Wikipedia:Reference desk/Archives/Science/2013 July 10

= July 10 =

Why can't I run an electric heater in reverse to cool a room?
Headphones convert electricity into sound. Plug headphones into a mic jack, and they can be run in reverse, that is, convert sound to electricity, and work as a crude microphone.

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

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


 * Because heat is a statistical representation of kinetic energy; and if you make something hotter than its surroundings, the probabilities are higher that energy will transfer out of the object: in other words, heat flows from high-temperature objects into lower-temperature objects. This is a direct requirement of statistics that define the probability of one air-molecule bouncing in to another one.
 * We quantify the average behavior using Newton's law of cooling, or the Stefan-Boltzmann law, or the Maxwell distribution; but they are all derivable using similar mathematical analysis. Nimur (talk) 00:57, 10 July 2013 (UTC)


 * No, there's no way to lower the temperature of a closed system, such as a sealed room, see the laws of thermodynamics. Intuitively, try to imagine unburning something to see why this won't work. μηδείς (talk) 01:15, 10 July 2013 (UTC)
 * No, you can sometimes lower the temperature, just not the entropy. We have a very brief stub on the instant cold pack. --Trovatore (talk) 01:42, 10 July 2013 (UTC)
 * Now that I think about it, I'm not sure, but Medeis did specify a closed system. Does an endothermic reaction in an idealized "box universe" lower the temperature of the whole system, or just transfer some kinetic energy from one part (cold pack) to another (surrounding air in the box)? SemanticMantis (talk) 02:28, 10 July 2013 (UTC)
 * It lowers the temperature of the whole system. --Trovatore (talk) 22:12, 10 July 2013 (UTC)
 * Right, and if you drop a rock from a few meters, it releases energy as heat (sound and vibrations) -- yet adding that heat to a rock on the ground will not cause it to jump a few meters in the air. The OP may also be interested in reading about the arrow of time, which some scientists and philosophers have interpreted in terms of entropy. SemanticMantis (talk) 01:23, 10 July 2013 (UTC)

Also an electric heater does not form a closed system with the room. If you check behind the device that converts electricity into heat you will usually find a wire that then connects through a series of transformers to a device that converts heat into electricity. Hcobb (talk) 02:33, 10 July 2013 (UTC)
 * Along the same line of reasoning: supposing we have a very warm room; and we connect it to the (colder) outside world using a copper wire. The thermoelectric effect is a real thing - a voltage could be produced, and the hot air in the room that impinges on the copper inside the room can excite some valence electrons, creating a voltage relative to the copper wire outside the room.  Current could flow.
 * However - we know this doesn't happen in practice. Why?  It's statistics, again.  Hot air impinging on a copper wire is more likely to transfer its energy as a phonon than to thermoelectrically-excite a valence electron - in other words, the heat transfer is more likely to occur through thermal conduction - so the copper wire will be a heat pipe conducting heat energy out of the room through thermal conduction.  For every electron that gets knocked into a conduction band by a thermal process, millions of thermal phonons (ordinary thermal vibrations within the atomic lattice) are created.  The magnitude of this effect dwarfs any thermoelectric effect, which is so far below the noise-floor as to be un-measurable.
 * A few very special materials do exhibit the thermoelectric effect in a way that is measurable, (but copper is not one of those materials). In principle, if you had a huge chunk of thermoelectric material, and you had a very warm room, and a very cold outside, you could hook up a wire and generate a non-negligible amount of electric current.  The current would carry energy out of the room.  The key point is, there is a cold reservoir - the outside world - where the heat-energy is getting dumped out.  Through the thermoelectric effect, electricity is just a mechanism by which that energy is getting transferred from hot to cold.  And this method would be very inefficient, compared to using a conductive material, or allowing regular air convection to run its course and transfer the heat by more conventional means.  Nimur (talk) 02:59, 10 July 2013 (UTC)
 * The OP specified: "in a closed room (i.e. without venting heat to the outside)". μηδείς (talk) 03:05, 10 July 2013 (UTC)
 * Exactly. Thermoelectric conversion involves moving heat from a hot junction to a cold junction in order to generate electricity (the Seebeck Effect) and the cold junction would have to be outside the room.


