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March 27

Meth addicts

Whenever you see photographs of meth addicts, they usually have scabs all over their face, as if they pick at their skin. Why is that? Thanks. Joseph A. Spadaro (talk) 05:02, 27 March 2014 (UTC)[reply]

According to this, they pick their skin obsessively due to a sensory hallucination of bugs crawling beneath the skin. The technical name for that is delusional parasitosis, also known as "crank bugs". Red Act (talk) 05:24, 27 March 2014 (UTC)[reply]

Thanks. Wow, pretty disturbing stuff in that link. Almost sorry that I asked! Ughhhhhhh. Thanks. Joseph A. Spadaro (talk) 15:58, 27 March 2014 (UTC)[reply]

Isn't a secondary reason that they don't feel pain when scratching open their cheeks ? StuRat (talk) 14:11, 28 March 2014 (UTC)[reply]

Angle of penis

Links in this question are NSFW.

The article Erection provides a table with the distribution of erect penis angles. But what does it tell us, how is the angle measured? Few penises are completely uncurved. Take the image in the article: at the root it has an angle of about 70° while at the glans it has an angle of about 35°. Which of the values is the correct one? Or does one have to draw an imaginary line through root and glans and measure the angle of this line?

I have no access to the original paper. Does anybody know or can look it up in the paper?

Also asked on Talk:Erection#Angle a few days ago, but with no answers so far. --31.16.110.207 (talk) 10:26, 27 March 2014 (UTC)[reply]

The excitation phases of an orthodox healthy phallus are quantifiable in terms of a 2-D Euclidean vector (Length, Angle) in the vertical plane, where Angle is readily estimable within ranges of 10 degrees or more, as given in the cited article, from photographs. This data does not apply to the minority of phalli that exhibit curvature, whether the origin of their additional vector curl component be congenital or pathological as observed by Gigot de Peyronie in 1743. Popular culture offers only qualitative, not quantitative, insinght to this non-linear male morphology, as evidenced in the Limerick prose: There was a young fellow of Kent / whose prick was remarkably bent. / To get over the trouble / he bent it in double / so instead of coming he went. 84.209.89.214 (talk) 17:32, 27 March 2014 (UTC)[reply]

Thanks. That's my new favourite limerick. InedibleHulk (talk) 20:10, 27 March 2014 (UTC)[reply]

As tedious as this point is, I add that the penis would more normally be described as having curvature rather than curl. Both in regular usage and strictly mathematical senses. Curl applies to vector fields. Penises are usually experienced as localised rather than distributed phenomena.

Agreed, and please sign your posts. The non-linear turgid phallus has a local curvature that could be quantified by a curvature vector, or in a more general 3-D parametric curve fitting method using B-spline analysis and control points.

However existence of distributed phallo-erectile vector fields quantifiable by time-dependent del operators cannot be ruled out. In practice such fields would be quantifiable by teams of volunteer males, selected preferentially for non-paraphilian Hypersexuality but disqualified for hyposexuality, and each fitted with a recording plethysmograph and satellite locator. Such phallometric field data, if collected, would be of direct value to the pornography industry, by extension also to planners of male-directed advertising, and might serve to validate B.Singer's model of sexual arousal (1984) which postulates vectorial responses from subject(s) towards attractive object. 84.209.89.214 (talk) 12:49, 28 March 2014 (UTC)[reply]

This is such jargon its unbelievable. — Preceding unsigned comment added by 84.92.32.38 (talk) 09:15, 30 March 2014 (UTC)[reply]

How do coil cords get kinked up the way they do?

Here's a link to a YouTube video on how to untangle a coiled cord [1]. My question is: how does a coil cord seemingly suddenly develop a "reversal turn" in the middle of the cord in the first place? I have a hard time visualizing it happening, because the cord on either side of the "turn" looks normal, and certainly nobody did anything like the opposite of the procedure in the video to put the "turn" there. Is there a better way than what's in the video to fix the problem? I fixed a coil cord once by shifting the "reversal turn" to one end, one turn at a time. But the thing is, the cord didn't look quite the same afterward. The length of the cord where the shifting of the "reversal turn" has passed through became visibly less tight than before. --96.227.60.84 (talk) 11:50, 27 March 2014 (UTC)[reply]

Original research on my part, but I find the easiest way to fix a telephone cord is to suspend the handset and allow it to spin round a few times, thus more or less correcting itself. How does it get like that? What seems to happen is that someone picks up the handset say with their right hand, and after a while they might pass it to their left hand in order to write something down. It then goes back to their right hand before replacement and during all this it somehow does a complete turn. Over the course of a few weeks, the cumulative twist builds up.--Shantavira|^{feed me} 13:03, 27 March 2014 (UTC)[reply]

