Wikipedia:Reference desk/Archives/Science/2009 December 20

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December 20

Tunneling marbles

If I have some marbles in a bucket and bring the temperature down close to absolute zero, is it possible for the marbles to tunnel out the bottom of the bucket? As the temperature is reduced the momentum of the marbles due to thermal energy becomes less and less and is consequently known with a greater and greater certainty. The uncertainty principle would have it as a consequence that the position of the marbles becomes more and more uncertain. There must come a point where the uncertainty in the position of the marble is greater than the thickness of the bottom of the bucket and the marble can tunnel through and fall to the floor. But surely not, can quantum effects such as these really be observed in macroscopic objects, even as a thought experiment? SpinningSpark 01:25, 20 December 2009 (UTC)

Surely quantum mechanical effects can be exhibited in all objects. It merely comes to defining the environment correctly. de Broglie waves have been observed in objects as large as fullerenes; C₆₀ will diffract, for example. Superfluid helium (aka Helium II) displays clear quantum mechanical effects as well, the super-low viscosity of both Helium I and Helium II can only be explained by invoking quantum mechanics. Bose–Einstein condensates display interference effects due to their wave nature as well. Hypothetically, YOU would display quantum mechanical effects; if one could properly define a set of observation conditions to highlight them. --Jayron32 01:38, 20 December 2009 (UTC)

So will the marbles drop out the bottom of the bucket or not? SpinningSpark 01:48, 20 December 2009 (UTC)

You are confusing two different things. Tunneling is one thing; uncertainty of position and momentum is another. Let us start with tunneling. As you may know, for a finite-width potential barrier (such as the bucket bottom, in your case) the tunneling probability of a particle (marble) approaches zero when the momentum of the particle outside the potential barrier approaches zero. Thus, decreasing particle momenta will do you no good in this case. Now, the uncertainty in the position and momentum is something else entirely. Indeed, to measure momentum very accurately you need your particle to be spread around a large area. That does not mean, however, that bosons (marbles) in a cavity, when cooled as much as possible, will spread outside the cavity. No. What this means is that you can not reduce their energy below the ground state of the cavity. Marbles in a bucket have a ground state, too, and that is where you'd find them if you chill them ad infinitum. Hope this helps. --Dr Dima (talk) 01:58, 20 December 2009 (UTC)

There are easier ways to lose your marbles (trust me). Clarityfiend (talk) 06:08, 20 December 2009 (UTC)

Strings

In M-Theory, a one dimensional brane is a string right? —Preceding unsigned comment added by 74.67.89.61 (talk) 01:57, 20 December 2009 (UTC)

SETI question

It seems that the development of advanced technology on Earth was highly dependent on the flammability of organic materials. If wood weren't flammable, fire wouldn't have been mastered. If coal and charcoal weren't flammable, smelting would have been difficult or impossible to develop. If oil weren't flammable, the industrial age wouldn't have occurred and the technology it led to would have taken a long time to develop.

Have any SETI researchers discussed this? It would seem to hamper the possibility of aquatic life becoming intelligent, since nothing can burn under water. --99.237.234.104 (talk) 02:36, 20 December 2009 (UTC)

We've sought materials to burn for an energy source, resulting in your list. Aquatic life might use hydrothermal vents as a rich energy source, just as a ready example. We can't fathom what might have happened had things been different. I don't think that SETI researchers would be uniquely interested or equipped to address these questions, nor does it seem like they'd adjust their searches on such a basis, but it seems reasonable to think they might have considered such scenarios. -- Scray (talk) 02:46, 20 December 2009 (UTC)

The fundamental assumption of SETI is that the other end are using radio telescopes or similar. If that's not what the other end are doing SETI are never going to find them no matter how long they listen at Arecibo. It is not very relevant how they got radio telescopes, they could have done the same as us (burn forests, bang rocks together) or they might have used some entirely different approach. Now we know how to make radios we can conceive of ways to build them without fire or smelting. Metallurgy started by just picking up pieces of native copper lying on the ground and did not at first require those technologies. It is entirely conceivable that a civilisation has found a much better technology than radio and simply does not use it, or once used it and has now abandoned it as obsolete. Scray's hypothetical civilisation around hydrothermal vents can certainly progress, but are unlikely to be doing anything with radio telescopes, at least until they get to the point in their explorations when they get to see the sky and can get an antenna out into free air. Such discussions certainly take place on SETI forums from time to time, but unless and until we have some of these alternative technologies ourselves there is little else we can do except listen on the radio. SpinningSpark 03:15, 20 December 2009 (UTC)

Wood and fossil fuels are ideal in many ways. Wood is readily available, burns for a long time, and has many other uses that encourage its production. I can't think of any fuel even remotely comparable to wood in accessibility and usefulness. As for fossil fuels, I'm 100% sure that no other energy source on Earth that people in the 1800's could have used is as potent. Otherwise, we wouldn't be having an energy crisis right now and global warming would be easy to fix. --99.237.234.104 (talk) 03:20, 20 December 2009 (UTC)

(ec) The OP may be interested in our featured article on the Fermi paradox, which touches on many of the problems regarding extra-terrestrial life. Matt Deres (talk) 03:24, 20 December 2009 (UTC)

I've been trying to find an expanded version of the Drake equation. I recall reading or hearing about an expanded equation that attempted to incorporate other, less obvious, obstacles that would affect the end result. I don't recall whether anything like what the OP mentioned were included, but there was stuff like fraction of planets that contain usable amounts of metals such as iron and copper and so on. Will keep looking. Matt Deres (talk) 03:31, 20 December 2009 (UTC)

