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November 9

do electric blankets save energy vs. an electric heater?

Is an electric blanke energy-efficient versus my electric heater, because I'm right next to it, and it heats into an insulated place? It seems it would only need to get a fraction of as hot as a normal heater, and there's no such thing as more or less efficient heat generation via electricity -- it's all 100% efficient, isnt' it? (though maybe not directed optimally, but the amount of total heat generation from every x-watt electric blanket pulling y amps is the same, isn't it? —Preceding unsigned comment added by 82.124.214.224 (talk) 02:47, 9 November 2008 (UTC)

if you operate an electric blanket at night and turn the thermostat down, you will probably save considerable energy. You can be cozy under the electric blanket while the house is allowed to become quite cool. When the trade-off is turning up the electric heater (as opposed to a gas furnace) the savings are even clearer. The downside is that some people worry about the small electric field from an electric blanket as an example of EMF Electromagnetic field which is hypothesized to be harmful. An ad for an electric blanket [1] says you can save 10% on your heating bill by turning the thermostat down while you sleep under the electric blanket. Edison (talk) 02:58, 9 November 2008 (UTC)

You appear to be presuming the OP is referring to central heating but I don't see any reason from the question to presume he/she is. The IP looks up to France, where I believe central heating is the norm, so you may be right but there is still the possibility the OP happens to live in a house without central heating. Definitely here in Auckland (or heck NZ) where central heating is relatively rare, it's likely you'd only heat your bedroom when your sleeping. While an electric blanket is still likely to be quite a bit cheaper, the costs savings are probably going to be less. Of course, if your me, a good feather-down duvet is enough for most winter nights in Auckland anyway. Nil Einne (talk) 11:14, 9 November 2008 (UTC)

The answer isn't a "yes" or "no". It is an "it depends". What is the watt rating on your electric blanket? What is the watt rating on your heater? I have a ceramic heater that is 12 watts and an electric blanket that is 35 watts. So, I figure I can run the little heater twice as long as the blanket and get the same energy usage result. So, you want watts to calculate kwatt hours used for some number of hours running each device. -- kainaw™ 03:05, 9 November 2008 (UTC)

I do not believe that you have an electric space heater which draws only 12 watts. Please check the nameplate more closely. I would believe 12 amperes. Electric blankets use far less power than any appliance calling itself an electric space heater. 03:07, 9 November 2008 (UTC)Edison (talk)

I agree with Edison that it is very unlikely that you would have a space heater of any kind that drew only 12 watts. (I would believe 1200 watts, or 12 amps, or somesuch.) In any case, just the rating on the packaging isn't necessarily going to tell you the whole story. Both blanket and heater will likely contain thermostats which regulate their output; neither device is likely to be operating at full power all the time. TenOfAllTrades(talk) 16:59, 9 November 2008 (UTC)

I'm sorry. I didn't mean to imply that I was referring to a space heater. It is a foot heater under my desk. I don't own a space heater. So, all I had to go on in my example is my electric blanket and my foot heater. -- kainaw™ 21:14, 9 November 2008 (UTC)

Unfortunately, heating your feet and heating your bed are rather different tasks, so the example isn't very useful. Space heaters use *enormous* amounts of electricity. --Tango (talk) 21:29, 9 November 2008 (UTC)

I can't even believe a small space heater under the desk only draws 12 watts. That is like a very small light bulb. Edison (talk) 22:00, 9 November 2008 (UTC)

Kainaw called it a "ceramic heater", perhaps it's like a heated ceramic tile that you rest your feet on? That could be quite efficient. --Tango (talk) 22:25, 9 November 2008 (UTC)

That is exactly correct. As I said - I don't have a space heater, so I just used what I did have for the example. My point was that when talking about power consumption, you don't have to guess. You can look at the power rating on the device and calculate rather accurately how much power it will consume over a period of time. -- kainaw™ 00:28, 10 November 2008 (UTC)

I don't think calculating it's that easy though. As you stated, you need to calculate how many kilowatt hours you use, but most heaters aren't on constantly so you'd need to work out how long the heater is actually on, e.g. by timing how long it's on for. I have used several oil filled heaters, either 1kW or 2.4kW. However even if the thermostat's at maximum, they don't usually remain on constantly. (And I personally have never felt the need to turn then on maximum except sometimes when I turn it off after I let it get very hot.) Indeed the 2.4kW one has 3 levels and then a variable thermostat. I'm not sure what the 3 different level setting does, it may adjust the power consumption (as opposed to simply affecting at what temperature the heater turns on and off). The simplest thing would be to get a power consumption metre you can plug the heater into. What is clear is that the electric blanket will win although by how much will vary. (Here in NZ again, our houses tend to be rather poorly insulated which would increase consumption of space heaters a fair amount Nil Einne (talk) 09:30, 10 November 2008 (UTC)

obviously, if the purpose is to heat your body from ambient temp to 65 or something, the less additional mass you have to heat, the more efficient. putting the heater in contact with your body is obviously a step in that direction, compared to heating the mass of air up in the room and wafting it over towards yourself.

on the other topic, yeah, 12 watts sounds about right for something you contact with your body/feet to keep warm, but inadequate for a space heater in anything but a small box (see above) if you think about the heat from a 12 watt bulb. Just for fun; the added heat from AGW currently is estimated about 1.7 watts per square meter, so imagine keeping your tootsies on that little warm tile. it's not insignificant.Gzuckier (talk) 20:23, 11 November 2008 (UTC)

You just reminded me that it is time for our local Darwin award nominees. Every year, about this time, people start setting their rooms on fire - usually killing themselves, by sticking space heaters under their blankets. -- kainaw™ 02:13, 12 November 2008 (UTC)

Speciation in the lab

What new species, if any, have been created in labs? NeonMerlin 03:24, 9 November 2008 (UTC)

See Mycoplasma laboratorium. --Arcadian (talk) 03:48, 9 November 2008 (UTC)

Not seeing species creation, at least not in that article... --98.217.8.46 (talk) 04:14, 9 November 2008 (UTC)

See Speciation#Artificial_speciation. --98.217.8.46 (talk) 04:14, 9 November 2008 (UTC)

spacetime deformation

If you have a supermassive object a great distance away from a planet or something.. The planet will gradually "slide down" the gentle (at that distance) slope of the object's gravity well, right? But a ball falling from a tower on the planet will accelerate far more rapidly than the planet is accelerating. So doesn't that mean that the gravity gradient is steeper locally than relative to the object? In other words, won't the planet just stay slumped in its own deformation of spacetime? Or is this just a trick of relativistic geometry? I know it's common sense that the planet doesn't have to labor up its own gravity well to move anywhere, but does relativity actually explain WHY it doesn't? This is what I mean: http://img204.imageshack.us/img204/2894/wellsbp1.jpg Thanks 71.176.179.91 (talk) 04:32, 9 November 2008 (UTC)

First, gravity wells are a Newtonian thing, not a relativistic thing—see gravity well. In Newtonian gravity the acceleration of an object depends on the net force acting on it, and the net force is just the sum of the individual forces. An object can't exert a net force on itself. So the forces acting on the planet are a bunch of internal forces, which are large but add up to zero (because they point in different directions), plus the force from the distant supermassive object, which is small but nonzero. The net result is an acceleration toward the distant object, and it's the same acceleration as if the internal forces hadn't been there at all. If you like, the object doesn't have to climb out of its gravity well because the gravity well is always instantaneously aligned with the object. Unlike the object itself, the gravity well doesn't have inertia. Gravity acts instantaneously and without any apparent mechanism.

In a relativistic field theory, like Maxwell's electromagnetism or general relativity, the field of an object can't be in constant "communication" with the object because of the light speed limitation. If the object's motion changes, the field won't know about it until some time later. So relativistic fields do have a life of their own, and they do have inertia. If you change the motion of a charged particle it experiences a force due to the delay in updating its own field, and I think this could be described as "laboring up its own potential well". (This force is called the "self-reaction" or "back-reaction", and Wikipedia doesn't seem to have a good article about it.) But that doesn't matter when the particle is being accelerated by gravity, because everything gravitates equally, including fields. The gravity of the distant supermassive object pulls on the planet and the planet's gravity well in equal measure, so the planet doesn't have to fight against the well.

