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November 28

Nuclear grenade

Could one of the elements with a lower critical mass (e.g. curium, californium) be used to make a nuclear grenade? --70.250.212.95 (talk) 01:07, 28 November 2011 (UTC)

Not a hand thrown grenade. The local neutron flux alone would kill the thrower.--Aspro (talk) 01:34, 28 November 2011 (UTC)

The OP may be interested in Tactical nuclear weapons. --Jayron32 02:04, 28 November 2011 (UTC)

I don't think there would be much use for a grenade that (1) will be WAY too heavy (and bulky) to either throw by hand OR to launch using any existing grenade launchers, (2) will have an explosive yield that is at the VERY LEAST equivalent to an eighteen-wheeler completely filled with dynamite when a tiny fraction of this explosive power will do for a grenade's primary application, and (3) because of this ginormous explosive power, will most likely kill any person attempting to use it, as well as any other friendly troops in the vicinity. 67.169.177.176 (talk) 06:08, 28 November 2011 (UTC)

I can't see on what basis you are asserting that there is a minimum yield for a super-critical nuclear reaction. — Preceding unsigned comment added by 129.67.38.22 (talk) 11:38, 28 November 2011 (UTC)

Because, as you say, it needs to be super-critical. That means you need at least the critical mass. That means the minimum yield you can get is the yield from a critical mass, which is still very high. --Tango (talk) 13:12, 28 November 2011 (UTC)

Critical masses of fissile materials in simple configurations are all of the order of several kg or greater. Even if you can reduce the critical mass to 1 kg, you still have (a) a very heavy grenade and (b) a device with a yield of at least 10¹¹ J i.e. the equivalent of about 25 tons of TNT. The smallest US nuclear warhead ever developed had a yield equivalent to 10-20 tons of TNT - enough to destroy a couple of city blocks. Since smaller and less powerful nuclear devices would have had plenty of military and civil applications, I imagine they would certainly have been developed if it were feasible. Gandalf61 (talk) 13:12, 28 November 2011 (UTC)

I'm not sure what applications they would have, actually. In reality, the only application of a nuclear weapon is as a deterrent (if you actually end up using the thing, you're dead anyway and are just trying to take the other guy down with you). For a deterrent, I'd say the bigger the better (but delivery systems are the important thing, really). --Tango (talk) 13:25, 28 November 2011 (UTC)

The development of different types of tactical nuclear weapon shows that many people believed nuclear weapons could be used for purposes other than threatening total destruction: proposed uses include for penetrating deep bunkers, other demolition e.g. to block enemy transport routes, nuclear mines, and in place of regular artillery. Biological and chemical weapons are also nearly as dangerous for the users as for the victims, but that hasn't stopped countries developing and even occasionally using them. --Colapeninsula (talk) 14:27, 28 November 2011 (UTC)

For civil applications see Operation Plowshare, Project Orion and Nuclear Explosions for the National Economy. The idea of using nuclear detonations in civil engineering projects and to launch spacecraft seems dangerous and bizarre now, but it was very seriously considered and studied in the 60s. Gandalf61 (talk) 14:48, 28 November 2011 (UTC)

In Paranoia, The Computer will provide its operatives with thermonuclear hand grenades. Of course, the kill radius of a thermonuclear hand grenade is significantly greater than the deployment radius... --Stephan Schulz (talk) 15:15, 28 November 2011 (UTC)

You don't get seven respawns in real-world warfare. I can't believe anyone still plays that game anymore... 67.169.177.176 (talk) 01:44, 29 November 2011 (UTC)

I don't know where all this baloney comes from about minimum yield but I have come across it else where before. The skill in bomb design is to get a good yield before the core flies too far apart for the runaway chain reaction to continue. Even in the definition of 'one point safe' the yield is not to be over 4 lb equivalent TNT - hardly a truck load. A tucker probably needs more Budweiser than that the night before -for the day ahead. Its more down to the point of why use a very expensive weapon where the yield is only a few multiples of the explosive forces required to compress the core to super criticality. Its just not economically feasible.--Aspro (talk) 15:47, 28 November 2011 (UTC)

Indeed—our article criticality accident lists any number of accidental creations of supercritical masses that were associated with negligible or nonexistent blasts. (Even the cases that did involve explosions were generally caused by high-pressure steam, rather than a violent explosion of the radioactive material itself.) Many of these non-explosions were nevertheless quite deadly to those in the vicinity due to the extraordinarily intense burst of ionizing radiation, but the military already has much faster and less costly ways to kills individual roomfulls of people.

That said, I don't doubt that there are serious engineering challenges involved in 'tuning' the output of a low-yield device; getting the precisely-correct miniscule fraction of the total critical mass to fission (not too much, and not too little) is probably kind of hairy. And there's no need for such low-yield devices to be nuclear—there are tested delivery systems already in place for putting a ton or less of high explosive down on a battlefield. TenOfAllTrades(talk) 17:22, 28 November 2011 (UTC)

A quick Google around for something old, yielded this (if you pardon the pun). It is dated 1978. [1] All this business about the minimum core mass yielding multiples of kilotons has more to do with the limitations of early nuclear devices than that which is physically achievable.--Aspro (talk) 18:00, 28 November 2011 (UTC)

This reminds of the FURY/TNW from the game Halo - a nuclear mine that is either remotely detonated or time-delayed. It is described as being of slightly under one megaton yield, with a blast radius of approximately 1.2 kilometres. It is not designed to be thrown as a grenade, it is to heavy to be thrown far enough unassisted by a human. However, with the use of a MJOLNIR/PAA, itself nuclear powered, it can easily be thrown two kilometres. The FURY has rarely been used in this role, as the MJOLNIR is itself a rare item. Plasmic Physics (talk) 11:42, 29 November 2011 (UTC)

There is also the problem of the EMP causing damage to the powered assault armour, unless the thrower manages to take cover behind EMP opaque barier like solid rock. Should the MJOLNIR be caught in the EMP, the system is forced into a reboot state which takes several minutes trapping the wearer in a giant paper weight. The MJOLNIR weighs approximately 400 kilograms, and has enough strength to easily lift a small car clear off the ground. Plasmic Physics (talk) 11:56, 29 November 2011 (UTC)

Excuse me, what's that Mjolnir/PAA thing? Is it something like the Titan armored walker from Tiberian Sun? 67.169.177.176 (talk) 06:43, 30 November 2011 (UTC)

It is a type of nuclear powered assault armour, among its attributes it increases the wearer's strength, and reaction rate, and obviously provides a level of protection from small-arms fire. Plasmic Physics (talk) 08:51, 30 November 2011 (UTC)

Thanks for the info. I'm a Command & Conquer fan, but I don't play Halo. 67.169.177.176 (talk) 02:50, 1 December 2011 (UTC)

The M67 grenade weighs 14 ounces. The truly remarkable table at Critical mass lists Cf-252 as requiring a 2.73 kilogram spherical mass - but perhaps wrapping it in beryllium or some other neutron reflector can reduce this? Making a nuke that is as handy to throw as a hand grenade is obviously a difficult technical feat ... but proving it to be impossible might be even more difficult. Suggestion: longer delay fuse! Just a thought. ;) Wnt (talk) 19:52, 30 November 2011 (UTC)

Problem with your suggestion: This will give the enemy more time to throw that thing back at you!  :-) 67.169.177.176 (talk) 02:46, 1 December 2011 (UTC)

Well, hopefully, by that point you've already told the cabbie you meant the other Republican National Convention, the one out in the suburbs, and step on it! Wnt (talk) 04:43, 1 December 2011 (UTC)

And what makes you think I'd make the Republican convention a primary target (as opposed to, say, the Ground Zero mosque)? 67.169.177.176 (talk) 05:31, 1 December 2011 (UTC)

Well that would just be silly! B^) Wnt (talk) 17:06, 1 December 2011 (UTC)

Using pulleys to open a coop door

I have a chicken coop and this motor. The door on my coop swings open from the top. Instead of adding side channels and converting the door to open by sliding up and down, I'd like to keep it a swing type door and just use a pulley. I'd also like to increase the weight of the door a bit. How could I use pulleys to be able to lift more weight? And does anyone see any major flaws in my idea? Dismas|^(talk) 01:40, 28 November 2011 (UTC)

I think everything you need to know is in the article pulley, where you can see how to design a compound pulley to get a mechanical advantage and lift a heavier weight. One possible problem is that the motor doesn't pull for long enough - the trade-off for lifting more weight is that you have to pull for longer, in exactly the same way that vehicles in lower gears move more slowly, so more rope will be used up. It's not clear to me whether "swings open from the top" means the door swings from the top (and hinges at the top) or opens from the top (and hinges at the bottom). If the latter, you'll need some component located below the level of the door, which might be awkward to secure in place and might lead to unwanted interference between the mechanism and the chickens.  Card Zero  (talk) 03:56, 28 November 2011 (UTC)

The hinges are on the top of the door. Dismas|^(talk) 03:59, 28 November 2011 (UTC)

Seems fine, then. You could hammer in some simple U-shaped guide for the rope (or cord, or whatever it is) somewhere above the hinge, to ensure it's still travelling straight vertical when it reaches the motor, in case that makes any difference - it might not like pulling at an angle. Nothing else springs to mind, apart from that something unanticipated always goes wrong ... huh, I see that page you linked specifically mentions converting hinged doors to sliding ones, I'm not sure why. I can't see what difference it makes, except perhaps that the motor might fail due to having to work at a non-constant rate (would that even be true?) ... I'm going to read the manual.  Card Zero  (talk) 04:05, 28 November 2011 (UTC)

The manual is no help ("IF YOUR DOOR IS A SWING-OPEN TYPE, FIRST CONVERT IT TO VERTICAL LIFT-LOWER", it says, without further explanation), but I suppose the problem is that the first half-inch or so of pulling a swing-open door (in the orientation in question) will be very difficult. I can't quite explain why this is: it may be equivalent to working in a very high gear (because the door is a lever - can a lever be arranged so as to make work harder? - oh yes, of course it can) or there may be something else going on, like friction. Pulling from a different point, which is not located directly above the door, seems likely to help - a point both above the door and some distance in front of it. You could have a stick with a wheel on the end projecting out from above the door, and run the cord over that wheel. (Uh, unless it opens inwards, in which case of course I mean some distance behind not in front.)  Card Zero  (talk) 04:30, 28 November 2011 (UTC)

Agreed. Note that this means the door won't open quite all the way, but I imagine anything past horizontal is fine. You might want to use bungee cords instead of rope, as the elastic might even out the differences in force needed at different relative angles to the door as it opens. StuRat (talk) 05:01, 28 November 2011 (UTC)

Bungee cord isn't an option. The cord would never fit. And the manual specifies using 80 or 100# fishing line. Dismas|^(talk) 05:09, 28 November 2011 (UTC)

NEVER REPLACE LIFT-CABLE WITH METAL CABLE OR NYLON CORD BECAUSE MOTOR DAMAGE WILL OCCUR! I'm not sure why it says this. It also says "Lift-Cable can stretch". I think perhaps the deal is that the lift-cable is designed to stretch - this might be a crude way of avoiding disasters when something jams. The cable is the intended failure mode.  Card Zero  (talk) 05:13, 28 November 2011 (UTC)

OK, then, it sounds like it's already sufficiently elastic for the purpose. StuRat (talk) 05:20, 28 November 2011 (UTC)

I'm wondering now whether putting a section of elastic, or a stretchy spring, or rubber band, at the end of the cable where it attaches to the door, might do the job, and allow the motor to pull from directly above - since the first work it would do would always be to stretch the spring, which wouldn't be all that difficult, so the motor wouldn't burn out or jam.  Card Zero  (talk) 05:23, 28 November 2011 (UTC)

It's worth bearing in mind that any door could be counterbalanced - a door hinged at the top possibly being simpler than a sliding door in this respect. I think what you need though is a pulley wheel attached to the door hinge axis, so regardless of where the door is, the leverage is about the same. One thing you need to consider though is whether the door is just there to 'fill the hole', or if it is there to stop chickens getting out - or foxes getting in. A vertically-sliding door is going to be harder to open when 'shut' by your motor than a hinged one. I think chickens have just enough sense to get out of a closed door by pushing on it, and I'm sure that any fox can open a door that opens towards it, given the incentive. AndyTheGrump (talk) 05:24, 28 November 2011 (UTC)

"No counter-weight needed" is one of the selling points of this device. It's a cunning plan to add one, though. There's nothing to be gained by attaching the wheel (or cable) near to the hinge - that's essentially the same problem as pulling from directly above while the door is closed; it's the worst possible point to pull from (unless your aim is to move the door as fast as possible while expending as much energy as possible). However, just making the pulley multiply force a lot is another possibility. That way the door creaks open painfully slowly, and all the chickens pile up behind it trying to shove through the gap (which probably helps), and the motor survives the process.  Card Zero  (talk) 05:33, 28 November 2011 (UTC)

(edit conflict)The reason I want to use pulleys to increase the advantage is because I want to add more weight to it and therefore make it harder for critters to lift it. And I'm not concerned with the chickens opening it on their own. I'll time it to open around sunrise and close around sunset. The birds are already in the coop by the time sunset rolls around, if you're thinking they may get locked out. And they're pretty active at sunrise. Dismas|^(talk) 05:34, 28 November 2011 (UTC)

I have a bad feeling that it won't be possible to set the motor to pull for as long as you'd like it to, in order to lift a really heavy door (slowly). The way this thing works is by moving "actuators" around, which are like little fingers that operate the on and off switch. "User adjusts Actuators closer to, or farther away from Stop Switch to set desired open and closed stop positions." They are positioned around a wheel, so the full circumference of this wheel equates to the longest pull time. I don't know how long that is, but in one of the picture they occupy a quarter of it, so it looks like you can have a maximum of four times the travel of a typical sliding door. I guess you'll want all of that extra length, and the mechanical advantage of the pulley, to go into making the door heavier; so finding or building a more advantageous point to pull from seems essential.  Card Zero  (talk) 05:54, 28 November 2011 (UTC)

I don't have the motor here with me. I wish I did. So, I can't see where these 'Actuators' are. But the instructions also say "Motor can be operated by AC timer switch, remote control, and X-10 control (control not furnished)." I have an Insteon controller that, unless I'm quite mistaken, I can program to turn the motor on for X number of seconds and then turn off, regardless of where these actuators are positioned on the wheel. Sorry for not pointing that out sooner but I didn't think it would come up. Dismas|^(talk) 06:04, 28 November 2011 (UTC)

That's great! You might have to mutilate the door-opener with pliers or something to get the actuators off, then. Hopefully they can just unscrew or something - or you could do something with the wiring to bypass the off switch. This is excellent, though - now you're limited only by how much space there is to physically contain the pulley system. The door can weigh half a ton and open in a geological timeframe. (I might question, with all this customization, why you need to buy a fancy-pants $87 motor. You're adding to its gearbox, with the pulley, and you're not using its timer or auto-off facility. Just salvage a low-voltage motor from somewhere and use that, surely? ... Oh wait you said you already have the motor. Carry on.)  Card Zero  (talk) 06:10, 28 November 2011 (UTC)

Hmmm, what bothers me about this scenario is that the wind pushing on a swinging door should push directly against the motor. If the motor isn't absolutely locked in place against such pressure, the door should end up at some odd position; then when the motor automatically closes it, perhaps it's partly open, or perhaps it is fully closed while the motor is still running. By comparison a door that drops down from above should get very little pressure up or down from gusts of wind. Does that make any sense? Wnt (talk) 20:00, 30 November 2011 (UTC)

Diluted Alcohol

How many parts (drinking) alcohol would it take per parts water to keep the water sterile for (say) a month in an emergency situation? Assume 95% grain alcohol is being used. I know there are probably more cost effective ways of keeping water purified, but I'm just interested in the ratio. --68.190.114.151 (talk) 11:55, 28 November 2011 (UTC)

If the water is sterile to start with, then you just need to keep it in a sealed container. --Tango (talk) 13:20, 28 November 2011 (UTC)

Like I said, I'm interested in the ratio, not the practicality. And if the container doesn't also keep light out, photosynthesizing microbes will grow in it. Water will not necessarily stay safe unless it's kept in complete darkness and free of nutrients. Yeast brings concentrations up to as high as 22%, but that's probably much higher than necessary. Perhaps I should rephrase, but I think the information I'm after is clearly expressed. --68.190.114.151 (talk) 14:13, 28 November 2011 (UTC)

Er...not really. As Tango says, if you start with sterile water in sealed, sterile containers, then you won't get any growth even at 0% ethanol because there isn't anything there to grow. (Completely airtight containers of clean water are generally pretty resistant to growing things too, because they don't contain a carbon source.) If you're trying to permanently kill any microorganisms in already-contaminated water, even straight-up ethanol won't be completely effective; some types of bacterial spores are quite capable of surviving for years (possibly indefinitely) in ethanol (see also Ethanol#Antiseptic and the reference there). This textbook notes that ethanol is bacteriostatic (stops bacterial growth and spore germination) at around 10%, and is increasingly bactericidal at 30% and up—though efficacy will depend on the specific bacterial species.

The concentrations required to inactivate viruses and kill yeasts vary depending on concentration and exposure time, but seem to be well above 20%. (Be aware most studies of the effect of ethanol concentration on pathogen survival are aimed at sterilization of medical instruments and food handling equipment, so tend to look at exposures of 5-60 minutes rather than days or weeks.) TenOfAllTrades(talk) 15:44, 28 November 2011 (UTC)

In medieval times, everyone (even the children) had to drink fermented beverages like beer or mead because water was often unsafe to drink due to bacterial contamination and/or in short supply (e.g. during a typical siege). This led to everyone being in a constant state of slight inebriation all the time, from breakfast until bedtime, which could explain some of the ill-considered decisions made both by actual historic characters in that time period, and also by fictional characters in that period's literature. 67.169.177.176 (talk) 01:13, 29 November 2011 (UTC)

Thank you, TenOfAll, that's the information I was looking for. I appreciate it. --68.190.114.151 (talk) 16:11, 28 November 2011 (UTC)

Most wild yeasts will be killed by 10% ethanol. Standard wine is 13% ethanol by volume, and it takes carefully selected strains to be able to ferment the wine any higher than that (which is why most alcoholic drinks above 13% are distilled or fortified with distilled ethanol.)

Hopped beer will not spoil for a month or two if it is kept in a sealed container, even if it is not brewed in the perfectly sterile conditions, at as low as 5%.--Itinerant1 (talk) 00:20, 30 November 2011 (UTC)

physics

sorry for the title :D. i don't wanna be misleaded, so can [[2]] be true?why?--Irrational number (talk) 19:34, 28 November 2011 (UTC)

If you wonder why you have not received an answer, it might be because you did not frame an answerable question here. I am loath to click on links placed here, and I may not be alone in that. So, you may get better results if you clearly state your question in words. If an off-WP link is essential, then please describe what viewers will see. I hope this is helpful. -- Scray (talk) 04:17, 29 November 2011 (UTC)

um... okay this is some guy explaining something he calls super ferrofluids, he says some thing like that, for example, some ferromagnetic particles mixed in a super fluid (which moves frictionlessly), will continue accelerating (or speeding up) in presence of a magnetic field, reaching relativistic speeds, warping spacetime and may be usable for interstellar travel, if I understood it well, now, is such a thing possible? Im skeptical to what he says because he seems to believe in UFOs and stuff like that... (I'm the OP)--95.82.51.215 (talk) 04:32, 29 November 2011 (UTC)

Thanks for explaining. Like Scray, I don't usually click on links here. I'm not an expert on superfluids, but a simple energy argument shows that the theory has flaws. The energy for the high speed particles has to come from the magnetic field, and presumably this has a limited energy input, so will have a smaller and smaller accelerating effect as the speed of the ferroparticles approaches the speed of light. It is unlikely that sufficient energy will be available in the field to create a significant gravitational effect to warp spacetime, and even if an enormous amount of energy is fed in, the effect will be only that of a large mass equivalent to the energy fed in. Perhaps an expert on general relativity can clarify further. Dbfirs 09:05, 29 November 2011 (UTC)

... or an expert on materials and superfluids (see below). Thanks Brains, I hadn't watched the video! Dbfirs 18:37, 29 November 2011 (UTC)

Full disclosure: In my opinion, anyone who calls crackpots "courageous" for having spoken up against some mysterious oppressing force is considered a crackpot in my mind.