I think that intelligent subaquatic lifeforms might be able, in time to make glass or to smelt metals using underwater volcanoes. It is hard to figure out why dolphins, sharks, or octopi would need tools or weapons, but it is conceivable that some dolphin empire would have dolphin factories making dolphin weapons. They could also conceivable contrive means of venturing onto land to build and operate blast furnaces, forges, etc. Metal oxides (ores) are refined in atmospheres lacking oxygen and too hot for human survival, so the factories where gadgets are made also contain areas where humans would not survive. So aquatic life might do some of their manufacturing on dry land or on floating islands. In our history, lumps of copper were found in nature, and campfires were the predecessors of smithies and iron furnaces, so the road to metal and glass technology might be longer and slower for aquatic civilizations. There are said to be some metal deposits such as manganese nodules also containing iron in the ocean, so maybe they would start with those. The same source says that underwater "black smokers" produce deposits of lead, silver, zinc, copper and gold. Electrochemistry could possibly extract minerals from seawater, using brine and dissimilar metals as a power source. Edison (talk) 04:23, 20 December 2009 (UTC)

Edison said "It is hard to figure out why dolphins, sharks, or octopi would need tools or weapons." Well, there is protection against humans for a start. Whales also, might wish for a torpedo or two being available when they are being hunted by Japanese whalers. All the species named are hunting species, and is it not obvious the use hunters could put weaponry to? The big difficulty for free swimming aquatic species is that they are not equipped with any means of manipulating materials in order to build something. Such things can evolve, of course, but in evolution it can only happen in tiny, continuous steps. A dolphin has nothing in this respect that evolution can start working on to improve and they cannot jump straight from nothing to a brand new feature. The exception here is the octopi, who are both intelligent and already equipped with useful tentacles. There does not seem any reason that octopi could not create a technology, they have just not yet put their minds to it. SpinningSpark 10:36, 20 December 2009 (UTC)

We had the recent news item about the veined octopus carrying coconut shells around for tactical use as redoubts. It seems reasonable that given time a future evolution of its species might be driving around in little cars. I note that there are plenty of clathrates under the sea, just lying around, and I have a vague feeling I read somewhere that they can be combusted underwater, but I'm probably wrong about that. Felis cheshiri (talk) 13:13, 20 December 2009 (UTC)

This is getting a bit off topic, but I think the big issue with octopi is their short life spans and subsequent lack of parental care; smart as they may be, there's no opportunity to pass on information. One man didn't invent metallurgy, and he sure didn't do it in three years. ~ Amory (u • t • c) 16:49, 20 December 2009 (UTC)

That's a good point. In higher primates (including humans) teaching is extremely important. It takes several years in some species (about 21 years in modern humans in today's society) before a child had learnt enough to not need their parents any more. I think there are some octopuses (note the plural!) that live long enough that they might be able to pass on a useful amount of information, but most species don't. It's also important to reduce infant mortality as far as possible - you can't afford to regularly spend a few years caring for your child and then have them die and have to start again. Apparently female octopuses typically mate once and lay 200,000 eggs - that suggests a survival rate (to reproductive age) of 1 in 100,000. That's never going to work if you are going to teach your young anything. --Tango (talk) 17:09, 20 December 2009 (UTC)

Another issue is that water-breathing animals have difficulty getting enough oxygen to support the metabolic requirements of large masses of neural tissue. If octopi invaded the land and developed lungs, they would have better chances of evolving in that direction. Looie496 (talk) 17:18, 20 December 2009 (UTC)

This question is about aliens, mind you, so they could have a metabolic pathway based on something other than oxygen, like some of the weirder microbes do. I don't know if that could yield suitably large amounts of energy either, but maybe. Perhaps some alternate reaction could even power a furnace? It could be electrical, but they'd need to have metallurgy already to make the wire... Felis cheshiri (talk) 19:01, 20 December 2009 (UTC)

Easier than that, we can just assume this alien planet has more oxygen dissolved in its oceans that Earth does. --Tango (talk) 19:18, 20 December 2009 (UTC)

This only implies that in an octopus society, the teacher-pupil relationship would be replaced by autodidacticism. The young octopus would have to seek its own knowledge without a mentor until most of its siblings were dead, whereupon it becomes economical for the adult octopodes to pay it proper attention. They do need to live ten or twenty times longer, though, yes. (Octopi is derived from an etymological mistake, but listed in dictionaries as an alternate plural.) Felis cheshiri (talk) 18:23, 20 December 2009 (UTC)

Seeking their own knowledge is what octopuses do now and it isn't fast enough to learn a large number of advanced skills. They would need to develop writing, or some equivalent way of storing knowledge, to allow significant amounts of autodidactism (that's how humans do it), and I'm not convinced that any species can learn to read without a teacher. --Tango (talk) 19:18, 20 December 2009 (UTC)

There are plenty of intelligent marine species on Earth, such as dolphins, which use more of their brain than do humans and have a language of their own. ~AH1^(TCU) 23:23, 20 December 2009 (UTC)

"which use more of their brain than do humans" Source and reason why this would be a good thing? 86.176.191.243 (talk) 23:43, 20 December 2009 (UTC)

(outdent, and fully embracing the off-topic direction this thread has taken...) The whole idea of "humans not using their entire brain capacity" is bogus. Although some places in the brain are undoubtedly intimately related to certain functions, such as sight or memory, practically the entire brain is active in order to perform nearly any conscious action, and most subconscious actions. Dolphins do not "use more of their brains" than humans. There are things that humans brains do that no other living thing is known to do, such as allowing awareness of one's own eventual death, and the capacity to perform significant abstract reasoning. Furthermore, some animals such as whales and elephants have much larger brains than humans do, and yet neither species has developed a technological civilization, so physical brain size is not necessarily an indication of how intelligent a species is. Elephants in particular are unusually well-equipped physically, as besides their large brain size, with their trunks they possess (excepting the primate hand) probably the most dexterous and versatile manipulating tool in nature. Also, elephants routinely live several decades, easily long enough to build a lasting civilization. Even so, they have not advanced past what is typical for large mammals. As far as I know, there are no obvious physical characteristics of human brains (that other animals do not possess) that would explain why humans have the mental capacities that they do, and the mechanism that led to human self-awareness and reasoning ability are not understood well, if at all. J.delanoy^gabs_adds 00:24, 21 December 2009 (UTC)