(I should add that I don't actually know if there's a gravitational version of the electromagnetic back-reaction. It's tricky to discuss such things in gravity's case because everything gravitates. You can do electromagnetic experiments by pushing charged objects around with uncharged sticks, but you can't do gravitational experiments by pushing massive objects around with massless sticks. Even light has a gravitational field. It may not even make sense to say that there's a gravitational back-reaction, because there's no way to change an object's motion that the gravitational field won't know about ahead of time.) -- BenRG (talk) 14:02, 9 November 2008 (UTC)

The article self-force looks fine to me; did you not find it? --Tardis (talk) 01:36, 10 November 2008 (UTC)

mechanical reactionless drive?

File:BalloonsReaction.jpg

Supposing you have two spherical balloons full of water connected by a pipe full of water all the way though. if you squeeze one balloon equally in all directions, the pressure change in the pipe will make the other balloon expand equally in all directions. If they were in outer space doing this would not move the system backwards of forewords since all forces cancel out. But hold on-the center of mass has been moved without reaction in violation of Newtons third law of motion. Rotate the deflated balloon around 180 degrees and reverse the process and you have a reactionless drive. Or am I missing something?

--Trevor Loughlin (talk) 06:20, 9 November 2008 (UTC)

You aren't squeezing "equally in all directions" if you have a hole for water to flow through. Dragons flight (talk) 07:14, 9 November 2008 (UTC)

And the apparatus would probably move away from you... Due to viscosity and friction concerns, forces YOU apply will not be 100% returned via the opposing balloon, and there will be a net force away from you that will be unopposed... --Jayron32.talk.contribs 11:30, 9 November 2008 (UTC)

I thought someone would bring up the "hole the water flows through" but since this "hole" is connected to a solid metal tube with water all the way through it (no air bubbles to be displaced) connecting to the other balloon, there is only a pressure change and I assume this would not cause a backwards reaction. As for friction and viscosity, what if you used liquid helium? An easier to understand thought experiment equivalent to the two balloons (in fact more practical) would be two bicycle chains with a j shaped weighted section on two spindles oppositely opposing each other in a reflection at the top of the j to prevent rotation. If both were synchronized and the weighted section was pulled up on the bottom j chain and down on the top, I am sure that the center of mass would move without any reaction in the opposing direction. I will of course try my experiment unless you can convince me I am wasting time and money, but (as with EM drive) a space based test would be the only convincing evidence.

It is not as if I haven't broken fundamental laws of physics before-I have already built and tested in (lucrative) real world applications a Quantum Superluminal Communication Device which violates causality by transmitting USEFUL binary data from the future to the past. But I am not putting the plans for that here because I intend to rule the world using it! —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 15:34, 9 November 2008 (UTC)

I think you'll find that you can move the center of mass around, but the balloons won't actually move anywhere. And rotating the balloons around is cheating- it requires energy from outside the system 71.176.166.28 (talk) 17:31, 9 November 2008 (UTC)

No, the hole implies a pressure imbalance, which implies a net force, and is what causes water to flow from one side to the other. Dragons flight (talk) 23:06, 9 November 2008 (UTC)

An electric motor with or without a gyro will spin the system. Without a gyro it will move in the opposite direction, but as long as its mass is similar to the reactionless chain assembly it WILL easily rotate the centre of mass.

The change in PRESSURE causing a reaction to spoil this system IS a more serious objection. But this applies to the balloon experiment. What about the chain based experiment in the image above? It also has four linked units to counteract all rotational forces. I will build this unless you can find a flaw.—Preceding unsigned comment added by Trevor Loughlin (talk • contribs)

Regarding the balloon drive, I think the fly in the ointment is the need to "Rotate the deflated balloon around 180 degrees". Is this rotating one balloon or rotating the entire system around the centre of mass? CBHA (talk) 06:12, 10 November 2008 (UTC)

The whole system is rotated by a motor, which will rotate in the opposite direction at the same speed if it is the same weight, but an alternative might be to have two separate motors on each balloon and alternately switch them on when each balloon inflates. The balloons would have to be connected by a U shaped solid tube or they WOULD impart a reaction and spoil the plan, because the balloon would push against the tube as it expanded outwards pushing the whole system backwards. But with a U shaped tube the expanding balloon would push DOWNWARDS forcing the system to ROTATE UPWARDS (not the required sideways movement from the top motor needed when the appropriate balloon has expanded. This problem is eliminated by pairing an opposing (upside down U) reactionless drive as a mirror image,so that each rotation cancels out, as with the chain drive version's. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 13:50, 10 November 2008 (UTC)

This is an easy one: The center of gravity (strictly, the center of mass) of the system composed of the two balloons, the water and the pipe would not move as you squeezed the balloon. So the whole machine would move as you squeezed - but then stop when you stopped squeezing. When you release the balloon and the water sloshes back again, the center of gravity still doesn't move - although the machine moves back the other way - and you're back exactly where you were. Rotating the system about it's center of gravity leaves that center of gravity in the exact same place - so there is no net motion and this doesn't buy you anything. To rotate it other than around the center of gravity requires reaction mass...so the only way to propel yourself forwards is to expel reaction mass...pretty much as you'd expect. SteveBaker (talk) 14:56, 10 November 2008 (UTC)

Rotating around a point other than the center of gravity could be accomplished by attaching two such devices at a common rotation point, and have them rotate in opposing directions. Of course, the center of mass would still not be changing position.

The problem of a reactionless drive has existed for ages. It's a staple of science fiction. The Dean drive is the most infamous example of a "real" reactionless drive. ~Amatulić (talk) 22:24, 10 November 2008 (UTC)

AHA-but if the balloons are connected by a U-SHAPED TUBE then this "sloshing back" will create a ROTATIONAL rather than a LINEAR reaction. This "rotational reaction" could be CANCELED OUT by a second version of the U+balloons linked in a mirror image, since the two rotations would be in opposing directions. (I am not talking about the desirable sideways rotation of the whole system created by the motor to spin the smaller balloon about the bigger one, but an undesirable top to bottom spin of the single U which force the centre of mass back to where it started.) —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 02:30, 11 November 2008 (UTC)

Look - you can make this as complicated as you like - it's NEVER going to work. The whole "every action has an equal and opposite reaction" thing means that you're screwed no matter how complicated you make it. The best you can hope for is to exhaust our patience in breaking down these increasingly bizarre (and useless) contraptions to find the 100% inevitable flaw in them. That doesn't mean that you succeeded in inventing a reactionless drive - it just means that you became boring and we gave up trying to explain one of the most fundamental laws of physics to you. Feel free to consider that this may already have happened. SteveBaker (talk) 04:02, 11 November 2008 (UTC)

I am fully aware of the implictions of Newtons third law of motion, and am skeptical of reactionless drives, otherwise I would have built and patented this design rather than put it in the public domain. However, rather than dismissing it out of hand, look at the diagrams and tell me how it will not work in detail-for example where do the forces NOT counteract, leading to the system moving back to where it started? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 05:14, 11 November 2008 (UTC)

Why bother though? Either Newton's laws work and the exercise is meaningless. Or (and this is important) Newton's laws don't work, and the whole thing is even more meaningless, because then we would literally have no way of predicting what your device (or any other device) will do in any untried situation.

If you have outside, physical evidence that Newton might be wrong about something, then that's a whole different story. But this question is simply asking us to use Newton's laws to prove Newton's laws. It's just an exercise in futility. APL (talk) 05:46, 11 November 2008 (UTC)

I agree with SteveBaker. My interest ran out when you suggested a U-shaped tube instead of a straight one, thereby changing the entire configuration.

But if you think the chain drive mechanism has potential, please do not be discouraged by negative comments here. A lot of good ideas have been subjected to negative comments. Go ahead and build one. If it works, I expect NASA or some other space agency will be interested to see the results. CBHA (talk) 05:59, 11 November 2008 (UTC)

I will. If it is going to pass the "swing" test it will need several blocks in series of the four unit drives illustrated so that there is always some momentum, like a four stroke engine (assuming it works) and if it can constantly pull a swing at an angle this might work. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 14:21, 11 November 2008 (UTC)

Come on guys, this one is easy. SteveBaker had the answer already. Let's assume frictionless pipes and zero viscosity water just for fun. Look at the first diagram, top left at the top of the section. When you compress the right balloon, it exerts a force against the balloon in every direction, all of which cancel out - except the upward/downward direction, since the water is free to flow down the pipe. It reaches the end of the "down" section and exerts a force downward on the down side of the horizontal pipe section, cancelling out the until-now-uncancelled up force it exerted on the top of the balloon during compression (thus this balloon will move slightly up, keeping the centre of mass fixed as the water travels down). Since it is stuck in the rightmost elbow joint and has stopped going down, it exerts forces on that joint in all the lateral directions too. These all cancel out except for the left/right forces, as the water flows to the left along the pipe. Eventually it reaches the end of the horizontal bit of pipe and exerts a force on the left wall of the pipe, finally cancelling the force it exerted to the right (so the pipe will move slightly right, keeping the centre of mass fixed as the water travels left). More forces in every direction, but the water can flow up into the left balloon. There's a delay between the force on the down side of the left end of the pipe and the force on the top of the left balloon, so this balloon will move slightly downward, keepign the centre of mass fixed at all times. So as you do this you will set the device rotating (in rotation that will be cancelled once you stop pumping water through as the forces cease in reverse order), but its centre of mass remains fixed at all times. Finding the inevitable flaws in "free energy" machines like this is a mildly entertaining but ultimately pointless endeavour. Maelin (Talk | Contribs) 14:41, 11 November 2008 (UTC)

Indeed.

