECIALLY dangerous during an instrument approach because while the pilot of a modern jetliner often has backup navigation systems for cruise flight (inertial, GPS, celestial, etc.), during an instrument approach he/she is totally dependent on ILS, and any interference with the ILS beam could easily lead to a CFIT-type crash with no survivors. Clear skies to you 67.170.215.166 (talk) 02:10, 28 June 2010 (UTC)

I'm almost a private pilot (hopefully take the checkride soon). My understanding is that I would have the authority to authorize (within reason) or ban whichever handheld electronics I see fit from a FAA legality standpoint. From an FCC standpoint, it is illegal to use a cellphone in flight, even if I authorize it. Period. When it comes down to it, if the flight crew, be it in a plane like I fly or a commercial airliner, says that you can't use your cellphone, it is highly illegal to do so, regardless of how much sense it makes. Heck, the flight crew could ban pet rocks, and you could be sent to jail (in theory) for refusing, purely because the law gives them complete and ultimate authority over anything and everything that happens on and around the aircraft. Falconus^{p t c} 05:10, 28 June 2010 (UTC)

P.S. 67.170 is right. While it probably won't cause a safety issue on a commercial airliner, you can't know that for certain, so don't try it, especially in clouds and on landing. Being out of contact with the world for a few hours won't hurt you. Falconus^{p t c} 05:14, 28 June 2010 (UTC)

It is also quite difficult to use cell phones at high altitude because the cell towers are designed to cover the ground. They try to design the towers so that it is not wasting energy straight up. A friend of mine who is a CAP pilot tells me that he can have 4 bars on the ground, but the same place at 5,000 ft AGL, he will have no signal. Also, on a commercial airline, it is good to turn your phone off because I have found that finding a new cell tower every 20 seconds drains the battery like there is no tomorrow (and no I was not trying to talk on it). 65.121.141.34 (talk) 13:45, 28 June 2010 (UTC)

Superoxide reactivity

I was under the assumption that superoxide reactivity is a result of the superoxide having such a great affinity for electrons that it grabs electrons from surrounding molecules (DNA, membrane phospolipids, etc.), thereby contributing to the danger to biologic viability in the immediate area of superoxide concentration. Is this accurate? How does the electron affinity of the deficient valence shell of a single oxygen atom (as in a superoxide) differ from the deficient valence shells of two oxygen atoms (as in binary oxygen) to produce such a reactive substance? DRosenbach ^{(Talk | Contribs)} 16:59, 27 June 2010 (UTC)

Yes I think that as an oxidizing agent it snatches electrons from reducible substances, creating lots of havoc. --Chemicalinterest (talk) 17:38, 27 June 2010 (UTC)

It's also a radical (chemistry), which gives it a direct method of attack on just about any inorganic substance eg:

R-H + O₂^-· → R· + HO-O^- (forms peroxide and a radical)

It's its radical nature in addition to the oxidising properties that makes it particularly harmful. This can be put another way by showing its reaction with water:

O₂^-· +H₂O → HO₂^- + HO·

ie hydrogen peroxide anion and a hydroxyl radical

Didn't understand the second part of your question, the electron affinities of O, and O₂ are given at Electron affinity (data page). I think the answer you are looking for is "molecular oxygen is less reactive since the bond dissociation energy is high.." O^-is even more reactive than O₂^- - a reason why it isn't usually found. 83.100.183.236 (talk) 18:15, 27 June 2010 (UTC)

Superoxide usually reacts as a reducing agent, giving up a single spare electron to produce O₂. The reason that it causes damage is the radicals it forms by one-electron reduction, which tend to go on and react with other cell components in a pretty uncontrolled way. Physchim62 (talk) 22:30, 27 June 2010 (UTC)

Superoxide is more reactive despite paradoxically being a) an anion, which theoretically should reduce its electrophilicity b) in a more reduced state. This is because the diradical species of normal O2 is quite stable, preventing spontaneous reactions while the superoxide is an unstable monoradical ... kinetically more unstable. The energy barrier is lower. There is almost no activation energy involved in radical-radical interactions.

Also, polarised molecules tend to be more reactive than molecules without a permanent dipole moment. John Riemann Soong (talk) 05:31, 28 June 2010 (UTC)

Superoxide has no permanent dipole moment: the unpaired electron is delocalized over both oxygen atoms. Physchim62 (talk) 10:08, 28 June 2010 (UTC)

Ants

When a queen bee dies, the female workers start to lay their own eggs as the queen isn't producing the pheromone anymore. Does the same happen in an ants nest when the queen ant dies? 82.43.90.93 (talk) 17:02, 27 June 2010 (UTC)

According to E. O. Wilson's wonderful article/story "Trailhead", the answer is basically "yes". "Soldier-queens" begin laying eggs, no longer inhibited by the queen's pheromones. However, the eggs are unfertilized and are thus all male drones, which can then go aid the beginning of new colonies, but their original colony will eventually die out after the queen has died. --Mr.98 (talk) 18:05, 27 June 2010 (UTC)

I'm only really familiar with honey bees (my grandfather is a bee-keeper), so other bees may be different, but that isn't my understanding of how it works. The workers don't start laying eggs (I don't think they are capable of laying). Rather, they start feeding royal jelly to existing larva (there is always some brood in a hive, I believe) so they become queens. It is also possible that there will already be a virgin queen in the hive who will simply take over as queen. I have no idea how it works with ants. --Tango (talk) 19:38, 27 June 2010 (UTC)

I know that some ant colonies have multiple queens,such as the Tapinoma sessile. 65.121.141.34 (talk) 13:39, 28 June 2010 (UTC)

It's true that they'll make a new queen with royal jelly if possible, but it's not always possible (a new hive might never have had a queen, for example). Worker bees can indeed lay eggs, but they're not very good at it --their patterns are spotty, and they'll sometimes lay more than one egg per cell -- and they're not fertilized, so can only lay eggs that will become males (drones). Sounds the same for ants, according to Sr. 98. Ants and bees have many similarities. --Sean 14:49, 28 June 2010 (UTC)

Scientific term for species who don't take care of their young.

Hi, I'm writing a story, and I want an adjective that means the species does not take care of their offspring. Is there a term for that? --Ye Olde Luke (talk) 19:33, 27 June 2010 (UTC)

I don't have a term to describe the species, but I know there is a range of altricial to precocious to describe birds depending on the level of maturity they possess at the time of hatching. The terms are defined by such things as whether the young hatch naked or with feathers already developed and what type of feathers are present, whether the eyes are open or closed, etc. Perhaps you can take a spin on that and term the species a precocious one if the young do not need the parents' attention. DRosenbach ^{(Talk | Contribs)} 20:04, 27 June 2010 (UTC)

There you go -- you can term the species precocial. DRosenbach ^{(Talk | Contribs)} 20:05, 27 June 2010 (UTC)

From the parental investment article, the term is r-selected, as opposed to K-selected. CS Miller (talk) 20:54, 27 June 2010 (UTC)

or as a made up term "non-incubatory" ?? 83.100.183.236 (talk) 20:55, 27 June 2010 (UTC)

Thanks all! For the species introduction, I think I'm going to use "non-incubatory," but I plan to mention all of these terms at leter parts in the story, since it would get redundant to just keep using "non-incubatory." --Ye Olde Luke (talk) 21:24, 27 June 2010 (UTC)

The common cuckoo is an example. 92.28.242.168 (talk) 21:25, 27 June 2010 (UTC)

Sort of. Except the cuckoo chicks still need to be taken care of, so the cuckoo has developed strategies to get other birds to do the hard work. As explained in the article, this is called brood parasitism, and is a different phenomenon from what the OP is thiking of. I think that sea turtles are a better example. The mother lays the eggs and leaves town, and when they hatch, the young are completely on their own. --Jayron32 22:16, 27 June 2010 (UTC)

Flying wings

I know that flying wing aircraft are stealthy because they reflect radar in few directions. How much more visible would a flying wing be on radar if it had vertical stabilizer/s? Also, do flying wings produce a lot of lift? --The High Fin Sperm Whale 21:54, 27 June 2010 (UTC)

Your questions are very unspecific. I'm not sure what kind of answer you expect other then "a bit" for your 1st question. If stealth is your primary concern, then you don't have them like the B-2 Spirit. For the second question, a lot of lift compared to what? The article says Theoretically the flying wing is the most efficient aircraft configuration what does that suggest? Vespine (talk) 23:01, 27 June 2010 (UTC)

See our article Radar cross-section. It is non-trivial to calculate how many dB additional reflectivity (or how many square meters of effective cross section) are added by adding a new part to an airframe. In practice, you can simulate, estimate, and so forth. Because radio reflectivity is complex and involves complete solutions of the full wavefield, simple approximations are rarely accurate. Furthermore, RADAR cross-sections are directional - so adding a vertical stabilizer might make negligible difference in the head-on view, but seriously increase the plane's reflectivity from the side. Nimur (talk) 23:54, 27 June 2010 (UTC)

The problem with vertical stabilisers is the point where they meet the fuselage. Interior corners make really strong radar reflectors. A corner reflector made of three surfaces at right angles will reliably bounce radar right back to it's source and sticks out like a sore thumb - but any concave junction between two surfaces does that to some degree and is basically undesirable for a stealthy design. SteveBaker (talk) 01:31, 28 June 2010 (UTC)

How would it effect stealth, especially on a flying wing, if the wings were either Dihedral or Anhedral? --The High Fin Sperm Whale 03:24, 28 June 2010 (UTC)

Relatively little because the angle is much larger than a right angle. SteveBaker (talk) 12:47, 28 June 2010 (UTC)

June 28

Listed ingredients

So I was drinking my Lipton Lemon Ice Tea (LLIT), and thinking, "damn, this tastes like bad water", and I realized (perhaps a bit late) that drinks, obviously containing huge amounts of water, rarely (never?) actually list water as part of their ingredients, at least where I live.

Is there any reason companies would wish to avoid printing water on their ingredient labels (other than the fact that it can always be assumed, and thus is just a waste of printing space)?

Why are the relative amounts of individual ingredients on packaging never (properly) listed? Is this a "printing space" issue as well? i.e. listing them in order weight eliminates a lot of information that may not be needed. I would have liked to know if LLIT was only 95% water, or like 99.9% water, mind you.

For the consumer, it seems that the more comprehensive the ingredients are, the better. Is there any other reason why companies seem only to publicize the absolute legal minimum when it comes to the ingredients of consumables? Thanks in advance. 210.165.30.169 (talk) 01:03, 28 June 2010 (UTC)

In the UK, drinks that contain added water do include water in their list of ingredients. --Tango (talk) 01:37, 28 June 2010 (UTC)

In the US, if you look at, say, a bottle of Diet Coke, the first ingredient is listed as "Carbonated filtered water", so I am not familiar with any type of product that is allowed to omit water from the ingredients list. As for why companies only do the legal minimum, one possible reason is that from the company's point of view, their recipe may be considered a crucial trade secret and they don't want to tell all their competitors how to clone their product. Comet Tuttle (talk) 02:50, 28 June 2010 (UTC)

Yeah I see labels that say "Flavor" or "Seasoning" instead of listing the ingredients. --Chemicalinterest (talk) 10:50, 28 June 2010 (UTC)

Also in the US, and I am under the impression that very few products put water in the label. I certainly only see it rarely. Falconus^{p t c} 04:58, 28 June 2010 (UTC)

Can you give an example of a product that contains added water (not just water contained in another ingredient) and doesn't include it in the list of ingredients? --Tango (talk) 15:53, 28 June 2010 (UTC)

Sometimes they put "aqua" instead of the word water, and talking about "bad" those tea leaves were probably decomposed slightly before making up the drink. Graeme Bartlett (talk) 05:16, 28 June 2010 (UTC)

As for why companies are not interested in detailed ingredient lists, it's in part because of trade secrets, as well as the fact that most of them don't get a lot out of telling the consumer that a bunch of scary-sounding (but probably innocuous) chemicals are added to their food in order to give it the flavor, texture, and color they desire. When questions of labeling have come up—say, in regards to BGH—the companies not in favor of labeling usually say, "hey, the FDA says it's safe—otherwise we couldn't sell it—and so why do we need to rile people up about something that won't hurt them?" I find it a pretty uncompelling argument—"people are too dumb to understand ingredients lists, so let's just keep them in the dark on it"—but there you have it. --Mr.98 (talk) 16:19, 28 June 2010 (UTC)

Sigma additivity in quantum mechanics

Is sigma additivity true for probabilities in quantum mechanics? Sigma additivity is one of the axioms of probability, what I would like to know is if it is an arbitrarily chosen axiom or if there is any scientific basis behind it (and the only application of probability in its purest form in science is in quantum mechanics). Also, do the other axioms of probability hold in quantum mechanics? ––115.178.29.142 (talk) 03:21, 28 June 2010 (UTC)

Yes, the probabilities in quantum mechanics are probabilities. If the definition of probability didn't apply, it wouldn't be called a probability. (I'm having difficulty seeing the motivation for this question.) Looie496 (talk) 04:25, 28 June 2010 (UTC)

I'm afraid I think that answer is a little reductive. Sigma-additivity is part of the mathematical theory of probability. Whether it has any direct physical counterpart is another matter entirely.

To elaborate: Sigma-additivity says that if you have a countably infinite (or, less interestingly, finite) number of mutually exclusive possibilities, the probability that one of the events happens is exactly the sum of all the probabilities of an individual event happening.