Yes, I was just about to post the same comment when I read Shantavira's explanation above. I used to go round the phones at work every week or fortnight, giving them a few twists in the opposite direction (usually anticlockwise), or spinning them to reverse the effect of people adding a clockwise twist when they replaced the handset. Perhaps we had an inadequate proportion of left-handed people? It never happens with my phone at home. Dbfirs 13:12, 27 March 2014 (UTC)[reply]

I've found two seemingly contradictory ways to keep a cord from tangling:

1) Constrain it more. Use zip ties to hold it all together so it can't twist. It also helps to avoid putting as much stress on it when coiling it up, by moving your body over or under the cord when you see it starting to twist, to relieve the stress.

2) Constrain it less. Just leave it all in a pile, rather than trying to make it look neat. You can put it into a trash can, for example, and just let it flop where it will. This puts less twisting stress on it, so the coils don't need to move to relieve the stress. StuRat (talk) 13:16, 27 March 2014 (UTC)[reply]

While cords can be an everyday frustration, understanding the dynamics via knot theory is a rigorous field of math that addresses some of these issues. While it historically was a "pure" and abstract study, it has proven useful for describing certain behavior of DNA. Some relevant articles for cords are Reidemeister_move, twist_(mathematics) and writhe. For the DNA applications, see Writhe#Applications_in_DNA_topology and DNA_supercoil, or check out the work of Craig Benham [2] if you want to see some of the detailed math. SemanticMantis (talk) 16:09, 27 March 2014 (UTC)[reply]

It seems to me that finding ways to prevent regular cords, ropes, wires, etc., from tangling was already a rather practical application of this field of study. It's not just a homeowner annoyance, to people like construction workers who deal with such problems every day, it's a real-world problem. Those who design products like "hose caddies" also must take twisting and tangling into account.

For pure science apps, though, we also have the twisting of tornadoes, especially multiples, and the entanglement of the Sun's magnetic lines of force (which is linked with the sunspot cycle), and many others. StuRat (talk) 14:00, 28 March 2014 (UTC)[reply]

Because people don't use Over/under cable coiling. This technique is used in the music industry and other places where cable coiling is done professionally. In normal coiling you introduce a twist with each loop. In under-over coiling the twists in successive loops cancel each other out. I regularly do it with all my cables and it cures a lot of problems with twisting a knotting.--Salix alba (talk): 18:28, 31 March 2014 (UTC)[reply]

Weights and rest

I heard that weight training (doesn't matter which part of body) shouldn't be done more than two days in a row i.e the third day should be resting or cardio if needed. Is it scientifically sound to say that even if i give rest to my body parts and concentrate on different part the next day still my whole body needs a day of rest ?? — Preceding unsigned comment added by 119.235.54.187 (talk • contribs) 11:54, 27 March 2014‎

Muscles need time to repair themselves. However, I've read that for young people this is a bit different. E.g. in the US army they let the recruits do many pushups every few hours every day. Count Iblis (talk) 15:35, 27 March 2014 (UTC)[reply]

LOL @ "let"...as if the recruits would do constant push-ups, if not held back by their concerned, overprotective drill sergeants. StuRat (talk) 14:18, 28 March 2014 (UTC) [reply]

The lucky ones are allowed to practice this variant. Count Iblis (talk) 18:03, 28 March 2014 (UTC)[reply]

What's the point?

Imagine for a moment that you're able to get one of these things to work. What's the point? As soon as you harness it to do regular work, won't it stop? I can't quite imagine all these people trying for generations to make a self-perpetuating plaything. Nyttend (talk) 12:31, 27 March 2014 (UTC)[reply]

Yes, if we harness it to do regular work it will stop. But it will also stop before being harnessed to do work, just as a result of friction between the moving parts.