 * Yes, as noted above, it is possible to lower the temperature of a room without dumping heat outside: just use a cold pack. The endothermic chemical reaction doesn't actually change the internal energy of the room--it just arranges the atoms so that some of the energy that used to be heat is now trapped as potential energy in the structure of the cold pack's molecules.  If this seems surprising, it shouldn't be.  Consider that you can turn the room into a 1000-degree inferno just by lighting a fire, and that definitely doesn't absorb heat from the outside!
 * These kinds of chemical reactions are irreversible, so once the cold pack is used, it can't return to its original state without releasing heat (and dumping it into the room). If you want a purely physical process, that would involve taking thermal energy out of the room, and that energy has to go somewhere.  You could maintain a temperature differential, where a tiny portion of the room is extremely hot and everywhere else is cold, but that differential requires additional energy to maintain--and the whole room will eventually heat up.  You could cheat by dumping the energy outside in a different form--for example, using a laser beam to shoot it into outer space, where it doesn't heat up the Earth.  You could convert the energy to another form of potential energy, for example by using it to lift up a heavy object.
 * EDIT: here's a very specific example of a physical process that cools a room. Suppose you have a giant cylinder with an airtight, and initially immobile, partition in the middle.  On one side of the partition is a vacuum, and a spring that attaches the partition to the top of the cylinder.  On the other side is a highly pressurized gas.  Now, you release the latch holding the partition in place.  The pressurized gas pushes on the spring and compresses it.  The gas cools due to adiabatic expansion, and some of the gas's thermal energy turns into the potential energy of the spring.  When the room reaches thermal equilibrium with the cylinder, it will be cooler than before.  --Bowlhover (talk) 06:24, 10 July 2013 (UTC)


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


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


 * In the end, we're running into the problem of entropy. The tendency of the universe to move from a more ordered state into a more disorderly one.  Electrical flow is very organized - heat is pretty much the ultimate in disorder (at the molecular level)...so the universe lets us convert electricity into heat (order-to-disorder) - but not the other way around.  Thermoelectric devices like peltier-effect gizmos work by increasing the orderlyness of one place at the price of increasing the disorder in some other place to an even greater degree.  The total amount of disorder in the universe is thereby increased and the laws of physics are happy!
 * SteveBaker (talk) 14:06, 10 July 2013 (UTC)


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


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

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

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

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

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

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

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

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


 * I think you mean to say vortex and vorticity; a vertex is something else altogether.
 * Symmetry breaking in the very early universe is a complicated topic. I found a nice website, on the topic, part of an elementary course on Cosmology from the University of Oregon.  All 26 lectures are available at no cost. I skimmed several of them, and read a couple in more depth - they meet with my approval, for what that's worth).
 * Before you jump to hypothesizing, it's not a bad idea to educate yourself about all the things that are factually known. Nimur (talk) 03:45, 10 July 2013 (UTC)

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

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


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


 * To clarify, two non-rotating balls have a net angular momentum before an off-center collision. To see this, imagine they just barely miss each other, but catch each other by a little hook - now they don't move on in either direction, but their entire energy remains as the two twirling madly around their common center of gravity.  The result is that if you have n particles moving through space, any two of them have some angular momentum around a given axis as determined by the lever arm of their torque, and only if all the net angular momenta happen to add to zero do you have a system with zero angular momentum.
 * There is, admittedly, something that seems haphazard about all this; just as it seems strange that angular momentum is quantized while the position in space seems not to be. I feel as if, somehow, we are viewing the universe in a fictional mental framework very different from its physical reality. Wnt (talk) 21:33, 10 July 2013 (UTC)