This property is important to make the mathematical theory work smoothly. What, if any, physical reality it corresponds to, is less clear — are there even an infinite number of mutually exclusive events to consider, in the physical world? There may be, but then again there may not.

You don't have to go to anything as exotic as sigma-additivity of measures to see this distinction. An example much nearer to home is provided by the real numbers. Mathematically, the reals are an inherently infinitary notion; each real number contains infinitely much information, all wrapped up in a neat little package. Does, say, the distance between two electrons truly encode infinitely much information? Perhaps, but I think the jury is still out (in fact the jury may well never come back). --Trovatore (talk) 08:08, 28 June 2010 (UTC)

So basically it's unknown whether or not sigma additivity is true in physics? Fundamentally what I want to know is if the axioms of probability are actually "true" in real life, so to speak. Axioms are meant to be self-evident, especially in mathematics, is this true for the axioms of probability such as sigma additivity?––Original Poster

Note that probabilities in quantum mechanics are the square of the norm of the wavefunction. The (complex) wavefunction itself is not a probability and does not obey the axioms of probability, even though certain terminology, such as "probability amplitude" might suggest otherwise. 157.193.175.207 (talk) 08:06, 28 June 2010 (UTC)

Note that sigma additivity of probabilities applies to sets of pairwise disjoint (i.e. mutually exclusive) events. It can appear to fail in quantum mechanics because events that we intuitively expect to be mutually exclusive are not necessarily so. For example, in a double-slit experiment, suppose event A is "particle goes through slit 1 and hits point X on screen", and event B is "particle goes through slit 2 and hits point X on screen". In classical physics we expect the particle to follow a single path from source to screen (even though we do not observe this path) and so we expect A and B to be mutually exclusive; this leads us to expect Pr("particle hits point X on sreen") to be Pr(A)+Pr(B). In quantum mechanics, Pr("particle hits point X on sreen") is not Pr(A)+Pr(B) - wavefunctions add, but probabilities do not. This is not because sigma additivity fails, but because A and B are no longer mutually exclusive - the particle can, in effect, go through both slits (see path integral formulation). Gandalf61 (talk) 08:49, 28 June 2010 (UTC)

obviously the probability amplitudes do not obey the axioms of probability because the probability amplitudes are not actually probabilities. However, do the probabilities derived from the probability amplitudes obey the axioms of probability? Basically what I want to know, as I stated above, is whether or not the probability axioms are actually true in nature or if they were just arbitrarily chosen. ––Original Poster

Ignoring quantum mechanics, have you tried rolling dice, or something else simple where you can test for yourself whether the axiom has a physically real basis, or are you already past that stage? What exactly are you asking - is this question specifically about quantum mechanical probabilities, or more general?

"However, do the probabilities derived from the probability amplitudes obey the axioms of probability" yes.87.102.11.74 (talk) 12:13, 28 June 2010 (UTC)

The result obtained from rolling dice is a deterministic system dependent on how you roll the dice. That's why a chose quantum mechanics ––OP

That's a false dilemma. The axioms of probability are not "just arbitrarily chosen" - they are carfeully chosen to provide a consistent mathematical framework that implements our intuitive concept of odds and probability. However, we cannot measure probabilities directly - we can only estimate them from the results of multiple trials. So it is probably impossible to say whether they are "actually true in nature". How would you design an experiment to test whether probabilities "in nature" do or do not conform to the axioms of probability ? Gandalf61 (talk) 12:11, 28 June 2010 (UTC)

How are the axioms of probability derived? Or are they self-evident, as many axioms in mathematics are? And if they are self-evident, doesn't that mean that they must be true in quantum mechanics?––OP

I think you may have misunderstood the term "self-evident". When we say that axioms are taken to be self-evident, this means that we do not have to prove that an instance of a mathematical structure, such as a probability, conforms to the axioms of that structure, because the axioms are taken to be part of the object's definition. This avoids the danger of infinite regress in mathematical proofs - each chain of reasoning in a proof eventually reaches an axiom, which we can take to be true by definition. "Self-evident" does not means "obvious" - the axioms for many mathematical structures are far from obvious. Neither does it mean "true in reality" - a mathematical structure may or may not be a good model of some part of reality, but this does not affect its axioms. Gandalf61 (talk) 14:00, 28 June 2010 (UTC)

Hmm, no, I don't really agree with that; that's a bit close to the sort of formalism that reduces mathematics to a meaningless game. It is important whether axioms are true in reality, for cases (like the natural numbers, or sets considered as elements of the von Neumann hierarchy), where the objects they are talking about are well-specified. And I think self-evident axioms do have to be obvious once correctly understood.

The point is that not all axioms are self-evident. There are different sorts of axioms. One sort is the self-evident kind; once you understand what it means, it is intuitively clear that it's true. The axiom of choice is an example of this.

Then there are axioms that are not intuitively clear at all, but for which evidence accumulates that they are actually true. Large cardinal axioms are in this category.

Then there are axioms for which there is no particular evidence, or even evidence against them, but which are convenient in certain contexts (e.g. the axiom of constructibility, Martin's axiom, although some might argue that Woodin's work provides evidence for the latter).

But the "axioms of probability" being discussed here are in still a fourth category, that of "definitions in disguise". When you speak of the "axioms" of a group, what you really mean is the properties that a structure must satisfy in order to be considered a group. Similarly, the axioms of probability are the properties that a function from your event space to the reals must satisfy, in order to be considered a probability measure. --Trovatore (talk) 19:02, 28 June 2010 (UTC)

Despite your poor opinion of it, formalism is a logical and consistent position and a mainstream branch of the philosophy of mathematics. Your taxonomy of self-evident axioms, axioms that require evidence, convenient axioms and axioms that are "definitions in disguise" seems highly arbitrary to me. To a formalist, all axioms are "definitions in disguise", and the idea of collecting evidence "for" or "against" them is meaningless. Gandalf61 (talk) 21:30, 28 June 2010 (UTC)

Formalism is understandably very popular among mathematicians who would rather not think about foundational philosophy at all, but it has severe limitations once you start to take it seriously. This is probably not the place to discuss them at length; let me just say that formalism has no satisfying explanation for the apparent coherence of the overall mathematical picture.

I disagree that "to a formalist, all axioms are 'definitions in disguise'" — actually you have to be a realist to some degree to make sense of that notion of axiom. Otherwise, what are you defining? I would say that formalists would more easily place all axioms in the "convenient" category. --Trovatore (talk) 21:50, 28 June 2010 (UTC)

The question "What are you defining ?" only makes sense in a realist framework. For a formalist, axioms define what they define. A formalist does not expect the structures of mathematics to have any "existence" or reference outside of themselves. If they do happen to have some contingent correspondence to some aspect of the real world, then that is a fortuitous coincidence. I don't see how or why a formalist would categorise axioms as "convenient" or "inconvenient". Gandalf61 (talk) 07:14, 29 June 2010 (UTC)

So you're saying that the axioms define — themselves? If all you have is the axioms, what is the point of speaking of them as "defining" anything? --Trovatore (talk) 07:26, 29 June 2010 (UTC)

No, I said the axioms define what they define. The group axioms define a group, and a group is a mathematical object for which the group axioms are true - nothing more, nothing less. For a formalist, all mathematical structures are like that; there is no need or expectation of some real world referent against which the axioms can be compared. Gandalf61 (talk) 12:15, 29 June 2010 (UTC)

But if there are in fact no mathematical objects, as a formalist would hold, then how can you make sense of the claim that a group is a mathematical object for which the group axioms are true? --Trovatore (talk) 18:27, 29 June 2010 (UTC)

LOL, all I was asking was if the axioms of probability were true in quantum mechanics (to which I still don't have a definitive answer...) Actually it appears that I do have a definitive answer from 87.102.11.74, but he didn't give any reason to support his claim. Does classical probability apply in quantum mechanics? ?––115.178.29.142 (talk) 22:15, 28 June 2010 (UTC)

{outdent} It's not clear to me that anyone can possibly answer your question. It's a little like saying, we measure mass as a real number, so do masses have the Archimedean property? I can't imagine how you would design an experiment to test that. --Trovatore (talk) 22:19, 28 June 2010 (UTC)

In that case, what's the logic behind using the axioms we do? And furthermore, is it OK to use classical probability in quantum mechanics?––115.178.29.142 (talk) 00:30, 29 June 2010 (UTC)

You might want to take a gander at The Unreasonable Effectiveness of Mathematics in the Natural Sciences. I don't think you're going to get any definitive answer here. This is stuff people will be arguing about for a long time. I would note in passing that there's all sorts of stuff in QM of which people could (and do) ask whether/why it's "OK". --Trovatore (talk) 00:39, 29 June 2010 (UTC)

The probability of finding particle A at position y at time x is 1/5. The probability of finding particle B at position z and time w is 1/10. What is the probability of finding particle A at position y at time x AND particle B at position z at time w?––115.178.29.142 (talk) 01:00, 29 June 2010 (UTC)

No idea - you haven't given us any information on whether the events are independent or correlated. I carry my umbrella on 1 day in 5 and it rains on 1 day in 10. What is the probability that I carry my umbrella on a day when it is raining ? Gandalf61 (talk) 07:14, 29 June 2010 (UTC)

Signal processing

Could anyone recommend a good textbook on circuits and signal processing? I would like something to read over the summer. 173.179.59.66 (talk) 07:58, 28 June 2010 (UTC)

Are you looking for an introductory circuits text, or a text on circuits for signal processing? This will significantly change what will count as a "good book" for you. Proakis and Manilakis, Digital Signal Processing, is the "standard" DSP reference. It's very mathematical and expects a solid understanding of discrete mathematics before your start. It also exclusively focuses on digital signal processing. This is the book if you already have a solid background, but it will be totally incomprehensible if you aren't mathematically inclined. (It will also "assume" that you understand how to map a z-domain algorithm back to a digital circuit - an easy task, but one that isn't explained in this book). I also recommend Physical Audio Signal Processing. This book focuses on modeling physical acoustic behaviors with signal-processing approximations, and then implementing those as simple algorithms in software or digital hardware. It also makes for "light reading" although it will jump to extremely mathematical treatments for one or two sections at a stretch. The fields of "circuits" and "signal processing" are extremely broad - and the best books for an electrical engineer would be totally incomprehensible to a non-engineer. If you've never had exposure to even basic circuits, you should start with an introductory text on electronics before you start to worry about signal processing. Fundamentals of Electric Circuits by Alexander and Sadiku is a good one, but if you've even had a cursory circuit training, the first half of this book will insult your intelligence. In any event, the book does cover methods all the way up to frequency analysis, resonance, and I think even does s-domain circuit solutions. If you want to proceed down the all-analog route, you may find a book on analog control theory or RF signal conditioning a "must" - signal processing entails a totally different skillset in the analog domain. For this, you will need Analog Circuits, by Gray and Meyer, or Planar Microwave Engineering. (You can buy this online or in any bookstore... but these are very advanced circuit theory books). Can you specify your baseline knowledge/background a bit more? Nimur (talk) 15:07, 28 June 2010 (UTC)

There is a course next semester that I'm enrolled to take called signal-processing (they don't have a textbook listed yet). Here's the course description: "Experimental research depends strongly on electrical and electronics instruments. Today, signals from various probes are most of the time transformed into some kind of electric signal follow by some kind of digitization. This course will review some of the concepts that are encountered in the treatment of such electric signals in order to optimize the quality of the measurements. Some of the main Course Topics that will be discussed are:

• dc circuits and networks • Linear circuit elements: R, L, C • Sinusoidal signals: phasors and complex algebra • Filters: High-pass, Low-pass and Resonance • Power, rectification and noise • Fourier methods"

I'm not sure which of the textbooks above fits with the course. And thanks for the swift and detailed response! 173.179.59.66 (talk) 00:28, 29 June 2010 (UTC)

Based on what you've described, it sounds like Alexander and Sadiku is the book you want. The others might be fun to look at but I think you'll need to work your way up to them. If you find that the Fundamentals book moves too slow, you can really skip or skim several of the first chapters. The other books I mentioned will probably be too advanced if you still do not know the basics of Fourier transforms and linear networks; but in time you'll have the foundations. Electronic engineering is very dependent on a solid understanding of the basics. Nimur (talk) 01:17, 29 June 2010 (UTC)

Thanks man, I really appreciate your help. 173.179.59.66 (talk) 02:31, 29 June 2010 (UTC)

Quantam Handwaveing

What is meaning of Quantam Handwaving ?  Jon Ascton  (talk) 08:41, 28 June 2010 (UTC)

See handwaving. Some context would be helpful, but it probably means a plausible but informal argument based on the principles of quantum mechanics. Gandalf61 (talk) 12:01, 28 June 2010 (UTC)

Maybe, maybe not. I've observed that putting "quantum" in front of anything can change its commonsense meaning quite considerably if done so by scientists (e.g. the meanings of quantum teleportation or quantum computer are not obvious from their names).