Prior to the industrial revolution all work was done by human workers or by animals. Around the start of the industrial revolution, simple machines were invented and built. These were a source of great interest but they all required a person, horse, donkey etc. to drive them. There arose a fascination with the idea of one of these new machines that would run by itself, without input by a person or an animal. In those early days there were no electric motors to conveniently drive these machines so there was a serious incentive to find something (other than people or animals) that would do so. Many people tried, unsuccessfully, and their creations became known as "perpetual motion machines". Ultimately, it was the electric motor and the reciprocating engine that would be put to use driving machines. Dolphin (t) 12:44, 27 March 2014 (UTC)[reply]

Folks who believe in these things hope they can be improved to be "over unity", meaning they generate energy. Simply breaking even, being "at unity", is, as you say, nothing more than a magical toy. -- Finlay McWalterჷTalk 12:49, 27 March 2014 (UTC)[reply]

Well, by all accounts the universe is a perpetual motion machine, creating space and dark energy and mass-energy out of nothing. I wouldn't rule out that someone can come up with a way - who knows, maybe even something that uses magnets - maybe they just need the right idea. But these ... aren't them. Wnt (talk) 13:28, 27 March 2014 (UTC)[reply]

If you could make this (or any other 'perpetual motion' machine) work, then there are two possibilities as to how you hypothetically managed to do that:

You somehow removed 100% of the friction and air resistance from the thing. That would require (at the very least):
1. Encasing it in a vacuum that's even more empty of stray atoms than deepest interstellar space to avoid all of the air-resistance.
2. To somehow avoid atoms that evaporate from the surface of the machine's parts and the container around it from gradually polluting your vacuum and causing "air resistance".
3. You'd also have to avoid photon pressure from remote light sources - so the machine would have to be kept in complete darkness.
4. ...and keep it from being bombarded with radiation of all kinds - including hard-to-stop things like neutrinos...but to do that perfectly requires that you encase it in an infinite thickness of some screening material.
5. Microscopic tidal forces on the machine due to gravitational forces from other objects in the universe would cause the machine to microscopically bend and flex - which would create heating, and therefore slow it's motion...so I guess your machine would need to be placed infinitely far away from any other masses such as galaxies and such.
6. Magnetic fields would also pose a problem because they to can cause "tidal" forces...so you'd better not even think about building a machine with magnets inside it!
You've somehow made it work DESPITE the air resistance, friction, tidal forces, etc, etc. If you could do that then it would actually be an "over unity" machine because it would produce waste heat. You'd be able to use a big pile of them to heat your home during cold winter nights - or to heat water to boiling point and have it run a steam engine to power your car! (All free energy ideas ultimately reduce to some nut wanting to run their car for free...I don't know why that is.) Since the laws of thermodynamics don't permit "over unity" operation, we know that this can't happen.

So even a perpetual motion machine that spins and does nothing is impossible. The need to avoid all of those things that would eventually slow it down is an annoying practical problem. As a "thought experiment", you could wave away all of those annoying objections, and the laws of thermodynamics would obediently allow you to build a machine that spins forever - an "at unity" machine rather than an "over unity" device. But as a practical possibility, even with the most extreme engineering imaginable, you can't make a perpetual motion machine that runs at exactly unity.

Perpetual motion of any kind is simply not worth consideration...it can't happen in a real universe.

SteveBaker (talk) 14:29, 27 March 2014 (UTC)[reply]

Well, as I said above, the universe itself seems to run by perpetual motion. In this case, entropy doesn't decrease, so there's no violation of the laws of thermodynamics, even as the amount of matter and energy continually increases. There just needs to be more and more space. I suppose if you had some kind of wannabe 'wormhole generator' that pinches off little vesicles of space and sends them sailing away into some higher dimension, you might be able to similarly claim increased entropy even while producing an unlimited stream of energy. It just requires some ... inspiration. Wnt (talk) 16:48, 27 March 2014 (UTC)[reply]

Superfluid helium-4 would seem to qualify for "unity" perpetual motion, if placed in just the right environment and stirred; mere superconductor rings with current flowing qualify at the electron level. I think. Issue: apparently the helium-4 and superconductors both have some non-superconducting component, and it's not clear to me that doesn't inevitably have a way to stop the motion over time. Wnt (talk) 16:54, 27 March 2014 (UTC)[reply]

Videos of a Brownian ratchet device apparently extracting rotational energy from random particle motions. These perpetual motion demonstrations and the automatic watch pictured give Maxwell's demon some explaining to do. 84.209.89.214 (talk) 16:34, 27 March 2014 (UTC)[reply]

You don't think it's worth evaluating the energy balance in that "granular gas" demonstration (before you start suggesting that the demonstration somehow challenges known physics)? Even if we concede that a bunch of ping-pong balls bouncing around in a plexiglass arena were a reasonable approximation of gas molecules... what energy source is supplying the ping pong balls (or gas molecules)? There's a "thermal gradient" with energy being supplied at the bottom of the container (the machine that's lobbing those ping-pong balls upwards!) That's not perpetual motion, it's extraction of energy from an external heat reservoir. Once that external energy supply runs out - i.e., when you unplug the ping-pong ball "popper" machine - the balls stop bouncing around, and the device goes quiescent. Throw on top of this the millions of "technicalities" about why ping-pong balls are terrible models of gas molecule brownian motion - and that very interesting ratchet demo is actually further evidence for why the Maxwell's demon though-experiment actually shows that the method fails to extract perpetual energy from the gas.