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

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


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

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

Thanks, - Alex174.52.14.15 (talk) 17:11, 11 July 2013 (UTC)
 * Tidal Force allows bodies to exchange angular momentum through gravitation. 209.131.76.183 (talk) 17:29, 11 July 2013 (UTC)
 * Alex - when you ask a question here, you might take the time to actually read what's written rather than triumphantly telling us that you now understand it all and we're wrong. Gravitation can cause rotation in the case when there are THREE or more bodies involved AND when the gravitational vectors are not parallel.  When you drop a ball, it pretty much falls DIRECTLY towards the center of the earth - and indeed, if the ball and the earth are the only bodies in consideration, your common experience of gravitation is correct.  But when there are multiple sources of gravity (the earth, moon and sun, for example) and the motion of the ball isn't conveniently directly towards or away from any of them - then induced rotation of all of those bodies is inevitable.  Your common intuition defeats you here.  Similarly, the nuclear forces do indeed operate at very small distances - but if they are inducing rotation in very tiny objects, and if there is enough time for their tiny influences to add up - then that's enough to break that "symmetry" and cause the onset of rotations.  But no matter, gravity is plenty powerful enough.  SteveBaker (talk) 01:32, 12 July 2013 (UTC)

Well, it might be true (actually it is certainly true) but we are talking about the primordial angular momentum when right after the inflation there was no angular momentum anywhere. At that time there was nothing to exchange. This is the enigma. How did it all start? - Alex174.52.14.15 (talk) 18:15, 11 July 2013 (UTC)
 * You're simply not understanding what we're telling you - you can get rotation from simple translation in the presence of forces such as gravity. I've shown you that in two previous responses.  Admittedly, a clockwise rotation induced in one object will be precisely equalled by anticlockwise rotation in the other - so the NET rotation of the universe is still zero - but multiple swirls and eddies will start to build even in an initially rotation-free universe. SteveBaker (talk) 01:32, 12 July 2013 (UTC)


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


 * Asking for how things changed from the state "just after inflation" seems particularly frustrating. I'm not an expert, but so far, I don't see what advantage the inflation model has over saying "well, God must have made it that way".  I mean, cosmic inflation is a whole quiver of models, meant to explain how the universe happens to be flat without very specific starting conditions by requiring even more specific starting conditions and some kind of gee-whiz inflaton physics based on no actual particle or force that seems to be nameable.  What the universe looked like afterward?  Who knows!  It seems to be defined by "it must have undergone some process of inflation to work out so that it looks like it does now". Wnt (talk) 20:52, 12 July 2013 (UTC)

Go fuck yourself
The phrase "go fuck yourself" is often censored as "instructed to perform an anatomically impossible act". Some time ago I encountered what appeared to be a photograph of a man with the tip of his penis inserted in his anus. Was this a photoshop job, or was he actually managing to have anal sex with himself? --67.160.38.148 (talk) 04:53, 10 July 2013 (UTC)
 * It is probably technically feasible given the ranges of sizes of various body parts. That is, a man with a particularly long penis could probably make it reach.  The Wikipedia article titled Human penis size may lead you to the necessary measurements to determine this on your own.  -- Jayron  32  04:57, 10 July 2013 (UTC)


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


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


 * There are some misguided people who oppose Wikipedia's coverage of autofellatio, but you'll find some folks have kindly donated more proof at Commons:Category:Autofellatio. (I'd look up the other thing but ... I haven't thought of what to call it!) Wnt (talk) 21:23, 10 July 2013 (UTC)
 * I've seen it called "self-sodomy" (a Google search on that term - NOT AT WORK - will confirm this), but that doesn't meet WP:RS. "Autosodomy" (ditto) is also used. Tevildo (talk) 21:57, 10 July 2013 (UTC)
 * I thought autosodomy was when you really, really like your Duesenberg. Clarityfiend (talk) 23:33, 10 July 2013 (UTC)
 * Not a problem as long as you don't stick anything in the tailpipe. DMacks (talk) 01:38, 11 July 2013 (UTC)
 * You can check your progress on the sodometer. --   Jack of Oz   [Talk]  07:25, 11 July 2013 (UTC)
 * No, no, no. You use a sodometer to find the exact amount pf sodness between steering wheel and driver's seat. - ¡Ouch! (hurt me / more pain) 07:01, 12 July 2013 (UTC)