I could come here and describe a Heath Robinson (Rube Goldberg for you Americans) contraption with hundreds of swinging, spinning, spring loaded parts with hydraulic and pneumatic connections using exotic mixtures of non-Newtonian fluids, clockwork parts, gyroscopes, magnets, complicated chemical and biochemical reactions, active electrical parts and photonic circuits, with complex computer software driving them using neural networks and evolutionary algorithms - being driven by a trained parrot...and then ask the people at the science desk to tell me why it doesn't work as a reactionless drive. The result is likely to be exceedingly difficult to analyse at a detailed level - it would result in days of complicated discussions and arrive at the same conclusion. You can't expect us to do that. It's utterly unreasonable - BUT it's also utterly unnecessary.

To analyse your machine (or mine), we simply place an imaginary black box around whatever bizarre contraption we are presented with and boldly assert (per Newton's first law of motion) that the center of gravity of "the system" (the black box) doesn't move no matter what happens inside because "the system" is in a state of motion that it will continue in unless some external force is applied to it.

In the case of a rocket engine - the exhaust from the engine remains inside the box - so the center of gravity of the rocket and all of it's exhaust gasses doesn't move. In the case of a light-sail, the light source, the craft and all of the photons are inside the box - and the box doesn't move. So for the craft to move bodily one way - something else has to go off in the opposite direction to keep the center of gravity of "the system" where it is. Hence there are no "reactionless" drives - per Newton's first law.

If you want to assert that this is not the case then you are explicitly denying Newton's laws - and we're going to laugh at you. If Newtons' laws are somehow incorrect at "human scales" of speed, mass, distance and time - then we're in a much weirder universe than we believe. It's utterly inconceivable that any device you could think up like this could break those laws without doing something relativistic or quantum-level or close to a black hole or in some other way radically 'pushing the envelope' of the realms of experimentation we've done as a civilisation for the past 300 years. Mundane stuff like pipes and liquids and spinning things are just too well tested for the laws to be incorrect at those scales.

The whole beauty of these kinds of fundamental law is that they allow simplification. We don't NEED to calculate the energy in each part of the system, analyse the torque and the tensors and the inertia and all of that stuff. We know for an absolute certainty that if we went to all of that trouble - the answer would be "NO!". We have a simple law of nature that's always proven correct that says that we can shortcut all of that analysis and treat the system as a black box. It's the same deal with perpetual motion machines - the laws of thermodynamics say "NO!". So there you go: "NO!" - and the explanation is very simple indeed. SteveBaker (talk) 15:05, 11 November 2008 (UTC)

I admit that this idea is so simple that it is highly probable that someone must have tested it at some time and failed, though I have made a search. It will not be my highest priority to build! So what do you think the chances of an idea that really does "push the envelope" such as EM drive, has of actually moving a craft in a straight line in space without rockets?

Certainly the device IN THE FIRST DIAGRAM will ROTATE about its centre of mass and not move anywhere when transfering the fluid. Worse still, without any air resistance or gravity it would end up on its SIDE by the time all the fluid is transfered, so instead of the motor being able to swing the small balloon around the big one, and then reverse the process, the motion is now upwards instead of sideways, and another cycle will put the device the wrong way round. But what about the second diagram, when two mirror image units counter each others rotation in the Z-axis? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 02:54, 12 November 2008 (UTC)

It's not necessary that someone tested something just like this. You're missing the "big message" here. Newton's first law says that if we draw a line around some kind of 'system' (your machine in this case) then unless some external force operates on it - it's just gonna sit there with it's center of gravity not moving by so much as the diameter of an atom no matter what weird-assed motion it's going through internally.

We've tested all of the parts of standard machines and we know how such things behave. So:

• The chances of a reactionless drive working with 'ordinary stuff' such as you describe is zero - not gonna happen.
• The chances of making a reactionless drive that uses some aspect of relativity or quantum theory (or preferably, both) seem exceedingly slim - the science is pretty well known.
• If I'm pushed into imagining some kind of experiment (likely, just a thought experiement) where there might be some doubt as to whether Newton's law might break unexpectedly - then I guess it's remotely possible that some insanely 'extreme' design that has the mass of three galaxies - or which was just over a 'planck length' long or only works when cooled within a billionth of a degree above absolute zero - or which would have worked within a picosecond of the big bang but cannot work at any time since - or which only works in 17-dimensional space....something like that might maybe expose a new aspect of the laws of motion that could perhaps require a small adjustment to Newton's first law that might just open a chink of hope for a ridiculously impractical reactionless drive.

But I really don't imagine any such thing could ever be remotely practical - simply because everything within the realms of "possible" have been so well researched.

SteveBaker (talk) 05:10, 12 November 2008 (UTC)

One other idea. Supposing you had two spindles with a heavy chain inside a rectangular box, and a motor at each end wound/unwound the chain from one spindle to the other. The box would rotate about its center of gravity due to the spin of the motor at each end. But if we have TWO of these boxes back to back what would happen? Would the box move linearly backwards as the in the opposite direction to the winding of the chain instead of spinning? If it did not, then mass would have been transered without reaction,so it probably would, but I am not sure what would happen. It certainly WOULD move backwards if the chain was pulled in without being still wound on the other spindle. But as long as the chain is attached to the two spindles, it can't move backwards(?), otherwise with large enough spindle and rope the device would move further than its length in any case,violating Newtons third law in any case(?)

LISTEN TO ME. NO! It's Newtons' first phreaking law. You will NEVER come even close to breaking it with any crazy contraption you can come up with. Give it up and go back to squaring the circle, performing a trisection with ruler and compass, making a perpetual motion machine, calculating the last prime number (and the last digit of PI)...those are all just as likely as you coming up with a reactionless drive. SteveBaker (talk) 01:18, 13 November 2008 (UTC)

Look. Whenever you have closed system consisting of one object exerting a force on another object and things moving each other around however you like, all the forces involved will end up balancing each other out perfectly, and the centre of mass of the whole system will continue with the exact same momentum as it had initially. If you have some complicated construction made of pipes and water and balloons and motors to spin bits around and pumps to move the water, no matter how you rig it up, if it's a closed system its centre of mass will stay exactly where it is the whole time. This is unavoidable.

Every time someone proposes a reactionless drive, or perpetual motion machine, or whatever else that will violate conservation of momentum (or conservation of energy, or entropy, or whatever), they have always taken a very basic machine and tacked on bits and altered it until it is sufficiently complicated that they can no longer understand how the forces will cancel each other out, then they say, "lo! a perpetual motion machine!". But it isn't. You can take one thing that isn't a reactionless drive, and staple it to another thing that isn't a reactionless drive, and guess what: you will still not have a reactionless drive. No matter where you move the water, the centre of mass stays the same. No matter how you rotate bits, the centre of mass stays the same. You can't escape conservation laws just by being complicated. Maelin (Talk | Contribs) 11:24, 13 November 2008 (UTC)

If the chain is continuous spiral winding/unwinding should not cause back reaction (I think) and the mirror image device in the same box will prevent rotation.

If the chain was not continuous it would be subject to Newtons third law and not work;

The statement above is about a reactionless drive finding a loophole in Newtons third law, not a perpetual motion machine breaking the first law of motion-that would be a tall order. This machine would use electric motors with either a solar panel or RTG battery as the power supply.