In any case, Googling for the phrase seems to show it cropping up somewhat informally in ID/Creationism/Big Bang debates, probably in reference to the theory that? quantum thermal fluctuations serves as a "first cause" in the Big Bang, which seems to be seen as a form of handwaving by ID/Creationist types (that is, you are appealing to quantum mechanics in a vague way to get the answer you want, but it is not very concrete feeling). --Mr.98 (talk) 15:59, 28 June 2010 (UTC)

Wind chill and perspiration

I am trying to understand the effect of wind chill on cooling the human body and its impact on perspiration. Anecdotally I find that when there is a strong breeze when exercising, I seem to sweat much less. I am not sure if they is because I am sweating as much as usual, but that the breeze is helping it to evaporate faster, or whether my body is being cooled by the wind chill, so I need to sweat less, or a combination of both. The article on wind chill mentions that it causing cooling, but doesn't actually go into the details of why that happens. My guess, is that the moving air is having the effect of providing a greater number of "cool" air molecules to absorb heat from the body, much like why a liquid cools objects faster than air. On that basis I would expect that, in fact, the wind chill is cooling the body so that less sweating is required. However, I have also been told that swimmers are advised to still drink a lot because they do actually still sweat. If my theory about the wind chill is correct, it would seem to suggest that water would cool even more and so reduce sweating even more. Any input would be appreciated. Thanks HappyHopper777 (talk) 11:31, 28 June 2010 (UTC)

I think both effects are significant, and the balance will depend on humidity and airflow over the skin. A person will perceive that they are sweating more under high humidity or in still air, because the sweat accumulates on the body, but people still lose heat through sweating in high winds and low humidity, even when there is no noticeable sweat on the skin. Dbfirs 12:35, 28 June 2010 (UTC)

It takes energy to convert liquid water into water vapor - that energy comes from the warmth of your skin - so when sweat evaporates, it cools you down. With less humid air, that happens more easily - and in 100% humidity, it doesn't happen at all. When there is no wind - or when you are wearing lots of clothing that traps air - the temperature of the air close to your skin goes up (because it's being heated by your body) and humidity of that air also goes up because it's picking up water vapor from your evaporating sweat. When that layer of air isn't moving at all, you start to feel really hot because sweat evaporation has stopped and the air is warm. Add a little wind - and/or remove clothing to allow some convection (hot air rises) - and the air next to your skin is replaced by fresh air from further away. Now you have cooler AND drier air and your sweat can do it's job. The situation with swimmers is a little different. Air is a really good insulator - so heat passes only slowly through it. Water conducts heat away quickly - so even though your sweat can't evaporate, the water is conducting the heat away very efficiently and you don't overheat so long as the water is cooler than you are. SteveBaker (talk) 12:44, 28 June 2010 (UTC)

Thanks Steve. That fits with my undestanding I think. That water is a good conductor, compared to air, because there are a lot more molecules available to absorb the heat from the object being cooled. Fast moving air seems to have a similar effect in that, for a given amount of time, it provides a greater number of "cooler" molecules (i.e. molecules with less energy). However, because of the cooling effect of the fast air or water, I would have thought that there would be less need to sweat (because the body could transfer heat more easily to the fast air and to the water). I need to digest what you said above a bit more. Thanks HappyHopper777 (talk) 13:15, 28 June 2010 (UTC)

Pitot tube constant

For an 's' type pitot tube, the manufacturer gives the pitot tube constant as 0.8. Does this mean my actual velocity will be 0.8 times indicated velocity? Since the pitot tube is a straightforward application of Bernoulli's theorem, what causes this constant? Thanks —Preceding unsigned comment added by 125.17.148.2 (talk) 11:38, 28 June 2010 (UTC)

You are correct in believing a pitot tube is a straightforward application of Bernoulli's theorem. The only error suffered by pitot tubes is alignment error when the axis of the tube is so far out of alignment with the oncoming flow that the pressure in the tube is less than stagnation pressure. I don't know what it means to say a pitot tube has a constant of 0.8. It certainly doesn't mean that your indicated airspeed at sea level is 0.8 (or even 1.25) times true airspeed. For type certificated aircraft there is a requirement that the airspeed indicating system must be calibrated in flight and the error may not exceed three percent or five knots, whichever is greater. (See FAR 23.1323(b))

There is an error in temperature probes used on aircraft because a probe causes the airstream to come to a stop (stagnate) and that raises the temperature of the air in the vicinity of the probe, leading to an error. However, temperature probes are not called 's' type pitot tubes so that doesn't explain the 0.8. If 's' stands for supersonic the 0.8 may be related to the fact that when the aircraft is flying at supersonic speed the pitot tube is operating behind a shock wave so the airspeed sensed by the pitot-static system needs to be processed before giving a meaningful indication of true airspeed. Is your 's' type pitot tube intended for a supersonic aircraft? Dolphin (t) 23:03, 28 June 2010 (UTC)

No there is nothing so technical about 's' type, it is just more suited for particle laden air than conventional 'l' type tubes. I agree with the alignment problem which may occur but that is something which is to be avoided while measuring and is not an intrinsic part of the tube. Certain sites give some sort of constant less than unity which must be multiplied to the velocity but I dont quite understand the logic behind that. Any sort of non-alignment issues can only give a constant greater than 1. Now the manufacturer does not seem too technically aware apart from the fact that there is 'some constant 0.8'. 0.8 incidentally is roughly what must be multiplied to the centre velocity to give average velocity in duct. But I dont think he is talking about that (and neither am I). So basically what is a pitot tube constant? Thanks —Preceding unsigned comment added by 122.175.68.41 (talk) 16:23, 29 June 2010 (UTC)

Contents of Cold Pack

Do cold packs only contain ammonium nitrate? I had one and reacted it with hydrochloric acid and it formed a precipitate of ammonium chloride, which is much less soluble than the nitrate. Nitric acid should be formed, but it didn't react with copper to form copper(II) nitrate. It turned brown when it was heated and formed a white precipitate. --Chemicalinterest (talk) 13:14, 28 June 2010 (UTC)

Are you talking about the gels that you pre-freeze before using, or the endothermic ones where you break&shake a room-temperature bag? Our cold pack article gives some possible materials for each one. DMacks (talk) 15:35, 28 June 2010 (UTC)

Break and shake. It contained a saturated solution of the chemical with a packet of water. --Chemicalinterest (talk) 16:38, 28 June 2010 (UTC)

At a guess, I would say that it's hydroxyethyl cellulose. It would be in there to increase the viscosity of the resulting solution, so that the cold pack sit more securely on whatever you're trying to cool. To see why that might be helpful, fill and tie-seal a smallish plastic bag with tap water and then try to balance it on your ankle... Physchim62 (talk) 21:03, 28 June 2010 (UTC)

Could be ammonium chloride rather than ammonium nitrate. You say you expect you started with an already (near-)saturated solution? You don't say how strong your HCl solution was, but it's easy to get HCl much more concentrated than NH₄Cl, so when you mix them you boost the overall Cl^– concentration a bunch and NH₄Cl might precipitate. Physchim62 has an interesting point that it might be some gelling agent rather than the actual "dissolves to cool" material. The ice packs I've used really do seem almost water-liquidy. But I'm not sure why adding (presumably) aqueous HCl to a water-solution of hydroxyethyl cellulose would cause it to precipitate, or if an aqueous acid solution of hydroxyethyl cellulose would turn brown and form a white precipitate when heated. Do you have access to silver nitrate? It's the classic test for chloride. Our qualitative inorganic analysis article has many of the classic near-definitive tests fir determining what ions you have (though some require chemicals you may not have access to). DMacks (talk) 14:22, 29 June 2010 (UTC)

My HCl was concentrated, about 12M. It was viscous, the solution was. the precipitate did seem to have similar solubility to NaCl, so it was probably NH₄Cl. The hydroxyethyl cellulose may have pyrolyzed when heated in the superconcentrated solution.

I have no silver nitrate; I wanted to buy it but it was too expensive, $12.95 for a couple grams.

So it doesn't seem like it has ammonium nitrate. It did react with household bleach sodium hypochlorite though (more criteria). --Chemicalinterest (talk) 15:16, 29 June 2010 (UTC)

Whats the decomp temp of hy eth cellulose? --Chemicalinterest (talk) 15:21, 29 June 2010 (UTC)

documentary

I'm looking for good tv documentaries on ants, specifically the Black garden ant. I've already watched Life in the Undergrowth but if just skipped about from different species without giving any really detailed info. I want a documentary that follows the entire life cycle of the black garden ant. Thanks 82.43.90.93 (talk) 14:10, 28 June 2010 (UTC)

Do OLED displays degrade with UV exposure?

Do the organic compounds in OLED displays degrade with UV exposure? Should devices with such displays be kept out of direct sunlight? --70.167.58.6 (talk) 15:00, 28 June 2010 (UTC)

Most toxic element

What's the most toxic element in its pure form? Note that I said toxic rather than harmful, so radioactive elements like uranium and plutonium don't count. --76.77.139.243 (talk) 15:03, 28 June 2010 (UTC)

Can I infer that what you're really trying to say is most chemically toxic element? Because plutonium, for example, is quite toxic (in aerosolized form), and the fact that the toxicity derives from its radioactivity does not change that (see toxicity). Toxicity does not distinguish between mechanism, but we can, for the sake of argument, ignore toxicity related to radiation, if that is what you are asking about. --Mr.98 (talk) 15:12, 28 June 2010 (UTC)

Well, discounting radioactives (polonium would easily win if you include radioactives), and going on U.S. permissible exposure limits (PELs) for the element (discounting compounds), the answer is beryllium. Physchim62 (talk) 15:14, 28 June 2010 (UTC)

Yes, I was going to suggest beryllium, judging from Median lethal dose. Of course, toxicity is tricky—as our beryllium poisoning article points out, there are a whole set of different toxicities and effects depending on the route of exposure. But it's pretty nasty stuff, worse than arsenic and other "traditional" elemental poisons. --Mr.98 (talk) 15:17, 28 June 2010 (UTC)

PELs (and LD₅₀s) are incomplete descriptors of toxcity, but it's noteworthy that the PEL for beryllium is 100-times lower than the PEL for elemental fluorine; that is, you're allowed to have 100-times more fluorine gas than beryllium dust in the air of a U.S. workplace. Physchim62 (talk) 15:44, 28 June 2010 (UTC)

There is also berylliosis which discusses the lung disease caused by beryllium. None of the articles explain why it is so toxic however, this paper says it inhibits enzymes that contain magnesium + calcium ions. It can also function as a hapten leading to apoptosis of macrophages in the lungs. 86.7.19.159 (talk) 16:12, 28 June 2010 (UTC)

See also the last time we talked about this, and other previous on the science and other ref-desks. Just type "most toxic element" into the ref-desk search-box at the beginning of the page. DMacks (talk) 15:39, 28 June 2010 (UTC)

Yes I remember asking a similar question a while back. One thing that the previous question brought up is that some elements are harmful if they are inhaled, but not all that harmful if they are eaten, since they are not absorbed into the body. So your question on which element is most toxic is going to depend on the manner of exposure. Googlemeister (talk) 16:19, 28 June 2010 (UTC)

High level nuclear waste

I thought all high level waste can be recycled and reused? But according to High level waste, it doesn't mention recycling anywhere in the article. Just disposal. 148.168.127.10 (talk) 15:20, 28 June 2010 (UTC)

Actually it does mention it quite a bit, but perhaps in a term with which you are not familiar: nuclear reprocessing. --Mr.98 (talk) 15:42, 28 June 2010 (UTC)

High-level waste is the highly radioactive waste material resulting from the reprocessing of spent nuclear fuel so the stuff is already recycled. Only the material which is not good for a nuclear reactor any more is disposed. There are highly radioactive elements not usable for fission especially the lighter elements produced by fission --Stone (talk) 15:53, 28 June 2010 (UTC)

The terminology seems to be: once you get it out of a reactor, it is spent nuclear fuel (SNF). If you reprocess that, the result is high-level waste (HLW). Now what's confusing is that our article on radioactive waste does not differentiate between the two even though they are quite different from an economic and a physical standpoint. I suspect this is because we are going by US definitions and the US is kind of muddy about such things, since it does not reprocess except for military purposes (and hasn't done that for awhile, I don't think), so we treat them as being basically the same from a waste perspective. In France, though, the distinction would be important, as they do civilian reprocessing. --Mr.98 (talk) 16:14, 28 June 2010 (UTC)

wormholes

I would like to win the nobel prize by building two wormholes, one leading to a very hot place (e.g. surface of the sun), one leading to a very cold place (lots are available), and use the heat difference to gain, in human terms, "free" energy. Also insofar as the wormholes are unstable and require energy, some of this energy could be invested in keeping them stable through some means. The key thing is that the wormholes don't have to be very big, now do they? An infitessimal point of high heat is enough to drive an engine, isn't it? Now, I would like to know how to make a wormhole, as I've looked on the Internet and no manufacturer sells such a solution, at any price. It will be very hard for me to find investors if I cannot even quote the price of what I am trying to acquire! Therefore, I would like to get a price estimate for building one very small, but stable wormhole. If it is in the billions of dollars, rather than a few hundred thousand or million, can someone explain why I have to pay so much, and can I somehow get around those billions by doing some of the work myself or in-house? In all, I would like to approach the subject much as an investment project in building a new power plant, however my real personal interest is in the Nobel prize. Thank you kindly for any help you may have to offer toward my goals. Very truly yours,
Philius Botsch —Preceding unsigned comment added by 84.153.206.127 (talk) 16:25, 28 June 2010 (UTC)

It cannot be done for any amount of money with current technology. Even if you had all the money of every intelligent race in the entire universe, you couldn't purchase a wormhole machine because they do not exist. -- kainaw™ 16:29, 28 June 2010 (UTC)