My point earlier was that a blast furnace is a container of a process which would be lethal to humans. Aquatic life might similarly use a device containing processes lethal to aquatic life to create refined metals, optical glass, semiconductors, etc, given some need and sufficient time. Spaceships bearing frog-, eel-, octupus-, dolphin-, fish-, squid- or shark-like creatures are not beyond reason. Edison (talk) 01:27, 21 December 2009 (UTC)

Buried in the middle of this BBC article [1] is a statement from a professor of psychology that he believes chimpanzees are aware of their own mortality - and projected life expectancy, he implies - but only before the age of 30. He thinks they lose their self-awareness at 30 to prevent them from freaking out over impending death. It's complete balls, but I thought I'd mention it. Felis cheshiri (talk) 02:03, 21 December 2009 (UTC)

It seems likely that elephants are aware of death, given the way they behave around remains, but I've yet to see it 'shown'. Brain size itself does not correlate with improved cognition, but brain size relative to body size does seem to be. Humans have a brain size that is out of all proportion to our bodies, if you were predicting it from other mammals or even other great apes. But yes, the whole 'use x percent of brain' thing is ridiculous. 86.176.191.243 (talk) 02:12, 21 December 2009 (UTC)

How do elephants behave around remains? The japanese beetle is repelled by the smell of dead japanese beetles, so elephants may be doing something similar. If they avoid dead elephants, that may just be an evolved tactic for avoiding death. Felis cheshiri (talk) 02:33, 21 December 2009 (UTC)

But that's just it: they don't avoid dead elephants. When they encounter elephant remains, they stop and examine the remains silently. From about 1 minute in. 86.176.191.243 (talk) 13:53, 21 December 2009 (UTC)

Yes- I've actually seen this in Kenya around a well known "elephant's graveyard". The walk slowly and quietly into the area where old elephant bones are to be found - then they gently pick the bones up (especially skull bones) and examine them from all directions while making low grunting noises - before gently putting them back down again. There are some theories that elephants are able to sense infrasound so well that they can use it to form images (kinda like a bat does with ultrasound) - and that they can recognize the skulls of other elephants (living or dead) from this infrasound 'signature'. Elephants have pretty poor eyesight - and it's possible that the infrasound image of the skull of a dead elephant may look to them exactly like that of the living animal and that this may explain why they do this. SteveBaker (talk) 20:30, 21 December 2009 (UTC)

Why is "modern physics" approached so historically in textbooks?

It seems strange to me that if one goes through your typical introductory physics text at college level, there is a significant amount of emphasis on principles and problem solving, with very little mention of the history. By contrast, "modern physics" seems to be approached nearly completely historically, especially the quantum theory parts of it. Instead of discussing quantum theory as it would actually be used (and understood) by a physicist of today, the "modern physics" books (e.g. Krane, Tipler) as well as "modern physics" sections of college physics texts, present the ideas of old quantum theory as though they are the most fundamental basis of quantum theory as it is understood today, even in cases where that is untrue. My question is, why is "modern physics" introduced historically even when "classical" physics is not? 69.140.13.88 (talk) 03:08, 20 December 2009 (UTC)Nightvid

There may or may not be a clear answear to your question. Text-book authors copy a lot from each other, so it could simply be tradition. My introductory book to QM [2] was by David J. Griffiths and I can't recall that old QM was dwelled on much. That said, there are two possible pedagogical reasons: First, the historical development of QM to some degree follow how you'd introduce it in a textbook. You'd start with non-relativistic QM then you move on to the relativistic part where the energy is high enough for new particles to be created in collisions. The second possible reason is that the students are not expected to have the math background to follow modern QM. I've heard this is especially a concern in the US, where (again this is what I've heard) a physics student may for instance go through maxwell's equations before knowing how to work with a gradient. Not that this isn't a problem here in Europe too. I wish I had a background in fourier transformations so that I could have seen how the uncertainty principle follows mathematically, instead of just having it stated as a mysterious principle. On the other hand, the younger me just wanted to start on the physics without having to wade through all the meaningless math first :-P EverGreg (talk) 12:31, 20 December 2009 (UTC)

It's of note that the historical path taken by textbooks in explaining the science itself is often not strictly correct, but has been streamlined and simplified for the points of pedagogy. A classic example is that you will often read that Planck invented the quanta in order to avoid the ultraviolet catastrophe. This has been long known to not actually be his motivation at all, and is an after-the-fact reconstruction of one reason the quanta was a good invention. It simplifies things, though, to talk about it in this way, and if they are students of physics, and not history, it is arguably better for them to learn whatever version is pedagogically more useful, rather than the very messy facts of the thing. However, on the other hand, some have argued that this "streamlined", "one thing easily leads to the other" approach actually obscures the real nature of scientific progress quite considerably. (This argument is, in part, the basis of Kuhn's The Structure of Scientific Revolutions.) --Mr.98 (talk) 14:43, 20 December 2009 (UTC)

You forgot to tell us what was Planck's original motivation. Dauto (talk) 16:42, 20 December 2009 (UTC)

Well, the Max Planck page kind of explains it (and Kuhn wrote a whole boring book on it... Black-body theory and the quantum discontinuity, 1894-1912—not as well known as Structure—for good reason). But it's just not as straightforward and elegant as the ultraviolet catastrophe approach (which nicely sets up a conceptual problem and then answers it... even if it doesn't have anything to do with what actually motivated Planck the historical individual). It has to do with very practical industrial problems he was hired to solve. Which in a way is its own lesson for the budding physicist, but not usually the one that physics textbooks are trying to teach! To actually express what motivated him take a lot more space (and is, I would again emphasize, fairly dull...), but if you are interested in the details, check out Kuhn... --Mr.98 (talk) 20:26, 20 December 2009 (UTC)

Another reason to follow the historical path is the fact that Quantum Mechanic concepts are so far removed from every day intuition and classical physics that dropping the students off the deep end might lead to brain seizure (figuratively speaking). Those concepts take some time getting used to. Dauto (talk) 14:33, 20 December 2009 (UTC)