Human brain -> computing power

Hi,

One thing I've wondered is how much memory space does the human brain harbour, in terms of computing power (eg Gigabyte, terabyte, etc.). I'd be interested to know the answer to this! Thelb⁴ 13:07, 9 November 2008 (UTC)

The best answer on this Yahoo! answer is pretty good. —Cyclonenim (talk · contribs · email) 13:55, 9 November 2008 (UTC)

Thanks, that's very interesting! 81.151.36.130 (talk) 14:23, 9 November 2008 (UTC)

But we don't store information like a computer. That explanation vaguely hints at "compression" but I think this misrepresents what we are storing. When a computer stores a video file, it stores every single pixel of every single frame, and every single sample of every audio signal, at some fixed sampling rate (30 frames x 320x240 pixels)/sec, + (44100 audio samples per second). Then, effective compression locates redundancy in these stored data, and removes that redundancy (with some "loss" in the exact representations, sufficiently engineered to be minimally noticeable to a human).

But when a human "remembers" a movie, it doesn't do anything at all like that! If you were asked to recall Pixel (122,61) at Second # 4051 in your favorite movie (that you've watched a dozen times and memorized all the dialog for), you would not be able to do ANYTHING like recall that information. You wouldn't even be able to get a glossy "key-frame", or the blurred-pixel-square representation from Second #4050 at Pixel (128,64) which you would presume is probably close to the request. You might not even be able to remember the color of the main character's shirt. At the same time, if a clever psychology-experimenter made you watch the same movie twice, with the only changed-detail being a different shirt-color on a minor character, there's a significant chance that you would have noticed that detail. How did your brain selectively notice something which you might not be able to recall if directly questioned? Clearly information-storage is selective and complex.

It's really hard to estimate the capacity for human brain's information storage system when we know so little about how it actually works, so I would be very reluctant to assign any numeric estimate of capacity - you're comparing serial, precise machine storage to a mash-up of biological/analog distributed fuzzy storage, where the concept of "one bit" probably does not apply. Nimur (talk) 17:23, 9 November 2008 (UTC)

It doesn't really make sense to discuss the information stored in the brain in terms of bits and bytes, so estimates of storage capacity in terms comparable to those of a computer are pretty misleading. But, your question can be answered, and the answer is surprising: the human capacity to store factual memory appears to be near limitless. A Russian neurologist named Dr. Luria studied a man named Solomon Shereshevskii who apparently had limitless memory. Since then it was taken for granted that the Luria case was an extreme outlier, but in 2006 researchers at UCI discovered first one, then almost immediately afterwards 2 more people with seeming unlimited memory, a condition they termed Hyperthymesia. The speed with which new cases were discovered suggests that this capacity may actually be somewhat common, but like synesthesia, affected individuals may take for granted that they are no different from the rest of the population. --Shaggorama (talk) 22:59, 9 November 2008 (UTC)

I don't believe in this limitless-capacity idea. A poem, even an epic poem, doesn't take much RAM to store. Moby Dick is only about 10⁶ characters long, and state-of-the-art compression algorithms can get it down to 100-200 kilobytes. The pi-memorization world record seems to be 67890 digits, which is only 28190 bytes (10⁶⁷⁸⁹⁰ ≈ 256²⁸¹⁹⁰). That's the record among everyone who's ever participated in these contents; I have a hard time believing that Luria's mnemonist would have done better.

There's a famous paper by Thomas K. Landauer, How Much Do People Remember? Some Estimates of the Quantity of Learned Information in Long-term Memory (Cognitive Science 10, 477–493 (1986), online here), which estimates the total memory capacity at about 10⁹ bits. There's no consensus that he's right, but at least his measurements are based on actual empirical tests of what people remember. The neuron-counting numbers are an attempt (though not a very principled one) to estimate something else, namely the number of bits necessary to describe "the current structure of the brain". But even in an analog computer the number of states is astronomically larger than the number of computational states. The raw physical states don't behave predictably enough for reliable computation. -- BenRG (talk) 13:36, 10 November 2008 (UTC)

Obviously, it's not limitless - but the idea that memory can become fuzzier and less detailed as the memory becomes less and less important does allow it to SEEM limitless because we're able to recall the important details but merely have a broad-brush fuzziness about the less relevant parts. This does indeed suggest that some pretty sophisticated 'lossy compression' is going on - and it's happening on-the-fly. So a new memory pretty much has to displace some older information - but it's not like a computer where you delete an old file to make room for a new one...learning calculus doesn't make you forget your wedding day...what it does is to make you forget the color of your best man's shirt and whether you gave your bride an orchid or a rose. This is more like turning down the JPEG or MP3 'quality' dial on older files to make them take less space so that there is room for new files. SteveBaker (talk) 17:48, 10 November 2008 (UTC)

I mean, I don't really know what to tell you guys. Whether you 'believe' it or not, the cases I described exist. BenRG, the paper you cite is from 1986, which is a pretty old citation for neurology paper. The neuron counting attempts look nice and produce impressive numbers, but they assume an antiquated, folk-scientific principle known as the "Grandmother Neuron," a theory which states that individual objects of memory are stored in their own respective neurons. How memories are encoded is still very, very unclear, but current community consensus is leaning more towards distributed neural network implementation, an idea which makes it very difficult to give an estimate of bits and bytes. If the neural net theory is right, then the net is signficantly greater than the sum of its parts (i.e. can retain more information than the number of involved neurons may suggest). Furthermore, related ideas may be stored in mapped areas, further compressing data. When it comes down to it, the fact remains: the architecture of the brain does not resemble that of contemporary computers, either in hardware or software, so these bitwise comparisons are meaningless to begin with. Obviously the human capacity for memory is not actually limitless: physical constraints on the brain obviously must put a cap on the possible amount of data we can store. But, since we just don't know how the data is stored, there's no good reason to just assume that the memory capacity of the brain necessarily must be exceeded in a human lifetime. Although they are outliers, the 4 cases I described (in particular the latter 3) strongly support this. As far as steveabakers "lossy compression" goes, current theory seems to suggest that its more likely lossy retrieval: memories are stored intact, but are cached in a way that permits for more rapid access of the most pertinent information (and consequently, normal people lose access to alot of the details). If it was just lossy compression, repressed memories wouldn't be so problematic for traumatized individuals: the bad parts just would have been erased/stored poorly. Instead, it seems that the bad parts just often aren't accessed consciously. --Shaggorama (talk) 16:29, 11 November 2008 (UTC)

Bell inequality

I get the idea behind it and I get the experiment and scoring. But I don't really understand the actual implications of the Bell inequality being violated. This is sort of how I understand it.. is one of these correct, or am I totally off? The article is tough!

1. After observing a particle's spin, you can guess its entangled partner's spin (even measuring orthogonally to the first measurement) with better-than-random success by guessing the same as the first particle's spin.
2. After observing a particle's spin, you can guess its entangled partner's spin (even measuring orthogonally to the first measurement) with better-than-random success by guessing the opposite of the first particle's spin.

71.176.166.28 (talk) 14:38, 9 November 2008 (UTC)

Mmm... you've kind of got the implications wrong. If we lived in a world without Bell inequality, you'd have 100% chance of guessing the spins. Then, as Einstein wanted it to be (see EPR paradox), quantum mechanics would allow you to have "complete" knowledge of a given particle despite the Uncertainty Principle, which would mean that Uncertainty Principle was based primarily on issues regarding observation. But lo! Because of Bell inequality you can't just guess the spin—you will be wrong a significant part of the time, and your knowledge of the universe is incomplete, per Uncertainty Principle, and thus Einstein was wrong. Does that clarify things a bit? It actually resolves a fundamental question about QM and the Uncertainty Principle, one that most people thought could never really be resolved (most thought that one's take on whether particles contained all information—but that some of it was just hidden due to UP—was a matter of epistemological opinion, and couldn't be actually tested). --98.217.8.46 (talk) 15:03, 9 November 2008 (UTC)

No, the original poster has it the right way around—the nonclassical correlations in quantum mechanics are stronger than classical correlations at somealmost all angles, meaning that you have a better chance of guessing the spin. E.g. if the two spin measurements are separated by 60° then given the outcome of one you can predict the outcome of the other with 3/4 accuracy in quantum mechanics, while you can't do better than 2/3 in any local classical theory. (That's the specific case used in the gambling-game example I linked below.) Newtonian physics is deterministic, but Bell's theorem applies to any theory that follows the rules of classical probability, even theories that have true randomness or theories in which measurement has an unavoidable effect on the thing being measured. -- BenRG (talk) 17:34, 9 November 2008 (UTC)

Same vs. opposite doesn't matter—it's just a question of how you set up the spins. If you started with the state |↑↑〉 + |↓↓〉 then they'll be the same, if you started with the state |↑↓〉 + |↓↑〉 then they'll be opposite. In practice the easiest way to get a Bell state is from the decay of a spin-0 system, which (by conservation of angular momentum) has to lead to antialigned spins. That's why you'll more commonly hear "opposite" in descriptions. But there's no deep difference—you can turn one into the other by rotating one of the particles 180 degrees, or by simply redefining your coordinate axes. In the remainder of this reply I'll assume equal (not opposite) spins.