I did not mean in the lower-class sense of purchasing something on the shelves, on display, or in the catalogues, I meant in the bespoke sense of paying for the work that will lead to the realization. Of course, in the former sense, if currently no mechanical watch includes a hydrometer, then even a hundred billion dollars will not buy you one off of any shelf or out of any display on Earth or anywhere in the Universe. To a prince, of course, far less than a billion is needed if he is to have a mechanical watch with a hydrometer. It is in this latter sense that I ask how much it will cost. 84.153.206.127 (talk) 16:37, 28 June 2010 (UTC)

I believe Kainaw understood the intent of your question. There is no reason to believe that a way of creating and maintaining a stable wormhole can be developed for any amount of money. This is more like "building a watch that makes time run backwards" than "building a watch with a hygrometer." -- Coneslayer (talk) 16:44, 28 June 2010 (UTC)

I was under the impression that it was fully possible under the standard model of physics, ie you do not have to change physics if you are to have a wormhole. What are the mechanisms being proposed that would allow for the very wormhole standard physicists (such as Hawking, Greene, etc) talk about, and, engaging in a bit of blue-sky thinking, what are - let me put it this way - what sum has been paid for comparable achievements (physically allowed, however nowhere realized upon inception, and with uncertain prospects) that have in fact been brought to fruition? (quantum computing, etc, etc, etc). That might give me a baseline to base my calculations on. 84.153.206.127 (talk) 16:56, 28 June 2010 (UTC)

You are under a false impression. As I say below, you need to add exotic matter to the standard model if you are going to get stable wormholes and there is no reason to believe exotic matter is possible (and plenty of reason to believe it isn't - for example, wormholes can mess with causality in ways that a lot of scientists suspect is impossible). --Tango (talk) 17:02, 28 June 2010 (UTC)

Thank you for dispelling my false impression. In your estimation, in that model which is the standard model with the addition of exotic matter (a model that granted might not describe our universe) what mechanisms could cause a wormhole? (if you know) or, if you don't know, what methods are good candidates to potentially cause wormholes. Thank you kindly for your input. 84.153.206.127 (talk) 17:12, 28 June 2010 (UTC)

If you want a Nobel Prize, you're going to have to earn it. Generating free energy in the way you describe would probably be worth a Nobel Prize, but the key part is creating the wormholes. Once you can create wormholes, using them to make a heat engine is trivial by comparison. Current theories suggest that useful wormholes (ones that remain stable for long enough for something to pass through, including energy) can only exist if you have exotic matter, in particular matter is negative mass. At the moment, we have no evidence that such matter is even possible. We have no idea how to create it. If you can solve that problem, you'll probably get a Nobel Prize. --Tango (talk) 16:42, 28 June 2010 (UTC)

Thank you for your detailed response. When you say "we have no idea how to create [it]" where "it" might not be possible, can you tell me which candidate methods are in the minds of serious, credible physicists who would even write the words "useful wormholes" in succession? No idea = no candidate methods at all, if I list everything I can think of that is physically possible to do with the objects of the universe, they would reply to each one "not worth a thought"? 84.153.206.127 (talk) 17:10, 28 June 2010 (UTC)

Assuming you're not just trolling, which I suspect to be the case, then no such method exists to create a wormhole, because there is very good evidence they don't/can't exist. No amount of money will buy you something which is impossible. Further more, if you want the Nobel Prize, it's usually a prerequisite that you develop the technology and theory yourself or as a group, not asking others to do the work for you and then claim it as your own. Lastly, I suspect this sort of theory would obtain several Nobel prizes. One of discovering the existence of wormholes, another for creating one, another for using the system to generate free energy. Good luck to you, sir. Regards, --—Cyclonenim | Chat  16:57, 28 June 2010 (UTC)

Thank you for your detailed response. I believe you are asking me to make a jump from your justified reasoning "because there is very good evidence they don't/can't exist" for the statement "no such method exists to create a wormhole" to the unjustified statement "there is no candidate method to create a wormhole" on the same grounds. Non sequitur. Clearly, there is something that impels physicists to talk seriously of wormholes: in their blue-sky thinking, what mechanisms could even be candidates for creating these? Kind regards, PB 84.153.206.127 (talk) 17:10, 28 June 2010 (UTC)

Some physicists believe that wormholes can exist. Some do not. Some believe that they do exist. Of those who believe that can and do exist, they mostly all believe that wormholes only exists for less then a nanosecond and are extremely tiny. To get the science-fiction version of a wormhole, you need tons and tons of energy. You can't use real energy. You have to use "negative energy". This is the energy that is the opposite of real energy. You pump negative energy into the wormhole to blow it up like a balloon. As you'd expect, negative energy doesn't react nicely with real energy, so we are basically discussing an attempt to keep a violent explosion much more powerful than a supernova under control. Further, there is no proof that negative energy exists. There is no way to detect it or create it. There is no way to detect a wormhole or predict where one will be. There is no way to inject energy that you cannot create into a wormhole that you cannot find. There is no way to control the wormhole if you had the energy you can get and the wormhole you can't find. In other words, this is all theory. It is not reality. Your best bet is to fund the creation of a time machine to jump millions of years into the future and bring back their technology since we are much closer to time travel than wormhole creation and use. -- kainaw™ 17:19, 28 June 2010 (UTC)

Thank you, your response has finally brought home to me just what I have to do. 84.153.206.127 (talk) 17:34, 28 June 2010 (UTC)

Just so we're clear, what you "have to do" is give up. At present, this cannot be done, and unless you are the most brilliant scientist in existence (and sorry, but I do not get that impression), then you will not succeed in this monumental, probably impossible-at-present, task. Regards, --—Cyclonenim | Chat  17:55, 28 June 2010 (UTC)

Seriously, I am glad you guys were not talking to Gallileo or Newton when they were doing science. If the guy wants to try to discover and then create wormholes, I say go for it. Just understand that the odds of success are low (but not zero). Googlemeister (talk) 18:25, 28 June 2010 (UTC)

Galileo and Newton were both experts on the existing science that they ended up overthrowing (actually did Newton really disagree with the established position on anything?). The OP has much to learn about existing science before he can hope to create new science. --Tango (talk) 18:30, 28 June 2010 (UTC)

I talked with God - it took 45 minutes of prayer - and you guys are absolutely right. He told me that wormholes are an impossibility. Everything several of you said above is exactly right, and so I must abandon this avenue of both basic research and development. Thank you for bringing me to the point where I seriously questioned my premises and invested the time to get a definitive answer. I hope you will be as helpful the next time I have plans on an equal scale. Very sincerely yours, Philius Botsch. 84.153.206.127 (talk) 18:43, 28 June 2010 (UTC)

Thanks for the trolling. I really hope I'm not the only person who can see that. Regards, --—Cyclonenim | Chat  19:06, 28 June 2010 (UTC)

You are not alone, at the very least it would be good if people understood that volunteers on this desk do not do it out of a desire to satisfy someone elses every whim, or do 99.9% of their work for them. But hey! who knows?Sf5xeplus (talk) 21:23, 28 June 2010 (UTC)

Re: Newton: postulating gravity as an "occult force" was considered pretty scientifically and philosophically controversial at the time. The issue, basically, was that Newton proposed gravity as a force that acted at a distance for reasons he did not understand. This was considered kind of shady by people who considered themselves to be serious thinkers. It also didn't help that Newton basically thought that the entire universe would fall apart pretty quickly if God wasn't actively holding it together constantly. In the long run, though, Newton's laws work pretty dang well, even if you don't know what the big G "really means" in physical terms. Even today—well after Einstein gave us a better explanation of what is going on with gravitational force—we are still trying to come up with a wholly satisfying explanation (i.e. quantum gravity). So yeah... Newton was controversial, definitely disagreed with the established position on a lot of things (and not all of which he published on). --Mr.98 (talk) 19:51, 28 June 2010 (UTC)

What makes the above question amusing but not very encouraging is 1. the desire is to do something that is assumed will be so scientifically revolutionary that it would warrant a Nobel Prize, 2. the question asker happily admits he has no idea how this could be done, and 3. the question asker would like us to supply the means of doing it. This is not a serious endeavor. If we knew how to do it, and thought it would work, why wouldn't we do it and win the Nobel ourselves? We aren't running a charity here. Or any other scientist for that matter, including those who have spent their entire lives dreaming about the physics of wormholes. I'm not saying it can't be done, but you aren't going to do it the way you're trying to do it. If there is a Nobel to be won, it won't be won by asking us to do the work for you! --Mr.98 (talk) 19:54, 28 June 2010 (UTC)

Actually, we are running a charity here... --Tango (talk) 20:16, 28 June 2010 (UTC)

The goal of Wikipedia is to provide information. We provided it. What the OP does with it is his/her business. Some of our OPs are serious and legitimately curious individuals who make good use of the free service we provide. Some OPs are giggly adolescents who don't realize the amazing learning tool that they have been given free access to. That's fine; we provide high-quality responses anyway. The world has ways of sorting individuals for us, we don't have to waste our time doing that. All we do is provide scientific references. OP: read Physics, if you actually have even a slight inclination or interest. Nimur (talk) 21:37, 28 June 2010 (UTC)

If you have a large pile of money - you could spend it on paying a bunch of physicists to try to build you a wormhole - but that is an unbelievably risky thing. We don't know that wormholes can exist - if they can, we don't know whether or where any can be found naturally, we don't know how to create them, even if we had one, it would probably be smaller than an atom - and the only way to make it bigger might be to somehow (we don't know how) feed it with 'negative energy' - which may also not exist, not be manufacturable, etc, etc. Safe to say, the probability of getting any return on an investment is microscopically tiny. You have (maybe) a one in a trillion chance of getting a wormhole by spending (let's say) a trillion dollars in research. The other 999,999,999,999 times, you blow all the money and have nothing but a lot of REALLY interesting (but useless) research papers to show for your money.

You can make money far more reliably by (for example) investing in electric car design or fancy new solar panel designs. Even a relatively modest (millions of dollars - but not billions or trillions) would produce a really good probability of making a decent profit on your investment. The problem here isn't about how clever your initial idea is - it's about risk. SteveBaker (talk) 23:37, 28 June 2010 (UTC)

Battery chemistry labs

Other than UT Austin where are the best battery chemistry laboratories, who has been running them, and what are they known for? 208.54.14.26 (talk) 16:27, 28 June 2010 (UTC)

The Cui lab at Stanford University got a lot of press a few years ago for some nano-wire lithium ion battery technology. They are a materials-engineering and chemistry research group. You can read brief introductions to their resesarch here and a list of scholarly peer-reviewed papers here. Nimur (talk) 21:42, 28 June 2010 (UTC)

Photonic computers

Why aren't photonic computers commercially available? They're much smaller and faster than electronic computers, so there would seem to be demand for them since people continue to buy new, faster electronic computers. --76.77.139.243 (talk) 16:42, 28 June 2010 (UTC)

I trust you've read optical computing? The last paragraph in 'Misconceptions, challenges and prospects' discusses why it is not in widespread use just yet. Regards, --—Cyclonenim | Chat  16:48, 28 June 2010 (UTC)

They use more power, but aren't they still faster despite that fact? --76.77.139.243 (talk) 16:58, 28 June 2010 (UTC)

It's not just about power and speed. Electronic computers combine multiple signals to perform complex computational tasks. Photons don't interact with each other (in this case) and so you can't combine signals easily. Regards, --—Cyclonenim | Chat  17:53, 28 June 2010 (UTC)

I don't think there is sufficient motivation to develop the technology yet because we haven't reached the limits of what we can do with electronic computers. There are at least a few more generations of electronic technology to go before we need to worry about developing photonic computers and the development cost of better electronics is much cheaper than developing photonics from scratch. --Tango (talk) 17:05, 28 June 2010 (UTC)

Our optical computing article is full of glaring errors and scientific inaccuracies. I'll try to rework it over the next night. For example, "Light, however, creates insignificant amounts of heat, regardless of how much is used." This is totally incorrect. Radiative heating occurs at all frequencies of electromagnetic radiation. Other discussion about interference, photonic logic, and so on, are all in need of attention. I would not recommend this article as a source of information until it has gone through significant editing with a reliable source. I'm hitting the library tonight to get a book on optical computing. The article does not seem to convey that light is just a different frequency of electromagnetic waves; some different physical phenomena are more common, and different materials have more desirable properties; but nothing is fundamentally different between optics and lower-frequency electromagnetic waves. Nimur (talk) 20:09, 28 June 2010 (UTC)

But electronic computers use electric current, not electromagnetic waves. Rmhermen (talk) 20:43, 28 June 2010 (UTC)

That's debatable. Modern computers use electromagnetic signaling - current is a parasitic effect. If we could design transistors that switched without any transient current, many of our power-density problems would be solved. E.g. zero-current switching. We don't use the current for anything - it is like "friction" in an engine, and only serves to dissipate energy. The work of calculating is done by switching signal-levels. At the fundamental level, information theory dictates that we must dissipate some tiny quantity of energy in order to store information. (This is sort of the "2nd law of thermodynamics" as applied to information computation, [25]). But the overwhelming majority of the electric current in a modern VLSI system is there because our transistors are "leaky." See the Power section and the logic section of our CMOS article, for example. Nimur (talk) 21:06, 28 June 2010 (UTC)

So Nimur wants to debate with Rmhermen... zero-current switching is an emi reduction technique that has nothing to do with computing. It is not only information theory and leakage that dictate some current flow in switching signal-levels. Any real conductor has capacitance and a flow of current is needed to change the voltage (= binary logic level 0 or 1) on it. Cuddlyable3 (talk) 12:18, 29 June 2010 (UTC)