There are many things he mentions in passing which I expect he doesn't understand, and several things he says which don't make sense. It would take multiple PhD's to understand all the fields he brings up, but I will just point out the things that I know off the top of my head as being problems (note that when I say "impossible", what I really mean is "highly, HIGHLY unlikely"):

1. A superfluid other than Helium-3 and Helium-4 at workable scales is impossible. The video speculates that an antigravity effect could be achieved with a substance that was both a superfluid and a ferrofluid, and helium is not a ferrofluid. Because of the complicated nature of quantum mechanical problems such as this (I'm not sure science even HAS an answer to this as of yet), but I would expect that any theoretical superfluids more complicated than helium would need to be cooled to exponentially lower temperatures than the current 2-4 K needed to achieve superfluidity in Helium, and that is just not practical even in the distant future.
2. A "mercury-based plasma" which is "supercooled" is impossible on the scale described. Plasmas can only be achieved at very high temperatures, or under extremely carefully prepared laboratory experiments. No one refers to any suspension of solid particles in a liquid other than the blood-related one as "plasma", so his disclaimer is moot.
3. He seems to think that you could somehow combine a superfluid and a ferrofluid to get this effect. This is not true: superfluids are ridiculously sensitive to disturbance; any contamination or mixing would destroy the needed properties.
4. Mercury is, by a large margin, the metal with the lowest freezing point. There is no way to use some sort of other metal to create an alloy, since any mercuric alloy would necessarily have a higher freezing point, and nothing else can dissolve in mercury (this point I'm actually not QUITE sure about, I'd like some independent confirmation from a chemist), there is no way to get mercury to stay liquid at 150K.
5. The fact that he thinks, not only that this is possible, but that his Youtube audience may be able to make some headway where researchers with million-dollar budgets have failed, suggests that he might not have the best grip on reality.

I usually try not to seem overly critical of budding scientists, but arrogant conspiracy-theorists are half the reason why the public doesn't trust the 99.9% of scientists who are working to better humanity. This guy can be safely ignored unless he changes his "the THEY are keeping this technology out of OUR hands" tune.-RunningOnBrains^(talk) 18:21, 29 November 2011 (UTC)

4. isn't true - it is common for alloys to melt at temperatures lower than either component (NaK, for example, melts at a lower point than either potassium or sodium). In particular, Thallium-Mercury alloys melt as low as -58^oC, (20 degrees colder than pure mercury), and are used in low temperature thermometers. Buddy431 (talk) 01:45, 30 November 2011 (UTC)

Thanks Buddy. -RunningOnBrains^(talk) 07:48, 1 December 2011 (UTC)

And don't forget to mention the fact that anti-gravity is impossible according to the Equivalence principle. Dauto (talk) 02:17, 30 November 2011 (UTC)

Unimpeded inferences:

Just in the first half-minute of the video, I thought of electromagnetic propulsion, and a magnetic (dipole?) torus must have weird effects as well. I've heard a claim that gravitational field lines are generated at right angles to the electromagnetic plane when a strong electric and magnetic field are intersected at right angles, though am doubtful about its validity, though it discussed zero-point energy. Maybe UFOs if they exist use quantum tunnelling. Quantum levitation works too, but it requires very cold temperatures capable of sustaining superconductors, temperatures only available in deep space. Many theories for gravity exist, including gravitons. One word in the video was gravitomagnetic (and spacetime manifold), but so far scientists have not found a unifying theory. Free energy is likely impossible unless one could synthesize antimatter using no energy. Based on the images of spherical droplets, the lotus effect (hydrophobic effect of water beading) comes to mind. The only minimally-plausible design seems to involve an impenetrable barrier separating near-absolute-zero superconductors from high-temperature-pressure plasma fluids within a spinning torus-shaped centrifuge. E-folding topological defects in Spacetime wormholes? Fractal tesla coils? ~AH1 ^(discuss!) 02:04, 1 December 2011 (UTC)

Is there a transparent rock tumbler anywhere in existence?

One of my best friends asked me to get him a see-thru rock tumbler for Christmas back in 2003 or 2004. Even though I told him that I could not find any online, I never completely let it go. It may be invented by now, or what was an even more obscure source back in those days may not be as much now.

Therefore, is there a see-thru rock tumbler anywhere? (It seems that Google beats around the bush on this one. Maybe it uses an esoteric set of keywords?) Hopefully I can finally put this matter to rest. Thanks. --129.130.212.185 (talk) 19:52, 28 November 2011 (UTC)

I suspect that the problem is that most materials wouldn't stay clear in that environment. Millions of tiny scratches would cloud up plastic and probably even glass.

You might find a vibrating one instead of a rotating one, though. This one here might work. APL (talk) 20:16, 28 November 2011 (UTC)

What about CVD diamond coated corundum? Plasmic Physics (talk) 22:05, 28 November 2011 (UTC)

Links for the curious: CVD diamond, corundum. -- 203.82.66.204 (talk) 23:42, 28 November 2011 (UTC)

Synthetic diamond is an amazing invention. Something alchemists have been looking for for countless �centuries, but I don't think they make rock tumblers out of it, yet. APL (talk) 23:50, 28 November 2011 (UTC)

No, no, no. A rock tumbler made from the much softer and less resource-expensive corundum, coated in a thin layer of CVD diamond. Plasmic Physics (talk) 11:22, 29 November 2011 (UTC)

Here's one: [3]. I'm pretty sure there is no diamond or corundum involved, though one does have to wonder about the propensity for scratches. Dragons flight (talk) 11:36, 29 November 2011 (UTC)

It's probably polycarbonate. --Colapeninsula (talk) 17:15, 29 November 2011 (UTC)

220v? That's odd. It's being sold on the American version of Amazon, but it needs european electricity. If you're in USA you're going to need a gizmo like this to convert from your American 110 to european 220. (One of those plug-adapters alone won't do it. You need an actual voltage converter.) APL (talk) 20:20, 29 November 2011 (UTC)

American houses typically have a few 220 volt outlets for things like ovens, refrigerators, and air conditioners. (That last is a hazard - I once lost some electronics to an apartment with a 220 volt outlet for an air conditioner (I'm told) that was exactly like a regular 110 volt outlet except things plugged into it died instantly!) Wnt (talk) 21:33, 29 November 2011 (UTC)

That sounds like it was a jury-rigged job done by a rental property owner who was too cheap to hire a proper electrician or to buy the correct parts. It's definitely a violation of whatever local electrical code applies to connect a 220V supply to a 110V (NEMA 5-15) receptacle. Similarly, there's no way that a 220V appliance would be sold with a 110V plug; someone no doubt did a bit of DIY repair and couldn't be bothered to get the correct replacement plug. If your landlord hadn't been doing something illegal, it wouldn't be hazardous—it's not physically possible to fit any standard North American 110V plug into a 220V receptacle, or a 220V plug into a 110V receptacle. TenOfAllTrades(talk) 01:55, 30 November 2011 (UTC)

Correct Speed?

The speedo on my Honda CRV reads about 2mph faster than the reading on my iPhone, which is the most accurate please?--85.211.153.242 (talk) 20:07, 28 November 2011 (UTC)

I would trust the GPS on your phone. Car speedometers aren't really very accurate. See Speedometer#Error

APL (talk) 20:19, 28 November 2011 (UTC)

Yes, GPS is much more accurate on a straight level road with a good signal. Your speedometer just counts revolutions of your wheel, and guesses at the effective radius of the tyre. It is set to over-estimate for a worn tyre and heavy load, so that it doesn't get you into trouble with the law by reading low for new tyres and a light load. The discrepancy is likely to be a fixed percentage of the speed (more than 5% high in some cases for old tyres and a loaded vehicle). Dbfirs 22:02, 28 November 2011 (UTC)

Agreed. When I put bigger tires on my Jeep, my speedo was about 6 mph off. I had to account for it all the time. Dismas|^(talk) 00:16, 29 November 2011 (UTC)

Note that the Honda's inaccuracy is likely doing you a favor. Most cars overestimate your speed, and that helps you avoid getting a ticket since you are generally going a little slower than you think you are. Mingmingla (talk) 18:13, 29 November 2011 (UTC)

Car manufacturers have an incentive to have the speedometer read fast, since you think you are getting more speed for a given gas mileage, as well as faster acceleration. Perhaps they are doing you and the driving public a favor by reducing the frequency and severity of accidents. At the same time, they are doing themselves a large favor by making any mileage based warranties expire sooner than they rightfully should have. There have been lawsuits over this. [4], [5] Edison (talk) 21:39, 29 November 2011 (UTC)

According to the article I linked earlier, in many nations they have a legal requirement that the speedometer never read low. So of course they add a couple of percent to the readout to give themselves a margin of error. APL (talk) 23:56, 29 November 2011 (UTC)

I wouldn't be surprised if even in countries which don't have such a law someone would think of suing a manufacturer if they got a speeding ticket even though the speedometer read a legal speed. -- Q Chris (talk) 11:22, 30 November 2011 (UTC)

In Pennsylvania, at least, it's not uncommon to find a radar speed reader with a visible display set up just before construction zones which displays your speed as you drive toward it. These are great for purposes of calibration - but my trusty old Chevy Lumina has always matched them down the mile. (Of course, I don't actually know they don't fool with those readings....) Wnt (talk) 16:00, 30 November 2011 (UTC)

In California and in Kansas, those are often found just before school zones. 67.169.177.176 (talk) 03:17, 1 December 2011 (UTC)

They have those in NZ. I occasionally drove a car where the speedometer would show the speed as about 50 km/h but these signs (plural hence I was fairly sure it was the car not the signs) would show it as about 40 km/h i.e. an error significantly above 110% maximum of some countries mentioned in the article APL linked to. I don't believe the tyres were singificantly underinflated. However it was a fairly old car so I presume it just fell out of calibration. New Zealand does require a yearly or 6 monthly (depending on age of car) Warrant of Fitness where the speedometer is checked, I presume the tolerance allowed to pass the WOF is or was greater then 10% as I don't believe it caused a problem for the car. Nil Einne (talk) 03:24, 1 December 2011 (UTC)

November 29

Sky of Venus

Lets say you are standing on Venus on a "clear" day (if that's possible on Venus). What color would the sky be? ScienceApe (talk) 03:33, 29 November 2011 (UTC)

WHAAOE: Extraterrestrial skies#Venus. Dragons flight (talk) 03:56, 29 November 2011 (UTC)

The high pressure and temperature of the venusian atmosphere would cause the horizon to have negative curvature due to extreme optical refraction. When the sun is located low over the horizon as at sunrise and sun set, it should have a bean shape due to that same effect. This is just a supposition, as the sun cannot actually be seen in the visibile range of the EM spectrum. Plasmic Physics (talk) 09:39, 29 November 2011 (UTC)

More spectral sky info from the Russian probes here.[6]--Aspro (talk) 12:09, 29 November 2011 (UTC)

Note that we also have an article Atmosphere of Venus.

As this page points out, the question is non-physical, since due to the extreme pressures the clouds are unavoidable. But if somehow you had a "clear" column, I would expect that Rayleigh scattering would cause the extinction of blue light (clear skies at Earth pressure are blue regardless of their composition due to this phenomenon!) to the point where the higher-frequency light would be completely absent from the surface, and you would be left with a very dim, yellow-to-red illumination.-RunningOnBrains^(talk) 17:28, 29 November 2011 (UTC)

One hypothesis is that the extra colour absorption is due to trisulfur gas. Graeme Bartlett (talk) 09:58, 30 November 2011 (UTC)

I remember several times reading the claim that if its atmosphere were perfectly clear and you had a perfect telescope, you could see the back of your head in it from all the way around the planet. But I never really believed it... probably a moot point to argue though, like how much the Pope would weigh if he were a cherry tree. Wnt (talk) 16:04, 30 November 2011 (UTC)

Nanotechnology to improve the efficiency of heat engines

Are there any ideas on using nanotechnology to improve the efficiency of heat engines? ScienceApe (talk) 20:08, 29 November 2011 (UTC)

Maybe with better lubrication. ApNano apparently makes a line of "nanotech" lubricants. --Jayron32 20:51, 29 November 2011 (UTC)

The second law of thermodynamics makes it very hard to improve heat engines to levels beyond what's already currently achieved (with or without nanotech). Dauto (talk) 02:05, 30 November 2011 (UTC)

At least until we can build these guys. :) Franamax (talk) 05:58, 30 November 2011 (UTC)

One way to improve is to make a better spark. If the whole vapour air mixture could be ignited simultaneously in an ICE it would be more efficient. Perhaps lasers could make 1000 bright spots, or even one ignition point at the optimal position, that could start burning in the cylinder at the same time. Or perhaps your nanobots could move in and start ignition at the right places and times. Graeme Bartlett (talk) 10:02, 30 November 2011 (UTC)

The Moon

Look at this picture, for example: http://commons.wikimedia.org/wiki/File:Apollo17.jpg How come you can actually see the curvature of the Moon, i.e. you can basically tell that it's round? You can't really see it here on Earth. Is it because the Moon is smaller? 80.122.178.68 (talk) 21:17, 29 November 2011 (UTC)

Quite a few of the photos that I've seen that were taken on the Moon used a wide angle lens, especially those that were taken from the lander/rover, which causes a "fish eye" distortion. I'd chalk it up to that. Dismas|^(talk) 21:19, 29 November 2011 (UTC)

Yes, it's definitely not due to the actual curvature of the Moon. The Moon isn't that small! For comparison, here's a photo taken on Earth that definitely doesn't show Earth's curvature: http://www.photoanswers.co.uk/Advice/Search-Results/Photopedia/Fisheye-lens-/ --140.180.15.97 (talk) 21:25, 29 November 2011 (UTC)

This is image AS17-134-20387. It is a very famous photograph. NASA's Apollo 17 Lunar Surface Journal leaves little to the imagination: the photograph was taken in 1972 (118:26:38 into the mission, during EVA-1, at the LM); you can read a transcript during which Gene Cernan and Harrison Schmitt discuss the actual conditions of taking that photograph; the original image was captured on Magazine 134, color film, in the Hasselblad camera with a 60mm f/5.6 lens. I would not call this a "fish-eye lens" or even "wide angle" - even on medium format. Of course, some visible curvature is attributable to the geometric distortion of the image; but let's make clear: this is a telephoto lens - and it's widely considered the finest of its type ever made. For comparison, have a look at these terrestrial photos using a similar (not identical) camera and lens: Hasselblad 60mm f/3.5 CF T photo gallery. It's probably more correct to say that the apparent curvature of the horizon in AS17-134-20387 is due to the unusual camera angle, not due to lens imperfection.

Transcript during the setup for this photograph

18:25:37 Cernan: Well, I want to get something here.

118:25:46 Schmitt: What's that?

118:25:47 Cernan: I want to get the Earth.

118:25:49 Schmitt: Okay. Let me get over here.

118:25:51 Cernan: Get around on that side.

    [Jack had moved west of the pole, and now moves back. He overshoots his mark and sprays dust as he stops.]

118:25:54 Schmitt: I don't think it's going...You're a little close, maybe, to have them both in focus. That might do it.

    [Gene starts to bend his knees and, in an effort to get Earth in the picture along with Jack and the flag, almost gets down on his knees. His first effort, AS17-134- 20383 gets the flag but very little of Jack and the Earth, his second photo, AS17-134-20384, is much more successful. After he gets up, Gene gives Jack the camera and they trade places.]

    [Using planetarium software, we see that, had cloud cover over the southwestern Pacific been lighter, the Antarctica would have been visible at the left and Australia would have been coming into view over the top.]

118:26:08 Cernan: Try that one time, then we'll give up and get to work. (Long Pause)

    [Jack holds the camera in his hand and gets it as low to the ground as he can without kneeling.]

118:26:26 Cernan: Point it up a little...Yeah. (Pause)

    [This is AS17-134- 20385.] 

118:26:32 Schmitt: Let me try it again.

118:26:33 Cernan: Okay.

    [This is AS17-134-20386. This photo shows the "red apple" actuator for the purge valve reasonably well.]

118:26:35 Schmitt: I don't know, Geno.

118:26:36 Cernan: Okay.

118:26:38 Schmitt: Let me get over here closer to you. (Pause)

    [Once again, Jack almost goes to his knees.]

118:26:43 Schmitt: Okay. That might have got it.

    [This photo is AS17-134-20387 and, in addition to having Earth in the picture, it shows Gene's checklist and watch/mirror band on his left arm, the OPS actuator on the right side of his RCU, and the OPS antenna on the top of his PLSS. The red bands on the suit and helmet show that this is Gene and not Jack.]

118:26:45 Cernan: Okay, very good.

118:26:47 Schmitt: Okay. All right, let's do it. (Pause)

Nimur (talk) 22:23, 29 November 2011 (UTC)

As can readily be seen from several photographs in the Apollo 17 article, the mission landed in a hilly area. The apparent "curved moonscape" behind Gene Cernan is, I'm pretty sure, just a small hill. {The poster formerly known as 87.81.230.195} 90.197.66.159 (talk) 22:31, 29 November 2011 (UTC)

In fact, you can see the ridge of a closer hill, sloping across the diagonal at the bottom right of the photo. One might even find AS17-134-20386 instructive. Nimur (talk) 22:36, 29 November 2011 (UTC)

And a wider view of the landing site, too. Nimur (talk) 22:52, 29 November 2011 (UTC)

Oh snap, it's just a hill. Thanks guys! 80.122.178.68 (talk) 23:38, 30 November 2011 (UTC)

Colour shifts in field of vision

I have noticed, in the context of driving at night and thus moving quickly relative to passing car headlights, static motorway street and tunnel lights, etc, that as lights move backwards out of the areas of foveal vision and into the areas of peripheral vision they become noticably redder. This is not apparent when moving one's head while stationary and looking at stationary lights, only when the relative movement is very swift (and the direction of gaze is kept fixed) as in the night-driving situation.

Is there a known name and/or explanation for this phenomenon? I have considered the possibilities of differential distributions of "red" v "blue" cone cells on the retina (with proportionally more red-sensitive cones further from the fovea, though references suggest that if anything the opposite is true, with the fovea being blue-cone poor), of chromatic aberration in the eye varying with distance from the axis of vision (which I believe exists, but is slight), and of it being an obscure consequence of the Purkinje effect (which as an erstwhile astronomer I'm familiar with, but would think should result in the opposite), but I haven't been able to find any definitive information.