I'm not completely sure what you mean by "orthogonal" since orthogonality of wave functions is different from orthogonality in space. (For example the spin states |↑〉 and |↓〉 are orthogonal as wave functions but parallel in space.) But if the spin measurements of the two particles are made at angles differing by 90° in space, then your same-spin guess will be right 50% of the time, i.e. it's no better than flipping a coin. If the measurements are made in the same direction (0°) then you will be right 100% of the time. If the measurements are made in opposite directions (180°) then you will be right 0% of the time. So far there's nothing very surprising here. But quantum mechanics says that, in general, if the separation angle is θ then you will be right cos² (θ/2) · 100% of the time, whereas there's an argument from fairly general classical assumptions that you can't be right more than (1 - θ/180°) · 100% of the time for those other angles, no matter what internal algorithm the two particles are using to decide the outcome of the measurement. (edit to add: sorry, silly mistake here. Obviously if the measurements are separated by more than 90% you can guess the opposite of what you saw and be right more often than that. The formulas should be max(cos² (θ/2), 1 − cos² (θ/2)) and max(1 − θ/180°, θ/180°) (for 0 ≤ θ ≤ 180°). The quantum formula is at least as large as the classical maximum for every θ and it's strictly larger except when θ is a multiple of 90°.)

But I wouldn't worry about it. There are lots of ways of showing that quantum mechanics is nonclassical, and Bell's is not especially clear. He proved too much—it's not necessary to get a result valid for any angle, you just have to show one example of quantum mechanics violating classical assumptions. I like this gambling-game version (which isn't original to me, though that explanation is mine).

All of the above assumes spin ½ particles (like electrons). If you're using spin 1 particles (like photons) then you should divide all of the above angles by two, and your Bell state will look more like |↕↕〉 + |↔↔〉 (or |↕↔〉 + |↔↕〉). -- BenRG (talk) 17:08, 9 November 2008 (UTC)

So the .707 figure means that if you guess "same" for the second particle you'll be correct 71% of the time, instead of the 50% that is the non-QM answer? I guess that makes sense, especially in light of your point about same vs opposite just being a matter of how you set up your axes 71.176.166.28 (talk) 17:41, 9 November 2008 (UTC)

(see my edit above) The probability depends on the angle between the measurements, and I don't think there's any simple angle for which it equals .707 (i.e. there's no simple θ for which cos² (θ/2) = √2/2). The non-QM maximum is 50% at an angle of 90°, and the QM prediction at that angle is also 50%. You need to use some other angle to get a difference. Note that the QM formula is a prediction of quantum mechanics, while the classical formula is not a prediction, it's a maximum over all possible physical theories that satisfy certain assumptions. -- BenRG (talk) 11:33, 10 November 2008 (UTC)

That link is great. So it's saying that if each player had a sheet of paper that says something like:

• If the number you're given is a 1, say YES
• If the number you're given is a 2, say NO
• If the number you're given is a 3, say YES

then they make on average (1 & 2 is +1) + (1 & 3 is -2) + (2 and 3 is +1) = ZERO. But they can actually make more money using entangled particles than with a predetermined answer key? That's amazing! thanks a ton 71.176.166.28 (talk) 18:36, 9 November 2008 (UTC)

Yes, but moreover I'm arguing that they didn't have any better option than to use a crib sheet like that, i.e. it's not just the best crib-sheet-based strategy but also the best strategy of any kind (subject to certain assumptions about the way the world works). -- BenRG (talk) 11:33, 10 November 2008 (UTC)

Is the space shuttle capable of breaking Earth's orbit?

Assuming that they wanted to, is NASA's space shuttle physically capable of breaking out of Earth's orbit? 67.184.14.87 (talk) 15:15, 9 November 2008 (UTC)

I've just done some research into that and I think the answer is "no". The main engines can get the shuttle into Low Earth orbit, they would then need about 3.2km/s of delta-v (according to that article) to reach an escape orbit. As far as I can tell, the only engine they could use for that is the Orbital Maneuvering System, which only carries enough fuel for 0.3km/s of delta-v, far short of what they would need. They also have Reaction control system engines, but I can't find the maximum delta-v for those, I very much doubt it's enough to make up the extra 2.9km/s they would need, though. --Tango (talk) 16:20, 9 November 2008 (UTC)

The main cargo bay should have ample capacity (volume and mass) to store enough extra fuel for escape. As far as I know nobody ever bothered to design a tank to be fit in the cargo bay, and it might also be a major problem to get the fuel from there to the main engines. —Preceding unsigned comment added by 84.187.126.130 (talk) 16:45, 9 November 2008 (UTC)

That's assuming the engines can handle a significantly longer burn. Even if they can, you're talking about a massive retrofit. --Tango (talk) 17:09, 9 November 2008 (UTC)

Maybe things like low energy transfers, Interplanetary Transport Network and gravity assist could eventually reach the needed speed. It would be too slow to be suited for a manned mission. PrimeHunter (talk) 17:00, 9 November 2008 (UTC)

There are dozens of other considerations, such as whether the radios and communications equipment has sufficient range to operate in other orbits; whether the life support systems can sustain longer voyages; if the crew compartment is sufficiently protected from radiation in higher orbits; whether it would be safe or structurally feasible to store fuel in the cargo bay; in short, the space shuttle was designed for its current orbit. With significant modifications, it could probably be retrofitted to do a lot of different things, but a sufficiently re-engineered vehicle would no longer be the space shuttle as we know it. Nimur (talk) 17:03, 9 November 2008 (UTC)

I don't think any of those things would help with getting from LEO to an escape orbit. Low energy transfers, etc, would require reaching a Lagrangian point, I think, which are all far above LEO. A gravity assist isn't going to help, that requires you to pass near a massive object that is in orbit around the object you're orbiting (usually the Sun), the only relevant massive object when you're in LEO is the Earth itself, and you can't get a gravity assist from the object you're orbiting (the moon does, in a sense, via tidal interactions, but it is many orders of magnitude bigger than a space shuttle and even it only gains altitude at a rate of centimetres a century). --Tango (talk) 17:09, 9 November 2008 (UTC)

In space aerodynamics are irrelevant, so they could add on whatever structure and supplies were needed for an extended mission. The extra food, fuel, life support assets, and even extra solid fuel rockets could be taken up in one mission and used in another. I do not think the low earth orbits of the shuttle are significantly less exposed to radiation than places farther from earth. The big problem I see is that the shuttle is designed to be strong enough and aerodynamic enough for reentry,with wings, control surfaces, parachutes, and landing gear, and that makes it more massive than a craft would have to be whose only goal was to get beyond earth orbit with a human crew. Or did someone say the craft should land on another planet, orbit another planet, or return the crew to earth? The devil is in the details of the mission requirements. If you want to send a shuttle out of earth orbit, it is certainly possible with today's technology, as long as you do not expect it to land a crew somewhere and come back. Edison (talk) 21:54, 9 November 2008 (UTC)

Surely when Apollo 11 orbited the moon it could have performed a gravitational slingshot out into space. It would only have taken a small tweak. It's not exactly the space shuttle, but it is ancient technology. Plasticup ^T/C 15:56, 10 November 2008 (UTC)

In fact, the maximum Δv capability of the Saturn V would have caused the Apollo capsules to approach the Moon much faster than they actually did, reducing the trip from three days to one day. The slight problem with that is that the capsules would have been on a hyperbolic lunar orbit, and wouldn't have been able to reduce their speed enough to enter a stable elliptical orbit, so they would have zipped past it.