I do not want a debate. You can read how information is conveyed in CMOS logic at the CMOS article. I can recommend several good books in addition. Digital Design: Principles and Practices ([26]) has an entire chapter dedicated to introducing you to the electrical behaviors and signal pathways in digital circuits. CMOS RFIC will introduce you to a more quantitative analysis of the characteristics of a modern VLSI circuit's electrical properties. Yes, any capacitor requires a current in order to charge. And it must by necessity dissipate that current as a resistive loss, or else it oscillates and information is not stored on it. Right now, the state of the art is such that the actual current is much higher than it theoretically could be, due to additional parasitic losses and leaks in the device. (In a photonics circuit, that would be analogous to "dielectric losses" - which are even worse than the thermal losses at VLSI scales). Any technique that improves CMOS switching current will reduce dynamic power dissipation in a digital circuit, whether the signal is propagated by light-frequency or RF. At present, though, there is no "CMOS" for optical frequencies because there are no practical optical transistors. Instead, photonic computer research usually focuses on other mechanisms to store information, such as in the form of frequency modulation, using nonlinear materials to perform frequency mixing. These techniques are at present not sufficiently developed to build a VLSI system. That is the primary reason we do not have optical computers - they can not be built in a way that their device counts compare to RFICs. Nimur (talk) 16:31, 29 June 2010 (UTC)

Least dangerous compound

I noticed that even seemingly harmless compounds, such as sodium bicarbonate, don't have all 0 for their NFPA 704; is there anything which is ranked 0 in all three categories? --76.77.139.243 (talk) 17:09, 28 June 2010 (UTC)

Lotsa stuff. See for yourself. --Ouro (blah blah) 17:51, 28 June 2010 (UTC)

Water? --Chemicalinterest (talk) 22:00, 28 June 2010 (UTC)

I was surprised myself! --Ouro (blah blah) 05:19, 29 June 2010 (UTC)

Am I missing something? The above ref lists water from "Mallinckrodt-Baker" as having a 0 for all three Nil Einne (talk) 09:40, 29 June 2010 (UTC)

Our article on Properties of water had it down as 0-0-1. Checking the criterion for R=1, "Normally stable, but can become unstable at elevated temperatures and pressures", water is obviously R=0. I've changed the infobox. Physchim62 (talk) 09:57, 29 June 2010 (UTC)

Ah okay I checked the link to water and couldn't find anything about the NFPA from a cursory glance/search so gave up although I wondered if there was an article which covered the chemistry in more detail. From the earlier ref, it doesn't list any NFPA for "Water Deionized and Bacteria Filtered" from CMS. I've been thinking that may be part of the reason is some feel imparting a NFPA rating on water particularly for Instability/Reactivity is questionable since the definitions are partially based on the reactivity with water Nil Einne (talk) 11:50, 29 June 2010 (UTC)

Applications of Wormholes

The last question got me curious about wormholes, and what they could potentially be used for. Assuming they exist, and they work, how many ways can they be used? The possibilities are enticing. Like what was mentioned before, they can be used as a heat engine, faster than light travel, time travel, weapons - I would assume sending a bomb through a wormhole would be pretty powerful, but you could also just open one mouth near a target on earth, then open the other in the vacuum of space, and you have a small black hole that sucks everything into it. 148.168.127.10 (talk) 17:46, 28 June 2010 (UTC)

By the word "applications", I assume you mean "worthwhile applications". Keep in mind that IF wormholes exist and IF we can find one and IF we had technology to keep one open so it could be used, it would take massive amounts of technology and energy to do so. So, if you wanted to send a bomb through one to blow up someone's city, you'd first have to smuggle in all the technology to hold it open on the city's end. Similarly, to open it to the vacuum of space, you'd have to smuggle in all the technology. It is the equivalent of shooting someone with a rifle by asking them to aim their end of the barrel while you pull the trigger on the other end. Further, if you had the technology in place to hold open a wormhole, you would have the technology in place to simply destroy whatever it is you want to destroy. -- kainaw™ 18:00, 28 June 2010 (UTC)

(ec) I'm not sure they would work well as weapons. I doubt you could just "open one mouth near a target". You would probably have to drag one mouth from your lab to the target, which makes it difficult to use as a weapon (you could just take a big bomb instead). Faster than light travel is the obvious application, although once again you would probably have to drag one mouth there at slower than light speeds, so the first journey to your destination would have to be by the slow route. Time travel is also a possibility, although it probably couldn't be used to travel back to before you created the wormhole. The heat engine idea would probably work - it's sort of like putting a solar panel right next to the sun, but you don't need to transfer the electricity back to Earth. Faster than light information transfer is probably another option - no more lag on satellite feeds. (You will notice that every idea I've mentioned has "probably" in it - the existence of stable wormholes requires some change in our understanding of physics and there is no way of knowing what else would change with it.) --Tango (talk) 18:05, 28 June 2010 (UTC)

you've smuggled your response to my heat engine idea down here, but I'm on the case. Just so you know, my proposal is for there to be TWO wormholes, and so you don't have to transport the electricity back to earth, because the heat exchange happens right in the Philius Botsch Power Center on Earth. In the power engine, you have both the other end of the "hot" wormhole (with its other mouth on the surface of the sun, or as far away from a sun as you require, e.g. in orbit around a sun at a certain (perhaps low) distance) and the other end of the "cold" wormhole (with its other mouth on some cold gaseous planet, for example). Then you just run the engine off of the heat difference. No interplanetary power transportation required! Very sincerely yours, Philius Botsch 84.153.206.127 (talk) 18:40, 28 June 2010 (UTC)

Yes, I understood the idea and, if you can get the wormholes, it should work. There is no real need for the "cold" wormhole - the Earth is cold enough. --Tango (talk) 19:10, 28 June 2010 (UTC)

with that mentality, you should work for an oil company! The reason for the cold wormhole is to stave off at least some of the global warming associated with the scheme. Kindly, T. Philius Botsch84.153.206.127 (talk) —Preceding undated comment added 19:15, 28 June 2010 (UTC).

asteroid mining

If hypothetically, there was an asteroid that was made of solid platinum, 99.9% pure, what is the largest ΔV for the break even point to send the platinum back using current technology?

For simplification, we can assume that we don't need to crash chunks of metal into earth, we have a nice space station in geosynchronous orbit. Also, despite bringing tons of platinum back, the price is not going to crash, and the mining equipment is already on site. Googlemeister (talk) 18:38, 28 June 2010 (UTC)

Assuming you throw out economics ("the price is not going to crash"), you can spend whatever you want to get that much platinum on hand and you'll still be able to buy half the planet. Say you get this asteroid at 1km across -- there are 1-2 million asteroids that size or larger in the main belt. That's 4 quadrillion cubic centimeters of platinum. 90 trillion kg of platinum. At $1500/oz, that's $4.5 quintillion USD of market value. By way of contrast, world GDP is $60 trillion USD. So spend whatever you like. No meaningful answer is possible. — Lomn 19:01, 28 June 2010 (UTC)

If you brought that amount back, the price of platinum would crash to that of for example water. 92.24.188.76 (talk) 19:27, 28 June 2010 (UTC)

I disagree that no meaningful answer is possible. For example, to lift things into low earth orbit costs somewhere around $10,000/lbm. that weight of platinum (if at $2,000/toz in reality is is like $1600/toz) is worth around $29,000, so obviously LEO is feasible, but the ΔV to get to mars would mean you can not put something on mars for $10,000/lb, it will cost more, so at what distance does that price equal that of platinum? Googlemeister (talk) 19:35, 28 June 2010 (UTC)

That seems to be a completely different question. The platinum asteroid is already in orbit; it needs negligible delta V to reach Earth. I don't see where a launch from Earth enters into the picture. — Lomn 20:37, 28 June 2010 (UTC)

(Edit Conflicts) No, similar question and not negligible, because as a first-order approximation*, if it takes X delta V to get something from the Earth's surface to LEO (or GEO, or Mars, or wherever), it will take the same delta V to get it from LEO (or wherever) to the surface: delta V is the difference in velocity between two different orbits (mathematically, everything is in an orbit) and therefore equals the change needed to get from one to the other, and is a scalar quantity independent of which direction the change is, so it will take the same amount of energy (hence, roughly, cost) to move a tonne of platinum from the Asteroid Belt to Earth as it would to move a tonne (of anything) from Earth to the Asteroid Belt. The article Delta-v budget may be helpful.

Since you've stipulated a return only to a GEO station (which presumably has some pressing need for vast quantities of platinum) you'll save the considerable delta V between GEO and Earth's surface (remember, there is a good deal of delta V even between LEO and GEO, and as Robert Heinlein famously said, LEO is "halfway to anywhere"), and need only consider that between the asteroid and GEO: this will depend heavily on the asteroids's initial orbit, and can be minimised by a carefully timed Hohmann transfer orbit plus additional necessary manouevres to allow for whatever degree of non-coplanarity is involved.

(*I say "first order approximation" because this ignores some cost of moving some of the fuel necessary for subsequent manoeuvres (see Tsiolkovsky rocket equation), the possible use of aerobraking, etc, but for this initial analysis it's close enough.) 87.81.230.195 (talk) 21:46, 28 June 2010 (UTC)

It takes a lot of thrust for a sustained time to get an object from the Earth's surface into a low Earth orbit. It clearly does not take a comparable sustained thrust to get it out of low Earth orbit. If there is an atmosphere at the destination, spacecraft do not "back down on the rocket" like in old space opera sci-fi films of the 1930's. (Granted, they did that on the Moon where aerobraking was impossible). All that is required is a brief and relatively weak retro-rocket burn for something in low Earth orbit to decrease the velocity by 1% or so. The object (space capsule or shuttle) then drops enough closer to the surface that air resistance slows it, while the ablative heat shield (on older Apollo capsules and such) or the insulating ceramic tiles (on the shuttle) heat up. A cargo mined from an asteroid would need to be sent on a carefully chosen approach to Earth for aerobraking to work. If the angle of approach is too direct, it will mostly burn up like a meteor. If it is too shallow, it will skip off on another trip through the solar system. If the angle is just right, and it has an ablative heat shield large enough relative to its mass, it will fall in a descending path partway around the Earth and land relative unscathed in the desert where it can be recovered. The Apollo missions returning from the Moon got to the ground this way. For a cargo of metal from an asteroid, a hard landing which does not hit someone or their property and does not bury it too deep in the ground would be a windfall. A parachute might not be necessary (at least not a huge one required for a gentle landing) if the payload is a hunk of metal. We have a very long history of using pass=bys of various planets to aim a spacecraft toward some other planet, and of achieving precise approach paths. No space pilot on board would be necessary or desirable. Since the cargo is starting a long way off, relatively small thrusters could make the midcourse corrections needed for a precise reentry trajectory in relatively short bursts. Edison (talk) 18:02, 29 June 2010 (UTC)

Where are you getting that the asteroid is in orbit around earth??? Obviously if that was the case, then the question would not make sense. If the asteroid was in orbit around the sun at the same distance as mars, though the ΔV is going to be higher. At what ΔV does this become uneconomical? Googlemeister (talk) 20:55, 28 June 2010 (UTC)

I should have been more clear: the asteroid is in solar orbit. Orbital mechanics allow for absurdly efficient transfer orbits. Given the vast amounts of handwaving already present in your assumptions, you cannot find a breakeven point. On the other hand, given reasonable assumptions, you also can't find a breakeven point. It's nicely symmetric that way. — Lomn 21:10, 28 June 2010 (UTC)

You know, if you are going to be obtuse, I would rather you not answer. Googlemeister (talk) 21:20, 28 June 2010 (UTC)

The assumption of fixed price is seriously flawed. There is no need for 90 trillion kilograms of platinum. What would we do with it? Who would pay for it? How could you expect to sell all of it at current prices? That would be 10,000 kilograms of platinum for every member of the planet, with 10 trillion kilograms left over. How could you expect a reasonable market to exist for this quantity of metal? If you want to justify space travel economically, you can't throw economics out the window. Nimur (talk) 21:02, 28 June 2010 (UTC)

Obviously a fixed price is not accurate, but then the question would not be answerable because you could not tell me how much the price would be impacted by adding 50 tons, or 100 tons or 500 tons of platinum to the market could you. And I never said the asteroid was 9e16 kg. Googlemeister (talk) 21:05, 28 June 2010 (UTC)

You're right. Specific numbers are tangential, since this is all hypothetical anyway. But the point is, space travel is rarely justified in the same way as trade down here on earth. If bananas are cheaper on another continent, you can go buy them there and ship them here. But space travel involves going someplace where earth economics are meaningless - things only have "value" if they contribute to some objective. So, if your objective is "get lots of platinum", then you have to demonstrate that the best way to do that is space mining. It's pretty unlikely that any resource is easier to get in outer space than down here on earth - so mining for commodity metal is not a very good objective. Most of human space exploration has been justified in terms of expanding our understanding of the universe, not in terms of economic benefit (though some politicians justify space exploration because of the peripheral technological and economic development it does create here on earth). Nimur (talk) 21:28, 28 June 2010 (UTC)

Find a large chunk of the platinum and than build a very simple catapult on it an throw 1 meter size balls on trajectory which will collide with the earth. Some 50% will evaporate, but that is not a big problem. Cheap an easy. Calculate 10 more likely 50 Ariane 5 launches each 250 mio Euro and another 10000 mio Euro for the program to bring people there and back (mining is not a job for robots). This makes a lot of platinum you have to get back.--Stone (talk) 21:27, 28 June 2010 (UTC)

The question isn't "How much should I spend to bring back an entire platinum asteroid?" It's "If I'm harvesting some small portion of the asteroid, how much fuel can I afford per ounce of platinum? And is that enough to bring that ounce of platinum home?" APL (talk) 02:00, 29 June 2010 (UTC)

What complicates this stuff is that some materials which are essentially worthless on earth (air, water, dirt) are phenomenally valuable when you put them someplace else. A ton of air can be had for free down here on earth - but just 200 miles away in low-earth-orbit, at $10k per pound of launch costs, that same ton of air is worth $20 million. Just taking an icy asteroid and smacking it into the equator of the moon or Mars - or getting it into any kind of stable earth orbit would produce a resource that would make a spectacular difference to the future of humans in space. In that sense, the mere fact of where you place this huge pile of metal is more important than what it's made of. Platinum is a bit of a pain to work with, and it's kinda heavy. Aluminium, water, oxygen or even reasonably fertile dirt would probably be worth more in those kinds of quantities because while platinum's value is due to it's rarity (which you're about to destroy), the value of other materials is due to the amount of fancy technology and rocket fuel you're saving by not shipping it up from Earth - and that's something whose value would be much harder to erode. SteveBaker (talk) 23:22, 28 June 2010 (UTC)

The article Asteroid mining might help. Cuddlyable3 (talk) 11:56, 29 June 2010 (UTC)

Getting rid of freezer odour

A couple of weeks ago I had the unfortunate experience of finding out my freezer had accidentally become unplugged (thanks to the stupidly short mains lead) and the contents had been in there rotting for at least a week. I just about managed to bag and bin the contents without being physically sick (the smell was so bad it would have offended the devil himself) and have cleaned the thing - thoroughly - several times, with bleach, disinfectant and various other such products but to no avail. The smell was on my hands for days and even white spirit (which is usually pungent enough to mask any other smells) only brought a temporary respite.