Black hole time

Does the singularity of a black hole experience time? --74.67.89.61 (talk) 15:06, 20 December 2009 (UTC)ConnorGoham —Preceding unsigned comment added by 74.67.89.61 (talk) 03:18, 20 December 2009 (UTC)

Well, it gradually evaporates due to Hawking radiation - so I guess it must. SteveBaker (talk) 04:16, 20 December 2009 (UTC)

It is actually the event horizon that evaporates. The singularity is an end point in time, as in the world lines terminate at it. If an object takes an infinite time to fall into a black hole (in an outside frame of reference) then the singularity never actually forms, as the black hole will have evaporated before anything makes it past the event horizon. Foloow on question: Can anyone prove how long it takes for something to fall into a black hole from an outsiders point of view? When I integrate the gravitational redshift, I get that it takes a finite time to fall in though. (even though redshift increases without limit). Graeme Bartlett (talk) 07:24, 20 December 2009 (UTC)

How long time passes between two events "from an outsider's point of view" is not really well defined in GR. When it is usually said that it takes forever to reach the horizon, it is in the naive sense that no matter how long the outsider waits, there is an event on the infalling particle's pre-horizon worldline that the outsider will consider simultaneous with his own "now". (Simultaneity is fairly fuzzy in GR, but here I think this means that the outsider is connected to the particle by a spacelike geodesic orthogonal to his own worldline).

When you integrate the redshift, what you get is much time passes from the infalling particle's own point of view (even though you're deducing this on the basis of observations made far away). Imagine that the particle emits a "click" every dt seconds, according to its own clock. The number of clicks an outsider ever sees is evidently exactly the number of clicks the particle emits before it crosses the horizon. But "integrating the redshift" is just a way to count clicks as dt goes to 0. –Henning Makholm (talk) 07:44, 20 December 2009 (UTC)

Storing a spring clock

If a clock with a spring and a pendulum is to be left stopped for a while, should its spring be wound first, or let to run down first, or does it matter? --Tardis (talk) 03:33, 20 December 2009 (UTC)

It is most certainly true that spring powered phonographs are best stored with the spring run down, so I assume it is true as well for clocks. Some energy storage capability is lost if the spring is stored for a long time in torsion, fully wound. Edison (talk) 04:11, 20 December 2009 (UTC)

A wound spring contains elastic energy because it is bent out of its "natural" shape (which is the unwound state). When time passes while the spring is wound, its idea of a "natural" shape will creep towards the wound shape, so the transition from the wound shape to the (new) natural shape will release less energy than the transition to the old natural shape. Creep cannot happen when the spring is unstressed, so unwinding it first will be better if all other things are equal. But the creep rate is extremely slow for a spring of good quality at room temperatures, so the difference will be minor. –Henning Makholm (talk) 05:13, 20 December 2009 (UTC)

Um hum. Edison (talk) 01:17, 21 December 2009 (UTC)

I over-analyzed Amphoterism and over-analyzed pK_a and now want to resolve a pedagogic discrepancy between Wikipedia vs my 3 independent chem books

For starters, I have read entirely all I could understand, plus my wade O-Chem book for several hours (about 20). Today, I frustratingly realized that pK_b is not an equilibrium constant for the reaction of a base into it's conjugate acid.

Looking at the bronstead-Lowry definition of an acid, and how it is computed as an equilibrium constant for the reaction of an acid into it's conjugate base, such as:

$K_{a}={\frac {[H+][A-]}{[HA]}}$

However, I erroneously concluded from this Wikipedia page that:

$K_{b}={\frac {[BH+][OH-]}{[B]}}$

and it even says "Historically, the equilibrium constant Kb for a base has been defined as the association constant for protonation of the base, B, to form the conjugate acid, HB+. It is now usually derived from the K_a." yet nowhere does it explain that K_b is only used to exclusively measure the strength of a conjugate base nor do I understand why?

Secondly, since many types of compounds can function as an acid and a base, then what is the point of their K_a when you might not even be using water as the solvent? (Granted, I am in chapter 1 of my organic chemistry book and it only devotes only 7 pages to the following topics: Arrhenius Acids/Bases, Bronsted-Lowry Acids/Bases & acid Strength, acid-dissociation constant, base strength, structural effects on Acidity including electronegativity, size, & resonance stabilization, Lewis Acids/Bases and I finally ditched my chemistry book and taught myself from Wikipedia and am getting every question right on practice tests!) If I'm wrong, then please correct me because I absolutely loved the explanation of acids/bases under this Solvent-system definition and that's why I'm so curious to resolve my anxiety. I like the way the Wikipedia articles discuss Acid-Base theory and it's the first time this confounded part of science has ever clicked for me before--as soon as I saw the Wikipedia idea of auto-dissociating solvents into their positive and negative species, solvonium cations and solvate anions respectively, it was a light bulb that went off for me and I instantly just "got it".

I am extremely nit-picky and want to know why I can't really use what my book micro-teaches me about acids and figure out why on earth I must use a negatively-charged base (e.g. NH2- or F-) and indirectly measure the strength of it's corresponding acid? For NH2-, I must ask myself "what is NH2- the conjugate base of? It is the conjugate base of NH3" so I look up the K_a of NH3 and it is 10 EE -33 and thus NH3 has a pK_a of 33, and then I use the negative log (base 10) of the water ion-product constant to calculate that pK_a + pK_b = 14, so I just get that the base-strength of NH2- is therefore -19 but all I really want to know is the base-strength of NH3.

It makes more sense in my opinion to calculate K_b independently, as in the bottom equation I pictured. It is trivial that an acid and it's conjugate base are related by a cute formula pKa + pKb = 14. Instead, I'd rather like to know for example the strength of an Amphoteric molecule as an acid and have a cute formula that then tells me what the strength of it is as a Base (in the same particular solvent).