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


 * A quick look finds a WiseGeek article on the safety of Mett, which states that it is intended to be eaten the same day the pig is killed, which should reduce the risks of a bacterial build-up. As with most foods though, cultural factors are often significant when it comes to issues of what is considered safe, and objective data on safety may be hard to locate. AndyTheGrump (talk) 13:03, 10 July 2013 (UTC)
 * The main risk of raw pork is trichinosis. At least in Germany (where Mett is popular), this risk has been basically eliminated by strict inspection codes for meat, especially pork, and by particularly strict production codes for all minced meat products. --Stephan Schulz (talk) 13:41, 10 July 2013 (UTC)
 * You might want to read this before you jump to conclusions about pork safety. ←Baseball Bugs What's up, Doc? carrots→ 10:18, 11 July 2013 (UTC)
 * I really don't quite see how the sale (or not) of a US pork producer (which will likely export to China) affects the effectiveness of food inspections in Germany. --Stephan Schulz (talk) 11:26, 11 July 2013 (UTC)
 * Maybe you should change the section header to make it clear this is only about German hogs. ←Baseball Bugs What's up, Doc? carrots→ 11:36, 11 July 2013 (UTC)
 * There may be some confusion here. In my original comment (the one you, at least according to our standard indentation patterns) replied to, I pointed out that in Germany, where Mett is popular, proper production codes and food inspections mean than pork is quite safe. If you did not intend to reply to my comment, sorry, but then please make it clear what you reply to. I really don't see a strong connection of your comment to any of the preceding posts. Indeed, now I'm not even sure if you warn us that pork may not be safe (because it might be imported from China?), or that pork can indeed be safe (as "several senators" seem to imply for meat meeting American safety standards). --Stephan Schulz (talk) 11:59, 11 July 2013 (UTC)
 * It's not that it doesn't cause infection. You can be sure that well cooked pork is safe against trichinosis and other bacterial infection. Raw pork can be safe or not, depending on the handling and inspections. In doubt, then, cook it. OsmanRF34 (talk) 16:39, 10 July 2013 (UTC)
 * In addition to trichinosis being rare in many countries, it's killed by freezing the pork before preparation. --Sean 20:06, 10 July 2013 (UTC)

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


 * See Haemophilia in European royalty for one possible issue. AndyTheGrump (talk) 16:37, 10 July 2013 (UTC)
 * Inbreeding increases the chances of a phenotypic abnormality with autosomal recessive genes, but doesn't really have anything to do with hemophilia, which is inherited as a sex-linked recessive gene. Hemophilia B spread through the royal families after a single mutation, and was inherited in the usual straightforward way, without any couples who *both* bore the mutation. - Nunh-huh 13:17, 11 July 2013 (UTC)


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


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


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


 * SteveBaker (talk) 18:48, 10 July 2013 (UTC)
 * I take your point, certain dog breeds are plagued with genetic disorders. But I wasn't referring to just any poodle. I mean the show winners, who may have several generations pedigree of ancestors that did not have e.g. juvenile renal disease. Very bad things have happened to breeds when they were obsessively bred to meet bizarre standards, and in those breeds, a pedigree with documentation of lack of a disease is a very valuable thing indeed. The fact that people in the past didn't breed their poodles with genetic disease in mind doesn't mean that selective line breeding can't be used to improve individual traits and performance, or that such practice must necessarily bring deformity and disease. For instance, this breeding project is very focused on dog health and longevity (and dire wolves) . Here's another example that illustrates a "positive" founder effect: all modern Thoroughbred racehorses are thought to descend from a single, very large-hearted 17th century mare! . Finally, I must confess I find all this artificial selection a bit creepy. I don't mean to defend inbreeding in general, but I do think "inbreeding=bad" is an overly simplistic message. Clearly, the sad state of poodles and Hapsburgs tells us that it can cause problems when taken to extremes, but cousin marriage doesn't really have many risks. You seem to understand the subtleties here, so I'm mainly pointing out to others that there are also potential benefits to inbreeding. SemanticMantis (talk) 19:25, 10 July 2013 (UTC)
 * "doesn't really have many risks" is not how I would interpret statistic that show a 50% to 500% increase in risk. Some drugs are sold with far less effects. Rmhermen (talk) 20:06, 10 July 2013 (UTC)
 * 500% increase in risk of what? I'm no expert, I was basing my claim on my reading of our article, which says "The children of first-cousin marriages have an increased risk of genetic disorders, though the incremental risk enhancement is relatively small, according to many researchers." Cousin_marriage says, with citation: "In April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40" -- so my understanding of our article is that cousin procreation poses a low-level risk to offspring, which is not very different from other "risky" procreation. SemanticMantis (talk) 21:47, 10 July 2013 (UTC)
 * 2.8+3=5.8 or almost 6 which is nearly 100% increase. Later in the article you will even higher increase in spontaneous abortion rate and infant mortality in various arrangements of cousin, second cousin and double cousin marriages. Rmhermen (talk) 21:19, 11 July 2013 (UTC)
 * There is a fairly detailed exposition on the subject of inbreeding in Robert Heinlein's Time enough for love, where Lazarus Long tries to figure out if it would be okay for twins to make babies together (the subject is relevant in other portions on the book, but lets pass on the details dreamed up by Heinlein's perverted mind), and the conclusion was that it was basically okay. I also remember reading something about an island where a goat couple was introduced, and then the island was pretty much left alone for a long time, and then when humans came back there was a large population of goats with a pretty good genetic diversity - and if I'm not mistaken, the explanation was that the island actually had predators for the goats which culled the (probably numerous early on) genetically defective individuals. The problem with the Rois faineants is that they were probably not under considerable evolutionary pressure, letting shortcomings accumulate (most people in the middle ages probably had a much lower of chance of surviving hemophilia than the average king). I'd love to provide references but my internet access is limited at work. I think the island in question may have been Arapawa Island? 64.201.173.145 (talk) 20:42, 10 July 2013 (UTC)