I then put the freezer outside with the door off and left it there for 2 weeks (no rain luckily) and there is still a conspicuously unpleasant odour, although a shadow of its former self. Is there any way I can exorcise this satanic stench permanently or is it best to get rid of the freezer? —Preceding unsigned comment added by 94.197.153.113 (talk) 19:00, 28 June 2010 (UTC)

You're probably going to have to partially take apart the freezer. There might be some rot hidden behind some of the plastic panels. Once you remove all the bulk rot material you'll want to force the bacteria to finish the job - i.e. get the rot going at high speed, make the freezer warm and humid, but aerobic (i.e. let oxygen in). Also, once you turn it on the cold temperature will probably stop the smell. And next time (hopefully not :) buy a gas mask in a hardware store. Ariel. (talk) 19:11, 28 June 2010 (UTC)

(ec)My freezer also failed while it was loaded with fish. I filled a window cleaner spray with undiluted chlorine bleach, sprayed every internal surface including the seals and latch, then shut the door for a day. After what had gone before, the lingering slight chlorine smell was a blessed relief. Cuddlyable3 (talk) 19:13, 28 June 2010 (UTC)

I agree that you need to let the bacteria finish the job they started. They are breaking the remaining food residue down and making the stink in the process - but eventually, they'll run out of stuff to decompose - and then you're done. The more stuff you can remove yourself, the faster that'll happen. Pay particular attention to small crevices, screw heads and places like that. The large, flat, smooth surfaces are easy to clean. When something similar happened to me, I found that leaving it outside (opened) and in sunlight helped.

Oh, and at the risk of sounding obvious, may I suggest getting an extension cord so that the same problem doesn't occur in the future? After all, you said that the freezer got unplugged because of a "stupidly short mains lead" -- sounds to me like an extension cord would fix that for good. 67.170.215.166 (talk) 00:59, 29 June 2010 (UTC)

On swallowing food items larger than one's own head...

Just saw this on YouTube. How long do you reckon it takes to digest that? How is there even room in the digestive system to hold and move that through? --Kurt Shaped Box (talk) 19:38, 28 June 2010 (UTC)

"this", btw, is a kookaburra eating a rat. --Tagishsimon (talk) 21:43, 28 June 2010 (UTC)

Don't know much about kookaburras, but I know a different species which can do that, too. --Ouro (blah blah) 05:33, 29 June 2010 (UTC)

NFPA 704

Why does sodium bicarbonate have a 1 in toxicity? People eat it all the time with no ill effects. --75.25.103.109 (talk) 19:59, 28 June 2010 (UTC)

I think that the solid can cause ill effects by reaction with gastric acid. --Chemicalinterest (talk) 20:03, 28 June 2010 (UTC)

Looking at the International Chemical Safety Card here, it could be because the powder is irritating to the eyes. Physchim62 (talk) 20:20, 28 June 2010 (UTC)

I don't know if this is related and it's been a while and I can't find any sources but I believe there are or were some regulations for labs which also oddly enough end up covering sodium chloride in NZ which impose some requirements or restrictions if you store it in large quantities that relate to the fact as with many things it is obviously toxic if you eat too much and while the level is fairly high (I think I've heard 500g), it's not considered high enough that you don't have to worry about it. This has unsurprisingly sometimes the subject of ridicule since someone in a fish and chips shop has no such requirements surrounding how they store their sodium chloride. Also from NFPA 704 "Exposure would cause irritation with only minor residual injury (e.g., acetone)" it doesn't sound like eating is the only consideration here as Physhim mention you don't generally want it on your eyes and for that matter open wounds or whatever. Nil Einne (talk) 11:40, 29 June 2010 (UTC)

evolutionary history of apoptosis and vertebrate immune systems

What was the precursor to the vertebrate immune system and its diversity? What did the very first white blood cells look like? (They seem a bit renegade...did they evolve from cells that had a little of a rebellious streak?) Also what were the predecessors to apoptosis? John Riemann Soong (talk) 21:38, 28 June 2010 (UTC)

Lot of questions - I'll try my best! Firstly, have you read Immune_system#Other_mechanisms? I'm not sure about the evolution of white blood cells, this might help though or other papers here. This discusses the evolution of apoptosis. Interestingly there are some analogies between plant and animal immune responses - systemin activates MAPKs in turn releasing jasmonic acid from the membrane, a similar system causes the production of prostaglandins in the mammalian inflammatory response (see this). Although systemin is only found in the Solanaceae, similar peptides have been found in Arabidopsis. 86.7.19.159 (talk) 23:37, 28 June 2010 (UTC)

anywhere I can buy movement protein?

I'm also using more professional sources, but I thought I'd try for a quick answer here...does anyone know if tobacco mosaic virus movement protein will work on garlic or onion cells (or similar edible rootlike tissues) and where I can buy it? John Riemann Soong (talk) 21:41, 28 June 2010 (UTC)

This paper discusses alfalfa mosaic virus movement proteins moving through the plasmodesmata of onion epidermis cells. I take it that this collection in Wageningen would have it, it would cost $75, or more likely be free. 86.7.19.159 (talk) 22:46, 28 June 2010 (UTC)

Onion cells ... exactly what we are using. (It's why I brought my potato peeler and various random vegetables to work today... I love this project.) THANKS. John Riemann Soong (talk) 22:49, 28 June 2010 (UTC)

No worries, this might be a better option, now that I've noticed you're in the US. 86.7.19.159 (talk) 23:41, 28 June 2010 (UTC)

Uhh can't seem to find a specific entry or price. My supervisor recommended me some large protein company, but I can't seem to remember the name. John Riemann Soong (talk) 16:17, 29 June 2010 (UTC)

Ancient lead

This story says that nuclear physicists are stoked that a cargo of lead ingots was found on the floor of the Mediterranean after having lain there for 2000 years, because almost all of the lead-210 has decayed by now, so they're going to use it to shield the "CUORE" neutrino experiment (our redlink article from the "Cuore" disambig page is Cryogenic Underground Observatory for Rare Events) and are happy to have some lead for this purpose that isn't going to emit any radioactivity. Why is this lead particularly different from any random amount of lead ore that was mined yesterday? Is the problem that metallurgists are unable to get "pure" lead of some stable isotope, and some heavier elements are always in the lead and eventually decay into lead-210? Comet Tuttle (talk) 23:16, 28 June 2010 (UTC)

Yes, that is the problem. It is very difficult to separate different isotopes of the same element because you have to use physics rather than chemistry. People 2000 years ago were able to purify their ore into nearly pure lead and all the radioactive isotopes eventually decayed away. We can also get pure lead, but it will contain lots of isotopes, and we can't easily remove the radioactive ones (which wouldn't have been lead 2000 years ago, which is why people then could remove it). --Tango (talk) 23:39, 28 June 2010 (UTC)

From this fact sheet from the Argonne National Laboratory, the culprit appears to be radon-222, which is a decay product of uranium-238. Rn-222 has a long enough half-life to spread small amounts of lead-210 (and hence polonium-210) quite widely in the environment, so I would imagine there would be a particular seeding of deposits of lead ore (often associated with uranium-containing minerals). Physchim62 (talk) 23:44, 28 June 2010 (UTC)

I've just noticed that the reader comments to the Physics World article give the same suggested answer (radon-222). Physchim62 (talk) 23:52, 28 June 2010 (UTC)

Thank you! Comet Tuttle (talk) 05:27, 29 June 2010 (UTC)

Ref Desk in the past has discussed how scientists also like to use steel from pre-1945 battleships as shielding, since after the first atomic bomb detonations, refined iron somehow contains works less well as shielding. It is surprising that in an era before modern chemistry or metallurgy they were able to refine "pure" lead, when all they had was empirical rules of thumb and superstition as guides, with no real way to chemically analyze the result. Edison (talk) 17:35, 29 June 2010 (UTC)

I have the same idea about how savages, such as chefs at four-star restaurants, can cook at all, let alone well, given that most of them don't have even a grade-school, or nineteenth-century understanding of the chemistry involved. 92.230.66.154 (talk) 20:54, 29 June 2010 (UTC)

June 29

Polaroid film powered radio...

As a boy (perhaps 20 years ago), a relative gave me a small blue radio that was powered by Polaroid film. You popped a cartridge in and it powered right up. Aside from the in-hindsight ridiculous wastefulness (and likely, terrible expense) of the device, I find myself now wondering how exactly it drew power from the film. Has anyone ever seen one of these? Any ideas? 218.25.32.210 (talk) 00:59, 29 June 2010 (UTC)

As our Polaroid film article describes, such film cartridges often contained a thin battery. -- Scray (talk) 03:09, 29 June 2010 (UTC)

I had a Polaroid instant camera when I was a kid. It had a flash but no batteries in the camera body. The batteries were in the film cartridge and would power the flash if needed. Dismas|^(talk) 10:44, 29 June 2010 (UTC)

The polaroid film battery by virtue of its slim form can be a component of a Letter bomb. Cuddlyable3 (talk) 11:41, 29 June 2010 (UTC)

The Polaroid Corporation introduced the Polaroid SX-70 in 1972. The camera was automated and highly motorized, so it was not necessary to pull out the film pack for each picture as in earlier Polaroid cameras. There was a fresh "Polapulse" six volt battery included in each filmpack, so there was not the "60 second disappointment" of weak batteries preventing the consumer from using up a film pack at about a dollar a picture (big bucks in 1972). The [27] was a flat lightweight zinc--chloride thin-film battery in a thin insulated pack, with two exposed metallic contact areas. It had pretty low internal resistance (so the motors would run smoothly). It was developed by Rayovac, and measured 3.5 by 2.75 inches, by 1/8 inch thick. (8.9 cm x 7 cm x 0.3 cm.) It was easily removed from the spent film pack after the 10 or so exposures were used up. It usually had lots of energy left in it. It could be connected via clip leads or wires taped to the metallic contacts to power a 6 volt flashlight or other device for quite a while. It possibly deserves its own article, since it had significant coverage in many books and magazine artilcles. Alkaline batteries today probably fill the niche it once, but it had a very high peak current capability of 26 amperes, decreasing to a still impressive 5 amperes after 30 seconds and 2.5 amperes after 60 seconds. and seemed able to supply high current for a long time without pooping out, from a very low volume and weight battery. It used conventional LeClanche carbon zinc technology, so it had that handicap to overcome compared to alkaline. I would be interested to see what a similar flatpack with alkaline battery or rechargeable lithium ion chemistry could do for applications where weight and size are at a premium. Metal cylinder batteries like AA or AAA are not always a good fit in designs for miniature devices. Edison (talk) 17:26, 29 June 2010 (UTC)

Double slit prob

Someone performs the double slit experiment. The probability that the electron passes through the first slit is 1/4. The probability that the electron passes through the second slit is 1/5. What is the probability that the electron passes through either slit? 1/4 + 1/5 = 9/20?––115.178.29.142 (talk) 01:26, 29 June 2010 (UTC)

if they are independent, then with 3/4 probability it will miss the firstslit. Also, it has to miss the second slit, which it does with 4/5th probability. If you want to roll two sixes independently, your chances are 1/6 * 1/6, if you want to miss both slits it is 3/4 * 4/5 = 12/20 = 3/5. So you don't go through either 3/5 of the time, then the rest of the time, 2/5 of the time, you must go through either. 92.224.207.131 (talk) 07:39, 29 June 2010 (UTC)

The issue that the original math misses is that of that 1/4 of the time when it does pass through the first slit, it also passes through the second slit 1/5 of that time. Isn't the whole point of the dual-slit experiment to demonstrate that an electron has wave-like qualities and go through both slits? These are two overlapping/nonexclusive sets of event probabilities (the electron can go through first and/or second), not additive. Say I have 20 scoops of ice cream, of which 1/4 (5) are chocolate and 1/5 (4) have peanuts. That's not 4 of the ones that aren't chocolate--by the strict probabilities, there is one scoop that is chocolate-with-peanuts. So there are 8 not 9 that are [chocolate and/or peanuts]. DMacks (talk) 14:04, 29 June 2010 (UTC)

The question is insufficiently precise. What circumstance do the 1/4 and 1/5 measure? If they measure the probability of going through slit A given that slit B is covered, and vice versa, then the question will make sense, but it is still not answerable in general. The interpretation of the double slit experiment only makes sense if 100% of the time that the electron appears on the far side of the screen it went through both slits and their wave functions interfered. In general, the probability that the electron is observed on the far side of the screen at all depends on that interference which occurs after the slits (which is just how weird quantum mechanics is). So the short answer is that the probabilities are not additive, and one needs further details about the configuration in order to determine the probability of observing the electron on the far side of the screen. Dragons flight (talk) 18:25, 29 June 2010 (UTC)

The inteference term should vanish upon integration. By the time the electron is at the screen, we can write the wavefunction foirmally as:

|psi> = |psi1> + |psi2>

where |psi1> and |psi2> are the (unnormalized) states correspond to the electron moving through hole 1 and 2, respectively. Then we have an interference term for the probability as a function of the position on the screen:

P(x) = |<x|psi>|^2 = |<x|psi1>|^2 + |<x|psi2>|^2 +

2 Re[<psi1|x><x|psi2>]

The last term is the inteference term. However when we integrate over x, tis vanishes because |psi1> and |psi2>, being different eigenstates of the observable that measures through which hole the electron went, are orthogonal. Count Iblis (talk) 19:06, 29 June 2010 (UTC)

Einstein twin paradox confusion

What is wrong with my logic here?