(And no, I'm not driving fast enough for it to be Doppler effect :-) .) {The poster formerly known as 87.81.230.195} 90.197.66.159 (talk) 23:01, 29 November 2011 (UTC)

I've got a stupid question : Do you wear glasses? I have particularly strong lenses and I've noticed a few unusual color effects near the edges where the lenses are thickest. APL (talk) 23:53, 29 November 2011 (UTC)

Not at all a stupid question, but although I have indeed worn glasses for the last 48 years (for modest myopia and astigmatism), I'm quite sure the effect is not due to my (not very thick) lenses, as it would be quite apparent when looking at lights or extended light objects (such as a computer screen!) to the side of the visual field when in a static situation. I do experience very slight 'barrel' distortion at the periphery of vision through my glasses - that is, vertical lines | | look very slightly bowed out ( ) - but there is no perceptible colour effect, and certainly no marked reddening such as in the lights zipping by as described above. At the next opportunity I will double check by removing my glasses (momentarily!) while night driving, but I'm almost certain that the effect is innate to the eye or perception rather than an artefact of spectacle lenses. {The poster formerly known as 87.81.230.195} 90.197.66.159 (talk) 01:15, 30 November 2011 (UTC)

[Addendum: It occurs to me that this apparent effect could have influenced some scientific observations, namely of the colours of meteors moving from nearer the centre of the visual field to the edge - they would appear to progressively redden. However, although I have myself made visual observations and counts of meteor showers and have naturally also read a good deal about doing so, I don't recall any mention of it. {The poster formerly known as 87.81.230.195} 90.197.66.159 (talk) 01:25, 30 November 2011 (UTC)]

Assuming you are looking through the front windshield/windscreen, it will be made of safety glass. Perhaps you are seeing a chromatic aberration due to the plastic layer sandwiched between the glass? The same effect would be visible if you were sitting in the car at the side of the road, but would disappear if you stepped out of the car. Or you could stick your head out the sunroof, but that would be less advisable. Franamax (talk) 05:52, 30 November 2011 (UTC)

Particularly as I don't have a sunroof - Ouch! I had considered this possibility briefly, but if it were the case I think I would long ago have noticed the effect when parked - I've had this particular car for over 4 years. Nevertheless, I'll make further observations with this in mind tomorrow (Thursday) night, which is the next time I expect to be driving after dark. {The poster formerly known as 87.81.230.195} 90.193.78.16 (talk) 10:21, 30 November 2011 (UTC)

November 30

Vanda Station and Hope Bay

Is these two places climate of Antarctica tundra or ice cap.it said these two place highest track temperatures is 15 C/59F. I am confused if the these places climate is ice cap or tundra. I never hear ice cap climates (EF) get temperatures 40F or higher. If I learn it happens that is weird.--69.228.24.198 (talk) 00:09, 30 November 2011 (UTC)

Neither -- that place is properly classified as a rocky desert. 67.169.177.176 (talk) 06:34, 30 November 2011 (UTC)

Vanda Station is actually in a rocky area, not tundra or ice cap.

Hope Bay is coastal, so it's not entirely surprising that they occasionally get warm breeze off the ocean. APL (talk) 08:49, 30 November 2011 (UTC)

Low-elevation nunataks may occasionally absorb enough sunlight to heat up. ~AH1 ^(discuss!) 01:37, 1 December 2011 (UTC)

Carbon cycle

through what process does the carbon move from plants to animals, and animals back into the air? — Preceding unsigned comment added by Denny636 (talk • contribs) 00:41, 30 November 2011 (UTC)

Through the carbon cycle. Plasmic Physics (talk) 01:31, 30 November 2011 (UTC)

First step is herbivory. Graeme Bartlett (talk) 09:01, 30 November 2011 (UTC)

The carbon cycle doesn't really explain it. After herbivory comes digestion and then cellular respiration. SmartSE (talk) 13:19, 30 November 2011 (UTC)

What are you saying, that the carbon cycle is a scientifically false concept? It explains exactly how carbon moves. Plasmic Physics (talk) 01:28, 1 December 2011 (UTC)

Consider agricultural emissions: belching of animals, removal of carbon sinks and eutrophication. ~AH1 ^(discuss!) 01:34, 1 December 2011 (UTC)

What's this SPAAV?

http://img.photobucket.com/albums/v43/Luigi/Choplifter%203/SPAAV.png

• 4 Autocannons
• 7 Roadwheels

--Arima (talk) 04:37, 30 November 2011 (UTC)

Super Pixelated Amphibious Assault Vehicle? -- 203.82.66.204 (talk) 05:49, 30 November 2011 (UTC)

Self-propelled anti-aircraft vehicle, I think.--Itinerant1 (talk) 06:02, 30 November 2011 (UTC)

Neocortex and suffering

I've been a vegetarian for a bit over a year, with the understanding that the animals we tend to eat, like cows (but probably not fish), can 'experience' suffering. But the other day, my friend made the claim that a well-developed neocortex was necessary to experience suffering, and that only humans have a sufficiently advanced neocortex for this. His claim seems spurious, but I don't know enough to refute him. What does the reference desk think? 74.15.136.30 (talk) 07:19, 30 November 2011 (UTC)

See Pain in Animals and Animal psychopathology.-- Obsidi♠n Soul 07:26, 30 November 2011 (UTC)

As an aside, at least animals can run away or fight back. Eating plants, which are tied to the ground and thus lack the ability for either flight or self-defense, now that IS immoral. We should be protecting those life forms which are most vulnerable! --Jayron32 07:29, 30 November 2011 (UTC)

Don't underestimate Plant defense against herbivory. :P -- Obsidi♠n Soul 07:38, 30 November 2011 (UTC)

That statement would appear self-evidently false to anyone who ever had a pet. Just imagine, say, pricking a cat with a sharp needle. Pain in animals says: "All vertebrates and some invertebrates are capable of nociception, a neural response to intense or damaging stimuli. Nociception can be observed using modern imaging techniques, and a physiological and behavioral response to nociception can be detected but, presently, there is no objective measure of suffering."--Itinerant1 (talk) 07:30, 30 November 2011 (UTC)

Yep, avoidance learning. Furthermore, the neocortex is the sensory and cognitive seat of mammals (certainly not humans alone), but that doesn't preclude similar functions of other parts of the brain in other animals which lack it.-- Obsidi♠n Soul 07:38, 30 November 2011 (UTC)

It's at least partially a philosophical question that hinges on how your define "suffering". Is it "suffering" if the animal is in an unpleasant or painful situation, but isn't capable of understanding that things could be better? Couldn't all of us be in an unpleasant or painful situation, compared to other possible situations that we're not even aware of? Is suffering relative? Or is there some objective level of unpleasantness and pain beyond which "Just life" becomes "Suffering"?

Better to restrict yourself to answerable questions like "Do animals react to pain?" and "Are livestock subjected to pain?" APL (talk) 08:44, 30 November 2011 (UTC)

Life is pain. Anyone who says differently is selling something. --Jayron32 13:39, 30 November 2011 (UTC)

(e/c)See also pain in fish. Also note that suffering includes more than physical pain.--Shantavira|^{feed me} 08:48, 30 November 2011 (UTC)

Okay, here's a question that confuses me: what would be the difference between a robot that was programmed to avoid certain stimuli, and an animal that suffers in response to the same stimuli? 74.15.136.30 (talk) 15:49, 30 November 2011 (UTC)

In my view, we attribute pain on the basis of expressive behaviors, such as wincing, squealing, trying to escape, having an unhappy facial expression, or verbally complaining. This view is not widely accepted, but I don't see any other explanation that works. Talking about robots raises difficulties because many people have strong prejudices, but I think it is more useful to ask whether pain would occur in an alien lifeform that has a humanlike shape, an ability to talk, and responds to bodily damage in the same way that humans do, but has a different sort of nervous system. Looie496 (talk) 18:25, 30 November 2011 (UTC)

Since it's a quale, you could also ask how we're sure pain occurs in humans.  Card Zero  (talk) 22:17, 30 November 2011 (UTC)

Without getting into the status of either issue, I think that there's a distinction to be made here between whether a "well developed neocortex" is required and whether a human neocortex is required. My vague recollection (very possibly wrong - I should look further) is that dissociative anaesthetics like ketamine interfere with transmission of stimuli from the thalamus to the neocortex (see [7], which I really ought to read). Now the thalamus is the seat of "consciousness", but apparently pain may be another situation. A person having a tooth pulled out under the influence of such a drug might be aware that it's being yanked, yet not report being in pain over it. Of course, just because a person doesn't remember or consciously speak of pain doesn't necessarily prove that there isn't some other part of the brain that is suffering terribly ... if you're going to worry about animal rights, might as well worry about the rights of your limbic system? Now in any case, as ketamine and other dissociatives are as effective (?) in cute furry animals as in people, this argues that their neocortices are up to the task, whatever that task is.

Really, the argument that animals don't feel pain is probably more a political sophistry than a real issue. I don't believe anyone watching dog-fighting or bear baiting is really cheering along while imagining that the animals are mere automatons miming the impression of pain. The meaningful issues are whether pain is "truly" felt by animals - whether they "truly" think and experience as we do - and whether human moral codes should extend to such situations. After all, cats play with mice, dogs tear prey limb from limb, and animals don't show much concern for animal rights that I can discern. Nature photographers are never called to account for allowing the lions to devour the elephant. Why should a human who puts, say, two dogs in a position to tear one another apart then be blamed for the immorality that the dogs commit? But such issues stray from beyond the purview of the Science desk. Wnt (talk) 18:42, 30 November 2011 (UTC)

All the brain does is to execute an algorithm that processes information. Therefore what matters is if some specific algorithm is running. E.g. people who experience phantom pain do so because the brain's internal model about the body still assumes that the amputated limb is still there. The brain uses certain algorithms to compute the state of the limb, but without visual input, this starts to drift (similar to how a plane's position determined by inertial navigation will slowly drift away relative to the true position). Then by using a mirror, the brain can be tricked into thinking that the remaining limb is the amputated limb. The brain then takes this as input for its internal model, the state of the amputated limb is now modeled as being in a less awkward state and the phantom pain is gone.

The very definition of a person's identity is also encoded in the algorithm the brain effectively runs. This means that to let someone experience pain, all you need to do is to run the right algorithm on some machine. The mere act of running that algorithm gives rise to the person and it experiencing pain. Count Iblis (talk) 01:00, 1 December 2011 (UTC)

It's a theory, one which I used to believe in, but now I've come to doubt it. Now I suspect that consciousness is based on some kind of property of neurons, specifically of conceptualization, which is not itself physical and can thus violate physical laws (like phase velocity which can exceed the speed of light); that the nondeterminism of the universe permits it to adhere to a fixed and immutable fate despite gradual perturbation in a spiritual temporal dimension; that this permits precognition and causality violation (from the perspective of this non-physical quality), which is the active mechanism by which meaningful free will (neither random nor predictable by physical law) is made possible. Now such might be called an algorithm in an extremely broad sense, but (like other quantum-mechanical events) it is not predictable even with perfect knowledge of the four traditional dimensions. Wnt (talk) 01:38, 1 December 2011 (UTC)

Something happened to you which made you renounce materialism? Who did this terrible thing? Were there any other casualties?  Card Zero  (talk) 05:47, 1 December 2011 (UTC)

This differs somewhat from a materialism argument in that I'm not asking whether I'm perceiving matter vs. a property of matter, but whether the seat of perception is matter or some property of matter. In this sense I doubt anyone is a materialist - the atoms and even the molecules in a live versus a dead neuron undergo pretty much the same pattern of thermal jostling, they're exposed to the same electrical charges and noncovalent interactions and so forth, and there's no easy way to explain how countless trillions of atoms know that they're part of one consciousness versus another. The question remains though, is the thing perceiving a stimulus a neuron, a collection of neurons, some kind of esoterically defined informational state summarizing the condition of the neurons? I'm not talking about something mystical here - not exactly, anyway - but something which is not necessarily a "physical object". Wnt (talk) 06:28, 2 December 2011 (UTC)

Sure, but since the question is "do animals run this algorithm", and for that matter "what is the algorithm, and how is it different from a simple robot reacting to a signal from a sensor on its end effector", that fact doesn't clear things up. Wondering what the algorithm might be itself causes me a certain amount of pain.

Besides, as Wnt says, even if we identify that the process is taking place, that doesn't necessarily have any moral significance at all. What is morality for? It might not be for bending over backwards to avoid the carrying out of a particular process ("pain") at any time anywhere. It's probably something to do with society, and probably includes various beings under its umbrella by means of arbitrary cut-off points - currently these arbitrary points are: all humans, from birth (or earlier in certain parts of the world), animals sometimes but not in any very consistent way (we can't hurt them, but we don't have to intervene when they choose to hurt each other, nor do we have a duty to rescue them from "natural" suffering, whatever that is), and pets (by proxy, through their owners - much the same as how you can't mess up the calibration of somebody else's robot). Card Zero  (talk) 05:51, 1 December 2011 (UTC)

Effeminacy

Is Effeminacy an inherited trait over which we have no control or is it acquired due to some psychological conditioning gaffe? — Preceding unsigned comment added by 119.235.51.130 (talk) 13:58, 30 November 2011 (UTC)

Neither. It is a culturally determined thing. The traits that define a person as distinctly "feminine" vary greatly from one culture to another, so I'm not sure you can say that any set of behaviors is universally "effeminate". That is, if you take a person whose behavior defines them as effeminate in one culture, and drop them into another, that culture may not see the behavior as effeminate. --Jayron32 14:05, 30 November 2011 (UTC)

well jayron excess of grace does make a person look feminine... a swaying gait or touch does make him look feminine

That is precisely culturally determined. What's a "swaying touch"? --jpgordon^{::==( o )} 15:55, 30 November 2011 (UTC)

means a graceful touch instead of a normal linear one — Preceding unsigned comment added by 119.235.51.130 (talk) 16:17, 30 November 2011 (UTC)

Precisely culturally determined. Two men holding hands -- obviously effeminate, right? --jpgordon^{::==( o )} 18:09, 30 November 2011 (UTC)

Better -- Obsidi♠n Soul 18:14, 30 November 2011 (UTC)

I think what the poster basically wants is twin studies of transsexuality or perhaps homosexuality or the like. See [8] [9] Biology_and_sexual_orientation#Twin_studies NCBI gave me only PMID 11037086 which I don't know what to do with. I get the feeling from these sources that finding a transsexual with an identical twin is a difficult thing, though perhaps in the age of the Internet this has gotten easier (except that then you'd have self-reporting bias... still no easy project). Wnt (talk) 18:22, 30 November 2011 (UTC)

Except that effeminacy has nothing to do with homosexuality. Not even sure if it has anything to do with transexuality, either. Dominus Vobisdu (talk) 18:27, 30 November 2011 (UTC)

I respect that position; the problem is, if I exclude sexual desires and responses and self-image, I have a hard time defining "effeminate" behavior at all. It is possible as others say above that the term is only meaningful in the context of some specific culture. Wnt (talk) 18:44, 30 November 2011 (UTC)

Jack Benny had some mannerisms that were considered "effeminate", and he was teased about it, regardless of the fact that he was straight as an arrow. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:46, 30 November 2011 (UTC)

See gender role and flamboyance. ~AH1 ^(discuss!) 01:31, 1 December 2011 (UTC)

It seems that masculinity/effeminacy femininity has many components:

1) Cultural.

2) Sexual. That is, most people attracted to men will choose to act effeminate feminine, and most people attracted to women will choose to act masculine, however that is manifested in their culture.

3) Hormonal. Testosterone tends to produce masculine appearance and behavior, and estrogen tends to produce feminine appearance and behavior. The hormone balance you end up with is largely determined by genetics, but diet, medications, and other factors also play a role. Having surgery to remove the ovaries or testes also has an effect. StuRat (talk) 01:40, 1 December 2011 (UTC)

most people attracted to men will choose to act effeminate -- to put it mildly. --jpgordon^{::==( o )} 03:53, 1 December 2011 (UTC)

And do you have a source indicating that most people (or even half) attracted to men will choose to act masculine ? StuRat (talk) 03:59, 1 December 2011 (UTC)

I've no data whatsoever. You've made a pretty bold assertion there, though, that may or may not be accurate. --jpgordon^{::==( o )} 04:18, 1 December 2011 (UTC)

I believe I've made a common sense assertion. So, if you doubt something so obvious, I'd like to see your proof, just as I would if you doubted that 1+1 really equals 2. StuRat (talk) 04:22, 1 December 2011 (UTC)

I'm with jpgordon here. I wouldn't say that people attracted to men are overwhelmingly "effeminate" is something which is necessarily common sense. Even if we limit ourselves to gay males, the majority of gay males don't display overtly "effeminate" behaviors. One generally doesn't describe a woman as "effeminate". She's just "feminine". So, I wouldn't call your assertion StuRat to be common sense. Commonly believed, but not necessarily "sensical". It seems like a very superficial and stereotypical belief about people, but that doesn't mean it should be assumed to be true without any evidence. People once believed that the world was obviously flat... --Jayron32 05:55, 1 December 2011 (UTC)

I'm using "effeminate" as a synonym for "feminine". What does it mean to you ? And "most" does not mean "overwhelmingly", it just means over 50%. I also wouldn't choose homosexuals as the best example, as there they have a conflict between the way the were raised and expected to behave (to be masculine if they are male or feminine if they are female) and the way they may choose to behave on their own. I also still say that the person who argues what is commonly believed is wrong bears the burden of proof. In the case of proving that the world was round, evidence was presented. StuRat (talk) 06:02, 1 December 2011 (UTC)

Commonly believed to be wrong by whom? By StuRat? This is the reference desk, not the place we disprove what random people believe, so it's perfectly resonable to ask people to prove any statements they make without evidence without having to provide evidence their beliefs are wrong. No one has specifically mentioned this but one of the other problems with your claim is you said they 'choose to act effeminate'. Even if they do act that way, how much of it is really a choice? It seems possible they don't really make much of a choice, they just learn to act that way. Nil Einne (talk) 09:32, 1 December 2011 (UTC)

The problem with asking for evidence that common beliefs are correct is that frequently nobody has ever studied them. Has anyone ever done a study to prove that humidity is higher after it rains ? Probably not. As for choice, I don't believe that desires are chosen, but how we actually act is. Anyone can choose to act in ways counter to their natural tendencies. Gay people who are "in the closet" frequently do, for example. StuRat (talk) 14:53, 1 December 2011 (UTC)

They can choose to against their natural tendencies, that doesn't mean when they are acting their natural tendencies they are always or usually choosing to act that way, they may not give enough thought about it that it can be considered a choice. Also there is a load of recorded empirical evidence that humidity is higher after rain, and I strongly suspect someone has studied it so see how different it is, plus it's also something with a well supported working theory behind it. None of this applies to your anecdotal example. Besides that, I don't ask for evidence in the form of peer reviewed articles which have analysed how the majority of people in the majority of cultures choose to act. Can you at least provide reliable secondary sources, which will meet our requirements if you wanted to include your claims in some article? It should be obvious we can easily do that for humidity and rain. Nil Einne (talk) 07:55, 2 December 2011 (UTC)

Let me put it this way. Effeminate men and masculine women are easy to spot, and in most cases if you conclude they were gay you'd be right, but how would you recognize a masculine gay man or a feminine gay woman? You'd very likely conclude they were heterosexual, hence worsening the sampling bias. Case in point, Rock Hudson was pretty much the ideal for masculinity in America for decades, but he was very much homosexual. Jack Benny has already been mentioned. It's like trying to determine what percentage of the population is Catholic by counting how many people wear crucifixes. It's false correlation and a stereotype. -- Obsidi♠n Soul 10:16, 1 December 2011 (UTC)

Just so. My own personal observation -- and I know and have spent much time with many gay men, in the workplace and elsewhere -- is that the effeminate stereotype fits for a noticeable subset, but not by any means most. Most are visually indistinguishable from their heterosexual counterparts. --jpgordon^{::==( o )} 14:44, 1 December 2011 (UTC)

As I've already said, homosexuals aren't the best example. However, since they're a small segment of the population, I don't expect them to change the "most people" balance the other way. Does anybody here seriously believe that the majority of straight men act effeminately or that the majority of straight women ask masculine ? StuRat (talk) 14:55, 1 December 2011 (UTC)

No, but as I noted above, your definition of effeminate is wrong. From the Wikipedia article Effeminacy: "Effeminacy describes traits in a human male, that are more often associated with traditional feminine nature, behaviour, mannerisms, style or gender roles rather than masculine nature, behaviour, mannerisms, style or roles." (bold mine) You cannot redefine a term to meet your own needs, and expect people to then agree with your statement. Effeminate is NOT a synonym for feminine. Females acting like females is called feminine. Males acting like females is called effeminate. They are absolutely and totally NOT interchangable terms, even if you personally, individually, and singularly really want them to be. They just are not. So, when you make a statement "most people attracted to men will choose to act effeminate", as you did, that is incorrect, as women acting like society expects women to is NOT described as "effeminate". That is still the wrong word. If you had said "most people attracted to men will choose to act feminine" you would be more correct. A woman acting effeminate would be a woman acting like a man acting like a woman. Which is still not the same thing as a woman merely acting as society expects women to act; effeminate behavior is not identical to typical female characteristics: it is its own set of unique charcteristics. --Jayron32 15:07, 1 December 2011 (UTC)