I have been out of school for a few years and am registered for the May 1st MCAT and am strong in both Chem & O-chem. I don't even need this for the MCAT, but's a personal odyssey now to know why K_a is logically derived as an equilibrium constant, but K_b isn't? I fear the answer is to draw attention to pKa + pKb = 14 which is not that big of a deal, seriously. I am sorry this post is so long, but I wanted to make sure someone knowledgeable enough to help me, knows I have deeply tried to resolve this own my own, and I grasp the way my book does it, but I just don't like why my book does it so unintuitively. I really liked WP's explanation of the overview of the acid-base theories. Thanks in advance to anyone who can provide any missing insight that I am struggling without. I still have over 5 months to review everything. 76.4.135.47 (talk) 08:40, 20 December 2009 (UTC)

I think you are assuming that the solvent is always water...that's fairly safe for simple Bronsted-Lowry Acids cases of gen-chem, but not for the full range of chemicals used in orgo. "pKa + pKb = 14" is only true due to the Self-ionization of water, not a general relationship for all solutions. And K_b=[BH+][OH-] / [B] also assumes that OH- is the alternate counteranion to whom you are comparing the H+ donation. Very strong bases can't be measured directly in water (they are so strong, there is not enough of an "equilibrium" to measure...some of the terms become zero), so other solvents are used (typically DMSO...its pKa can be calculated, and a base-strength measured in equilibrium to it, so you can try to approximate/extrapolate the aqueous base-strength). DMacks (talk) 09:49, 20 December 2009 (UTC)

Thank you so much. I just really am very nitpicky about learning stuff correctly. Reading the dimethyl sulfoxide has helped me see it better. Your sentence about "pKa + pKb = 14 is only conditionally true" is what I needed to hear. My gen-chem and Ochem books allows a student or reader to misunderstand acids/bases yet believe they have learned it. It wasn't until I read the explanation about solvent-system definition that I started to question the completeness of my knowledge of acids & bases. I was livid when I realized that you can't simply calculate K_b directly by knowing only the initial and final concentrations of the base, the protonated base (BH+), and the OH-. Thus, K_b is needlessly entangled to K_a and I wish that K_b was defined autonomously as its own equilibrium constant for the attachment of a base to a proton given up by a solvent molecule. Either way, I'm glad to know that I don't have this frustration for other solvents. All I have to learn is qualitative analysis for other solvents. For water, I have to learn the quantitative reasoning, which just feels "wrong" to have to learn formulas I do not agree with; but, at the end of the day, I walked away with a much better understanding of acids & bases, and I also have a much more solid grasp of how important are the dynamics between solvent and reactants. I used to think that each solvent had different "rules" as a way to understand and simplify processes taking place within the boundaries of each solvent; but, now I can rely less on memorization of individual solvent properties and rely more on theory, which is the way it should be. Thanks again.76.4.135.47 (talk) 14:03, 20 December 2009 (UTC)

power generation using hybrid wind-water turbine

how can we generate the energy at the same time from both wind mill and a water turbine using a hybrid combination of wind mill and water turbine ? —Preceding unsigned comment added by 203.175.69.210 (talk) 09:44, 20 December 2009 (UTC)

You'd get both turbines to feed into the same energy storage device, and then tap that for your power. For instance, the windmill could pump water into the reservoir for the water turbine; or if it's a sea turbine, they could both feed energy into the same spring or weight or battery. (The problem here is finding an efficient form of storage.) Felis cheshiri (talk) 12:44, 20 December 2009 (UTC)

A water turbine takes a different shape than a wind turbine because of the different densities of the fluid. There is a hybrid of a sort - a turbine that is powered by wind rushing through a tunnel as ocean waves compress it: Wells turbine. 75.41.110.200 (talk) 16:38, 21 December 2009 (UTC)

How does this thermometer work?

I have an indoor/outdoor thermometer. The "indoor" part is exactly the popular image of a thermometer: a tube with red liquid, with the level of the liquid indicating the temperature. The "outdoor" part looks very similar: a tube with blue liquid, with the level of the liquid indicating the temperature, but coming out of the bottom of this tube (or out from near the bottom of this tube) is a longish wire which connects to some sort of probe. To all appearances, this thermometer does not use batteries or make use of electricity in any way. How then does the display of outdoor temperature work? —Preceding unsigned comment added by 75.37.237.242 (talk) 13:42, 20 December 2009 (UTC)

May be the probe is a thermocouple. Dauto (talk) 14:20, 20 December 2009 (UTC)

It is probably one of these in which case the "wire" is not a wire at all, but a capillary and the probe is a bulb filled with a reservoir of the working liquid. A modern indoor/outdoor thermometer is usually all electronic which might use thermocouples, or as in this home electronics project, thermistors. SpinningSpark 15:59, 20 December 2009 (UTC)

I can't read Dauto's link - it says, "You have either reached a page that is unavailable for viewing or reached your viewing limit for this book." Regarding your question: I have an indoor/outdoor thermometer like yours with the wire. On mine, the wire conducts heat from the outside, so you put the probe outdoors and then the metal wire conducts the heat indoors to where the thermometer is so that the correct outside temperature is registered. Could this be how your thermometer works? 66.178.138.170 (talk) 00:46, 22 December 2009 (UTC)

Zero Point Energy Power Source

Couldn't the casimir effect be used as a power source? Imagine having a large number of tiny uncharged metal plates stacked next to each other seperated by pizoelectric crystals or something similar to them, then as the casimir force pulls the plates together the pizoelectric crystals would generate electricity. Although the electricity generated would be small, because the plates are also small a large number could generate electricity in parallel. Even if the casimir effect never is able to produce enough power to be used at are scale in a practical way, what about at smaller scales like as a power source for nano-machines? 74.67.89.61 (talk) 14:25, 20 December 2009 (UTC)ConnorGoham

Well, they do it in science fiction, so it must be possible! Staecker (talk) 14:46, 20 December 2009 (UTC)

The Casimir effect works to generate power once -- the plates are attracted. Then they're together, the Casimir effect is gone, and you must work to separate them again. Per thermodynamics, that takes more energy than you gained from the effect itself. So no, no ZPE here. — Lomn 15:10, 20 December 2009 (UTC)