Going back to the original question, the Shuttle doesn't have enough fuel to get out of Earth orbit right now, but it could have if an extra fuel tank were added inside the orbiter (with the tradeoff of a significant safety risk, orbiter redesign, and a drastically reduced payload capacity), and/or larger SRBs were used. The SSME's should handle it, as they are [supposedly] designed for multiple uses. Titoxd^{(?!? - cool stuff)} 19:12, 10 November 2008 (UTC)

Apollo 11 was launched with much a much bigger rocket than Space Shuttles are. Making bigger rockets isn't that difficult, it's just more expensive. --Tango (talk) 21:49, 10 November 2008 (UTC)

Even with a cargo bay full of fuel - there could still be significant problems: The cargo bay doors MUST open because without them the orbiter doesn't have enough electricity to keep going for more than a few orbits - and it doesn't cool properly without them opened to increase the surface area of the orbiter. I very much doubt they are strong enough to stay open while doing a burn to a higher orbit...so maybe this is still impossible...I'm not sure. Certainly there would be MANY other obstacles...not least, on reentry, the orbiter would be going much faster than it's designed to come in at...so right there is a big problem. Certainly many of the onboard computer systems would have to be reprogrammed (a not inconsiderable task because every flight-critical software function was written independently by several different teams of programmers and the results compared so that software bugs may be eliminated (mostly!). It's not a simple matter. But the shuttle is already being phased out - this could never happen. SteveBaker (talk) 21:56, 10 November 2008 (UTC)

Please source the bit about the bay doors having to be open for electric generation. Solar cells? radiators from fuel cells? The rockets to boost out of earth orbit need not be as powerful as the ones to lift off from Cape Kennedy, so they can be sized to as low a force as the structure can withstand. 1 G of acceleration is certainly within the structural capabilities of every part of the shuttle, since it endures it on earth, and it would allow an amazing velocity over a little time. Reentry? Where? The question was LEAVING earth, not landing safely back at earth or on Mars or elsewhere. The biggest problem, as I stated, is all the extra mass the reentry equipment represents. A craft to leave earth orbit and go BEYOND need not be aerodynamic at all, and need not have wings, landing gear, parachutes, etc, unless a landing stage for Mars or somewhere is desired, and that does not need to be the whole interplanetary craft. Add enough booster rockets, or enough fuel for the present shuttle, and we could get the thing out of earth orbit with today's technology. The program modifications are relatively trivial. Edison (talk) 03:23, 11 November 2008 (UTC)

Inside the cargo bay.

You shouldn't really need a source for that - just take a look at any photo of the shuttle in orbit and note that the inside of the shuttle bay doors are completely covered with thermal radiators and solar cell panels. Those have to be on the inside because they'd never survive launch and reentry if they were on the outside. Here is a (google cache) explanation of how those radiators matter so much in orbit: [2].

I guess, technically, the OP's question doesn't require the successful return of the craft - but in practical terms, it's bloody stupid to send a reusable spaceplane on a one-way trip. It's not unreasonable to assume that the OP was really talking about a return capability - and for that the re-entry issues are surely significant (and, I believe, insurmountable). SteveBaker (talk) 03:50, 11 November 2008 (UTC)

So we get rid of the wings, the landing gear, parachutes, possibly add a landing craft, add whole new rockets and fuel tanks, etc. In what way is this still the Space Shuttle? You've just constructed a whole new interplanetary craft, and yes, we know we have the technology to get to Mars, we've sent numerous probes there. The only difficult bit is life support (and man rating everything), we've done everything else. --Tango (talk) 11:37, 11 November 2008 (UTC)

Yes - exactly. You wouldn't be able to take people to Mars in the shuttle anyway - there isn't remotely the space or facilities you need to allow people to exercise - or to generate spin gravity - and for sure you couldn't carry enough oxygen, food, water, recycling gear, etc. (Particularly because you filled the entire cargo bay with fuel tank already!)...you'd also find so many other little subsystems that you'd have to replace: Are the radios powerful enough to reach earth from that distance? Does the inflight software cope with radio transmission delays greater than a second when communicating with earth-based systems without 'timing-out' and giving up? Can the antenna be pointed with enough precision to aim at a more distant earth?...and that's considering just one of dozens of critical subsystems. SteveBaker (talk) 14:33, 11 November 2008 (UTC)

If the point was simply to leave orbit for the sake of doing it, perhaps a large solar sail could be used. It probably wouldn't require major structural changes to the shuttle. Given enough time, and a large enough solar sail that can be furled and unfurled strategically you could get pretty far away. The shuttle could carry an enormous sail in it's cargo bay and still have room for extra oxygen and water supplies. The longer time frame of the mission could (in part) be offset by a smaller crew.

The problem with this idea, of course, is that there's no good design for a solar sail of that size yet. The obvious designs don't hold up in computer simulations. APL (talk) 16:18, 11 November 2008 (UTC)

There's another potential problem - there is still a significant amount of atmosphere in LEO, atmospheric drag from the sail would probably be greater than the light pressure. You could try having it only open when it would be angled in line with the direction of travel, but I think the best time to have it open is when the light would push the shuttle forwards, rather than up (see the discussion somewhere above about the opposite case of pushing backwards being a better way to de-orbit that pushing down), so it would be extremely inefficient. If it worked at all, it would probably take months to get up to escape velocity, far longer than even a small crew could survive on even a modified shuttle (you could probably do it with major modifications, but then you're back into the realms of it not really be a space shuttle any more). --Tango (talk) 16:33, 11 November 2008 (UTC)

I think that we have established that the answer to the bare question is "Yes, the shuttle could be rocketed out of earth orbit." Other answers are "No, it could not do it as presently configured and equipped, due to a lack of fuel. And the crew could not survive indefinitely, although the habitability could be extended considerably by carrying extra food etc. And since it is built with much of its mass devoted to reentry into the earth's atmosphere, it would be silly to use the energy required to send all that useless mass out of earth orbit." Many of the objections could be answered by a little creative engineering. Do you recall that a Saturn stage was adapted to be a Skylab, and that was a far greater re-purposing than just accelerating the shuttle with sufficient thrust for sufficient time to increase its velocity to that needed for escape. The shuttle has been called the most complicated machine made by humans, and maybe the idea would be just to push it out into the solar system on its own as a monument. The radios aren't powerful enough? Give me a break. More powerful transmitters and more sensitive receivers are not very high technology, and 1970's technology allows communication with probes at the edge of the solar system. The radiators inside the doors must be exposed to space? Then open the doors. There is no wind resistance. The real problem is the lack of a mission or purpose or goal in the project. How much would the target mass be for a manned mission to Mars, compared to the shuttle? Wikipedia articles on space exploration are very short of such numbers. Space shuttle says the mass of the craft is 2,029 metric tons, apparently including the external fuel tanks, loaded, and the solid fuel rockets. The space shuttle orbiter(Endeavor) had an empty weight of 68.6 metric tons, per Space Shuttle orbiter. The proposed Russian Martian Piloted Complex of 1975 would have a mass of 1630 metric tons, apparently the mass when it was assembled in low earth orbit before blasting off for Mars. Edison (talk) 17:06, 11 November 2008 (UTC)

Yes, Skylab was partially adapted from a Saturn V but no-one would describe it as one. You could certainly use the Space Shuttle as a starting point to design and build an interplanetary craft (it probably wouldn't be very wise, though), but it wouldn't be a Space Shuttle afterwards, they would share very little in common. Adapting the Space Shuttle would be far harder than you make out. The crew surviving longer than the week or two Shuttle missions are designed to last would require far more than just carrying extra consumables. You need to consider radiation shielding, room for exercise, room so they don't go stir crazy cramped together in a tiny Shuttle for months, etc. You basically have one cargo bay to work with, it can probably be used to solve each of the problems, but not all of them together. It can't serve as a fuel tank, an extra engine, more pressurised space for the crew and storage for additional consumables all at the same time. Your only option would be to attach more things to the outside which means launching them separately, which means you're even further away from it actually being a Space Shuttle, it would be a larger craft which happens to contain a modified Space Shuttle as one component. --Tango (talk) 17:42, 11 November 2008 (UTC)

I'm reminded of the (terrible) film "Deep Impact". In that film the passenger compartment of the space ship looked like a hastily retrofitted space shuttle, essentially just bolted onto a set of much larger engines (in orbit, apparently.) The design of that ship was my favorite part of that film. APL (talk) 17:57, 11 November 2008 (UTC)

i would so no, a priori, because 1) if it were, they would have done it at some point and 2) conversely, if it were capable of doing that, it would be heavier than if it weren't, and adding excess unneeded weight onto the space shuttle so it could do things it never actually does, and thereby requiring all the extra fuel to hoist the extra mass up into orbit, is a big nono. Gzuckier (talk) 20:12, 11 November 2008 (UTC)

Total ship water displacement

Dear Wikipedians, what might be an educated guess towards how much water the world's shipping displaces? And, I seek to know, how much has the ocean risen from this displacement? Curiously and humourously yours, 80.202.246.253 (talk) 16:55, 9 November 2008 (UTC)