Our article is wrong to exclude women. Here are some dictionaries that don't limit effeminacy to males: [10], [11], [12], [13] (see first example), [14], [15], [16]. A Google search on "effeminate woman" yields over 5000 results: [17]. But, since some seem to restrict the usage of the term to men only, I will replace the word with "feminine" in my first post to make it clear. StuRat (talk) 15:29, 1 December 2011 (UTC)

Social context matters a lot. Small subsets of the society demand either a macho stance from men or a more sensitive persona. As a man I know I adapt my behavior to fit in with the group that I am in. For instance I am perfectly capable of addressing the nuances of a cultural entity. But I don't speak up about my interpretation on a cultural topic that might be mentioned if I am among a group of people who would clearly find the observation that I am about to provide to be too loaded with implications of effeminacy. Personally it is a little bit of a conundrum, but I just accept it for what it is, my point just being that one can't just say that effeminacy is an absolute. In fact it varies with the social context, that is, the composition of the people present. On the other hand if I am among creative people or other more culturally aware, or culturally current people—I don't know what language to use—I would would just about be exercising self-ostracism if I did not relate to for instance the finer points of an interpretation of something of basically a "cultural" nature. And this would not be considered effeminate behavior at all in that social setting. Bus stop (talk) 15:39, 1 December 2011 (UTC)

My point number 1 was the cultural impact. Perhaps "subcultural" should be included, as well. StuRat (talk) 16:32, 1 December 2011 (UTC)

I suggest you check your Google search. For me, the first search result is one of those random pages which is a search result page itself [18] which has nothing to do with effiminate woman. The 4rd result is something about 'effeminate "woman-haters"'. The fifth result is 'Effeminate/Woman' and about God not coming in that form. The 7th result is 'soft−cheeked, effeminate, woman−hating man'. The 8th result refers to a 'soft−cheeked, effeminate, woman−hating man' is some sort Greek lexicon where effiminate is given as meaning something akin to 'woman-like' and also 'womanish, feminine' etc. The 9th result appears to be the same thing as the 7th result. The 2nd result refers to an effeminate woman [19], but it's actually referring to a man and says if the phrase be permissable, the man in question was not only like a woman but an effiminate woman. It's also from 1905 (a number of the results seem fairly old although that probably relates partially to the public domain issue). (It's a NZ newspaper so I would guess it doesn't show up under your results.) The 2nd result for the book 'After identity: rethinking race, sex, and gender' is using the phrase in a similar context to you. Primarily I think because the author is trying to make apoint about the ban on same sex marriages as it relates to complementary qualities. Similarly the 10th result is appears to be using the phrase in the way you did although since it's Associated Content, one of those community contributed article sites where random people write stuff for pay and the quality of which people often find questionable. You may want to consider how many of these '5000' search results (and as we've discussed before, precise results over 1000 aren't really that meaningful) are relevant to your point. I think it's clear effeminate is very rarely used to refer to a woman. Nil Einne (talk) 07:55, 2 December 2011 (UTC)

Is it possible for Man to destroy the Sun?

Is it possible for Man to destroy the Sun? 205.156.136.229 (talk) 14:43, 30 November 2011 (UTC)

No. -- kainaw™ 14:47, 30 November 2011 (UTC)

Short answer: No. Long answer: Maybe, if we could create a black hole with a powerful particle collider and somehow get that in the sun (perhaps a space-built particle collider). Goodbye Galaxy (talk) 14:59, 30 November 2011 (UTC)

Don't try this at home. -- Q Chris (talk) 15:23, 30 November 2011 (UTC)

If we somehow managed to create a micro-black-hole with a mass of one ton, the Schwarzschild radius would be about 1.5×10^-24m. That is roughly one billion times smaller than the radius of a proton (as far as one can assign a radius to elementary particles). The black hole will dissipate its energy due to Hawking radiation in about 0.000000085 seconds. The energy release is about equivalent to 20 Gt of TNT, or about 400 Tsar Bombas going of at once. You would need to stuff 11764705 tons of material per second through a hole that is a billion times to small for a proton, and all that against the radiation pressure of the above mentioned 400 Hydrogen bombs (not per second, per 0.000000085 seconds!), just too keep your micro black hole the same size. I think we can put this beyond the realm of science fiction. --Stephan Schulz (talk) 15:49, 30 November 2011 (UTC)

Further, the question asked if man can destroy the Sun, not a black hole. No matter how you fling a man at the sun - even if you send all the men at it at once, the Sun won't be destroyed. -- kainaw™ 15:52, 30 November 2011 (UTC)

Sure you can. You just have to throw the poor bastard hard enough. See Relativistic kill vehicle. ScienceApe (talk) 20:18, 30 November 2011 (UTC)

I thought about this, but I'm not sure that would work for the sun. I would expect the relativistic man to fly straight through the sun, and out on the other side, taking nearly all of his kinetic energy with him, and leaving a trivially small tunnel in the sun behind him that would be immediately closed by gravity. --Stephan Schulz (talk) 00:18, 1 December 2011 (UTC)

Probably. You can increase the amount of energy transferred by making him blow up into tiny bits before he hits though. ScienceApe (talk) 13:49, 1 December 2011 (UTC)

What if you had a lot of tinfoil on your hands? Super duper duper thin, reflective, heat resistant (alright, maybe not literally tin), and you unwrap it in a shell around the Sun. Call it a Dyson sphere or something. Can you heat up the outer layers of the Sun enough that they start flying off into space? (I mean, much more than they already do as solar wind) Wnt (talk) 18:15, 30 November 2011 (UTC)

What a waste of good hat-making tinfoil.-- Obsidi♠n Soul 18:19, 30 November 2011 (UTC)

Interestingly the sun has negative heat capacity so your tinfoil would actually cool down the sun's outer layer making it expand. Dauto (talk) 18:47, 30 November 2011 (UTC)

I know that's true at equilibrium, but according to Sun that equilibrium is on the order of 30 million years. If you just string up some tinfoil over the course of, say, 10,000 years, I think the outer layers would get hotter. (I'm sure it's all very clear in the math shown in virial theorem; I'll look over that... any time now...) Wnt (talk) 19:06, 30 November 2011 (UTC)

No, they would get cooler. Virialization happens much faster than you describe. Dauto (talk) 19:13, 30 November 2011 (UTC)

I'll take your word for it. ;) Wnt (talk) 19:15, 30 November 2011 (UTC)

He said is it POSSIBLE, the answer is yes, but we don't have the technology to do it any time soon. Turning it into a black hole seems to be the best route to do it. ScienceApe (talk) 20:17, 30 November 2011 (UTC)

Maybe it is possible to intervene to cause the sun to undergo a super-nova. Perhaps by seeding it with lots of heavy metal elements to age it prematurely for a star of its mass. If you found a large enough clump of antimatter that would suffice too if it could be maneuvered to collide with the sun. SkyMachine (talk) 21:12, 30 November 2011 (UTC)

I don't think dumping heavy elements would work well. Even if nuclear fusion stops at the core of the sun suddenly it still takes thousands of years for it to collapse and go supernova. ScienceApe (talk) 00:03, 1 December 2011 (UTC)

Time involved is a minor problem as physical imortality is an easier technological solution to achieve than stellar engineering. SkyMachine (talk) 08:29, 1 December 2011 (UTC)

Maybe self-amplifying lasers using energy equivalent to a sizeable fraction of the Sun mounted on Dyson spheres at resonant frequencies aimed at the sun would cause its internal pressure to exceed its gravity, causing an explosion. Or maybe a relativistic nuclear-antimatter device that uses chain reactions and sets off a reaction enveloping the entire Sun could work, too. Don't try that at home, either. ~AH1 ^(discuss!) 01:28, 1 December 2011 (UTC)

Even destroying only the Earth alone (as a planet, not as a biosphere) is hard enough to be considered impossible by our technological level, and most probably continue to be so for quite a long time. — Preceding unsigned comment added by 91.23.225.204 (talk) 22:29, 1 December 2011 (UTC)

Wood not decomposing after 400,000 years?

How is it possible for wood to remain non-decomposed after 400,000 years (see Schöningen under "History" section of article) ? 129.2.171.55 (talk) 15:14, 30 November 2011 (UTC)Nightvid

Anaerobic conditions. The Schöningen spears were waterlogged and buried under layers of plant material and anoxic mud in a former bog. In addition to being oxygen-starved, peat bogs are highly acidic, a result of tannins from plant tissues - common antimicrobial chemicals found in plants (and used also for tanning/preserving leather, hence the name). As you can guess, this environment is very hostile to decomposing bacteria and fungi. There are similar discoveries in peat bogs in other parts of Europe, including very well preserved human remains (bog bodies, like the Tollund Man).

Other reasons for wood to be preserved (or at least be readily identified as such) are carbonization (being charred or burned results in inorganic carbon which is less appealing to bacteria and fungi), permineralization (being petrified), mummification (being subjected to extremely cold or hot environments with very little humidity, like in permafrost or desert sands), and as impressions and other indirect evidence like remains of attachment points or organic "smears" of dead bacterial colonies where the wood they'd eaten away once existed (in paleontology, these are known as trace fossils).

There are also much older perfectly preserved wood than the Schöningen spears, like the 2-million-years-old remains of trees buried in a landslide found in Ellesmere Island. These were not permineralized, but are actual wood. They were mummified by the extremely harsh environment of the Arctic during the onset of a glacial age in the Pleistocene.-- Obsidi♠n Soul 15:51, 30 November 2011 (UTC)

Note that for petrified wood and fossil wood, the original carbon-based molecules have been replaced by silica minerals, and can last almost indefinitely. ~AH1 ^(discuss!) 01:22, 1 December 2011 (UTC)

Is there a quantum of mass?

Or rather, a theoretical minimum for a measurable quantity of mass? Like the planck length, but for mass (and not the planck mass!) Goodbye Galaxy (talk) 15:55, 30 November 2011 (UTC)

Yes, if the Compton wavelength is larger than the size of the observable universe, then the mass can't be determined accurately. Count Iblis (talk) 16:29, 30 November 2011 (UTC)

Heh, um, what? (I tried reading the article on Compton wavelength but it's not very comprehensible). --Goodbye Galaxy (talk) 17:01, 30 November 2011 (UTC)

Quantum mechanics: all particles are actually something of a wave. Until you actually bump into one and say "hey, look, a wave just hit me right here right now", the wave is in this spread-out state (you can think of water if you want). If the amount that it's spread out is larger than the universe, what is observable, then there might as well have been no wave at all (like if on the ocean you had a wave whose crest spanned the entire ocean - then that's just sea level - it's no longer meaningful to call it a wave).

The Compton wavelength is a nice quick measure of the wavelength (spread) of a particle, and the span of the universe can be super-approximated by its age T times the speed of light c (the limit of what's observable). Put it all together: mass > h / (c² × T_universe) ≈ 10^-68 kg. Wow. I'm thinking that's off by a square, but since the upper limit on neutrino mass is about 10^-36 kg, this seems a decent starting point. SamuelRiv (talk) 18:53, 30 November 2011 (UTC)

Lets back up three setps and approach this from a simpler point of view. Mass is energy. Two names for the same thing. See mass-energy equivalence. Energy is quantized, ergo mass is quantized. QED. --Jayron32 20:59, 30 November 2011 (UTC)

And what is the quantum of energy? I'm having trouble finding it. Goodbye Galaxy (talk) 21:40, 30 November 2011 (UTC)

Energy is not quantized. In some systems the energy levels form a discrete set (e.g. the bound states of electrons in atoms), in others they form a continuum (e.g. kinetic energy of free electrons). Also, mass and energy are not the same thing.--Wrongfilter (talk) 22:39, 30 November 2011 (UTC)

For the smallest mass, you could start by looking at the smallest known particles that have mass: electrons, leptons, quarks, muons and possibly gluons. Perhaps for photons the mass-energy equivalence will yield a quantum mass from its inherent energy? ~AH1 ^(discuss!) 01:19, 1 December 2011 (UTC)

It is possible to find the particle with the smallest rest mass in the standard model. But that is not really a quantum of mass, as (AFAIK) the other particles are not a multiple of that mass, nor (AFAIK) is there some clear common unit mass, of which all particles are multiples. Also rest mass is not the only game in town... 88.112.59.31 (talk) 02:14, 2 December 2011 (UTC)

Stars: death, birth, spreading, clumping

How far apart do scientists estimate was/were the dying star(s) that supplied the elements that comprise our sun, planet, and us? With stars so far apart and expansion of space (as I understand it) carrying things further away still, it would seem to be a low probability occurrence for sufficient quantities of elements blown out from across many light years to accumulate to birth a star system.

And another related question, it would seem that when a star went supernova and blew heavier elements in all directions, that would result in mass densities for future star nurseries far away from the dead parent that were much lower than what the parent had, so won't favorable conditions for star births monotonically decrease? 20.137.18.53 (talk) 17:13, 30 November 2011 (UTC)

The answer is basically gravity. If a star is large enough when it explodes, it's possible that its supernova remnant could still be dense enough to form smaller stars eventually. Otherwise, the stellar dust will fly out into space, orbiting the galactic centre until it clumps up with other dust clouds from other stars, potentially creating enough density to form another star. Note that universal expansion only really applies between galaxies, not within them. Goodbye Galaxy (talk) 17:24, 30 November 2011 (UTC)

(e/c) Remember that virtually all stars form within galaxies, and galaxies are self-contained systems. i.e. It's not stars that are drawing apart from each other, it's galaxies. Matter from a supernova within a galaxy really has nowhere to go but back to the galaxy itself, and galaxies (far more rapidly during the earlier ages of the universe) also capture gas wandering through the intergalactic space like vacuum cleaners. Nevertheless, when hydrogen within the galaxies run out, the galaxies themselves start to die. See Galaxies are running out of gas (Katy Storch, Cosmos Magazine). -- Obsidi♠n Soul 17:50, 30 November 2011 (UTC)

I believe another effect is that the ripples created by novae or supernovae can cause existing clouds of gas to clump together, and this "seed" can gradually grow and pull in gases from the supernova, too. StuRat (talk) 18:11, 30 November 2011 (UTC)

I am revising the heading from "How could the spread out remains of dying stars spread over multiple light years result in sufficient density to start clumping for a new star?" to "Stars: death, birth, spreading, clumping". (See WP:TPOC: "Section headings".)

—Wavelength (talk) 18:18, 30 November 2011 (UTC)

Take a look at stellar evolution and protostar. Ripples in supernova remnants often acquire enough local density to become a gravitational hot-spot, attacting ever more mass as it rotates and falls toward its own centre of mass. When enough heat is generated to start nuclear fusion (formally 8% of solar mass), the star has a chance to blow off the surrounding gases and create a partial vacuum. By nature star formation is very chaotic, and typically occur in nebulae, possibly interstellar gas and even more rapidly around supermassive black holes, where gravitational attraction alone is enough to produce significant clumping. ~AH1 ^(discuss!)

Something else that needs to be appreciated is the vast scales of time involved. That is, while the gravitational attraction of particles of a cloud spread out over light years seems insignificant, and is on human timescales, over billions of years it can become quite significant and pull the cloud together to form stars. StuRat (talk) 01:29, 1 December 2011 (UTC)

this is my favorite subject, ok. [[akbar mohammadzade]]:the supernova explosion cases main star body to escape with 1000Km/s so the remnant nebula will expand very fast(coming here from alphacenturi after 1300years) , this means one parcel of matter will be after 300 years at distance of one light year ,our solar system fathering supernova supposed that was at 15 light year distance of our global Orion cloud , so the parcel which made our body elements specially terrestrial planets came here after -about 20000 years very short time in astronomy-the speed of separating was measured for crab nebula] .[[akbar mohammadzade ]]--[[Special:Contributions/78.38.28.3|78.38.28.3]] ([[User talk:78.38.28.3|talk]]) 09:51, 1 December 2011 (UTC)

Only I can say that we are working on some new ideas about formation of stars specially galaxy formation, we have some difficulties in existing theories of gas dynamic.akbar mohammadzade --Akbarmohammadzade (talk) 10:15, 1 December 2011 (UTC)

"First Human"

Hey guys, I just wanted to ask a quick question. I believe in the theory of evolution, but I'm having trouble understanding something. When our common ancestor became human, would he have to mate with some other human to produce more human children and keep the species alive. But there weren't any other humans when one of the common ancestors became/produced a human child, and thus he would have to mate with one of our common ancestors. But wouldn't cells of a first human and our common ancestor be different, and thus the reproduction couldn't happen? 64.229.180.189 (talk) 21:06, 30 November 2011 (UTC)

There isn't some magic single person who would be the "first person". You need to think of it more as a continuum rather than a magic event. That is, at no point does a single organism become a new species different from that of its parents; what instead happens is that, as populations (large groups capable of interbreeding) breed over time, their genetic and physical makeup will gradually change as the environment in which they live changes to favor certain traits. Evolution happens in fits and starts; a population may remain relatively stable for a long time, then change relatively quickly. There isn't a "hard and fast" line where a new species is said to exist (there isn't even a good definition of what a "species" is!), but in general, when a population has become genetically different enough that it could no longer interbreed with another population (either a contemporary one, or an ancestral one) it could be considered a distinct species. But that sort of thing isn't defined by a single birth of a single individual; it is a slow and gradual thing (at least, on a human timescale). If you are interested in reading up more on the idea, see Speciation for more details on how new species may arise. --Jayron32 21:14, 30 November 2011 (UTC)

Richard Dawkins addresses this in his book The Magic of Reality. As long as individuals (of oposite sex) are of the same gene pool they can mate and produce viable offspring. To speciate there needs to be physical isolation between 2 descendant populations of this original gene pool for long enough for genetic drift and different selection pressures to make the 2 descendant gene-pools different enough that crossed-offspring are no longer viable, and this usually takes several thousands of generations. So (assuming you are a man) if you had a time machine and felt randy (grandfather paradoxes aside) you could go back and father children with women for several tens of thousand generations prior to your own before these offspring started to die without being able to go on and breed themselves. SkyMachine (talk) 21:51, 30 November 2011 (UTC)

A fascinating phenomenon which illustrates some of these points is ring species. When I learned about this, it made the idea of speciation a lot easier to grasp. Vespine (talk) 22:04, 30 November 2011 (UTC)

Actually, this is more of a language problem than a science problem; the thing is that most of the words we use every day don't have strict yes/no definitions but rather describe a continuum without clearly defined borders. This is a very old, very common and, if I may add, ultimately very pointless problem in the philosophy of language. Consider the pile of sand paradox for a classic example: you have a pile of sand and start removing single grains one after another. At some point, your pile stops being a pile and becomes a loose association of grains, and at some point you end up with a single grain of sand. Now, when did your pile stop being a pile? After you removed the 1.000th grain? The 1.001st? The problem is that you can't clearly define how many grains make a pile, and speciation works not much different from the pile of sand. There's nothing really mysterious about it, it's just the way language works (even though we would like to have clearly definable terms for everything, in reality that's just not possible because "pile" or "species" or "planet" or whatever are just arbitrary concepts we try to force on reality - and of course I'm intentionally using "planet" as an example because lumps of matter floating in space are just lumps of matter floating space and don't care very much whether we call them "planet" or "moon" or "asteroid" or whatever) -- Ferkelparade π 22:05, 30 November 2011 (UTC)

(ec) I found Ring species really useful for understanding this, although our article starts unhelpfully for a new reader. I suggest starting with the section "Larus gulls". 86.164.60.202 (talk) 22:08, 30 November 2011 (UTC)

Another helpful way to think about this is to make an analogy with evolution of languages. Did the first English speaker find himself unable to find anybody to speak with because all his ancestors were not speaking English? Dauto (talk) 22:39, 30 November 2011 (UTC)

• It is not helpful to think in terms of first speaker, first human or first member of the species. Helpful is not to think on terms of someone being the first. Quest09 (talk) 14:16, 1 December 2011 (UTC)

Isn't that what I said? Dauto (talk) 17:05, 1 December 2011 (UTC)

Incidentally not. Evolution of languages in not comparable with evolution of species. In the case of languages there is possibly a first member, Many scientists defend the idea of instantaneous emergence of language in 'perfect' or 'near-perfect' form is, but none consider any species arising spontaneously. Quest09 (talk) 20:50, 1 December 2011 (UTC)

I studied linguistics, and I'm not aware of any scientist saying that, unless you count artificially constructed languages. There's no "perfect" form for a language. thx1138 (talk) 22:41, 1 December 2011 (UTC)

There's also another easy way to summarize everything said in a single sentence (particularly Jayron's post): individuals do not evolve, populations do." -- Obsidi♠n Soul 00:28, 1 December 2011 (UTC)

Don't forget about horizontal gene transfer through viral fossils, which can help a species evolve from one to the next (via epigenetics). ~AH1 ^(discuss!) 01:08, 1 December 2011 (UTC)

Horizontal gene transfer is basically just the acquisition of new genetic material that is not from an ancestor. It's comparable to mutation in which an individual also suddenly acquires genetic material very different from the rest of the population/species it belongs to. An individual which acquires new genetic material through those kinds of processes is not automatically a new species. The changes need to be positively selected in the individual's population for the population to effectively evolve. In most cases, they are lost after several generations. It's like being gifted a new tool that you can try out to see if it helps or makes things worse, as opposed to gradually developing the tool yourself.