1. An astronaut checks her watch and then leaves Earth at some huge percentage of c.
2. Rather than go out in a straight line, she orbits the Earth, always keeping it in sight.
3. After her watch advances a few hours, she returns to Earth and lands.
4. She finds that three months have passed on Earth.
5. But if the Earth was always in sight, wouldn't she have noticed that the Earth had gone a quarter of the way around the sun?

Sorry, I'm sure this is elementary Einstein physics, but I just don't get it. Is this different than the typical "astronaut-leaves-earth" scenario because my astronaut is not going in a straight line? So is actually in several different inertial frames? Wknight94 ^talk 01:27, 29 June 2010 (UTC)

Well, the astronaut isn't in an inertial frame since you have to accelerate to go in a circle, but that isn't an issue since the astronaut in the original version isn't in an inertial frame either since they turn around and come back (that's the solution to the paradox). The time dilation is compensated for by length contraction, so each observer sees everything as being consistent. I'm not exactly sure what would happen in this case (non-inertial frames are complicated), but if you do the maths it will all work out right in the end. I guess the astronaut will see the Earth's orbit as much smaller than the Earth sees it, so it isn't at all odd for it to do a quarter of an orbit in a few hours. The orbit ought to change shape as the astronaut changes direction, though, so I'm not exactly sure how it would work. --Tango (talk) 01:44, 29 June 2010 (UTC)

If the astronaut went fast enough - in a circle - and waited long enough, billions of years could go by and the sun would burn out, etc., right? Wouldn't the astronaut see all that in the short time she experiences? Wknight94 ^talk 03:20, 29 June 2010 (UTC)

The answer is yes, if this thing somehow happened, she would have noticed that the Earth had gone a quarter of the way around the sun. If she got up to a sufficient fraction of the speed of light, she would see the Earth whirling around the sun at a furious pace. I don't see any contradiction anywhere here. Looie496 (talk) 03:31, 29 June 2010 (UTC)

Just a note though, if you are close enough to actually see earth, then the acceleration from traveling at that speed in a circle is going to kill you. You need to have a radius of 1 ly in order to keep it down around 1g, but of course you can't go around in a circle that big. Googlemeister (talk) 13:51, 29 June 2010 (UTC)

What if you had a really thick mattress? Heh, thanks. I guess the ridiculous-sounding result stems from my ridiculous scenario. Wknight94 ^talk 14:20, 29 June 2010 (UTC)

Sumo

Why don't sumo wrestlers have heart problems? --75.25.103.109 (talk) 02:24, 29 June 2010 (UTC)

First, perhaps we should ask whether sumo wrestlers have heart problems at a rate higher than Japanese men at a similar age? If you have statistics at hand, please cite them. -- Scray (talk) 02:43, 29 June 2010 (UTC)

There is actually some literature on this. Apparently the story is that because they combine high levels of exercise with high levels of calorie intake, they develop a lot of subcutaneous fat but not much of the more harmful visceral fat; see PMID 7859591. Even so they have higher levels of hypertension than the Japanese public as a whole, and after they retire, their levels of visceral fat and heart disease skyrocket. Looie496 (talk) 03:46, 29 June 2010 (UTC)

"Chronical outfit of disposition" - jargon or gibberish

In the article 78391 Michaeljäger an editor recently added the statement "Its chronical outfit of disposition, defined through the Gödel metric, is 0.4206." Is this jargon or gibberish? If the former, what does it mean? -- Tom N (tcncv) talk/contrib 02:36, 29 June 2010 (UTC)

Well, since the reference makes no mention of anything remotely connected to it and "outfit of disposition" returns zero ghits, I vote for vandalism. Clarityfiend (talk) 02:51, 29 June 2010 (UTC)

Well, my google search found a couple more Wikipedia articles where similar statements have been added: HD 171028 b and 1801 Titicaca (reverted, but Google hasn't updated their index yet). Since the Goedel metric is to do with clouds of dust in General Relativity (and asteroids and extrasolar planets aren't made of dust - there is significant EM interaction) and "chronical outfit of disposition" doesn't mean anything that I can find, I'm inclined to agree that it is nonsense. It's good nonsense, though! I've removed it from the two articles I can find it still in. If anyone can provide a reference for it making any sense, feel free to revert me. --Tango (talk) 02:57, 29 June 2010 (UTC)

This IP editor made about a dozen changes to random articles, and they are all clearly vandalism, and have all been reverted as far as I can tell. End of story. Nothing to see here. Move along. Looie496 (talk) 03:35, 29 June 2010 (UTC)

Maybe they're hoping to get a job as a Star Trek writer? Nil Einne (talk) 09:28, 29 June 2010 (UTC)

Blended wing bodies

Are Blended wing bodies stealthy? --The High Fin Sperm Whale 05:50, 29 June 2010 (UTC)

The article cited mentions the the B-2 Spirit stealth bomber. Cuddlyable3 (talk) 11:29, 29 June 2010 (UTC)

That still doesn't really answer the question, since the B-2 is only BWB-ish. --The High Fin Sperm Whale 16:52, 29 June 2010 (UTC)

Along similar lines, it's fair to say that blended wing bodies are stealth-ish. Certainly blended wing concepts can be used in a stealth aircraft (the aforementioned B2), but stealth aircraft can also forego blended wing concepts (the F-117A). Similarly, it would be very easy to make a non-stealthy blended wing aircraft (the exposed engines on the X-48 certainly fit the bill). Throw in that "blended wing" is a term that doesn't appear to be rigorously defined, and I'm not sure that a "yes" or "no" can possibly be provided to the original question. Even "stealth-ish" is fairly useless. By the same arguments, flying wings are also stealth-ish, as are more traditional designs. — Lomn 18:56, 29 June 2010 (UTC)

Are dogs capable of love?

I have two of the sweetest, most wonderful dogs in the world. Do they love me, or am I just projecting human emotions on them? A Quest For Knowledge (talk) 10:04, 29 June 2010 (UTC)

Definitely. Love is strong affection and attachment to someone or something. Dogs and many other animals are capable of love. 82.43.90.93 (talk) 10:35, 29 June 2010 (UTC)

Your opinion, anon. --Chemicalinterest (talk) 10:40, 29 June 2010 (UTC)

A dog is by ancestry a pack hunter. It's emotions are better viewed in terms of Pair bond and pack dominance and subjugation than human emotions. However it's ok for us to love them. Cuddlyable3 (talk) 11:20, 29 June 2010 (UTC)

Love is a very vague term. Since you're on the science desk I suggest you read chemical basis for love, and of course puppy love, and Cupboard Love. And how about Greyfriars Bobby?--Shantavira|^{feed me} 11:15, 29 June 2010 (UTC)

Or Hachikō... Physchim62 (talk) 11:22, 29 June 2010 (UTC)

Rolls eyes skywards. Reading puppy love tells nothing about dogs. Cuddlyable3 (talk) 11:25, 29 June 2010 (UTC)

Get a cat. Then you know that that feeling is simple condescension with a bit of pity... --Stephan Schulz (talk) 11:51, 29 June 2010 (UTC)

There's actually a long debate between people who argue that dogs really like humans, and those who say, "oh, they've just evolved to simulate what humans consider love, in order to get fed." I tend to think that if it looks like love, it probably is love, with full reference to the fact that we don't have a strong scientific definition of "love" that isn't muddled down by centuries of cultural baggage. My dog seems to genuinely enjoy my company even when the food supply is not an issue. --Mr.98 (talk) 11:50, 29 June 2010 (UTC)

I have a good pet named Peacy. My Peacy will do anything in its power for me and will never get tired. It can sing for hours straight without a murmur. It never falls asleep when I am playing with it. It is vulnerable to viruses though; an occasional shot of anti-virus should help that. It eats a food known as Electric Power Pet Food. It drives hard for perfection by means of an internal hard drive. (WARNING: Do not take this content seriously). --Chemicalinterest (talk) 12:47, 29 June 2010 (UTC)

Right, but we understand exactly how a machine works in this respect. We don't really understand an animal quite so well. And at some level, inquiring into the "does this other highly evolved mammal really love/think/whatever" gets into a question of whether we "really" do any of those things either, and what one really means by that. I haven't seen any good evidence to suggest that dogs are incapable of such things. Dogs do seem to go fairly "above and beyond" what would be required for a minimal level of opportunism, but there's no way to quantify that. --Mr.98 (talk) 13:55, 29 June 2010 (UTC)

Its mostly a matter of opinion. We can't understand dogs' feelings (whether they have them or not). --Chemicalinterest (talk) 14:07, 29 June 2010 (UTC)

But there seems little reason to assume they don't have feelings, which would seem to be the harder case to argue. We know that we have feelings, whatever that means, and we see fairly similar behaviors in dogs (excitement, eagerness, friendliness, moping, shame), though we of course don't know if these are "real" feelings or if they are either conditioned reactions to our expectations or just projections. The "they just fake it" argument seems rather unproven to me, the kind of cynical response that people give because they don't like the fact that people seem to get enjoyment out of pets. The "projections" argument seems highly possible and indeed there must be a lot of projection going on, but considering that some of these behaviors seem extremely ingrained to both dogs and wolves ("play" behavior, apparent "joy" at meeting a sibling, "sulking" behavior), it seems unlikely to me that they are totally manufactured by humans. It seems to me to be a larger stretch to posit that dogs lack feelings than it does to say that they have them in some form or another (and obviously there has got to be a lot of variation in the "some form or another"). And again, at some point, depending on how we define these things, it gets tricky to even say whether humans act the way we idealize as (is there really "love" between humans that is not just rooted in some kind of evolutionary drive?). --Mr.98 (talk) 15:01, 29 June 2010 (UTC)

Since evolution selects for a reasult whether or not the subject has real feelings or not, this suggest that the functional AI hypothesis is correct. The moment you have a system that acts as if it has feelings, it has real feelings. Otherwise it would be huge accident that 4 billion years of natural selection happens to have led to people with real feelings instead of zombies that act as if they have real feelings. Count Iblis (talk) 15:12, 29 June 2010 (UTC)

free radicals

Do free radicals actually cause cancer, or is this just a myth that I've heard perpetuated enough times to sound plausible? If so, what kinds?