If you want other physicists to explain Maxwell's demon, all you have to do is read any textbook on thermodynamics or any reputable physics website on the internet. Here's a nice one I found at Auburn University, with a fun cartoon of the demon: Maxwell's Demon, from a lecture series on "concepts of science." You can also read our article, why the ratchet fails. Ultimately, it comes down to using a correct definition of thermal equilibrium in the thought-experiment; or, in the practical demonstration, making a device that would hypothetically work, without actually supplying external energy. Nimur (talk) 17:13, 27 March 2014 (UTC)[reply]

The page of videos you linked, made by the Department of Science and Technology of the University of Twente, makes no claim of perpetual motion or free energy. The automatic watch is, of course, wound by motions of the wearer and will run down if not worn. -- BenRG (talk) 17:34, 27 March 2014 (UTC)[reply]

As I said in the last thread, a "perpetual motion machine" is a device that violates the first or second law of thermodynamics and not, despite the name, one that moves forever. -- BenRG (talk) 17:34, 27 March 2014 (UTC)[reply]

Extraction of useful energy on a large scale from tidal forces is uncontroversial, yes? SB suggests above the impossibility of isolating a device such as Brownian ratchet from all "Microscopic tidal forces on the machine due to gravitational forces from other objects in the universe". Please do not interpret the present scientific consensus that perpetual motion is impossible, as it would violate the first or second law of thermodynamics, as also providing the definition of PM. For that we should be allowed our individual understandings of perpetuality that are essentially as finite as ourselves: "For generally the infinite has this mode of existence: one thing is always being taken after another, and each thing that is taken is always finite, but always different. Aristotle, Physics, book 3, chapter 6. 84.209.89.214 (talk) 18:20, 27 March 2014 (UTC)[reply]

You seem to be suggesting that any machine could be considered a perpetual motion machine, for sufficiently small values of "perpetual". I am not sure this is a useful approach - rejecting a scientific definition in what is essentially a question of science (and engineering). - Eron^Talk 18:29, 27 March 2014 (UTC)[reply]

Perpetual motion machines, as defined by a device that outputs more energy than it takes in and can do this indefinitely, violate the first law of thermodynamics. It doesn't matter whether the scientific consensus supports the first law or not--by definition, such a device violates the first law. --Bowlhover (talk) 18:40, 27 March 2014 (UTC)[reply]

Alright... take a region of intergalactic void. Lay two pieces of cable from one end to the other. One is anchored to a heavy object at one end, one is anchored to a heavy object at the other. They receive minimal energy from other regions of space. Nonetheless, as the universe expands, inevitably the two heavy objects drift further and further apart, causing the cables to move relative to one another. Plant generators along the strands to take advantage of this motive force, and enjoy your perpetual motion machine. Wnt (talk) 00:24, 29 March 2014 (UTC)[reply]

Neat but... Wouldn't the molecules in the links of the cables and generators also expand at the same rate and so generate no relative motion? draw your mechanism on an expanding soap bubble. I'm not saying you are wrong, but may have missed something. Greglocock (talk) 00:43, 29 March 2014 (UTC)[reply]

Assuming the temperature remains the same (or colder) the optimum interatom distance should not increase. Of course, the expansion of space should tend to spread the atoms apart, but the point is that a tension force should develop, with the heavy weight at one end determining which way the cable ends up moving under this tension to keep a stationary center of mass. (I recognize of course that this is not a practically workable perpetual motion machine, and that harnessing local gravitational variations in the Solar system would be way more productive, but my point is: the universe is a perpetual motion machine and this energy is extractable, and maybe there's a better way to extract it yet to be discovered. I hate it when people tell us that it's possible there could be a Big Rip or the decay of a false vacuum or the collapse and rebirth of the universe and half a dozen other impossible things, all of which I'm supposed to believe before breakfast, only to be lectured just afterward that it's absurd for me to think perpetual motion can be real. Wnt (talk) 03:59, 29 March 2014 (UTC)[reply]