From Displacement (ship), "A floating ship always displaces an amount of water of the same mass as the ship." So, you are essentially asking for an estimate of the total tonnage of shipping (transport/cargo, military, recreational, etc). I would estimate that cargo ships make up the lion's share of worldwide tonnage, with other contributions probably being negligible. If I don't mention it first, Steve Baker will probably have to remind me that this is the Science Desk and not the Speculation Desk, so I would focus my efforts on locating actual reasonable estimates for international shipping before excluding any quantities. Nimur (talk) 17:07, 9 November 2008 (UTC)

Doing the calculation the other way around (working out how much shipping would be required to raise sea levels by a certain amount) is somewhat easier, so I'll do that. According to ocean, the oceans cover approximately 361 million square kilometers. If we ignore curvature (which I think we can for very small increases in sea levels) and assume all coastlines are vertical cliffs (again, reasonable for small increases), we find that a 1mm increase in sea levels would increase the volume by 361 billion metres cubed, corresponding to a mass (ignoring salinity) of 361 trillion kilograms. I'm struggling to find numbers for the mass of container ships, but it seems the biggest has a deadweight tonnage of 300,000, that's not a measure of displacement, but I reckon it gives us a rough order of magnitude at least, so let's say a container ship weights 1 million tonnes, or 1 billion kg. That means we would need 361,000 of the biggest container ships to raise see levels by 1mm. I can't find estimates of how many ships there are, but even with the most generous estimates I can't see the sea level rise caused by all the shipping we have being more than a few millimetres. --Tango (talk) 17:34, 9 November 2008 (UTC)

This says that in 2005, the total deadweight tonnage of the world's bulk cargo ships was 960 million tons - and that, fully laden, that goes up to 7100 million tons...which is 6x10¹²kg - or 6 billion cubic meters of water (OK - that's pure water, not salt) - which falls well short of the 360 billion that Tango estimates we need for a 1mm raise. So roughly 1/60th of a millimeter - which gets us to (as the popular press would be SURE to say) "about the thickness of a human hair". But since global warming has been raising the sea level by about 1.8mm per year for the last century (surely much faster that over the past few years)...I don't think we have to be too concerned about the displacement of our shipping fleet! SteveBaker (talk) 18:29, 9 November 2008 (UTC)

Here is our discussion of this topic from June. — Lomn 15:37, 10 November 2008 (UTC)

Input resistance of nerve fibres

Why is the input resistance of nerve fibres (accroding to cable theory): rinput = 0.5*sqrt(rm*ri) where rm is the membrane resistance and ri is the internal resistance ? 131.111.8.104 (talk) 17:57, 9 November 2008 (UTC)

Nerve fibers conduct nerve impulses electrochemically, not by electrical conduction like a wire or coax cable. The question makes an unwarranted assumption. Edison (talk) 21:44, 9 November 2008 (UTC)

low-cholesterol heart attacks

I was reading this, which starts

“ People with low cholesterol and no big risk for heart disease dramatically lowered their chances of dying or having a heart attack if they took the cholesterol pill Crestor, a large study found. ”

But goes on to say

“ [the drug] gave clear benefit in the study, but so few heart attacks and deaths occurred among these low-risk people that treating everyone like them in the United States could cost up to $9 billion a year — "a difficult sell," one expert said. ”

I don't get it: the group is already low-risk. Wouldn't they prefer to receive even $1 billion as life insurance payoff to the families of the dead among them than to force the whole group to both take an unneeded pill and pay out $9 billion for the privilege? Or is my logic off... 82.124.214.224

Hi, 82.124.214.224, please sign to avoid confusion. Julia Rossi (talk) 22:36, 9 November 2008 (UTC)

Well, I would prefer to live than give my surviving relatives a million Euro each, but that's just me (a selfish fecking bastard :-) ). But other that that, you are correct. What the article says is that a study proved that there is a benefit. This is proved by many studies very often. But cost-benefit analysis comes in at this point. There are numerous things that we could do to save a few extra lives each year, but the costs are just too high, and the money better spent elsewhere. This appears to be one of those cases. Fribbler (talk) 00:11, 10 November 2008 (UTC)

To the OP; that's the idea. Drug companies are looking for a way to make money off of people that don't need to take their drugs by convincing them that if they don't, they will DIE. Turns out that most statin drugs, while they lower cholesterol, don't actually increase your lifespan, life quality, or otherwise prevent heart attacks in any measurable way. It's the old "correlation is not causation" or post hoc ergo propter hoc problem. People with high cholesterol have more heart attacks; however, there is no mechanistic connection. Turns out, that you can lower cholesterol levels via these drugs and have no appreciable effect on heart attacks. It could very well be that high cholesterol levels are likely a symptom of the underlying health problems, and not the actual cause of them. However, methods that lower cholesterol via lifestyle changes do lower chances of having a heart attack. So, rather than taking drugs to cure a symptom, it's better to change your lifestyle to fix the underlying symptom. However, you will never hear this from the health system because that message doesn't make drug companies any cash... --Jayron32.talk.contribs 03:22, 10 November 2008 (UTC)

Just for the record, check out Cholesterol#Clinical_significance. The connection isn't well understood, and there are some skeptics, but the mainstream opinion is that high cholesterol increases the risk for a heart attack. Saying that there is no connection isn't a "flat earth" opinion, but it's definitely an unusual stance. SDY (talk) 16:08, 10 November 2008 (UTC)

I should note that the linked quote doesn't support your claim. It says that people who take Crestor have a dramatically lower chance of having a heart attack, but these people already have such a low chance that it isn't a big drop in the number of people dying from heart attacks. However our article statins does support your claim Nil Einne (talk) 09:08, 10 November 2008 (UTC)

Except there were TWO problems with the Crestor study cited above (and I am familiar with that 1 study). 1) Its primary sponsor was Astra Zeneca, who, um, makes Crestor. Creates a major conflict of interest problem. 2) The study was stopped early, according to the company because, and I am paraphrasing here, "this drug is so fucking awesome, it would be a crime to stop people from taking it by waiting for the study to finish". However, as noted the number of people effected in a positive way by the drug was so statistically insignificant that the shorter study likely only prevented more reliable data from being obtained. They basically stopped the study early because the results, though likely a statistical abberation, were in their favor. The company who made the drug had nothing to gain by keeping the study going, since increasing the participants would only have averaged out the outliers, and would have reduced the "good results" they got. There have been DOZENS of truly independent studies (i.e. those NOT done and controled by the drug companies) that support the idea that Statins like Crestor don't actually improve quality or length of life. --Jayron32.talk.contribs 15:14, 10 November 2008 (UTC)

Please don't use the RefDesk to spread non-sense like this. The test was ended prematurely because the independent review board concluded the results were so obviously significant (>99.9% chance of reducing major cardiovascular events) that further study was unnecessary and delaying the release of the results was contrary to the interests of public health. Yes, you can criticize them by saying that most of the people in the study would have been healthy anyway, but among that fraction who wouldn't be, it did show a clear benefit in this study. Saying the result were statistically insignificant is simply wrong. Dragons flight (talk) 17:12, 10 November 2008 (UTC)

So according to data extracted from our articles on statins, heart attack and stroke - and this claimed $9 billion cost to treat 300 million people (which seems a little low to me - but let's go with that): $9 billion for 300 million people is just $30 per person per year. They estimate a 60% reduction in risk of a heart attack across the board, a 17% reduction in stroke risk and a possible 50% reduction in colorectal cancer risk - balanced against a new 0.00044% per year risk of the rather nasty (and sometimes fatal) muscle issues that are the major side-effect and an even smaller (and presumably non-fatal) risk of some increased production of liver enzymes. So to put numbers on this: if we dosed every American with this stuff - we'd expect to get around 13,000 new cases of the nasty muscular problems per year - versus maybe 600,000 fewer heart attacks and (since 40% of those are fatal) 240,000 less deaths as a result. The cost of treating a heart attack averages to around $40,000 in the first 90 days - so if the treatment reduces your personal risk of a heart attack by only one part per thousand each year - then it's worth the $30 just in the savings in the cost of treatment. To paint the "big picture": the US spends $110 billion annually on treatment for heart attacks - so the $9 billion cost only has to reduce the number of heart attacks by 10% to be cost-effective...since it's claimed to reduce them by 60% then regardless of the humanitarian issues - the cold cash benefits are hard to deny (IF you believe in the results of the study). Free provision of these drugs could be funded by adding a 50c tax on every burger McDonalds sells...or considerably less if we put the tax on every fat-rich fast food item. SteveBaker (talk) 14:41, 10 November 2008 (UTC)