No. Dauto (talk) 16:20, 20 December 2009 (UTC)

The problem is that the Casimir effect is a force it is not energy. There is a force exerted between the two plates - but it's no different in principle from the force exerted by fridge magnet onto the door of your refrigerator - or the force exerted by a book sitting on a table...and you can't extract energy from those "effects" either! The failure to distinguish between force and energy is the number one cause of misunderstanding amongst 'free energy' nuts. That's an amazing thing since it's so easy to understand. SteveBaker (talk) 01:41, 21 December 2009 (UTC)

You cant extract energy from a book falling of the table! It is more of a matter of how much and what type of energy! Plus how do you think we get energy, we get it from forces, like the force of water turning a turbine in a hydroelectric power station! —Preceding unsigned comment added by 74.67.89.61 (talk) 10:25, 21 December 2009 (UTC)

No, we extract energy when the water flows (falls down), not when we hold it high. If you put a cork in the downstream/outflow of a turbine, it stops turning no matter how much water force is behind it. Many people confuse force as we experience it from human exertion with the actual physical unit. It takes you energy to keep holding a book up, but that's just because humans are lousy at generating a constant force. DMacks (talk) 16:24, 21 December 2009 (UTC)

You can indeed (briefly) extract energy from a book falling from a table...but not from one that's sitting still on the table. Energy transfer is called "work (physics)" and Work=Force x Distance. So only when the force causes the book to move is energy transferred from it. You could also (exceedingly briefly!) extract energy by allowing the two plates in the Casimir effect experiment to come together (again: a force moving through a distance). But once the book hits the floor (or the Casimir effect plates collide) - that's your lot. You have to expend energy to put the book back onto the table (push the Casimir places apart again) before you can repeat the process. The energy you need to do that is always more than the energy you got from the falling book (colliding plates) - so there is no net win.

Now, if you are one of the free-energy/perpetual-motion-machine nut-jobs (and I surely hope that you are not) then you're probably going to try to come up with some incredibly devious way (probably involving magnets and/or cold fusion) to pull the plates apart again. Then you'll come back to us with your shiney new idea - and I can utterly, 100% guarantee you that it'll be wrong for some more or less subtle reason. If history follows it's usual course, you'll then set up a web site with too many fonts and too many colors and lots of centered text - and get bitter and twisted because nobody in mainstream science will believe you. At some point you'll claim to have a working car that's powered that way - but because "Big Oil" are out to get you, you'll refuse to show it to anyone. At this point, you'll either dupe a bunch of gullible investors out of a lot of money and eventually wind up in jail - or you'll die old and penniless while still trying to convince people that you can save the world.

...and all of this because you refused to believe in the laws of thermodynamics.

SteveBaker (talk) 20:20, 21 December 2009 (UTC)

No i am not one of those people who beleive in free energy. I knew that once the plates were together that they would become useless and it was only when they were coming together that you can extract energy. I was thinking that if the crystals were stronger, and more greatly resisted the plates coming together (but didn't resist it enough to completely stop the plates) the plates would travel slower and it would take longer for them to collide. In this longer period of time i was wondering if you could extract some energy —Preceding unsigned comment added by 74.67.89.61 (talk) 10:04, 22 December 2009 (UTC)

Work (Energy) = force X distance. Time does not come into it. The total enrgy you can extract remains the same regardless of how slowly the plates come together. All that will be achieved by increasing the time is that the power (the rate at hich energy is generated) is reduced inversely. Power = Energy / time. Zunaid 14:21, 22 December 2009 (UTC)

Voltage and curent in series and parallel circuits

I have now studied the rules of voltage and current in series and parallel circuits and even though I can apply them, I lack an intuitive understanding of why it works like it does.
Given a series and a parallel circuit with one cell and three components, to me it would make more sense if...
1) the current flowing through each component in the series circuit would be bigger than the current in the parallel circuit, because the current in the series circuit doesn't split up, whereas the current in the parallel circuit does split up.
2) the supply voltage in each component in the parallel circuit would be divided amongst the three components.
I know this is not the case, but why not?? As I said, I am looking for an intuitive understanding, an explanation that makes sense, rather than a mathematical explanation with a lot of formulas. Lova Falk (talk) 19:26, 20 December 2009 (UTC)

One way to get some intuition about those rules is to use a mechanical analog. Think of two separate water reservoirs. Now let h be the difference of water level between the two reservoirs. Then connect the two reservoirs with a pipe. The height difference h is the voltage and the amount of water flowing is the current. Now add a second pipe. Adding the second pipe has no effect on the height h. That should answer your second point. Since the height doesn't change, the flow through the first pipe doesn't change either. That should answer you first point. Dauto (talk) 20:43, 20 December 2009 (UTC)

But a parallel circuit appears to be like connecting the two reservoirs with one pipe, which forks and joins up again. Felis cheshiri (talk) 21:06, 20 December 2009 (UTC)

The pipes are the resistances. The wires connecting the resistances to the battery are part of the reservoir because they offer no resistance. Dauto (talk) 22:17, 20 December 2009 (UTC)

The way I think about it is that individual components "use up" voltage but current flows through them. So, components in parallel will have the same voltage and components in series will have the same current, the opposite is also true: Components in parallel will share the total current and components in series will share the total voltage. My personal water analogy is current equals how much water is flowing and voltage is how hot the water is. Parallel circuits split up the flow but each component gets equally hot water i.e the flow is shared: In a series circuit everything gets the same flow but each component cools the water down before it reaches the next one; the temperature is shared. Vespine (talk) 21:21, 20 December 2009 (UTC)

The temperature isn't a very good analogy because it doesn't follow ohm's law. Dauto (talk) 22:17, 20 December 2009 (UTC)