The incorrect assumptions regarding the metric expansion of space your little "ball and cable" thought experiment introduce are too profound to counter here, so just read the article please. Let me quote the relevent bit, and hope you understand it " Once objects are formed and bound by gravity, they "drop out" of the expansion and do not subsequently expand under the influence of the cosmological metric, there being no force compelling them to do so." Your balls-and-cables will not drift apart under the "force" of the metric expansion of space. They will remain stubbornly stable and do no work for you. Thermodynamics wins again. --Jayron32 04:25, 29 March 2014 (UTC)[reply]

I was careful to specify "intergalactic void". Still, to be clear, two objects that are "at rest" relative to one another, and not subject to a net gravitational pull relative to one another over a few billions of years for whatever reason, whether it is balancing of masses or just being very remote, will end up further away from one another. That's what metric expansion of space means. If gravity does not apply the force to move them together, the force needs to be applied by some other means, which implies that usable work could in concept be harvested. I recognize, of course, that as strong as electromagnetic forces are, building cables that is so long but so light that the masses required to anchor them would not attract one another would be quite implausible - the point of the thought experiment is only that "over unity" can be done.

Perhaps a simpler version of the experiment would be more straightforward: suppose you have a very long piece of very light, very weak string floating in intergalactic space. As space expands, the string must break. Where does the energy to break it come from? This is, as I suggested, a very mild version of the Big Rip scenario where supposedly every atom gets torn apart. How can a force be strong enough to pull apart atoms but not exist? Wnt (talk) 13:14, 29 March 2014 (UTC)[reply]

Again, please provide a reference or stop making these over-unity claims. Even if you could "slow down" a distant galaxy by tying a rope to it and harvest the energy, so what? How does that give you free energy? By analogy, suppose a bomb explodes in space and its pieces go flying in all directions. I can in principle tie a string between one piece of debris and another. The string will break, the pieces slow down, and the energy to break it comes from the kinetic energy of the pieces. After I've connected enough strings between enough pieces, all the pieces will be at rest and I'll be unable to harvest any more energy. You seem to be saying that harvesting energy from the universe is somehow the equivalent of over-unity perpetual motion. Did you realize that the universe has nearly limitless starlight, and that harvesting that is much easier than your scheme (and also not free energy)? --Bowlhover (talk) 16:03, 29 March 2014 (UTC)[reply]

Wnt, please provide a reference or stop repeating your incorrect claims about the expansion of space. The universe is NOT a perpetual motion machine. It is NOT true that matter is being created; in fact, the amount of matter in the universe remains constant, and is being diluted as the universe expands. Your thought experiment does not work, practical or not, because objects bound by electromagnetic or gravitational forces don't expand with the universe. Hence, the Earth, the solar system, and even the Milky Way will be exactly the same size 100 billion years from now--because they're not affected by the metric expansion of space!

Lastly, it's true that the amount of dark energy in the universe is increasing. However, if dark energy really is the zero-point energy of space, extracting energy from it is impossible--it is by definition the lowest possible energy. If it's not zero-point energy, then we don't have a plausible physical theory of what it is. You can of course propose a theory where dark energy allows for perpetual motion machines, just as I can propose a theory where dark energy is comprised of angels flapping their wings while dancing on a pinhead, and neither theory is appropriate for the reference desk because no reputable scientist would say either is true. --Bowlhover (talk) 05:20, 29 March 2014 (UTC)[reply]

We had this discussion in a thread above. As the universe expands, Unruh radiation from the retreating "edge of space" produces mass-energy. Indeed, the thread above suggested the universe had only about a Planck mass in a Planck volume early in its development. (Please do correct me if I'm wrong, as I had Bowlhover's impression before, but I think I have it right this time) Wnt (talk) 12:55, 29 March 2014 (UTC)[reply]

I don't know which thread you're talking about, but there is no Unruh radiation from the "edge of space". Please give a reference if you think there is. It's also not true that the universe had a Planck mass early in its development--it's entirely possible that the present-day universe is infinite, which would imply that the universe always had infinite mass and infinite size. --Bowlhover (talk) 16:03, 29 March 2014 (UTC)[reply]

Hunting around, I found a bit of a different reference which gives some sense of the conservation question [3]. I have no idea whether you're going to say this is fringe or old hat, but here's the issue: "While in one view it is speculated that the universe has been evolving with a constant mass but increasing radius, (e.g. Lemaitre [3]), on the alternative view it is variously mentioned in passing that total energy being the sum of the positive energy of matter and the negative energy of the scale factor or radius is what is conserved as the universe evolves [4-6]." And "To obtain Ω ~ 1 immediately after inflation, the mass of the observable universe after the event must not be more than 675kg!" But admittedly that one doesn't say Unruh; someone else mentioned it. Wnt (talk) 22:08, 29 March 2014 (UTC)[reply]