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


 * For most of human history in most societies, marriage of cousins (not always necessarily first cousins) has been the norm (since nearly everyone within walking distance was related). We've survived, though often at the cost of high infant mortality in the past.    D b f i r s   06:10, 11 July 2013 (UTC)
 * ...but with very much of that infant mortality not being the result of genetic defects, but of bad nutrition and infectious diseases. Marriage between close relatives is primarily a problem in the case of recessive gene defects, it does not magically create monsters. --Stephan Schulz (talk) 07:12, 11 July 2013 (UTC)
 * (Anecdotal evidence:) No, cousin marriage certainly is not an instant recipe for mutants. I am the product of many generations of cousin marriages (including an avunculate marriage or two), and none of my close relatives on any side are monsters—or particularly unhealthy in any way. הסרפד  (call me Hasirpad) 23:05, 11 July 2013 (UTC)
 * I have found the relevant passage from Time enough for love on Google Books: - however, some parts are missing and the page numbers are not indicated. Searching for "Unfavorable gene reinforcement" should lead to the proper page if you can find a complete electronic edition. 64.201.173.145 (talk) 12:54, 11 July 2013 (UTC)
 * It's one of Heinlein's best books if not best. One should read the whole work. μηδείς (talk) 18:03, 11 July 2013 (UTC)
 * Royal intermarriage has a (rather disappointingly) short section on inbreeding.
 * For those interested in inbreeding in general ;-), we have an article on Patrick Stübing who had four children with his sister, one of them healthy, one with a heart condition and two with severe disabilities (could be case specific, maybe neither of them should have children, period.) Ssscienccce (talk) 13:56, 12 July 2013 (UTC)

Aren't "nonpaternity events" a cure for inbreeding of royals? They can be pretty sure that the mother is the mother, but without simple DNA testing, they can't be sure who the father is. Would a DNA result which showed the father was not really the mother's husband make a baby ineligible to become the monarch, or would they fall back on the usual practice of pretending the mother's husband is the father? Edison (talk) 19:04, 12 July 2013 (UTC)

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

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

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

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


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


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


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


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


 * SteveBaker (talk) 18:30, 10 July 2013 (UTC)
 * See Chester General Rail Crash for a virtually identical accident (with less serious consequences) in the UK. The train involved in that accident wasn't fully-fitted, but did have sufficient continuous brakes to prevent the runaway - _if_ they'd been connected correctly.  Not that we should speculate about Saturday's accident beyond the officially-published investigations. Tevildo (talk) 19:57, 10 July 2013 (UTC)
 * And this incident report from 2007 contains a detailed description of the failure mechanism that Steve describes. Tevildo (talk) 20:00, 10 July 2013 (UTC)