Another analogy is a crowd of people waiting to get through a ticket barrier. Supposing this takes 1 second for each person, the flow rate is 1 per second. If a second identical barrier is opened alongside, then assuming no interference between the two, it too will pass 1 person each second, so the total flow is now doubled. Alternatively, if the second barrier follows the first, with nobody allowed to start the process until their predecessor has left, then each person will take 2 seconds to clear the system and the flow rate will be 0.5 per second.——86.155.184.142 (talk) 21:56, 20 December 2009 (UTC)

Not the best analogy either. Doesn't follow ohm's law. Dauto (talk) 22:19, 20 December 2009 (UTC)

Have you actually thought about this? If the time to negotiate each barrier varies, it would be a perfect analogy to electrical resistance, as the flow rate would be inversely proportional. I agree that voltage is hard to analogise, but it can be deemed to be constant, and this model considering only the OP's first (current) query.——81.131.165.44 (talk) 13:48, 21 December 2009 (UTC)

Putting aside ohms law, I think the parallel / series concept is well illustrated by both of the above, i personally think the reservoir / height difference model is more difficult to imagine.. Vespine (talk) 23:51, 20 December 2009 (UTC)

Why would you want to put ohm's law aside? it's the corner stone of the relationship between voltage, current and resistance. Any model that doesn't include it is seriously incomplete and will inevitably lead to misunderstanding sooner or later. Dauto (talk) 04:25, 21 December 2009 (UTC)

Note that Ohm's Law was rejected by many when he first published his ideas, because they did not understand that batteries all have some internal resistance. The hydraulic analogy is the best mental model for understanding. Solve many problems, analyze many circuits, and it will become intuitively clear. Edison (talk) 01:08, 21 December 2009 (UTC)

Thank you all for your answers. I've read the water resevoir analogy before, but I always thought the pipes were the wires. Dauto you say that the pipes are the resistances, so in this imaginary parallel circuit with one cell and three components, these three components are the three pipes... that makes sense to me. That's the voltage part. I have to think more about the current. Lova Falk (talk) 08:48, 21 December 2009 (UTC)

Longevity of the British royal family

It seems that the royals are living to a ripe old age - the Queen Mum to 100+, Princess Alice to 100+, the Queen herself still being active. 1) Is there anywhere in the internet where it is easy to see the progression of the ages at death of the royal family since Victorian times? I think in Victorian times many of them died young. 2) Is there any evidence for the idea that high-status, high self-esteem people live longer than others, disregarding factors like better diet etc? 89.242.211.123 (talk) 22:14, 20 December 2009 (UTC)

I've seen studies in the last 5 years linking positive mindsets to longer lives, but I don't have any citations for you. My question to you is: why are the Royals assumed to have high self-esteem? Charles' life hasn't been a bowl of cherries, and his two sons lost their mother in a terrible accident. These sorts of things tend to affect the psyche. They're (literally) a privileged class - with the best diet, doctors, and retinue money can possibly buy. Why, assuming no accidents or self-inflicted harmful behavior (smoking, excessive drinking, etc.), should they not approach the maximum limits of human lifespans? 218.25.32.210 (talk) 01:48, 21 December 2009 (UTC)

His personal life has not been unusual - divorce is common. Early death of a spouse is not so unusual. He has a lot of flunkies, country and other estates, official engagements, titles, fabulous wealth, grovelling and syncophants to have a stratospheric self-esteem. The queen is said to have once said that being in heaven would not be an improvement for herself. 92.24.103.234 (talk) 13:46, 21 December 2009 (UTC)

There was a time when medicine was so bad, is was often as likely to kill you as the ailments it was supposed to treat. George Washington, for example, was wealthy enough to afford the best medical treatment in the country. During a particularly bad cold/flu he sent for the best doctors he could find. After draining his body of 5 pints of blood, choking him with leeches around his mouth and nose, and treating him with toxic mercury containing "medicines" (calomel), he died of shock and asphyxiation. I've read accounts where his last acts before dying were cursing out his doctors and trying to claw the leeches off of his face; the leeches likely choked him to death. Had he been poorer and less famous, he likely would have slept it off over a few days, and would likely have lived longer. --Jayron32 01:59, 21 December 2009 (UTC)

Though I have little doubt that medical care at that time (sometimes in our time) could cause terrible complications, the characterization of death by leeches sounds hyperbolic - do you have a source? As our leech article describes, attached leeches are generally painless; people can have a hard time telling they're being bitten except for those few individuals who develop a leech allergy. Leeches are used, to a limited extent, in modern medicine and (when used carefully) can be quite beneficial, e.g. PMID 15134999 -- Scray (talk) 02:36, 21 December 2009 (UTC)

I struck that little bit about the leaches. The actual cause of death, per [3] and [4] and several other reliable sources: see [5] was a combination of inflamation of the throat and his weakened state due to huge blood losses after multiple bloodlettings. I was mistaken about the leeches. Still, it can't help to be drained of 5 pints of your own blood, when already weakened with infection. There does seem to be general agreement among modern doctors that the treatment he received was an exacerbating cause of his death. If the bloodletting did not outright kill him, it certainly sped the process along. --Jayron32 03:39, 21 December 2009 (UTC)

While I can't directly answer the OP's question, he may be interested in a few thoughts. The Queen Mother, while being a member of the titled class since birth, married into the Royal Family and therefore is only related by marriage. Her own husband (George VI, Victoria's great-grandson) died relatively young at the age of 57 of lung cancer. His father George V died aged 71, also of lung cancer. Edward VII died aged 68. Princess Alice also married into the Royal Family (although, like the Queen Mother, was a member of the titled class). Queen Elizabeth II is the longest lived monarch since Queen Victoria, and I can't find any monarch of England/Great Britain/United Kingdom who has actually lived longer. (I haven't had time to fully check this out though.) It would appear that the female line is more robust: or you may also consider that the Queen is a lucky recipient of some very strong genetic influences through her female relatives. --TammyMoet (talk) 09:55, 21 December 2009 (UTC)

Don't forget Princess Margaret, dying at 71 despite the same genetic influences. Of course, rather then her sister's life of quiet dedication, her's was one of smoking, drinking, sexual excess and total self-indulgence, so maybe the surprise is that she lasted so long.——81.131.165.44 (talk) 13:59, 21 December 2009 (UTC)

The Princess Margaret article says that she was a heavy drinker and a heavy smoker. Lesser known fact that smoking causes heart and circulation problems, perhaps leading to the strokes. 92.24.103.234 (talk) 17:06, 21 December 2009 (UTC)

Go out for a spacewalk in that?