It doesn't take much hunting. Our article on Unruh effect says: "The Unruh effect was first described by Stephen Fulling in 1973, Paul Davies in 1975 and W. G. Unruh in 1976. It is currently not clear whether the Unruh effect has actually been observed, since the claimed observations are under dispute. There is also some doubt about whether the Unruh effect implies the existence of Unruh radiation."...so this "effect" is a dusty old idea from the 1970's that nobody has been able to effectively demonstrate - and even if it is an actual "effect", it's far from clear that any radiation would be produced. So why would you use it to say that this is definite proof for the universe being a perpetual motion machine? Basically, *if* some entirely hypothetical (and rather unlikely) thing were true *then* there is a very remote possibility that the universe *might* be a perpetual motion machine. But without proof or scientific consensus of any kind, Occam's razor says that there still aren't any perpetual motion machines out there...not even the universe itself. SteveBaker (talk) 13:43, 31 March 2014 (UTC)[reply]

The Unruh effect is well established even though it has not been observed. You have to consider here that physics is a far more fundamental scientific discipline than any other scientific discipline and you can then have a purely theoretical result which is a consequence of a well established theory (with strong experimental foundations), in this case quantum field theory. Other examples are the scattering of light by light, and the prediction by John Bell of the violations of the Bell inequalities. These are all rather straightforward predictions of quantum (field) theory, and therefore extremely unlikely to be wrong. The violation of Bell inequalties have been verified a long time ago, but then at the time no one believed that the experiment would falsify quantum mechanics.

Most of the time, the problems in this field occur more at the experimental side, take e.g the "faster than ligh neutrinos", the anamolous PVLAS results, Cold fusion etc. etc. So, while in principle, experimental results are all that counts, in practice when experiment clashes with a theoretical result (well verified to be valid from the point of view of theory), then the experimentalists have made a mistake. Count Iblis (talk) 15:59, 31 March 2014 (UTC)[reply]

Lots of things that are obvious to us, are obvious because someone discovered it, and stated it as a principle. Many Superseded scientific theories were solid for past generations, but just hilarious fringe theories for us. Take into account too that people back then couldn't understand magnetism and gravity well enough to discard a mechanism build for extracting energy of these too fields. OsmanRF34 (talk) 19:37, 27 March 2014 (UTC)[reply]

This is a common meme amongst free energy nuts: Roughly: "There are lots of failed scientific ideas - so maybe our current science will fail and we can all have free energy." But this claim doesn't really stand up to close observation:

Failed ideas from before about the late 1700's when "The Scientific Method" became well-established should be discounted because they don't tell us anything about the likely failure rate of ideas that employ more modern scientific rigor.
You should also discount theories that were superseded without being entirely nullified...Newtonian mechanics was indeed found to be incorrect by Einstein - but only under very extreme conditions, well beyond the limits at which Newtonian mechanics had been tested. Indeed it took considerable ingenuity to devise an experiment to demonstrate that. All new ideas have to predict the same results that existing ideas have demonstrated in order to match experimental reality. Sure, a new theory of motion can come along, but it can only apply in areas where Einsteins theory has not yet been successfully tested.
Ideas in some of the fuzzier sciences (where we don't normally talk about rigorous proof) are frequently overturned - so it's not fair to point to failures in (say) psychology (a notoriously 'soft' science) and use that to say that established science in modern physics (probably the 'hardest' of the sciences) might very well be overturned.
You can't count "hypotheses" - those are not things that modern science claims to be "truth".

Now look back at that list of Superseded scientific theories and let's see which ones pass those tests...

Basically, all of the Biology section pre-dates the scientific method except for the Out of Asia theory of human origin - which was an idea that wasn't so much overturned as merged into the Multiregional origin of modern humans (that's what our Out of Asia theory article says).
All of the Chemistry section pre-dates the scientific method.
In Physics, everything except the Newtonian mechanics and the gradual refinement of atomic theory is too old, and Newton wasn't incorrect in the realms for which his results could be tested. Since Rutherford, atomic theory hasn't been shown to be dramatically WRONG - it's simply an evolving set of hypotheses that are gradually turning into hard answers. No doubt we'll have more and more refined models - but every new model has to produce the exact same results as the existing models in the areas for which they've been tested - so any new discovery in that area would not overturn what we already know about the conservation of mass/energy and all that stuff.
Astronomy has undergone many changes since the 1700's - but not many hard theories have every been overturned - generally these were untested hypotheses that were finally tested.