However, yes, in organisms that are capable of asexual reproduction, an individual that acquires novel genes through these process can effectively give birth to a new population very different from its parents (a classic example is the evolution of antibiotic resistance in Staphylococcus aureus). Horizontal gene transfer is actually a very important and very prevalent mechanism in prokaryotic evolution, as opposed to higher animals. However, populations that originated like this are properly strains, not species, because in virtually all cases, they have not acquired reproductive isolation yet. -- Obsidi♠n Soul 09:16, 1 December 2011 (UTC)

These guys have this well in hand, but the moral of this story is that when you look at a tree of life, the branches have a certain "thickness". There is a single last common ancestor, yes, but his contribution to any given genome is absolutely miniscule. While the story of Adam and Eve is deeply rooted in the Western psyche, in genetic terms, this is known as a population bottleneck. A species subjected to any such narrow passage loses so much of its rich gene pool that it is difficult for it to adapt to any change in environment, or even to survive in an existing one (See cheetah). One consequence of this is that when species are subjected to extreme changes in environment, as is happening today, they often blur old boundaries and hybridize freely, gaining an advantage by having a wider pool of genes to draw upon. The emergence of hybrid species represents a real ecological problem for us, because of things like West Nile Virus spreading from birds to humans because the human-biting and bird-biting mosquitoes started cross-breeding. I wouldn't be overly surprised if it turns out that some previous advance in human evolution likewise emerged from a hybrid population at a time of stress, though such a thing would be very difficult to prove. So the branches of the tree of life are not merely thick, but in certain circumstances can branch apart, fuse back together, then branch out again. Wnt (talk) 02:05, 1 December 2011 (UTC)

Reminds me of an old joke that goes like this: College anthropology professor (pointing to a chart on the board showing the human tree of evolution): "As you can see from this diagram, the first human ancestors were a species of apes known as Australopithecus." A student (raising his hand): "But, Professor, the priest at our church says that the first human ancestors were Adam and Eve. How can you explain this?" Professor (completely unfazed): "And why do you think that apes couldn't have been named Adam and Eve?"  :-D 67.169.177.176 (talk) 03:04, 1 December 2011 (UTC)

Because Australopithecus hyoid bones were more ape-like than human-like. Their names were more likely to have been *Yawn* *Sniff* and *Grunt* *Grunt*. :D -- Obsidi♠n Soul 10:47, 1 December 2011 (UTC)

I thought it was pretty well established that humans did go through a fairly serious population bottleneck (although obviously not as serious as two people!), probably about the same time as most of the other hominids died out. And that non-African humans, at least, are indeed hybrids in that our ancestors bred with neanderthals. I may be misreading your comment, Wnt, but it sounds like you're saying these are only suggested ideas, rather than pretty firmly established theories supported by lots of evidence and widely held in the field? 86.164.60.202 (talk) 14:20, 1 December 2011 (UTC)

I was actually saying humans didn't go through an Adam-and-Eve style bottleneck without addressing what bottlenecks did occur (which weren't so severe, as evidenced for example by the range of blood and tissue types maintained to the present day). And while humans did hybridize to some extent with Neanderthals, I haven't actually seen evidence that this contributed to their adaptation to local environments, though it has been suggested and it seems very possible. (Also it still isn't universally accepted that Neanderthals were a separate species; the main argument for that was that they didn't interbreed with humans...) Wnt (talk) 22:06, 1 December 2011 (UTC)

Comment: I assume there had to be a single first individual with a fused chromosome (Chromosome 2), who had offspring with only 23 chromosomes, who then intermixed with the general population having 24. --George100 (talk) 04:34, 2 December 2011 (UTC)

As explained here, the human chromosome 2 is essentially a Robertsonian translocation of two chimp chromosomes. Now Robertsonian translocations in contemporary modern-day humans are actually pretty common, about 1 in 1000 according to the article. There are problems with them - some people carrying them have developmental delay, and many will have problems producing children (i.e. frequent miscarriages) when breeding with people who don't carry the translocation. Still, there's a random chance in any given small population that a translocation will randomly become the only form of the chromosome left (fixation (population genetics)). That is unlikely but not impossible - but it is also possible that some phenotype of the fusion happened to be positive. Contemporary Robertsonian translocations can lead to "developmental delays", to use a particularly inept euphemism ([20]); the fact that such regulation of mental development is prone to alteration by this mechanism illustrates the possibility that some particular translocation might have turned out the be beneficial. Still, a translocation with a large effect would be unlikely to be beneficial. The bottom line is that this first individual with a fused chromosome would probably not be observably different from others of his species at the time, and very probably not very much so. Wnt (talk) 06:14, 2 December 2011 (UTC)

December 1

Electrical generation via the urban heat island - mesometeorology

Hi. Over the atmosphere of major cities, the urban heat island effect often makes the air up to 8-10°C warmer than areas surrounding. Vast thermals rise to higher regions of the troposphere, and there appear to be some similarities between this urban thermal plume and the much smaller stack effect that occurs in chimney-shaped thermal solar updraft towers and solar power towers. Since both the heat and uplifting air contain large amounts of energy, it would potentially be possible to generate electricity from this. Some possible sources of the electricity include:

• Turbines and rotating devices to convert thermals to electric current, similar to current concept designs for high-altitude wind power
• Circulation of air masses between the high-temperature air "dome" and surrounding cooler air in balloon-like systems that feed on turbulence
• Solar panels that would capture more sunlight and for a longer time than near the surface in the polluted city
• Direct energy generation via condensed water vapor (certainly there are small-scale battery-size devices that already do this)
• Materials that generate large amounts of static electricity from opposing air masses of different densities and vapor content that converts to electric current
• Airborne vehicles that rise given the temperature gradient and pull on ground-based generators via tethers that yank and spin turbines
• Reflector dishes that concentrate and focus waste energy such as waste heat, light pollution and light domes, noise pollution that might be trapped by air masses, or transparent materials that "steal" from the greenhouse effect at infrared wavelengths
• Electromagnetic propulsion

Of course, this type of power generation would be quite different from high-altitude jet stream power, as it uses large moving masses of stable air rather than narrowly-focused stratospheric air that moves at 400 km/h. The energy could potentially be used for various purposes, with unknown efficiency:

• Feeding directly to the city's electrical grid
• Providing cooling of the city during the summer or heating during the winter via electricity or other direct air circulation methods
• Blocking incident radiation from entering the city
• Using the higher carbon dioxide levels of the city and rising water vapor (which is both a greenhouse gas and contributes to higher summer Humidex) and synthesizing oxygen or converting to synthetic fuels or Synthetic biodegradable polymers
• Minimizing stress and heat/energy waste on electrical grid during peak hours
• Scrubbing pollutants and unwanted tropospheric chemicals
• Direct carbon dioxide air capture from the atmosphere at high altitude
• Sending signals to off-course artificial satellites
• Electrolysis and hydroponics
• Floating platforms could potentially be useful for transportation.

I came up with the initial idea for this less than a year ago while researching alternative energy. My question is: is such a mode of energy production feasible, or will the required size of such a device make it so heavy that it crashes onto the city below and poses a danger to its inhabitants? Has there been any current or former scientific research done on a similar such concept? Thanks. ~AH1 ^(discuss!) 00:52, 1 December 2011 (UTC)

For one thing, people wouldn't appreciate being cast in shadows by it on most days (maybe during heat waves they would). I'd urge you to think small scale. How about a series of tiny but strong wind turbines hanging over the edges of a tall buildings to capture the updrafts ? They could be plugged right into regular electrical outlets to provide some of the electricity needed for the buildings. Solar panels can also be placed on roofs.

I think your 8-10°C temp difference is more than typical, and, in any case, the problem with using that to generate energy is that there are many kilometers between that air and the air at the normal temperature. StuRat (talk) 01:16, 1 December 2011 (UTC)

Seems you'd be better off going in the opposite direction, and getting geothermal electricity.  Card Zero  (talk) 09:21, 1 December 2011 (UTC)

The idea is valid (it's not altogether that dissimilar from wind energy); but the engineering is implausible. You can do some back-of-the-envelope calculations to determine the total energy that is possible to extract from such a thermal. The answer will be "not much," and "it will require building a huge, probably-expensive contraption that would test the limits of 21st century engineering." You might start out by reading about carnot efficiency to learn why a 10-degree temperature difference above ambient atmospheric conditions can never be very efficient at performing useful work. So, if it's not efficient, you're relying on massive scale to extract large quantities of energy from a very inefficient process. You might read about some of the topics linked from energy economics to see why that is impractical in today's economy. Nimur (talk) 16:51, 1 December 2011 (UTC)

The UHI effect is not persistent -- depending on the causative factors in a given place it may be appreciable only under certain conditions such as night, calm days, or clear skies. It's unlikely that building the infrastructure for a power source of such an unreliable and intermittent nature would be economically practical. Interesting to think about, though. Short Brigade Harvester Boris (talk) 01:02, 2 December 2011 (UTC)

Range of a liquid fired from a hose related to pressure

According to Fire hose they have pretty high pressures, 290 psi. If you were to constantly increase the pressure, would the range of the stream produced continue to go up or would it drop off eventually? If so, why? ScienceApe (talk) 01:18, 1 December 2011 (UTC)

Assuming you keep the diameter of the hose constant btw. ScienceApe (talk) 01:20, 1 December 2011 (UTC)

It would approach a maximum limit asymptotically, because air resistance would increase and break the stream up into finer particles and eventually water vapor. In other words, you would end up using energy to accelerate more and more air at higher speeds. In a vacuum, however, the speed might very well go up proportionately. StuRat (talk) 01:23, 1 December 2011 (UTC)

This would occur with all liquids? ScienceApe (talk) 01:33, 1 December 2011 (UTC)

Yes, to some extent, although oils would tend to stick together better at moderate speeds and evaporate less. Mercury has an even more minimal tendency to evaporate in air at room temperature, so that would be less of a problem with it (although the portion that did would be toxic) and it's higher density might allow it to travel farther before air resistance stops it. StuRat (talk) 01:45, 1 December 2011 (UTC)

So the liquid encounters enough air resistance to the point of where it boils and turns into a gas? Changing the boiling point of the liquid could extend range then? ScienceApe (talk) 01:48, 1 December 2011 (UTC)

A liquid with a higher boiling point might well travel farther before turning into vapor, yes, and that would reduce the effect of air resistance somewhat. However, at high speeds the liquid will be heated to thousands of degrees by the air resistance, so you might not find anything that stays liquid at those temps. After all, small meteors manage to evaporate when they strike the atmosphere. Also note that even if it did stay liquid, it would still be broken into tiny droplets and encounter huge amounts of air resistance. StuRat (talk) 01:54, 1 December 2011 (UTC)

Does this imply that you could use ultra high pressure water as a "fan", to move large amounts of air without blades or turbines while consuming a negligible quantity of water doing so? Wnt (talk) 01:49, 1 December 2011 (UTC)

I wouldn't think it would be very efficient at that, as the turbulent air movements it would create would mostly be dissipated as heat. So, the energy would ultimately go to warming and increasing the humidity in a large quantity of air. StuRat (talk) 01:56, 1 December 2011 (UTC)

However, it can be (and often IS) used as a vacuum pump. 67.169.177.176 (talk) 03:08, 1 December 2011 (UTC)

What about a Magnetorheological fluid? Should have better range if a current is run through it yes? ScienceApe (talk) 04:46, 1 December 2011 (UTC)

You'd need to have a strong magnetic field over the entire course of the fluid. If you're going to do that, you might as well fire it in a vacuum. StuRat (talk) 04:49, 1 December 2011 (UTC)

What about a Electrorheological fluid? Can't you just run an electric current through it? ScienceApe (talk) 05:21, 1 December 2011 (UTC)

Don't they sometimes use electrified water for riot suppression? 67.169.177.176 (talk) 05:25, 1 December 2011 (UTC)

Do you mean Electrified water cannon (linked from Water cannon#Electrified water cannon)? If so the answer appears to be no Nil Einne (talk) 09:16, 1 December 2011 (UTC)

No regarding what though? Electrified water cannon demonstrates that you can run an electric current through a fluid fired from a cannon, but it's not a electroheological fluid. ScienceApe (talk) 13:55, 1 December 2011 (UTC)

As should be clear from the indenting, I replied to 67 so of course I meant no to what 67 said. It should also be obvious from the refs I provided that the answer to 67's question appears to be no. Nil Einne (talk) 21:17, 1 December 2011 (UTC)

Can't be too careful. Sometimes people just indent for consistency sake. ScienceApe (talk) 21:45, 1 December 2011 (UTC)

Well I don't really see how my answer could be intepreted as a reply to your comment even if we ignore the indenting, but I guess it doesn't matter. Nil Einne (talk) 08:00, 2 December 2011 (UTC)

North-South flying jet lag?

Is there any sleep disturbance associated with long distance North-South flies? You won't be changing time zones, but seasons, and that within one day, so, I thought that maybe that's too much for us humans to handle, since during evolution we didn't flied around. Quest09 (talk) 01:28, 1 December 2011 (UTC)

I wouldn't think it would cause sleep disturbances, but other health problems might result, if you end up wearing inappropriate clothing for the season. StuRat (talk) 01:47, 1 December 2011 (UTC)

The solar angle may be different, meaning differing times of sunrise/sunset and potential for hypersensitivity for example given seasonal affective disorder. ~AH1 ^(discuss!) 02:55, 1 December 2011 (UTC)

When I fly long distances in the same, or neighboring, time zones, such that so-called "jet lag" caused by crossing many timezones, shouldn't be a problem, I still feel wiped out for a day or so just from the experience of sitting in a tiny seat in a little metal tube breathing recycled air all day. The physical and psychological effects of boredom and confinement are probably something which affects people to a small degree. --Jayron32 05:09, 1 December 2011 (UTC)

Another factor of spending a long time on an airplane is cabin pressurization, which is often the equivalent of spending time at 8,000 feet (2,400 m) or so. Not everyone is equally effected by this, but having spent a lot of time in Colorado at altitudes that high I know I am. It tends to make me feel generally exhausted and headachey--much like I do after spending a few hours on a jet plane. I'm hoping the newer airplanes, like the Boeing 787, might make this factor of air travel more bearable. Pfly (talk) 23:59, 1 December 2011 (UTC)

Maybe you'd be happier if they brought back the Connie -- that plane was AFAIK pressurized to sea level, and the seats had more legroom as well. But then of course the flights took 2 to 3 times as long, and the cabin was also noisier than in today's jets. 67.169.177.176 (talk) 06:28, 2 December 2011 (UTC)

Add the fact that inside the plane you won't get much exposure to sun light and you get your North-South jet-lag effect. The effect would probably be the same if you stayed at home under the same conditions. — Preceding unsigned comment added by 80.58.205.34 (talk) 18:06, 2 December 2011 (UTC)

Current limits in different thicknesses of wire

Can 6mm² wire be used to supply a sustained 25A current at 13.7V or do I need to upgrade to 10mm² wire? It is ordinary PVC insulated multi-strand copper wire. The length is about 1.5m. Roger (talk) 09:16, 1 December 2011 (UTC)

I assume your cable is made of copper. With a length of 1.5 m there will be no problem with 6mm^2. It wont even get warm. Heat is in fact the only limiting factor in the current carrying capacity of a wire although a rule of thumb in elec eng is a max current density of 1000A/cm^2.(or 10A/mm^2).So using this current density your cable could carry 60A and still be within the (IMO arbitrary) limit. I never did find out who made up this rule.--78.148.138.159 (talk) 14:19, 1 December 2011 (UTC)

The length and voltage are not relevant to the question (as long as the wire is not looped around itself. The rule is not arbitrary. Too much current will melt the wire potentially causing a fire. Dauto (talk) 16:58, 1 December 2011 (UTC)

Thanks! Roger (talk) 17:11, 1 December 2011 (UTC)

Length is significant only if there might be a problem with voltage drop over the total resistance in the length of the wire, but that is very unlikely to be a problem in a 1.5 metre length. Heat might possibly be a problem if the wire is in a restricted space with exceptionally good heat insulation, but overheating is unlikely at 25 amps. (I have taken the liberty of correcting "c" to "m" in 78.148's helpful reply which applies to unbunched wire with reasonable heat conduction.) Dbfirs 17:11, 1 December 2011 (UTC)

American wire gauge has a nice chart of the "official regulations" for current-carrying capacity of various wire sizes. DMacks (talk) 17:15, 1 December 2011 (UTC)

As Dbfirs noted, voltage drop needs to be considered in addition to carrying capacity, and as acceptable voltage drop is usually given as a percentage of the nominal voltage, voltage and length are important in wire size calculations. In general, carrying capacity is the limiting factor for higher voltage circuits and shorter runs, and voltage drop is the limiting factor for lower voltage circuits and longer runs, but both must be satisfied. (That is, you don't want your wire to get too hot and you don't want your application to be undervoltaged due to drops in the wire, and either problem can happen independently of the other.) As your example is short and low voltage, both limitations need to be considered. Using this online voltage drop calculator (which includes carrying capacity tables -- a search should yield one in metric units), a 5ft (1-way) run of 10AWG (5mm²) copper in a 12vdc circuit carrying 25amps will drop 0.257volts or 2.14%. This is acceptable for either critical circuits (3% limit) or non-critical (e.g. general lighting) circuits (10% limit), so your 1.5m 6mm² run should be fine. Note that if your run was twice as long, while the previous arguments about carrying capacity would still hold, your 6mm² wire would exceed the critical circuit voltage drop limit. -- 203.82.66.201 (talk) 01:47, 2 December 2011 (UTC)

Reply to User:Dauto, When i said there would be no problem with the length, i was of course referring to the voltage drop due to the resistance of such a short length. I reiterate that there is no fundamental limit to the current density in a conductor as long as the heat is removed and that therfore 1000A/cm^2 is indeed arbitrary and you could easily start a fire at that current density if you pushed it through a high enough resistance.92.25.106.108 (talk) 13:39, 2 December 2011 (UTC)

The point is that a 1 mm^2 of copper gives a resistance low enough that a 10A won't start a fire. Dauto (talk) 14:46, 2 December 2011 (UTC)

Depends how long it is, whether its coiled tightly and how good the heat transfer to the heatsink is.--92.25.106.108 (talk) 15:16, 2 December 2011 (UTC)

Jupiter's role on changing uranus axis

can we find any role for jupiter on changing uranus axis 97 degrees?Akbar mohammadzade--78.38.28.3 (talk) 09:37, 1 December 2011 (UTC)