Thanks - flagitious (talk) 10:55, 29 June 2010 (UTC)

I accidentally double posted, can someone delete one of these for me - I don't know how. flagitious (talk) 10:58, 29 June 2010 (UTC)

Done. See Radical (chemistry)#Free radicals in biology. The bits about the harmful effects are all unsourced...which is unhelpful. Vimescarrot (talk) 11:07, 29 June 2010 (UTC)

Thanks. Yeah, I read that and I was really wondering because the section seems to be screaming . To the google I go! flagitious (talk) 11:58, 29 June 2010 (UTC)

There's also Reactive oxygen species which does contain some sources. Essentially free radicals will react randomly with DNA in a cell which could potentially damage important genes (like p53) which normally kill cells with damaged DNA through apoptosis. If the damaged cell can't be killed then they can potentially grow into a tumour. 86.7.19.159 (talk) 12:08, 29 June 2010 (UTC)

Free radicals produce reversible damage to body cells. Normally your body can heal the damage. If there is too many, it can form tumors and other malfunctions of the cell. They contribute to cancer risk, but they probably don't cause it. Antioxidants or reducing agents absorb the shock of the free radicals themselves, protecting your body. --Chemicalinterest (talk) 13:06, 29 June 2010 (UTC)

However, if some random skin or health food product promises to fight free radicals, be highly skeptical. The best way to fight free radicals is to eat tons of Vitamin C and Vitamin E(particularly a la Linus Pauling). There are very few edible and bioavailable radical scavengers. John Riemann Soong (talk) 16:36, 29 June 2010 (UTC)

Be skeptical. Ironic that you would then recommend to "eat tons of Vitamin C and Vitamin E". Where is the evidence that taking excessive amounts of vitamins would be any more helpful than "some random skin or health food product"? In fact, the evidence for C and E supplementation is pretty ambiguous. For example, a large randomized, double-blind, placebo-controlled factorial trial of vitamin E and vitamin C showed no benefit for cardiovascular disease and no benefit for preventing cancer. --- Medical geneticist (talk) 17:48, 29 June 2010 (UTC)

Manganese

Is the punny name a coincidence? --76.77.139.243 (talk) 12:59, 29 June 2010 (UTC)

??? Don't under stand what you mean. --Chemicalinterest (talk) 13:03, 29 June 2010 (UTC)

Is it a WP:Troll? --Chemicalinterest (talk) 13:03, 29 June 2010 (UTC)

If you want data, look at Manganese#History. --Chemicalinterest (talk) 13:10, 29 June 2010 (UTC)

No,manganese has nothing to do with the language of mangas... Physchim62 (talk) 13:14, 29 June 2010 (UTC)

If it's unrelated to manga, where does it come from? --76.77.139.243 (talk) 14:19, 29 June 2010 (UTC)

You have already been pointed to Manganese#History. Why you think that an ages old metal should bear the name of a relatively new art form is puzzling. --Tagishsimon (talk) 14:31, 29 June 2010 (UTC)

Not even the first time someone has asked that here. 76.77, you ask a *lot* of questions, at least some of which are easily answered by reading the very obvious articles and/or searching the ref-desk archives or wikipedia/google--please help conserve the limited time of ref-desk participants. DMacks (talk) 15:41, 29 June 2010 (UTC)

Or ask me on my talk page. My talk page is the haven for all chemistry questions. --Chemicalinterest (talk) 17:04, 29 June 2010 (UTC)

Making Fatty Acid Methyl Esters

Hi all. Recently I've been doing fatty acid extractions and I've been wondering how my method works. In short the method involves putting a biological sample + methanol + acetyl chloride + hexane into a test tube and cooking it for a while. As far as I can tell I'm breaking existing ester bonds (triglycerides) and making new ones (methyl esters). Why is the methyl ester the prefered form? Why do the existing ester bonds break? I thought you needed a basic enviroment for that. —Preceding unsigned comment added by 137.224.252.10 (talk) 14:12, 29 June 2010 (UTC)

"As far as I can tell" how do you know (or at least suspect) that's what's happening?--are you following some published procedure and seeing predicted positive results, or just seeing some physical change that you are trying to rationalize? (I'm not trying to be rude here, just trying to to figure out what your level of experience/background is here.) Our ester article has a section about reactions, including notes relevant to your "Why do the existing ester bonds break? I thought you needed a basic enviroment for that." concern. DMacks (talk) 15:34, 29 June 2010 (UTC)

The method is published and relatively old (oldest paper I can find that fully describes it is from 1984). The trick is to extract fatty acids (actually triglycerides) and subsequently methylate them. The methylated fatty acids are then analysed using GC. It's a method that's been used in my lab for ages however when I ask the researcher who first started using it how the method actually worked (the chemistry behind it) he just smiled and said " it just works ". My background is not in chemistry as I'm more on the biology side of things. I did have some introductionary organic chemistry courses. Enough to understand a reaction mechanism, just not enough to figure this out. —Preceding unsigned comment added by 137.224.252.10 (talk) 16:00, 29 June 2010 (UTC)

OK, you're going to need a bit of thermodynamics to understand why the reaction goes in the direction it does... Imagine a triglyceride, something like a letter E with three long dangly bits hanging off. Now those "long dangly bits" (the fatty acid chains) want to move around in solution, and they do, but they are tied together at one end. If you methanolyze the glyceride linkage to form a methyl ester, the chains can move around even more, because they're free at both ends. In technical terms, they have more conformational degrees of freedom. And more degrees of freedom means a higher entropy (positive ΔS). ΔH is as near to zero as makes no difference, because the bonds being broken and the bonds being formed have about the same strength, so the positive ΔS leads to a negative ΔG and the reaction goes towards the methyl esters.

As for the mechanism, it is an acid-catalyzed nucleophilic acyl substitution: the acid comes from the acetyl chloride you add, which reacts with a bit of the methanol to release HCl. Physchim62 (talk) 18:11, 29 June 2010 (UTC)

Can I ask why the acetyl chloride is so necessary? It seems pretty hazardous for someone who doesn't understand the chemistry to handle. Why not just add up straight up HCl? I don't think nucleophilic or Lewis acid catalysis is involved.

Also, it's enough to think about kinetics without even thinking about thermodynamics. A heavy polyol that already has partially been esterified will find it difficult to nucleophilically attack your methyl ester, while methanol being light and numerous will find it easy to attack triglycerides. It can be a simple case of numbers: if you have enough methanol, you will end up with mostly methyl esters. I bet a lot of tri/di/mono glyceride is left behind though.

Your lab's method is pretty outdated and hazardous and I think needs to be changed. The trend in vogue today is to add some peptide coupling reagents. You just stir in powder and that's it. Far more selective, less harsh and has a much higher yield. You don't have to deal with HCl gas. Ugh.

Btw, base is used when you want saponification. When you use base, carboxylates are not electrophiles so they don't react further so there is usually no equilibrium reaction. However ions don't undergo GC very well... being well, ions that will probably stay in the liquid phase. John Riemann Soong (talk) 18:56, 29 June 2010 (UTC)

Ooof! If you can't handle acetyl chloride, you shouldn't be in a chemical lab. full stop end of sentence. The method is a standard method for determining fatty acids in triglycerides by gas chromatography, in use for at least forty years now.

And the reason you add acetyl chloride is exactly to avoid using (expensive, fiddly) hydrogen chloride gas. You can't add hydrochloric acid, because you don't want to add any water to your system of fats and hexane, that doesn't really go very well, now, does it. On the other hand, if you add a bit of acetyl chloride (cheap, available in most decent chemical labs, and a substance that any chemistry student worth their salt will already have handled), it will both scavange any stray water in your methanol and it will produce enough HCl in solution (and a controllable quantity, much easier than working with a cylinder) to provide the acid catalyst to protonate the ester carbonyl group and promote the transesterification. Physchim62 (talk) 19:08, 29 June 2010 (UTC)

Umm I'm sure acetyl chloride is an even more dangerous reagent than HCl. Most biological labs I know do not have it. And the reaction is just so UGLY though! There's so much opportunity to end up with a mix of products. Why not a mild reagent, like DMAP, and a Lewis acid catalyst you can recycle? John Riemann Soong (talk) 19:33, 29 June 2010 (UTC)

Btw, I'm curious why you don't think acyl chlorides are intimidating reagents to work with. Plus inventory-keeping and storage are such a pain in the ass. The fat-solubility of acetyl chloride is also another issue, making it more hazardous than even concentrated HCl or sulfuric acid. John Riemann Soong (talk) 19:38, 29 June 2010 (UTC)

Please tell me you joking? or just trying to wind me up? Physchim62 (talk) 19:46, 29 June 2010 (UTC)

Um no? I don't like reagents that react whenever you add some random nucleophile to it...and God forbid if your fatty acid has a hydroxyl group somewhere like in a lot of natural plant products. John Riemann Soong (talk) 20:19, 29 June 2010 (UTC)

General anesthetic

What's the fastest-acting general anesthetic? --76.77.139.243 (talk) 14:44, 29 June 2010 (UTC)

Try Googling fastest general anesthetic. --Chemicalinterest (talk) 14:52, 29 June 2010 (UTC)

I tried already, and I couldn't find anything. --76.77.139.243 (talk) 15:01, 29 June 2010 (UTC)

Blunt impact to the head? —ShadowRanger ^(talk|stalk) 14:58, 29 June 2010 (UTC)

I'm no expert on anesthesia, from reading General anaesthesia I gather that there are different stages of anesthesia so the answer to your question could be complicated by this. After reading General_anaesthesia#Induction_of_anaesthesia and the links from there I'd have a stab at a volatile anaesthetic such as sevoflurane being pretty fast acting. This paper says it takes between 37 and 70 seconds for "loss of eyelash reflex" to occur depending on the age of a patient. This paper (not free) found it was faster acting than thiopental (an intravenous anesthetic), taking on average 42 seconds to cause loss of eyelash reflex compared to 45 seconds. 86.7.19.159 (talk) 16:40, 29 June 2010 (UTC)

Tin(II) sulfide formation

Why does it list a reaction between tin(II) chloride and hydrogen sulfide to form tin(II) sulfide and hydrogen chloride? I thought that the reaction went the other way. --Chemicalinterest (talk) 15:05, 29 June 2010 (UTC)

Depends on the concentrations, as with many chemical reactions. Tin(II) sulfide is very insoluble in soluble in water, which means that H₂S will precipitate it even from mildly acidic solutions of tin(II): this sort of reaction used to be very important in qualitative inorganic analysis (tin is in group II, cations that form sulfides in acid solution). It takes concentrated hydrochloric acid to push the equibrium back in favour of SnCl₂ and H₂S. Physchim62 (talk) 16:34, 29 June 2010 (UTC)

So only concentrated HCl will reverse the reaction? --Chemicalinterest (talk) 16:53, 29 June 2010 (UTC)

Actually, looking at the figures, bench dilute hydrochloric acid would probably do it. But don't forget that, when you are precipitating tin sulfide, you are only making a stoichiometric amount of HCl, that's rather different from adding hydrochloric acid onto tin sulfide precipitate (when acid will be in large excess). Physchim62 (talk) 19:25, 29 June 2010 (UTC)

Mercury(I) oxide

Why doesn't it have an article? --Chemicalinterest (talk) 16:53, 29 June 2010 (UTC)

What makes you think it exists? Physchim62 (talk) 17:56, 29 June 2010 (UTC)

Any other metal oxide exists. --Chemicalinterest (talk) 20:24, 29 June 2010 (UTC)

Hg(0) + Hg(II) is more stable than 2 Hg(I), as can be seen with the reactivity of mercury(I) chloride. As I imagine, it quickly decomposes even shielded from catalytic agents. Any Hg(I)-O-Hg(I) is probably covalent in nature; the oxygen pulls electrons from one mercury(I) atom and returns another pair of electrons to the other. John Riemann Soong (talk) 20:43, 29 June 2010 (UTC)

Second question: What makes certain substances more stable while others disproportionate easier? --Chemicalinterest (talk) 20:54, 29 June 2010 (UTC)

Are you asking why Hg(I) chloride doesn't disproportionate spontaneously? I'm guessing it's because the oxygen is actually rather "unhappy" with the whole Hg-O-Hg arrangement and can get much better electron density by proceeding with disproportionation. Whereas chlorides are relatively 'content'. John Riemann Soong (talk) 21:04, 29 June 2010 (UTC)

This is complete speculation, but with Hg2O, the oxygen does the reducing and oxidising, which it seems apt to do (oxygen can be both electron-donating and electron-withdrawing at times). With Hg(I) Cl, the mercury atoms have to reduce/oxidise each other directly ... which is difficult without the help of say some UV radiation. John Riemann Soong (talk) 21:06, 29 June 2010 (UTC)

what are these strange holes in the ground in afghanistan?

Here are coordinates,31.63779,65.050017. The town is "Pir Zadeh". Look it up on google maps. There are lines of deep looking holes crossing the terrain, it looks like perforated paper. These lines of holes continue up that river all the way into the mountains. I don't think they are for storing water because they occur in the mountains where there are no fields or orchards. What are these holes? —Preceding unsigned comment added by 75.164.144.81 (talk) 18:45, 29 June 2010 (UTC)

They're Quanats, an ancient and effective method of channeling water from hills to areas where it is needed for irrigation etc. Mikenorton (talk) 19:22, 29 June 2010 (UTC)

31.63779°N 65.050017°E / 31.63779; 65.050017, fwiw. --Tagishsimon (talk) 21:04, 29 June 2010 (UTC)

Soreness from a Shot

What is the origin of residual pain in your arm after a vaccine injection? Is the soreness from damage to the tissue by the needle or is it something to do with whatever is being injected into your arm? Not a request for medical advice, just idle curiosity. —Preceding unsigned comment added by 72.85.199.192 (talk) 19:40, 29 June 2010 (UTC)

where did this stupid idea that investment is a trade-off between risk and returns come from?

where did this stupid idea that investment is a trade-off between risk and returns come from? I mean, I see how it applies to someone with a very poor understanding of the market, industry, and the factors, such as reputations and technology involved, but this adage (risk/return tradeoff) seems to be stated as though it applies to everyone, even people who understand, correctly, exactly what they are doing and why it will get a high return, in that case, without any particular risk. Thank you. 92.230.66.154 (talk) 20:58, 29 June 2010 (UTC)

Name these plants?

I've seen the this plant, which was about 1 metre high, in many places in the southern UK, both gardens and wild, and have always wondered what it was. It has the 5 leaf lobes like a mallow, but its a lot bigger than a mallow. http://img134.imagevenue.com/img.php?image=45121_DSCF0002_122_247lo.JPG http://img186.imagevenue.com/img.php?image=45114_DSCF0001_122_462lo.JPG

This one is interesting too, about a foot high: http://img232.imagevenue.com/img.php?image=45106_DSCF0003_122_185lo.JPG http://img134.imagevenue.com Thanks 92.29.119.46 (talk) 21:11, 29 June 2010 (UTC)