...you get the idea.

The things on that list don't provide evidence that large and important chunks of hard science are going to be overturned. Broadly speaking, modern ideas in the hard sciences that have been awarded the "LAW" or "THEORY" label are unlikely to be drastically wrong simply because they fit all of our modern experimental data so perfectly. Hypotheses are just that - ideas that could easily be proven wrong.

The laws of thermodynamics are perhaps the strongest pieces of science we have - and they are proven correct in countless studies with incredibly careful experimental technique. If they are ever proven wrong, it would have to be in some incredibly strange situation...maybe inside a black hole or at some kind of quantum level weirdness or something. They definitely AREN'T ever going to be shown to be false by some amateur tinkering with magnets and such like.

SteveBaker (talk) 14:18, 31 March 2014 (UTC)[reply]

The solar system could be considered a "perpetual motion machine" for practical purposes. We get constant energy from the sun, for example. But it doesn't really pass the test in the long run, as that "perpetual" energy will be used up someday - just not for many millions of years. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:47, 31 March 2014 (UTC)[reply]

Steve this is the science reference desk, and science is empirical, therefore subject to falsifiability. But you know that, so please stop with the diatribes. --Modocc (talk) 16:37, 31 March 2014 (UTC)[reply]

I do think WNT has a point here, conservation of energy does not apply to systems that are not invariant under translations in time. If some system is not invariant due to changing boundary conditions, the change in the energy can be accounted for by work done on the region outside the system. But if the system is all that exists then the notion of energy has to be modified so that it is still conserved. Obviously, you are still free to invent a fictitious external world such that the physics within the system is reproduced correctly. Within that larger system energy will then still be conserved, but this comes at the price of assigning energy to fictitious degrees of freedom. Count Iblis (talk) 16:14, 31 March 2014 (UTC)[reply]

Can right handed living organisms be created in the lab?

Synthetic DNA has been created ab initio in the lab, so I was wondering if right handed DNA together with all the right handed variants of the molecules of a simple organism can be synthesized and put together in a cell. Count Iblis (talk) 19:00, 27 March 2014 (UTC)[reply]

Assuming you mean "can" as in "we can do this tomorrow because we know how to do it", then no, I don't think so. We can't even get any sort of totally synthetic thing sustainably reproducing in a lab. AFAIK Synthetic_biology#Synthetic_Cells describes the latest significant published results in the area, but I could be wrong.

Also, I'm not sure what you're getting at with the chirality. We see both right and left-handed DNA in nature, but maybe you are thinking about some novel assembly of the chirality among the important molecules? DNA#Alternate_DNA_structures says a bit about what we do and don't see in nature, and there's a decent table of info at Z-DNA#Comparison_geometries_of_some_DNA_forms. I suspect @Wnt: might have something to add? SemanticMantis (talk) 22:32, 27 March 2014 (UTC)[reply]

I think Count Iblis refers to DNA built from L-deoxyribose. I.e. take a bacterium and create its mirror image. As for the question, I don't know of anything beyond Craig Venter's bacterial chromosome (which presumably could have been synthesized with mirrored molecules without much difficulty, other than the resulting chromosome not working with the enzymes and other molecules in the DNA-free target bacterium). One would have to synthesize a number of proteins from D-amino acids. Icek (talk) 00:38, 28 March 2014 (UTC)[reply]

Ah yes, that makes sense. But your "other than..." strikes me as very apt, and a big obstacle to the fully synthetic creation of some "mirror image" life! SemanticMantis (talk) 15:12, 28 March 2014 (UTC)[reply]

See http://www.darwinismrefuted.com/molecular_biology_04.html.