No, there is none. The tilt is a result of angular momentum transfered from a passing or colliding body, possibly a consequence of the Tyche (hypothetical planet) incident. A fifth gas giant hypothesised to have been disrupted from its orbit between Jupiter and Saturn, may have made a close pass with Uranus, trading angular momentum in the process. Plasmic Physics (talk) 11:20, 1 December 2011 (UTC)

modeling of system (for the effect of solar wind) shows that any effect simlar to wind tunnel created by two giant planets had made uranus to turn 97 degrees in self rotation --81.12.40.120 (talk) 08:46, 2 December 2011 (UTC)

That definitely sounds surprising to me. Do you have any reliable source for that claim? --Stephan Schulz (talk) 09:50, 2 December 2011 (UTC)

Trichloroethylene residue

I bought a aerosol container containing trichloroethylene. It was a cleaner and was advertised as leaving no residue, designed for things like degreasing metal etc. The thing is is that it appears to be leaving a residue. For example when I get it on my hands even after I rinsed them off it still leaves a minty smelling residue that is very drying to the skin. The fact that it's difficult to wash off and drying to skin makes me think that it might be cutting fluid? Is it possible that there is cutting fluid left over from the manufacturing process on the inside of the metal aerosol can? Or is it that trichloroethylene does in fact leave a residue? --Jrbsays (talk) 09:50, 1 December 2011 (UTC)

It is de-greasing the dead layer of skin (epidermis) on the surface which makes it look dry. The smell is from the trichloroethylene that the dead skin adsorbed and is now slowly evaporating. It can be detected by smell down to a few parts per million in air. Therefore, its not surprising you can still smell it for a time afterwards. You ought not get this stuff on your hands, as the natural skin oils are part of the body's bio-defence. Spray it on a clean piece of glass, wipe with a clean tissue and spay again. Look for any residue on that. Do this in a well ventilated area.--Aspro (talk) 11:31, 1 December 2011 (UTC)

Spay whom??? 67.169.177.176 (talk) 07:13, 2 December 2011 (UTC)

When my skin is dried out by cleaning fluids, I find moisturizer helps to replace the oils. StuRat (talk) 16:28, 1 December 2011 (UTC)

I regularly work with other solvents such as mineral spirits, toluene, and acetone and I have not experienced any residue on my hands with these products. That's one of the reasons why I think that something in this cleaner is leaving a residue. Is this possible? For example cutting fluid --Jrbsays (talk) 05:17, 2 December 2011 (UTC)

I haven't worked specifically with trichloroethylene, but I've worked with other halocarbons and once spilled a beaker of methylene chloride all over myself. Well, let me tell you, my hands smelled of that stuff till next morning (and AFAIR they felt kinda sticky-wet, too, even after I rinsed off all the solvent and wiped my hands off). And that was chemically-pure methylene chloride from the stock bottle, not the aerosol variety, so there couldn't have been any cutting fluid in it. 67.169.177.176 (talk) 07:12, 2 December 2011 (UTC)

drywall mud

I Was looking at the MSDS sheet for a powdered drywall mud that you mix with water and hardens in 20 min. what was strange to me is that it has formaldehyde in it, presumably as a biocide. I don't see any functional purpose for this as it's a powder and it dries in 20 min. can anyone shed some light on this? The link to it is below --Jrbsays (talk) 11:26, 1 December 2011 (UTC)

http://www.usg.com/rc/msds/joint-compounds/sheetrock/durabond/sheetrock-durabond-20-joint-compond-msds-en-61205014.pdf

I'm certainly not an expert on building materials, but the the text above the carcigenicity table in that data sheet says, "All substances listed are associated with the nature of the raw materials used in the manufacture of this product and are not independent components of the product formulation," which clearly implies that they're not intentionally using formaldehyde as an ingredient in the product. My guess is that both acetaldehyde and formaldehyde may be given off by the "vinyl alcohol polymer" that is an ingredient in the product. Deor (talk) 13:13, 1 December 2011 (UTC)

It's not the EVA, I don't think, otherwise the MSDS would mention the formaldehyde as a decomposition product, no? --jpgordon^{::==( o )} 15:11, 1 December 2011 (UTC)

It might get damp from time to time from condensation, especially on an exterior wall, such as when it's cold outside and you've just taken a shower nearby or boiled water on the stove. A roof leak or window left open during rain could also dampen it occasionally. StuRat (talk) 16:26, 1 December 2011 (UTC)

"BGC Multipurpose Joint Compound Data Sheet" says "trace amounts of residual vinyl acetate monomers, acetaldehyde and formaldehyde may be associated with the production of the emulsion polymer". So it's a by-product of the manufacture. --Heron (talk) 19:20, 1 December 2011 (UTC)

I don't think it's a leftover product, because other MSDS sheets from the same company on a different type of drywall mud do not list formaldehyde as an ingredient. That MSDS sheet can be found below

http://www.usg.com/rc/msds/joint-compounds/sheetrock/sheetrock-all-purpose-joint-compound-msds-en-61320001.pdf

In addition other brands of drywall mud such as "dap" brand do not list formaldehyde on their MSDS sheet.--Jrbsays (talk) 05:25, 2 December 2011 (UTC)

Was Ernst Haekel really that ridiculous?

An early version of part of Haeckel's "tree of life"

Could someone with access to the full article in ref 17 in our article neanderthal see if it really does say that Ernst Haekel wanted to call it homo sapiens stupidus, or (as the most recent version of the article says) homo stupidus. Either is ridiculous, and it seems to have appeared in an edit by User:Dave Sousa at 19:19 on 24th May this year. I'd give the diff, but pasting doesn't seem to work in the edit box at the moment. It's diff 430719602 in the edit history.

And if it really is true, I'd be interested in any background information. 86.164.60.202 (talk) 15:17, 1 December 2011 (UTC)

A quick check on Google Scholar seems to confirm this, though I can't access the relevant journal: [21]. AndyTheGrump (talk) 15:33, 1 December 2011 (UTC)

The paper you link to Andy only confirms the existence of "Homo 'stupidus'" as a proposed designation, it attributes it to an 1899 book in German by Haekel, but doesn't clarify if he originated the name or provide enough information to link that proposal to Neanderthals. Dragons flight (talk) 16:06, 1 December 2011 (UTC)

I'm not ordinarily one for spelling flames, but let's spell his name right, please: it is Ernst Haeckel. I don't know specifically what he wrote about "homo stupidus", but he did write extensively about suboptimal design in biology, which he called dysteleology, so that would fit with his basic themes. (See also argument from poor design.) Looie496 (talk) 17:21, 1 December 2011 (UTC)

Let me give a bit of follow-up info. Haeckel was actually writing before any Neanderthal fossils had been discovered. One of the things he is noted for is being the first to visualize evolution as a tree -- the tree of life. In his tree-drawing from 1868, he attached a label "homo stupidus" to a point in the tree underneath homo sapiens -- it was intended to represent a hypothetical but as-yet-undiscovered ancestor. I have attached a picture of a drawing he made in the 1860s -- you can clearly see the label "homo stupidus" near the top. Looie496 (talk) 18:01, 1 December 2011 (UTC)

The same tree was published in Haeckel's later Last Words on Evolution (1906). The journal article cited in the Neanderthal article does not discuss this, but the TalkOrigins page cited does. I think it only looks "ridiculous" to you because you don't realize that stupidus is a real Latin word — it is not faux Latin. It is also worth noting that the associations with words shift over time. "Moron" was originally a technical term; now it is not, for example. --Mr.98 (talk) 18:08, 1 December 2011 (UTC)

Also I think the OP means User:Dave souza Nil Einne (talk) 21:13, 1 December 2011 (UTC)

It was better than his first choice, Biggus Diccus. --Jayron32 18:33, 1 December 2011 (UTC)

The wiktionary link is not very comprehensive. One, and obviously the relevant English synonym of the Latin stupidus is "speechless". Hurriquake (talk) 03:30, 2 December 2011 (UTC)

Cluelessness (battery life)

If I have a battery (12v, 100 ampere) and a LED TV (45 watt, 12v) how long can I provide power to the TV? 45 watt divided by 12 volt is 3,75 ampere. 100 ampere divided by 3,75 is 26.6667 hours. Is my calculation correct? Wasbeer 16:11, 1 December 2011 (UTC)

Unfortunately, it is not that simple. First, you've made a unit-error, dividing 100 amps by 3.75 amps and mysteriously obtaining "hours." This is incorrect, and provides a clue to the error: you're missing a critical piece of information. A battery can only provide 100 amps for a limited period of time. For this reason, you will often see a battery rated in amp-hours - in other words, this is the rated period of time that the battery will deliver 100 amps at 12 volts.

Such a battery is typically used for short bursts of high current - things like driving an automotive starter motor - which only lasts a few seconds. So it's very unlikely that you'll get several dozen hours out of the battery, even though you aren't using its full rated current capability - you're using the battery in an unintended way.

As a last comment, dealing with such batteries can be dangerous. Even though the voltage is low, the current drive is quite high, and there's a lot of stored chemical energy in such a battery that can rapidly convert to electrical or thermal energy. Even if you don't get a zap, you may be risking a fire. Consider using a lower current battery intended for long duration use. Nimur (talk) 16:20, 1 December 2011 (UTC)

No. The voltage and amperage describe how quickly electricity flows from the battery, but says nothing about how much energy is stored in it. You would need a rating for watt-hours or kilowatt-hours (kwh) to answer the question. Also, most types of battery will have a voltage drop that makes them unusable before they are fully discharged. If you can tell us what battery type it is, perhaps we can research it. I added to your title to make it more useful. StuRat (talk) 16:17, 1 December 2011 (UTC)

(E.C.) Your calculation would be roughly correct if by "100 ampere" you meant to say "100 ampere-hours" (or amp-hours for short), a measure of the battery's capacity. If instead, your "100 ampere" was its cranking amps (CA) or cold cranking amps (CCA), then no, your calculation is not correct. Our articles dimensional analysis and especially units conversion by factor-label may also be of interest to you. -- 203.82.66.201 (talk) 16:42, 1 December 2011 (UTC)

If your battery is a lead-acid battery designed for use in a motor vehicle, then it is not designed for deep discharge. The recommendation is that you should not discharge it much more than about half-way before recharging, if you want it to have a long life. Batteries of a similar capacity, but designed for low-currents and deep discharge can be obtained from marine and other suppliers. If you need to use a 100 ampere-hour car battery, then I would recommend that you recharge it after about 12 hours of use at just under 4 amps. Dbfirs 17:01, 1 December 2011 (UTC)

Wow, thanks a lot for all the help everyone! Wasbeer 04:16, 2 December 2011 (UTC)

Color of flame

According to flame, "The spectrum of a premixed (complete combustion) butane flame on the right shows that the blue color arises specifically due to emission of excited molecular radicals in the flame, which emit most of their light well below ~565 nanometers in the blue and green regions of the visible spectrum."

I'm not sure if I understand this. Let's say you are burning propane. Some of the valence electrons in propane move from a higher energy state, to a lower energy state and give off photons in the blue visible light spectrum as a result of changing to a lower energy state. This is what produces the blue flame, is this correct? 198.151.130.148 (talk) 16:12, 1 December 2011 (UTC)

Also is hydrogen a radical? 198.151.130.148 (talk) 16:19, 1 December 2011 (UTC)

Flame color is a complicated mix of incandescence (that is, light due to the blackbody radiation of the gas); and spectral emission related to the combustion chemistry; and a variety of other spectral emissions due to the various constituents and impurities in the air around the flame. In the case of burning propane, I have always been led to believe that the blue flame is due to the much higher temperature that results when the correct fuel-air ratio is used (providing a lot of oxygen, effectively raising the flame temperature).

We have a chart for the butane flame spectrum, linked from Fourier transform spectroscopy. If that data is credible, there's a strong C-H line that is prominent in the blue part of the spectrum. Nimur (talk) 16:28, 1 December 2011 (UTC)

But is the statement I'm saying regarding electrons moving into lower energy states correct though? 198.151.130.148 (talk) 16:53, 1 December 2011 (UTC)

Right; it's an atomic spectral line, and we call the whole process "spontaneous emission." I never liked this term, because the "emission" is only half the story: to emit energy, the electron first had to absorb energy. Of course, the electron took that energy from the heat of the fire.

Individual electrons gain thermal energy because they're part of molecules that bumped into other molecules (the exact mechanisms are inter-molecular collisions governed by statistical mechanics; and individual collisions are described by some type of scattering or collision, (the "correct" type of physical model to use depends on whether you're an atomic physicist or a molecular physicist or a chemist). Now, an individual molecule can't just "have" excess thermal or kinetic energy: one individual molecule is small enough to be governed by quantum mechanical rules, so after undergoing a collision and gaining energy, one or more electrons have been placed in an excited state. Other possible ways to store the excess energy are far less likely. But, we can't rule out any other excited quantum states - nuclear reactions, and so on. In fact, a quantum-mechanical treatment of an intermolecular collision deals with all of these details by "solving the wave function" for both molecules prior to, and after, the interaction; the result is a probabilistic set of quantum states that satisfy the collision.

In plain English, we can say that the kinetic energy of a molecule was converted in to an increase in the electron's energy-level. We skip over this entire process in high school chemistry classes, mostly because nobody actually enjoys solving molecular quantum mechanics problems - not even high school chemistry teachers. The details of "absorbing" energy through molecular collision are actually quite difficult compared to emitting a photon (which can be described using high school algebra).

After some period of time, the excited electron will spontaneously decay back to a lower state. This releases a photon. For the most common C-H excited state transition, the photon appears blue. Nimur (talk) 17:26, 1 December 2011 (UTC)

Is it possible for a reaction to produce green or violet photons, and thus produce green or violet flames? 198.151.130.148 (talk) 18:34, 1 December 2011 (UTC)

If copper, iron, sulfur, chromium, or a few other elements are present, the flames can be very colorful. We used to create "rainbow flames" by mixing in a small amount of various metal salts into a beaker of ethanol, for part of our "Chemistry Magic Show" outreach program. It's been a while, but I recall chromium as a deep blue, copper as a solid green, iron as a very deep red, and I do recall a purple flame (potassium chloride, maybe?) Unfortunately the most interesting colors were produced by the more noxious chemicals. You can also read about coloration in fireworks and pyrotechnics. Nimur (talk) 18:42, 1 December 2011 (UTC)

The article Flame test contains a good list of colors associated with burning various elements. --Jayron32 18:47, 1 December 2011 (UTC)

Phalanx versus Tercio

I hope I did not chose the wrong category, and "military science" belongs here...

Would one of the sides have a decisive advantage if a classical greek/macedonian phalanx would fight with an equal number of tercio pikemen? Let us assume it would not be a complete surprise so they would have at least a short moment to learn the capabilities of the equipment of the other side.

Steel is superior to the bronze used in classical antiquity, but would it matter that much? And would it make a great difference if they were only phalanx pikemen vs. tercio pikemen, or both sides could bring their auxiliaries (javelin throwers for the phalanx and a 10% - 20% of matchlock arquebusiers as used in early tercios) --91.23.196.250 (talk) 17:59, 1 December 2011 (UTC)

Something that armchair archaeologist forget/ignore, is that whilst steel is far superior to bronze weapons, it was only once the importance of steel production was recognised by the governing forces (in this case the Romans) that steel weapons could be made in greater quantities, due to to the greater abundance of known and workable deposits of iron ore; compared to that of copper and tin. A good steel weapon (swords etc.) that would not shatter during mortal combat - needed a lot of skilled art in its making. Yet labour, was cheaper than the raw material. It was both the greater organised industrial base taking advantage of this common metal and the ability to mobilise larger bodies of military force, that fought in disciplined units, that enabled Romans win out over the Gauls etc.. The average Roman solder however, didn't have it easy. A bronze sword, strong enough to be to be worthy of such a name, was very heavy and could ruin your whole day if you only used your little Roman sword to fend it off -instead of your shield. Roman swords were only good for stabbing a close range. --Aspro (talk) 22:09, 1 December 2011 (UTC)

OK, let's make some things clear here...

First of all, the word "tercio" was completely unknown in ancient Rome -- this term denotes a type of infantry unit in the armies of Renaissance Spain and Portugal. The Spanish (not Roman!) tercio was built around a pike square, with musketeers deployed at each corner, and sometimes also lightly armed swordsmen deployed as skirmishers and/or to protect the musketeers against enemy cavalry; the Portuguese tercio had a similar composition. Note that the use of the term pretty much implies that the auxiliaries are present on the battlefield -- if not, then the unit is no longer a tercio, but a simple pike square.

Second of all, when you use the term "phalanx", you have to be specific about what type of phalanx you're talking about: i.e. whether you mean a phalanx of hoplites armed with short spears and shields, or a phalanx of sarissiers armed with extra-long pikes, but no shields. (The outcome of this hypothetical battle may be affected by this.)

Third of all, is this supposed to be an all-infantry battle, or can the cavalry also deploy with the infantry (Companion cavalry with the phalanx, and dragoons with the tercio)? This can also be a decisive factor in this engagement.

That said, here's how I see the three different scenarios:

(1) Pikemen only, no auxiliaries: This would be a close match, especially if the phalanx consists of sarissiers. Essentially, in this scenario two forces of pikemen would clash together and stab at one another with their spears, trying to grind each other down in terms of casualties. The "tercio" would have a little bit of an advantage because of its better ability to maneuver, but not decisively so. In short, this engagement would boil down to which force has better discipline. If the phalanx consists of hoplites, on the other hand, the battle would be not so much a draw as a non-engagement of the Monitor-versus-Merrimac type -- the hoplites' short spears wouldn't reach the "tercio"'s front ranks, while the "tercio"'s long spears would be stopped by the hoplites' shields. Now that I look at this scenario for the second time, the "tercio" should win here too: if the Spanish commander is smart, he'd deliberately leave gaps between adjacent pike squares (as in Scenario #2) -- then, just as in Scenario #2, the pike squares stop the phalanx to their immediate front, the phalanx advances into the gap, and the "tercio" pikemen face outward and cut down the hoplites (or sarissiers) from their unprotected flanks. (Incidentally, AFAIK this is exactly how the Roman legionaries defeated the Greek hoplites.) No musketeers or swordsmen necessary to achieve victory (though they really help the tercio win with fewer casualties).

(2) Infantry with auxiliaries, no cavalry: In this scenario, the tercio would most likely mop up the street with the phalanx -- the tercio's musketeers would easily drive off the shorter-range peltasts, and then pour their fire into the phalanx, while the swordsmen dive under the phalanx's pikes (using their bucklers to ward off the spear thrusts) and cut down the nearly defenseless sarisseers. This would allow the tercios to cut into the phalanx, allowing it to partly (or completely) envelop the tercio formations (via the gaps deliberately left between adjacent tercios), at which point the pike squares join in the fray, facing their pikemen outward and thrusting at the sarisseers' or hoplites' unprotected sides and rear. If the phalanx was made up of hoplites, this could allow them to defeat the tercio's swordsmen, but the end result would still be the same.

(3) Infantry and cavalry: This one really depends. On one hand, the tercio's dragoons can add their fire to that of the musketeers, and/or charge the phalanx's flanks, where they can then proceed to cut down the hoplites (or sarisseers). On the other hand, the phalanx's Companion cavalry could charge the tercio and drive off the musketeers, at which point the peltasts could reenter the fray and inflict casualties on the tercio's pikemen and swordsmen, perhaps to the point where the pike squares could no longer hold off a determined charge by the phalanx. On the other other hand, the dragoons could form up again to the rear of the tercios and start firing through the gaps, once again putting the peltasts to flight. In other words, this scenario's outcome depends on a lot of things: (a) whether the phalanx's Companions or the tercio's dragoons win the cavalry skirmish; (b) if the dragoons are defeated, whether they're able to re-form and continue fighting; (c) once again assuming that the Companions win the cavalry engagement, whether the tercio's swordsmen are able to stop them from attacking the musketeers; and (d) if the musketeers are put to rout, whether the phalanx has enough peltasts left to keep up the harassing fire against the tercio's pikemen. (Am I forgetting any other factors?)

In short: The forces' respective composition makes an enormous difference regarding the outcome of the battle.