There is some research being done (by M.I.T. for one) in regards to Space activity suits. Or alternately, mechanical counterpressure suits. I understand the advantages to such a get-up, but I can't get my head around the idea of stepping out into say, the moon's surface in such wear. The suit's only a fraction of an inch thick, correct? The temperature in near vacuum is -150 or so in the shade, correct? I know you can't lose body heat in a vacuum and regular NASA suits actually use coolant to well, keep astronauts cool. But -150 (or +150 degrees for that matter) so close to your skin? Wouldn't you feel the terrible cold through that thin wear? Why wouldn't your skin turn into frosty stuff? Mytg8 (talk) 22:39, 20 December 2009 (UTC)

If you aren't losing heat, you don't feel cold. Things feel cold when we lose heat to them: that's how heat works. It sounds like you've got to a stage where intellectually you know that they aren't going to lose heat by conduction (although they can still lose some by radiation), but you can't quite accept it intuitively.

Imagine you have double glazing. Really good double glazing with a perfect vacuum between the panes. It's nice and warm in your house, but very cold outside. You put your hand against the window on the inside and it feels like room-temperature glass, nowhere near as cold as the glass on the outside. Now imagine the glass is very thin. The glass on the inside will still be at the temperature of the room, and will feel like room-temperature glass. Now imagine we add a few molecules of air (10?), and the temperature of the near-vacuum between the panes is -150. Will adding those 10 molecules cause the glass inside to feel very cold? Of course not. 86.176.191.243 (talk) 23:40, 20 December 2009 (UTC)

Since space is a vacuum, how can is its temperature be measured? a) the measuring device will retain its previous temperature because of the insulation from the vacuum, b) if its a vacuum (almost), what is there to measure the temperature of? 89.242.211.123 (talk) 23:50, 20 December 2009 (UTC)

Actually, even a perfect vacuum will have a temperature, see Temperature#Temperature_of_the_vacuum and cosmic microwave background radiation. Temperature of even a perfect vacuum can be measured by the zeroth law of thermodynamics, which defines temperature by the relative transfer of thermal energy, not by absolute molecular motion. --Jayron32 01:41, 21 December 2009 (UTC)

a)The measuring device still can emit and receive radiation. b)Radiation. Dauto (talk) 01:39, 21 December 2009 (UTC)

In The Forever War, a lot is made of the fact that you won't get cold in space, but you also can't vent heat very well, for the same reason. If you are actively generating heat (as your body will), then the problem is not overheating, not overcooling. --Mr.98 (talk) 00:01, 21 December 2009 (UTC)

You lose considerable heat energy through radiation alone, its probably enough to cool you pretty quickly in a vacuum. I don't know the numbers, but I can't imagine you'd overheat as your basically "glowing" in the near-IR range, throwing off lots of energy even without the conductive cooling of an atmosphere. Without the insulation of an atmosphere, radiative losses may be enough to freeze you pretty quickly. --Jayron32 03:43, 21 December 2009 (UTC)

NASA has a page that explains vacuum survival. To quote the summary, "If you don't try to hold your breath, exposure to space for half a minute or so is unlikely to produce permanent injury. [...] exposure causes no immediate injury. You do not explode. Your blood does not boil. You do not freeze. You do not instantly lose consciousness."

This page describes some of the theory behind the suit the OP mentioned (do a ctrl-f for "Mechanical Counter Pressure"). It also describes some of the challenges faced by designers of space suits of any type. Essentially, from what I could gather from both, a conscious human being at Earth's distance from a star as bright as the Sun will produce (and absorb) more heat than will be radiated away, so the primary issue with space suits is keeping the body from overheating, not freezing. J.delanoy^gabs_adds 04:31, 21 December 2009 (UTC)

I stand corrected. --Jayron32 15:36, 21 December 2009 (UTC)

Those poor experimental animals - they must have suffered. 92.24.103.234 (talk) 13:41, 21 December 2009 (UTC)

The double glazed glass is a very good analogy--thanks. With all those bright people working on the suit, something so intuitively obvious should not be a problem, right? Perhaps it is similar to the 400 mph winds on Mars--such extremes in our atmosphere and near vacuum are two different things. Re: the overheating problem, it seems the 'smart suit' is also porous. If I understand correctly, your sweat would soak the garment and cool you off. So, you would walk around the moon with a layer of frost on your suit? :) Mytg8 (talk) 13:11, 21 December 2009 (UTC)

Physiology of states of boredom or high motivation?

Do these two psychological states have corresponding physiological states? Are there drugs of any description that can induce one or the other? Personal research - having a cup of tea this evening made me feel a little less bored. 89.242.211.123 (talk) 23:56, 20 December 2009 (UTC)

There are numerous neurotransmitters and other hormones which are closely linked to changes in mood. You may be interested in such things as cortisol and seratonin and Norepinephrine and dopamine. In general, ALL psychological states can be correlated to physiological states. There is always something physical behind everything psychological. --Jayron32 01:38, 21 December 2009 (UTC)

Generally speaking, psychomotor stimulants such as cocaine and amphetamine induce states of high motivation, while the opposite group of drugs, neuroleptics such as thorazine or haloperidol, induce an amotivational state that could probably be called boredom. There are, as Jayron says, lots of other drugs that affect arousal, but the dopamine-affecting drugs I mentioned are probably the ones that have the most direct effects on the rewardingness of activity.Looie496 (talk) 15:34, 21 December 2009 (UTC)

I wonder if there are any healthy ways, such as eating the right foods, to try to keep yourself in the high-motivated state? 92.24.103.234 (talk) 17:10, 21 December 2009 (UTC)