—Wavelength (talk) 01:40, 28 March 2014 (UTC)[reply]

@SemanticMantis: I have read the articles you linked to, and they are crystal clear. I have two side-questions:

This article Chirality_(chemistry) has it that "all life on Earth being homochiral". Perhaps that phrase should be modified a bit then to mark what is actually homochiral in "all life"?
This article http://www.bbc.com/news/science-environment-26768445 claims to the synthetic dna in cells now being able to reproduce. You added "sustainably". Could you please expand a bit on that? Star Lord - 星王 (talk) 09:53, 28 March 2014 (UTC)[reply]

@DanielDemaret: I'll answer based on my knowledge, but this is not really my area of expertise. 1)I definitley agree that that part of the article should be clarified, but I don't have the expertise (or time to make up for it) right now. I think the issue is sort of the scale of the chirality being discussed. The DNA articles I've linked above both mention different chiralities of the DNA helix being found in nature. So clearly all life isn't homochiral in terms of Nucleic_acid_secondary_structure, but there are other levels of organization above and below that (e.g. quaternary structure, etc.) -- So maybe the "all" is supposed to apply to the chirality of the constituent amino acids, with e.g. all known life using left-handed amino acids (Not sure if that's even true...). Anyway, thinking more on it, I think Iblis was getting at this lower level of amino acid chirality, which does seem to be more uniform across known organisms. However, IMO this makes it even less likely to fully synthesize life that way, esp. since, as I said above, we can't even do the "easy" case yet, using all the same handedness molecules as the natural variants do. Anyway, I'd suggest dropping a note on the talk page, asking for clarification. Hopefully you'll get a response and improvement from an actual subject expert.

2) I'm just being careful and skeptical, and thinking about the ecology of such a critter in a teleological sense (this is closer to my expertise). Reproducing for a few generations doesn't mean it can do so indefinitely, and without human support (we probably wouldn't want that anyway!) Think of an analogy from cloning: Cloning#Dolly_the_sheep was in some sense a "perfect clone", but she experienced rapid senescence, probably because of something to do with her telomeres shortening. Lacking evidence to the contrary, I don't see any reason to believe there is not some kind of breakdown in these synthetic critters that pops up after several generations. Hope that helps, but I better get back to my day job :) SemanticMantis (talk) 15:09, 28 March 2014 (UTC)[reply]

Clear and to the point as ever, @SemanticMantis:, thank you! If I recall the Dolly problem correctly, (I am NOT checking now, this is just from the top of my head), the problem was that the DNA used already had shortened telomeres. This was later rectified with telomerase, which was promoted by Genentech. Star Lord - 星王 (talk) 15:21, 28 March 2014 (UTC)[reply]

Yes, I was asking about creating the mirror image of existing life forms. So, this isn't going to be feasible anytime soon, I guess. Count Iblis (talk) 04:02, 29 March 2014 (UTC)[reply]

It isn't feasible yet, but it might be feasible before too long. Progress in this area has been remarkably rapid, and our synthetic biology article has fallen a bit behind. For example, this report from just a couple of days ago describes the first creation of a fully synthetic chromosome. Looie496 (talk) 15:41, 29 March 2014 (UTC)[reply]

Looking at the article Prokaryotic translation, one would need mirrored (synthetic) ribosomes, initiation factors, release factors, Ribosome Recycling Factor, and aminoacyl-tRNAs for an in-vitro translation system, and then mirrored mRNA of the genes necessary for the survival of the bacterium.

That means some proteins have to be built synthetically. What is the record length of a peptide synthesized as described in peptide synthesis?

And am I correct in assuming that chirality doesn't really matter for the phospholipids of the cell membrane? Icek (talk) 20:52, 31 March 2014 (UTC)[reply]

I'd suggest that saying "it might be feasible before too long" might be a premature projection. Assembling the rest of the cell in functional mirror image (including each protein) to house the chromosomes has not been achieved, and would be necessary. Correct protein folding is likely to present a chicken-and-egg problem, needing the correct environment (ribosomes etc.). Even with the correct molecules, assembly into organelles and a complete cell is a severe challenge. —Quondum 23:19, 31 March 2014 (UTC)[reply]

Paid mourning

How does paid mourning work? Ever since reading about it in the Bible as a kid, I've found it hard to understand, since I can't cry when I'm not emotional and not cutting onions. How could paid mourners cry "on command?" 2001:18E8:2:28CA:F000:0:0:BA27 (talk) 19:04, 27 March 2014 (UTC)[reply]

Actors have techniques to enable themselves to cry when necessary. The usual comment you hear is that they think of something sad. Googling "crying on demand" yields various results, starting with this one. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:07, 27 March 2014 (UTC)[reply]

Crying may not even be required but silence, or keening or ululation. Paying mourners dressed in black to march with the body [4]. In New Orleans, they play jazz. You could read Professional mourning but its only a stub. 75.41.109.190 (talk) 12:14, 28 March 2014 (UTC)[reply]

A little more at Funeral#Mutes and professional mourners. Alansplodge (talk) 23:09, 28 March 2014 (UTC)[reply]