67.169.177.176 (talk) 00:37, 2 December 2011 (UTC)

Note that the Arquebus is a slow, heavy, short-range weapon. It's main advantages are ease of use and logistics, not tactical strength. If the phalanx is accompanied by auxiliary slingers, they may well have comparable or better ranged weapon support. --Stephan Schulz (talk) 10:07, 2 December 2011 (UTC)

The arquebus had a shorter tactical (not extreme) range than the slingshot, but had many times more stopping power, especially if both sides were wearing armor. And both these weapons had a much greater range than the throwing javelins of the Greek peltasts. Anyway, if you insist on adding auxiliaries that were not normally part of the unit (such as your example using mercenary slingers to reinforce the phalanx), you might as well also hire crossbowmen from the nearest town's militia to augment the tercio, in keeping with your spirit of using all the weapons available at the time rather than only those normally part of the unit. And of course the crossbow has a longer range than the sling, so there! 67.169.177.176 (talk) 21:09, 2 December 2011 (UTC)

December 2

Unidentified moss

Unidentified moss

Can anyone identify the type of moss shown in File:Moss closeup.jpg? Apparently, the photo was taken in Beacon Hill Park, Victoria, Canada in March 2007.  Chzz  ►  00:37, 2 December 2011 (UTC)

Looks like Sphagnum to me, but as to which of the 200 or so species, it may be tough to narrow it down. The picture of Sphagnum flexuosum in the infobox of the Sphagnum article looks like a halfway decent match, but there could be dozens of other sphagnums which look similar. --Jayron32 05:02, 2 December 2011 (UTC)

Need a moss specialist. I don't think you can identify it as Sphagnum with any confidence whatsoever though. Shame it doesn't have sporophytes yet. Some species found in B.C. which resemble it (the most likely candidate is Grimmia trichophylla):

• Grimmia trichophylla (dry rock moss): [22], [23], [24], [25], [26], [27]
• Dicranum tauricum: [28], [29], [30]
• Polytrichum formosum (beautiful haircap moss): [31]
• Polytrichum juniperinum (juniper haircap)
• Polytrichum commune (common haircap): [32]
• Polytrichum longisetum (slender haircap)
• Atrichum selwynii: [33], [34]
• Atrichum tenellum: [35], [36], [37]
• Atrichum angustatum: [38], [39]
• Atrichum undulatum: [40]

Also see Moss photos, Bryophytes of Stanley Park, Bryophytes of British Columbia -- Obsidi♠n Soul 09:45, 2 December 2011 (UTC)

Classified US space rocket launches during the Cold War

So, my dad and I watched Apollo 18 (film) tonight and got into a discussion about the feasibility of secret space missions afterwards. My dad asserted that there was no way that NASA (in real life) could have sent up a Saturn V without the whole world being aware of it, on account of it being a huge, very distinctive, very conspicuous rocket that anyone living within 300miles of launch could've seen going up - to which I responded that he'd missed the bit in the film where it specifically stated that it wasn't a 'secret' Saturn V launch, rather that the US govt. had put it about that it was a Saturn V carrying a classified military satellite to earth orbit (i.e. a normal launch with a 'secret' cargo).

Anyway - my question is thus. When the Cold War was on, how did the US government actually deal with media and local interest into rocket launches containing classified payloads, when it was impossible to hide the launch itself from the public? Was it a case of saying 'Yes, we're launching a rocket - but we can't tell you any more about in in the interests of national security'? --Kurt Shaped Box (talk) 01:15, 2 December 2011 (UTC)

That's pretty much how they did it. I dunno what they'd have to do in order to carry out a classified manned launch, though... 67.169.177.176 (talk) 01:21, 2 December 2011 (UTC)

A few small points:

1. Saturn Vs are huuuuge and were used for veeeerrry heavy payloads. Which is to say, people. If you want to put up a satellite, or test an ICBM warhead, generally speaking you don't need that much payload, and you can do much more nimbler operations. If you were just putting up a satellite or something you'd use a much smaller rocket, and you can launch those from much more isolated areas (e.g. Johnston Atoll, where the US sent up the rockets with its spy satellites early on).
2. The government is actually in a much better situation when it can admit to doing classified things for the reason you describe. It's easy to say, "yes, there's a secret program involved here," than it is to try for a complete cover-up. So the Manhattan Project was a huge pain for security people, because the fact that the US was working at all on atomic weapons was a secret, and even the fact that there was a secret of it was a secret. In the postwar period, it was a lot easier, because the government could say, "well, we're doing secret stuff over there," and leave it at that — a lot less work to do. When the US gov't detonated the first atomic bomb in the summer of 1945, they had to put out fake press releases claiming an ammunition dump had blown up, and then check around the local towns to see if anybody suspected otherwise. When nuclear testing was a known thing, they could just say, "yeah, it was another nuclear test, but we can't tell you anything about it." Much easier.

I'll see if I can dig up actual press coverage of the first spy satellite launches — it would be interesting to see how much detail was given out, if any. --Mr.98 (talk) 01:51, 2 December 2011 (UTC)

You mean like mission USA-226, launched in March?  Card Zero  (talk) 01:59, 2 December 2011 (UTC)

There's really no such thing as a "secret launch" of a satellite, regardless of where it's launched from or whatever orbit it's heading for. Firstly you have to tell anyone who might fear you're launching an ICBM at them that you're launching, lest they get the wrong idea and panic. When the detect a launch, Soviet warning systems can't immediately distinguish between a Titan launcher putting a satellite in orbit and a Titan missile (which is just about the same thing) chucking a suite of thermonuclear MIRVs at Moscow. So a few days before a launch the US would post a notice that it intended to launch, which had the launch window(s) and some of the characteristics of the launch trajectory. Other launcher and ICBM countries would do the same. Secondly, as any launch may fail and scatter debris downrange, the launching agency has to issue a NOTAM to make sure no civil aircraft is in the credible debris footprint. You might think the public information about the launch trajectory would be enough to determine the final orbit of the satellite (which is vital for tracking it), but they don't advertise much information, and nothing about the settings of the last (usually third) stage. So you don't know the elements of the final orbit. And many military satellites carry quite a lot of fuel, so they can adjust their own orbit repeatedly, and try hard to be difficult to spot optically or with radar. As Mr.98 notes, Saturn V was only used for Apollo and Apollo/Soyuz; US military launches variously used Atlas/Centaur, Delta, and Titan - these are smaller rockets which launch lighter payloads. I guess it's not impossible someone could cobble together a lunar mission out of multiple Atlas/Centaur launches, but with a bunch more docking in orbit and certainly not with the same equipment used in Apollo. As for military payloads in general: the US and Russia continue to launch military payloads (recon, mapping, communication, launch detect, etc.) and they just announce that it's a military payload and leave it at that, and won't be moved as to what's what and what went where. The US didn't really admit the NRO existed for decades, and still says essentially nothing about which launches are for it or what they might be doing. You might think that a look at the rocket, prior to launch, might be informative; but probably not much. The payload is integrated with the rocket in an indoor building, and is covered by an aerodynamic faring, so you can't see it. We only know details of classified payloads decades later, when they're declassified, or we find out odd things by association, such as KH-11 Kennan's apparent similarly to the Hubble Space Telescope. 2.122.75.79 (talk) 17:59, 2 December 2011 (UTC)

Ah, I forgot - there were also a few classified Space Shuttle launches, such as STS-51-C. The role of these missions is also classified. 2.122.75.79 (talk) 18:07, 2 December 2011 (UTC)

Atoms

Scanning tunneling microscope image showing the individual atoms making up this gold (100) surface

What do atoms really look like? I mean a real picture with electron microscope, not the usual diagram showing nucleus etc. And is it possible to see what protons and quarks look like? Money is tight (talk) 01:18, 2 December 2011 (UTC)

Regarding your second question: No, it's not possible to see individual subatomic particles, let alone quarks. 67.169.177.176 (talk) 01:38, 2 December 2011 (UTC)

When you start talking about things that are in the same order of magnitude as photons themselves, you have to start asking what you mean by look like. We tend to think about vision as a straightforward thing, but it's the reflection of photons off of things. (Colors are the way our brains interpret the frequency of the photon in question.) Things smaller than photons cannot really be visualized. What you can do is find ways to make data that you can convert into visualizations — so a scanning tunneling microscope can register very small changes in voltages that coincide with electron rings, and you end up with visualizations of things that we can say are "atoms" but really what we mean is "here is the change in voltage on a very small scale and it looks like a little ball." Is that what one means by look like? We don't have any way of visualizing bare protons or quarks (we can see their tracks in a bubble chamber but that's not really seeing the particle, just evidence of its passage). --Mr.98 (talk) 01:40, 2 December 2011 (UTC)

The above response is much better than I could manage; I just wanted to add the picture really. I think the best we can say is, it's a "fuzzy blob" - the bits whiz around, mostly within a certain area. Colour has no meaning at that level (the pic colour is 'fake'). We can't "zoom in", because of the problems mentioned above; it's just... fuzzy, uncertain.  Chzz  ►  02:18, 2 December 2011 (UTC)

You are seeing atoms and exactly what they really look like right now. You just can't distinguish them (technically the photons they emit) from each other. In effect, no different from asking what grass looks like, except that with grass we can get close enough to distinguish individual blades. But you wouldn't, sitting up in the stands, tell the guy next to you that he wasn't actually seeing what grass really looks like. The problem is assuming that things have an inherent look. But appearances are always relative to the perceiver, the perceived, and the conditions, including scale. Hurriquake (talk) 02:33, 2 December 2011 (UTC)

Oooh, I must disagree. The OP is asking about seeing individual atoms, not aggregates. The equivalent is trying to see blades of grass from outer space. If someone was able to tell, from outer space, that grass was green, and had theoretical reasons to believe it was made of blades, well, that's great. But that's not the same thing as being able to see individual blades, and the kind of information you get from the different levels of scale is significant. Even more significant is the fact that quantum effects kick in, which do, in fact, bring into question what one would even mean by "seeing", because you simply cannot "zoom in" on a proton in the that you can on a very small, but still macroscopic, object. --Mr.98 (talk) 19:04, 2 December 2011 (UTC)

Guess who saw Frank Wilczek give a presentation on this very subject in 2006?! End result (after thousands of hours of computation time based on iffy measurements): a quark, the most basic building block of matter we know, looks like an oblate spheroid. The reason it's "oblate" (that is, bulges out) is because of its spin, which is analogous enough to actual rotation that it "looks" the same. Of course, what the "image" actually means or if its worthwhile scientifically is hard to say -- as a lay-audience talk, the image of a quark was more for a "wow" effect.

As for an atom, that's easy: we can image individual atoms using a scanning tunneling microscope - IBM loves to show off how good it's got at this. As you can see, they're essentially spheres or spheroids. Boring.

But these are big, heavy atoms that are easy to see, which means that their outer electron shells (which is the thing we interact with when we touch any matter) are thick and round. If you look at our article on atomic orbitals, however, you'll see that the outer electron shell can make fun, cool shapes (scroll down to the table). These are only visible on the lightest atoms, such as hydrogen, however. Except now we can even image individual hydrogen atoms on graphene! Which means maybe soon we'll be able to see atoms that aren't just spheres! Cool! SamuelRiv (talk) 03:28, 2 December 2011 (UTC)

p-wave AFM lets you detect and visualize the shapes and phase/node patterns of the HOMO and LUMO molecular orbitals specifically (unlike normal s-wave AFM that only gives overall electron density). So some of the π and π* (composed of p atomic orbitals) of pentacene becomes visible. A few years ago someone had published direct evidence for the shape of d_z² and others, but I can't find the reference. DMacks (talk) 17:12, 2 December 2011 (UTC)

Though I would suggest that being able to infer the shape of a quark is not quite the same thing as being able to actually "see" one. --Mr.98 (talk) 19:04, 2 December 2011 (UTC)

Sea Level Rising

Hi.

I'm a 6th grader working on a science project about sea level rising. I have one question about it. If the sea level gets to high what would happen? My teacher asked that I get information from an expert source so I hope to get the answer to my question. — Preceding unsigned comment added by SentryBravo (talk • contribs) 02:14, 2 December 2011 (UTC)

I'm glad you're working on an important topic like this. One of the most important things for a scientist to do is to make sure that the terms he or she uses are very clear. Think about what "too high" might mean: a sea level that is "too high" for one purpose might be just fine for some other purpose. It might help if you can think of a more specific term than "too high" (unless that is what your teacher told you to do). Short Brigade Harvester Boris (talk) 02:18, 2 December 2011 (UTC)

Start by reading the article Current sea level rise it's quite thorough and even has a section on effects of sea level rise. Depending on what your teacher means by "expert source" that might not include wikipedia, in which case you should look at the sources which are referenced by our article. Vespine (talk) 03:08, 2 December 2011 (UTC)

"Too high for whom?" is a good question. If you were living on a boat, the sea level would never get too high. If you were living on a very low area near the ocean, too high might, over ten years or a century, mean that area would soon be permanently flooded with water. Another article to look at is mean sea level. Answering the question "what is the sea level?" is a lot harder than it seems. The water is constantly moving, and the ocean can be very different heights in different parts of the world. Imagine asking what the height of land is? It's actually many different heights, and it changes over time. Just because water appears flat, doesn't mean it's all the same height. It is also a fact that land itself and the continents can rise and fall according to their temperature and weight. When the earth goes through Ice Ages, the amount of ice on land is strong enough to press the land downward with extra weight, and when the ice melts, the land will actually rise up, out of the ocean. This is called isostasy, eustasy, and post-glacial rebound. Mac Davis (talk) 15:42, 2 December 2011 (UTC)

Low-lying islands, coastal cities, and megadeltas (regions where multiple mouths of rivers empty out into the sea, like the Ganges Delta and the Nile Delta) would be engulfed by the sea. Also see Climate change in Tuvalu, Regional effects of global warming, Effects of global warming#Sea level rise, and Current sea level rise.-- Obsidi♠n Soul 17:04, 2 December 2011 (UTC)

Unidentified Cricket

click for bigger version

Can anyone identify this insect? Family members in New Jersey have had their house overrun by them, but the species has never been seen with decades at the same location. The length of the body is about a centimeter. (The cricket is photographed on a standard sized paper table napkin.) They do not "sing". The stripes are brown and orange. At least half a dozen have been found in all levels of the house including in a bath tub.

Also, the "crickets" appear to have multiple "fingers" forming hands at the end of their limbs. (This is visible in the full size picture.) I have never heard of or seen such a thing. Which insects have this feature? What might it be called?

Thanks. Hurriquake (talk) 02:19, 2 December 2011 (UTC)

Well i'm not much of a bug guy and I don't live in the states, but my google fu was strong today. First I thought it had more then a passing resemblance to weta, but after a bit more digging, I found this pest control site specific to New Jersey, I present Rhaphidophoridae, which does actually include "cave wetas" so I wasn't far off at all:) But this one is specifically a Camel cricket. Vespine (talk) 04:18, 2 December 2011 (UTC)

Camelback crickets seem to be common in the mid-Atlantic area this year; I've got a few in my basement and had never seen them there before. Acroterion (talk) 05:13, 2 December 2011 (UTC)

If you're interested in reading more about the critters, you might try chapter 13 of Sue Hubbell's Broadsides from the Other Orders, in which she describes her observations of them. Deor (talk) 11:54, 2 December 2011 (UTC)

Catalase

What food has the most catalase? More than chicken liver that is.--KAVEBEAR (talk) 04:00, 2 December 2011 (UTC)

Second question: Does soybean have much catalase?

You can't get catalase from food. You have to make your own. Any catalase you eat is destroyed during digestion and cannot be absorbed in useful form by your body. Dominus Vobisdu (talk) 04:18, 2 December 2011 (UTC)

That's not exactly the question he asked. He asked which food has the most catalase, not which food can your body obtain it from. Liver is a good bet, but something like raw blood sausage or other blood-based food may be another good one. --Jayron32 04:56, 2 December 2011 (UTC)

orbitals...

I tried to find where is the place around the nucleus that has the most amount of probability density and what the amount of is in that point. now, since for 2p_x and 3p_x orbitals we know that this point is in xy plane, and on the x axis, I replaced y and z in the wave function equations with 0, and found the derivative for psi^2, and found the root for d(psi^2)/dx=0 and placed the root in the psi^2 equation.Now the strange thing is that the amount of psi^2 in the anti-node of 3p is 0.135 while it's 0.005 for 2p. but shouldn't it be more for 2p? what is my mistake?and please give me answers that are clearer than "it doesn't work that way" and stuff like that.Thanks in advance.--Irrational number (talk) 12:30, 2 December 2011 (UTC)

What makes you say it should be more for 2p? Dauto (talk) 14:31, 2 December 2011 (UTC)

since it is nearer to the nucleus, it must have a more probability density near the nucleus?--Irrational number (talk) 17:24, 2 December 2011 (UTC)

Just because the mean of one probability density function is greater than the mean of a second PDF, doesn't mean the mode is. Red Act (talk) 17:50, 2 December 2011 (UTC)

Ha, I get it.... but a little more explanation makes it better...

I still don't understand what's the problem. The 3p is further out but more concentrated. Dauto (talk) 18:48, 2 December 2011 (UTC)

now I get it.--Irrational number (talk) 19:00, 2 December 2011 (UTC)

Mitosis

Hi there. Not a biologist here, just an interested onlooker. During anaphase of mitosis, when the two (identical?) sister chromatids of a chromosome split, one chromatid ends up in each daughter cell. I've looked up different references (including Wikipedia), but none seem to go into the details of how each chromatid becomes a genuine chromosome in each daughter cell. As I see it, each daughter cell inherits one sister chromatid from each chromosome in the parent, leaving it with half the number of chromatids it needs to have a full complement of chromosomes. What's going on? Do they make copies of themselves somehow? It's been years since I studied biology, so be gentle! Thanks, Icthyos (talk) 12:59, 2 December 2011 (UTC)

The DNA is copied before the division, not after it. Dauto (talk) 14:27, 2 December 2011 (UTC)

Ah-hah, I see. Does this happen during interphase? So during the entirety of mitosis, the cell already has double the number of chromosomes it normally does? I remember asking my high school biology teacher this, and she said the new cells reproduced the new required chromatids. I never quite bought that... Icthyos (talk) 15:09, 2 December 2011 (UTC)

Yes, this happens during Interphase, during the S-subphase, between the G-phases. The classical scheme of mitosis you learn in school textbooks is a bit outdated and simplified for pupils. A real cell, after the S-subphase of the interphase, is already preparing for a cell division. A cell that has doubled its number of chromosomes only has one way to go: into mitosis. If it doesn't, there are controls in place, in a healthy human cell for example, to ensure that such a defect cell dies. So from a modern, conceptual view, it probably would be better to group the S-phase already into the "mitosis-part" of the cell cycle. The original naming of phases was all done by light-microscopy, where the cell mostly looks the same during the whole interphase. --TheMaster17 (talk) 15:28, 2 December 2011 (UTC)

I think there is a misunderstanding here. After cytokinesis, the two daughter cells have each the exact same chromosomes that the parent cell had had before entering mitosis. A "normal" chromosome, outside of mitosis, consists only of a single strand of DNA. The double structure (looking like an X) you see often depicted when someone talks about chromosomes is in reality only present in a cell during the metaphase of mitosis, after the doubling of its chromosomes into two sister chromatids. Have a look at the first picture in mitosis and follow each chromosome from the parent to the daughters, perhaps this already clears up the misconception. --TheMaster17 (talk) 15:18, 2 December 2011 (UTC)

Okay. That's perfectly clear now, thanks. The doubled-up chromosome (with the two chromatids) picture had stuck with me for some reason, and I thought that's what a 'normal' chromosome looks like. Perhaps because most of the pictorial flow diagrams I'd seen missed out that first picture, and there was never any mention of anything like interphase. Thanks! Icthyos (talk) 15:23, 2 December 2011 (UTC)

Note that you don't really see chromosomes under a microscope during the bulk of the cell cycle - chromatin condensation is a process which is done pretty much specifically for the purpose of dragging them apart (caveatting that "purpose" is something we assign, not the biology, and probably messing with the process would foul up something else). So the X-form chromosome is not really uncommon in the sense that when you see a chromosome it often looks like that. But hunting around for cells with any visible chromosomes on a mitotic spread is not so easy; mitosis is a short phase of the cell cycle and so such cells are not common even in rapidly dividing populations. Wnt (talk) 00:45, 3 December 2011 (UTC)

Late C19—early C20 British diplomat and entomologist named Alfred E. Wileman

Hi all,
One Alfred E. Wileman appears to have been a late C19—early C20 British diplomat and entomologist, and the binomial authority for Abaciscus costimacula, Taicallimorpha albipuncta, and so on. Possibly a fellow of the Royal Entomological Society of London.
Looking for refs to start article. Any clues about when he was born, died, and so on?
Thank you!--Shirt58 (talk) 15:03, 2 December 2011 (UTC)

Hm... I figured out his middle name - Ernest. Searching for "Alfred Ernest Wileman" and "AE Wileman" gives you more results. He was consul-general to Hawaii, the Philippines, Taiwan, and Vice Consul/Consul for Japan (and [41]).