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


 * What is ridiculously flawed is not the engineering or the design, but the railroad's operations procedures! Had they followed proper safety procedures by parking the train on the siding (rather than the mainline like they did), and then not just screwing down the handbrakes but also blocking the wheels and/or applying the derail, the whole disaster wouldn't have happened even if all the air brakes failed!  No amount of safety engineering can prevent disasters if people ignore the safety procedures, as they did here!  (I believe the technical word for blocking the wheels is "scotching", and the blocks used for this are known as "sprags" -- or is that only in British English?) 24.23.196.85 (talk) 02:27, 11 July 2013 (UTC)
 * Scotch says you're right about scotching (and notes chock as a similar concept...that's the more general term I've heard in the US for many different types of wheeled vehicles). Sprag sounds like a different approach. DMacks (talk) 04:25, 11 July 2013 (UTC)
 * Given that they were actually blaming the fire company, are these established as universal safety procedures? And from a counterterror perspective, how much extra protection does setting handbrakes and/or chocks actually provide?  I'd feel a lot more comfortable if they followed the rules of the rest of the world and parked their train (true, in a proper parking space, not the middle of the road) with the ignition off, the brake set in some permanent way, and preferably, with the turn of a key required before it can be started moving again.  Why are they so insistent on having their engines idling uselessly and bothering the neighbors? Wnt (talk) 05:01, 11 July 2013 (UTC)
 * Note that on most sidings, both the switch and the derail (if equipped) are secured in position with padlocks to deter tampering. As for leaving the engine running, the reason why they do that is because starting a diesel locomotive is not as easy as starting your car -- the procedure for doing this is more involved (more like starting a plane engine), and can take several minutes. Plus, after starting, the engine must warm up for 10 minutes or more before the train can safely be moved. 24.23.196.85 (talk) 01:43, 12 July 2013 (UTC)
 * The parallel plane and train disasters of this past weekend, both potentially due to (whose?) negligence, remind me of Sean Connery's comment in Rising Sun: "In Japan, they fix the problem. In America, they fix the blame." ←Baseball Bugs What's up, Doc? carrots→ 10:11, 11 July 2013 (UTC)

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


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


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


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


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


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


 * One possible confound is that regular Coke has a lot of sugar in solution in addition to the carbon dioxide in the liquid. The presence/absence of the carbon dioxide in solution should make less of a difference for regular Coke than for Diet Coke, which has less material in solution than regular Coke, and which freezes at a noticeably higher temperature, or more quickly in the same freezing compartment. Edison (talk) 18:56, 12 July 2013 (UTC)


 * I used to do that with beer. Changes in pressure and amount of dissolved co2 have little to do with it, it's mostly supercooling.
 * the amount of CO2 that escaped was minimal, and considering that for an ideal solution the amount of freezing-point depression is only a function of the solute concentration (i.e. the molality) which won't change much when a bit of gas escapes. (on the other hand, when the water starts freezing, the co2 concentration in the remaining liquid will rise.)
 * freezing is an exothermic process that releases a lot of heat (for water: heat of fusion is 80 cal/g, while raising the temperature one degree (C or K) requires only 1 cal/g), so a slight rise of the freezing point because of changes in solute concentration or in pressure would only require a small amount of the liquid freezing to be compensated. In other words, if your beverage is only 1° undercooled, it can't produce much ice.
 * Pressure: the pressure has little effect on the freezing point, for example: 50 psi lowers it with just 0.03°F (http://www.nytimes.com/2006/02/21/science/21ice.html?pagewanted=all&_r=0)
 * supercooling: just like supersaturated mixtures can remain quasi-stable for a long time (sugar solutions take ages to start crystallizing), so can supercooled liquids and mixtures. Supercooled water can reach temperatures as low as -40°  Heating_pad with sodium acetate solutions are based on this, they are supersaturated but stay in solution until you trigger freezing by creating nucleation sites. Something similar happens when you open the bottle, you create bubbles that form nucleation sites.
 * There's also a phenomenon called Melting-point depression, but that's for nano-particles. Ssscienccce (talk) 07:03, 14 July 2013 (UTC)