Wikispecies gives his year of birth and death as 1860 to 1929.

From a preview of The Diaries of Sir Ernest Satow, British Minister in Tokyo (1895-1900): A Diplomat Returns to Japan, I have:

Alfred Ernest Wileman (1860-1929) was appointed a student interpreter in Japan in 1882. Employed as Assistant in the Japanese Secretary’s office from October 30, 1894 to March 31, 1896. H. M. Vice Consul for Hiogo (i.e. Kōbe) and Osaka from December 28, 1896. Transferred to Hakodate on April 1, 1901. (Foreign Office List, 1930)

From The Correspondence of Sir Ernest Satow, British Minister in Japan, 1895-1900:

Alfred Ernest Wileman (1860-1929). Collector and breeder of butterflies and moths. Fellow of the Entomological Society of London. Appointed student interpreter in Japan, 1882. Assistant Japanese Secretary and British Vice-Consul at Tokyo, 1892. Acting Japanese Secretary 1892-94. Assistant in the Japanese Secretary's Office from October 30, 1894 to March 31, 1896. In 1896 promoted Vice-Consul for Hiogo and Osaka. Acting Consul at Hiogo, 1898. Vice-Consul at Hakodate, 1901. Consul for Tainan, Formosa, 1903. Acting Consul-General, Yokohama, 1907. Consul-General for the Philippines, 1909. Retired 1914. (See Kuwata, 2003, pp. 481-482)

A Japanese author also seems to have written biographies of him (but they're probably both in Japanese):

• Esaki, Teiso (1953). "Foreigners' collecting in Kyushu" [in Japanese]. Shin Konchu, 6y(3):2-7. Itineraries of J. J. Rein, G. Lewis, J. H. Leech, A. E. Wileman, H. Fruhstorfer, & F. Silvestri recorded. Chronology for 1690-1939 supplemented.

• Esaki, Teiso (1956). "Alfred Ernest WILEMAN (1860-1929)". TINEA 3(1/2):127-128.

There's also this Lepidoptera blog which mentions Wileman thrice, in what seems to be a biography. It's in Japanese though and Google Translate results in gibberish. The Natural History Museum has a picture of him and a short description in this file. That's pretty much all I can glean from the internet.-- Obsidi♠n Soul 16:45, 2 December 2011 (UTC)

Melting plastic

Odd question- suppose I bought this nice tool I saw today, a heat gun for stripping paint off stuff, 2000W, 350-600°C, then suppose I wanted to use it to melt the surfaces of a couple of pieces of plastic and press them together so they stick as they cool, would it work? What sort of effect would it have on the plastic, would they melt properly, and would they actually stay stuck if I tried something like this? If not, what other sorts of tools are there around that could do the job?

148.197.81.179 (talk) 15:53, 2 December 2011 (UTC)

It depends on what type of plastic is involved. Also there is a high probability that you will make a mess, since the air from a heat gun is hard to control. Looie496 (talk) 16:13, 2 December 2011 (UTC)

OK, is there any way of finding out which plastics this would or would not work with? 148.197.81.179 (talk) 16:18, 2 December 2011 (UTC)

Soft plastics are usually thermoplastics, which should behave as you want. Hard plastics are generally thermoset plastics which will just smoke if you heat them. In any case make sure you do this outside, as heated plastics give off toxic fumes, and be careful as getting melted plastic on your skin will severely burn you. StuRat (talk) 16:31, 2 December 2011 (UTC)

Start in Category:Plastics and read up on plastics' melting points. I know from friends' MakerBots that Acrylonitrile butadiene styrene, polylactic acid, and high-density polyethylene are thermoplastics with relatively low melting points. ~Alison C. (Crazytales) 16:39, 2 December 2011 (UTC)

(e/c)And both pieces of plastic need to have the same melting point for this to work. The manual welding of plastics is a skilled job and even more tricky than welding metalwork. Use of a solvent adhesive is a much safer bet, otherwise be prepared to lose a few pieces of plastic before you succeed in welding them.--Shantavira|^{feed me} 16:44, 2 December 2011 (UTC)

(ec) Be careful with heating and burning plastics - some common, household plastics give off very noxious gases when heated.

If you buy stock plastic material from a supplier, like McMaster-Carr, you can get detailed technical information (including safety information) on the exact chemical compound. "Plastic" is such a generic term that it covers tens of thousands of different commonly-used chemical compounds. If you're using "home-supplied" plastics, you can often check the recycling code to determine the chemical makeup of a particular plastic (at least to get a ballpark idea about what "general class of materials" the object was made from). Unfortunately, though, most plastic you find around the house is pretty "anonymous." Here's Identifying Plastics by Burn Test - also from McMaster. By browsing their website, you can find a lot of other useful information - which glues/epoxies/bonders are compatibile with different plastics/substrates/metals, and so on. Nimur (talk) 16:46, 2 December 2011 (UTC)

So, if I have the right sort of plastic, enough to practice on a few times, and a good place to work, what do I then use to heat the things up? The paint stripping gun was the only heat based tool I could find around the shops, would there be anything better I could look for or ask for that wouldn't cost a fortune? 148.197.81.179 (talk) 19:46, 2 December 2011 (UTC)

Something that hasn't been mentioned yet is that plastic items often still has traces of mould-release compound adhering to it. This is a very tenacious lubricant that can make it difficult to achieve a good homogeneous weld between the two plastic surfaces. Therefore, remove this with some fine glass paper. The roughened surface will also act as a guide to when it has reach melting point because it will start looking wet. Quickly Press the two bits together hard.--Aspro (talk) 20:19, 2 December 2011 (UTC)

There are of course Hama Beads (what? No article?) that are welded together with a clothes iron (through a piece of greaseproof paper). 109.148.238.255 (talk) 00:20, 3 December 2011 (UTC)

Heating with an electric heater

Is it possible to be efficient here or do all the electric heaters convert all electricity to heat? — Preceding unsigned comment added by 80.58.205.34 (talk) 18:09, 2 December 2011 (UTC)

No. Some electric heaters produce light. Light is not heat. -- kainaw™ 18:15, 2 December 2011 (UTC)

But, won´t this light be converted to heat when it hits (heats?) a curtain or wall? — Preceding unsigned comment added by 80.58.205.34 (talk) 18:26, 2 December 2011 (UTC)

Yes. :All of the electricity is eventually converted to heat, though. The light energy wll eventually be absorbed by a surface and be converted into heat. Dominus Vobisdu (talk) 18:30, 2 December 2011 (UTC)

But, light converted to heat by another object is not electricity converted to heat by the heater. It is electricity converted to light by the heater. -- kainaw™ 18:36, 2 December 2011 (UTC)

The question was about the relative efficiencies of electric heaters for the purpose of heating a room. Whether the heater does this directly or indirectly is immaterial. Actually, any electrical device is exactly 100% efficient in heating a room: a refrigerator, and electric shaver, a blender, a cell phone, a vibrator. All of the electricity consumed will eventually end up as heat. Dominus Vobisdu (talk) 18:47, 2 December 2011 (UTC)

You're being pedantic, which isn't very helpful. Light gets absorbed by the atmosphere or other objects and becomes heat. ScienceApe (talk) 19:12, 2 December 2011 (UTC)

I'm actually trying to be practical. If I want an "efficient" electric heater, I want to turn it on, sit near it, and get warmed up quickly. But, the answer here is that I could turn on a vibrator and sit near it and somehow I'll get warmed up because all that electricity will, eventually, be turned into heat. When running a heater, it isn't important that you will eventually get the paint on your walls to warm up a tad. You want to get immediate heat transferred to your body. -- kainaw™ 19:19, 2 December 2011 (UTC)

I wasn't implying that heating with vibrators was practical, just that they are as energy efficient as heaters as any other electrical device. And if you want to get your legs warm as fast as possible, you do NOT want a heater that releases heat, but one that releases light, specifically infra-red light, which gets converted into heat when it hits your legs. You forgot that light can be delivered in a focused beam much more precisely and more comfortably than hot air can in a directed stream. Dominus Vobisdu (talk) 19:32, 2 December 2011 (UTC)

You might want to read what Dauto posted here about light being heat here http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2011_October_22#More_redox_questions

But you're still being pedantic anyway. What's the point of a heater if it only makes you warm when it's blowing directly on you, but the rest of the room is ice cold? I want the whole room I'm in (at least) to be warm. ScienceApe (talk) 19:28, 2 December 2011 (UTC)

And yet, it is possible to do better than that by using a heat pump instead of an electrical heater. Dauto (talk) 18:35, 2 December 2011 (UTC)

Err, aren't those mostly used in air conditioners? I'm pretty sure generating new heat is more efficient than pumping heat out of an already cold environment. ScienceApe (talk) 19:16, 2 December 2011 (UTC)

Heat pumps can be more efficient, but only at certain times of year. To heat efficiently, you need the ground or outside air from which you steal the heat to be warm. StuRat (talk) 20:54, 2 December 2011 (UTC)

No, a heat pump is more efficient than an electric heater. It might be more efficient to use a stove and burn fuel instead of using electricity because electric power is produced by a power plant which usually has an efficiency in the range of 35% to 40%, so that gives the stove a head start relative to any electric device. But if you're comparing an electric heater with an electric heat pump than the heat pump is better every time. Dauto (talk) 20:57, 2 December 2011 (UTC)

Not according to our heat pump article:

"When there is a high temperature differential on a cold day, e.g., when an air-source heat pump is used to heat a house on a very cold winter day of say 0 °C, it takes more work to move the same amount of heat indoors than on a mild day. Ultimately, due to Carnot efficiency limits, the heat pump's performance will approach 1.0 as the outdoor-to-indoor temperature difference increases for colder climates (temperature gets colder). This typically occurs around −18 °C (0 °F) outdoor temperature for air source heat pumps. Also, as the heat pump takes heat out of the air, some moisture in the outdoor air may condense and possibly freeze on the outdoor heat exchanger. The system must periodically melt this ice. In other words, when it is extremely cold outside, it is simpler, and wears the machine less, to heat using an electric-resistance heater than to strain an air-source heat pump.:

So, it would be the same efficiency as an electric heater, if you didn't have to melt the ice that condenses on it. This brings it below the efficiency of an electric heater at outdoor temps under −18 °C (0 °F). A geothermal heat pump solves this, since below ground temps rarely got that low on Earth. StuRat (talk) 21:19, 2 December 2011 (UTC)

The efficiency approaches 1 from above, so the efficiency is always higher than the electric heater efficiency. There is no need to melt the ice outside, except that the ice might cause some problems but that is a matter of poor design that could be solved. No engineer bothers solving this problem since that's not the intended use for the heat pump. Dauto (talk) 21:29, 2 December 2011 (UTC)

You have the cause and effect backwards. The reason why heat pumps aren't intended to be used to heat homes when the outdoor temp is that low is that they would be inefficient. If you have a solution that makes them efficient at low temps, I suggest you patent it and get rich. StuRat (talk) 21:36, 2 December 2011 (UTC)

Modern heat pumps are, in effect, 300 to 400 "% efficient" at mild exterior temperatures, with the "% efficiency" gradually dropping closer to 100 as the exterior temperature falls. "% efficient" is not really the appropriate term, but reflects the fact that the amount of heat delivered to the room is always more than the amount of electricity used, except when the system fails to circulate at extremely low temperatures. I thinks that's actually what you both said above! The reason that heat pumps are "inefficient" in another sense at low external temperatures is that the motor will be working very hard for very little benefit, and will thus cost much more to maintain than the extra heat is worth. Dbfirs 00:18, 3 December 2011 (UTC)

Btw, Dauto mentioned that light IS heat. I recalled him saying that, and I found the section here, http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2011_October_22#More_redox_questions

So if Dauto is right, then a heater DOES convert all electricity into heat. ScienceApe (talk) 19:23, 2 December 2011 (UTC)

Dauto is wrong. The OP used the term heat meaning infrared radiation, light is heat only when heat means entropy. Obviously, a heater does not make energy disappear, it just transform it into other forms of energy (IR and sometimes light). — Preceding unsigned comment added by 88.14.196.65 (talk) 00:39, 3 December 2011 (UTC)

Infrared radiation IS a frequency of light. ScienceApe (talk) 02:05, 3 December 2011 (UTC)

A couple points:

1) The light generated from electric heaters, whether visible or infrared, is a very small portion of the electricity used.

2) Of that light, only a tiny portion escapes the room, through windows.

So, the efficiency of an electric heater at changing electricity into usable heat is probably over 99%. Of course, this doesn't mean it's always the best choice, since electricity costs more than many other energy sources, especially natural gas. It works out that heating the entire house with electricity is usually prohibitively expensive (unless you live someplace where it only gets a little bit cool in winter). However, if you only heat the room you're in at the time, and let the rest of the house remain cold (but not so cold that the pipes freeze), then an electric space heater can be more economical. As for type, the oil-filled electric convection heaters that look like radiators don't have an annoying fan or make a burning smell when you turn them on, and, if you leave them on low, probably won't get hot enough to burn you or cause a fire. They do tend to heat the ceiling, though, but that's not bad if you don't mind heating the room above you, too. StuRat (talk) 21:10, 2 December 2011 (UTC)

Diameter of an electron

What is the diameter of an electron? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:26, 2 December 2011 (UTC)

did you read the article Classical electron radius? I have created a redirect for those that ask the same question. As a number the diameter from this point of view would be 5.6 attometers. Graeme Bartlett (talk) 21:37, 2 December 2011 (UTC)

The "classical" part is important here, as it refers to size estimates that predate the modern understanding of quantum mechanics. While it is useful for some calculations (such as the scattering of photons against electrons), this is not actually a measure of the size of an electron. As far as we know, electrons are point particles with no intrinsic size at all. The current limit is that an electron has no internal structure larger than 10^-18 m, consistent with zero size and already 1000 times smaller than the classical electron radius. Dragons flight (talk) 00:15, 3 December 2011 (UTC)

Galilean moons and longitude

In Greenwich Time and the Discovery of the Longitude, Derek Howse discusses Galileo's discovery that the Galilean moons could be used to demonstrate one's longitude; as he notes, Galileo observed that moons appear to be eclipsed behind the planet at the exact same time, regardless of where on Earth the observer is located. How did Galileo discover that their eclipses appear worldwide to be simultaneous? Or did he simply calculate it and find no reason to disbelieve the calculations? I've checked the article on the moons; you'll see that I added a citation to Howse for the longitude sentence, which was previously uncited. Nyttend (talk) 22:15, 2 December 2011 (UTC)

Hmm, that's perhaps not a sufficiently clear question. I'm essentially trying to ask the following: how did Galileo discover that observers anywhere in the world would see the eclipse at the same time? Nyttend (talk) 22:20, 2 December 2011 (UTC)

Maybe the parallax of Jupiter (against the background of stars) indicated that this planet was so far away, that he reasoned that these eclipses would appear the same from wherever there are viewed from earth. The earth revolves, so he had a base line, roughly the diameter of Earth from which he could try and ascertain the parallax. --Aspro (talk) 22:33, 2 December 2011 (UTC)

Whoops... Or should we include the Earth's orbital diameter as a base line - for distance estimation as well?--Aspro (talk) 22:42, 2 December 2011 (UTC)

Well, we need the distance from the Earth to Jupiter, which, at the minimum, is Jupiter's minimal orbital diameter minus the Earth's maximum. I get 740 million km minus 152 million km, or 588 million km for the min distance. The Earth's diameter is around 12,740 km. I get under half a degree when I take the arctangent of 12,740/588,000,000. So, not much difference will be visible with only half a degree in parallax. I imagine the moons will cover up a slightly different spot on Jupiter, depending on your longitude on Earth, but you'd need a rather powerful telescope to be able to distinguish that. StuRat (talk) 23:10, 2 December 2011 (UTC

Since Galileo was a smarty-pants he wouldn't have any difficulty in working out its 11 or 12 year orbital period based on several years of observation and then sussed out the the angular orbital change of position around the sun (he was, I believe, famous for this rearrangement of the firmament) in six months (a diameter). From that he could work how far away Jupiter was in units of 10 inch pizzas or what ever units of measurement they used in those days.--Aspro (talk) 23:35, 2 December 2011 (UTC)

Interesting... Would this be a practical method for determining longitude (assuming of course that your GPS receiver got fried by a lightning strike)? 67.169.177.176 (talk) 22:59, 2 December 2011 (UTC)

No easy answer to that question. It could be, but other factors have to be taken into account and if one was on say a sailing ship, then the delay whilst one did all the corrections could end up with one's ship on the rocks. One problem that springs to mind is that due to the distances involved one would have to allow for the the time it takes light to travel from Jupiter to Earth (the moons obit the same period regardless). The Earth's orbit alone is about 17 light minutes in diameter. Then one has to consider the constantly changing distance to Jupiter. Lastly, as the Royal Navy used to issue a tot of good Jamaican rum each day to the crew. I wouldn't trust any of them to punch the right keys on their slide-rules (given the rums proof -which was something like 60). Personally, I would rather have my rum on the rocks than my vessel. --Aspro (talk) 23:56, 2 December 2011 (UTC)

I believe the navigator would be an officer, and, as such, would be expected to remain sober while on duty. A more serious problem would be trying to locate Jupiter in a telescope on a swaying ship. A stable platform is a must for such work. StuRat (talk) 00:00, 3 December 2011 (UTC)

What about using the Gatty bubble sextant for this job? 67.169.177.176 (talk) 00:04, 3 December 2011 (UTC)

The bubble only provides and artificial horizon. It magnification is chosen for solar/lunar sightings. On a heaving ship it would be difficult to view Jupiter with a hand-held telescope but for Galilean moon sightings I think I could just do it with a low power scope. However, to get a good fix one need to take several sightings and take the average. Whilst this is easy with a celestial body like the Sun, the eclipses of Galilean moons are a momentary events. Then there is human reaction time and the slowness of the moon appearing/occulting. It would be easy to end up with several several nautical miles of error. Not much use if one is sailing between the Islands of Penzance. --Aspro (talk) 00:31, 3 December 2011 (UTC)

Using Galilean moons is one of several astronomical methods of measuring longitude proposed before the invention of the marine chronometer. It was used successfully on land during a few occasions, but the technical difficulties made it too hard to actually use on a moving ship. Dragons flight (talk) 00:22, 3 December 2011 (UTC)

Flame without combustion

Can you have flame without combustion? Like lets say a meteor falls from the sky and burns up, or a slug of metal is fired from a railgun and creates a plume of flame, is there a combustion reaction going on in both cases? ScienceApe (talk) 02:07, 3 December 2011 (UTC)

Titan lakes

Are the lakes of Titan (such as Ligeia Mare) drinkable? If it was on Earth, could aquatic life live in it? If not, is it possible that life could adapt to the conditions in the lake? 64.229.180.189 (talk) 02:12, 3 December 2011 (UTC)