Or we could use a cheaper generic statin with less of a chance of side effects. Crestor is a bit of a loose cannon, and some groups have even called for yanking the approval on it because there are drugs without the problems. See Crestor#Debate_.26_criticisms. SDY (talk) 16:08, 10 November 2008 (UTC)

Was it $9b to treat everyone, or $9b to treat all the low risk people (with the high risk people already being treated since they're high risk)? If it's just the low risk people then that increases the cost per person (I'm not sure how much by, but I'd guess significantly - how many Americans actually have low cholesterol?). Also, are they recommending statins for children or is it just everyone over a certain age? --Tango (talk) 17:28, 10 November 2008 (UTC)

Thank you very much for your detailed analysis, it is greatly appreciated! (just out of personal interest). Will you tell me if you really mean "600,000 fewer heart attacks", this doesn't at all mesh with my understanding that heart attacks are nearly unheard-of among people with extremely low cholesterol (to begin with, independent of any drug). Will you explain how you arrived at that figure? —Preceding unsigned comment added by 82.124.214.224 (talk) 17:31, 10 November 2008 (UTC)

I haven't checked Steve's arithmetic, but it's important to remember that there are lot of people in the US so even if the risk of an individual having a heart attack is very low you still end up with a fairly large number of heart attacks in total. --Tango (talk) 17:40, 10 November 2008 (UTC)

Ok, I've done my own research and checked Steve's numbers and his look right but they are numbers for the population as a whole, not for low risk groups. So, Steve's conclusion is actually that, if everyone's risk was the same it would be worth treating everyone, but that's a false assumption. Generally speaking, you get better value for money treating high risk people than low risk people, which may well mean it doesn't make good financial sense to treat the lowest risk people. --Tango (talk) 17:55, 10 November 2008 (UTC)

Certainly you get better bang for buck by only treating the needy - but I was attempting to demonstrate that there was essentially nothing to lose (and a heck of a lot to gain) by simply treating everyone regardless of whether they need it or not (a similar argument to putting vitamins in milk or flouride in the water supply). Remember - there is a 'cost' to testing everyone too. Could you give everyone in the USA a cholesterol-level test every year - and pay for that by the savings you get by not treating those who pass it? Would the deaths due to preventable heart attacks amongst the false-negatives be less than the additional deaths due to side-effects from the stattin drug? I don't have numbers - but I strongly doubt it. I doubt you could administer the cholesterol test for less than $30 (it's a blood test - so you need a professional and a clean needle - and you've probably broken the $30 barrier right there) - and because heart attacks are SO common, I bet more people would die from the occasional unnecessary heart attack death following a screwed up test that said "don't take the drug" than would die from the side-effects of taking the drug unnecessarily. So I believe that you're STILL better off treating everyone, regardless. SteveBaker (talk) 21:47, 10 November 2008 (UTC)

don't forget, the study was done, published, and presumably the press releases sent out by the manufacturers of crestor. so, guess what they would answer to the question "wouldn't it be better to just give the money to the people at low risk rather than buy them all crestor?" Gzuckier (talk) 20:09, 11 November 2008 (UTC)

November 10

physics

what is meant by magnetic flux and magnetic meridean? —Preceding unsigned comment added by Kunal pdj (talk • contribs) 07:15, 10 November 2008 (UTC)

Have you read magnetic flux? Can't help with the meridean I'm afraid. Feel free to come back if you have more questions. —Cyclonenim (talk · contribs · email) 07:25, 10 November 2008 (UTC)

I'm just speculating here but perhaps the magnetic meridian is like a line of longitude for the Earth's magnetic field, like a line that goes through the north and south magnetic poles. This is just a guess, though. --WikiSlasher (talk) 07:56, 10 November 2008 (UTC)

correct [[3]]. I'm adding it to the meridian article, so magnetic meridian should now give an explanation EverGreg (talk) 09:22, 10 November 2008 (UTC)

scientific names

Hi all,

What are the scientific names of the two macroscopic invertebrae phylum with hard parts which have successfully invaded and thrive in all three major habitat: marine, freshwater and terrestrial.

Thanks —Preceding unsigned comment added by 122.108.248.74 (talk) 08:50, 10 November 2008 (UTC)

"The reference desk is not a service that will do homework for others." Otolemur crassicaudatus (talk) 11:01, 10 November 2008 (UTC)

Indeed. But you could start with our invertebrate article, which has a list of the 9 invertebrate phyla with examples of members of each one. Gandalf61 (talk) 11:29, 10 November 2008 (UTC)

Putting things up your ass

Please don't be put off by the title- it's a serious question!

Am I right in thinking that when you put a drug up your ass, that works by going into the bloodstream. And yet if you put, say, an apple in your ass, you probably wouldn't absorb the apple into your bloodstream - it would just sit there?

If you put a load of sugar up your ass, say in cube form - would that just stay there, or would it absorb into your bloodstream? And would it make you fat? Or energised? Given that it never gets into the stomach.Jacobsen's Ladder (talk) 11:37, 10 November 2008 (UTC)

You can, indeed, absorb things through the rectum and colon. See Enema. I expect you are correct that an apple would not be absorbed, at least not quickly (and if it stayed there too long it would probably do serious harm, see Bowel obstruction). Sugar should be pretty easily absorbed, since it will dissolve in the natural moisture present in the colon and be absorbed into the bloodstream. There should be no difference between absorbing sugar that way and eating it, you would gain the calories and you can either use them or store them as fat. --Tango (talk) 12:10, 10 November 2008 (UTC)

Glucose (also known as dextrose) can be absorbed rectally[4]. Glucose is often used in energy drinks etc because it can be absorbed directly through the intestinal wall when swallowed. Sucrose is the form of sugar in table sugar, and when eaten is broken down into simpler sugars (glucose and fructose) by enzymes in the intestines before being absorbed. Some sucrose would be broken down by enzymes in the lower intestine if administered rectally, but I'm not sure how effective this would be (a quick search doesn't show up any relevant research, though a lot of people are doing funny things to locust rectums[5]). So, glucose administered anally would work, but sucrose would be less well absorbed. The above mainly refers to sugar solutions. If administered in cube form, you would have to wait for it to dissolve, which would slow the process. --Maltelauridsbrigge (talk) 12:13, 10 November 2008 (UTC)

these people did the experiment, though I am not sure that their results are reproducable... --Jayron32.talk.contribs 14:58, 10

November 2008 (UTC)

The rectum is a well accepted route for the administration of both hydrating fluids and drugs. Where drugs are not tolerated orally by the patient or where an infusion by needle is inappropriate then the rectal route serves. Generally the substance needs to be in solution as the interior of the rectum is only moist and a dry substance may not be easily absorbed or it may irritate the mucosa. The glucose, fructose or whatever is not likely to have any greater energising effect than that taken orally. Energy is largely (though not exclusively) a psychogenic phenomenon. Taking lots of sugars or other carbs won't necessarily give you boundless energy. Richard Avery (talk) 16:19, 10 November 2008 (UTC)

I have heard from an unreliable source that you can put cocaine up your ass and it will have the same effect. The advantage will be that you won't destroy your nose or vein due to your addiction. The hole history sounds plausible to me, but I don't know if some people do it actually. 80.58.205.37 (talk) 16:15, 10 November 2008 (UTC)

It wasn't that long ago that the blogs were quickly copying the story of a wife who killed her husband with a 3L sherry enema. You can also find many sources that explain how to use a tampon and alcohol to get drunk without drinking - for those days when you apparently want to get drunk but don't want to hold a glass or can or bottle or box... 16:24, 10 November 2008 (UTC)

I don't think the wife was responsible (although she probably should have stopped him). The man won a Darwin Award, I think. --Tango (talk) 16:37, 10 November 2008 (UTC)

Delivering analgesics by suppository has the advantage of avoiding first pass metabolism. (No puns intended.) Axl ¤ [Talk] 19:04, 10 November 2008 (UTC)

Anyway: the reference desk will not do your homework for you :) --PMajer (talk) 20:32, 11 November 2008 (UTC)

electricity

how many watts is mesaraed as units in india —Preceding unsigned comment added by 118.95.124.242 (talk) 12:56, 10 November 2008 (UTC)

Ministry of Power at this site can be useful for answering your question [[6]]Hope this helps User:Maheshkale

Asperger's and phone conversation - is it talking or just calling?

I red that those with Asperger's Syndrome have anxiety about talking on the phone. I was wondering, is that really right? Or is it just making the call they have problems with?

It seems more intuitive that - if a person has a condition wherein they need things in fixed patterns, need to plan out how things will go if they go out, etc. - that the mere calling of someone on the phone would be the biggest problem, not talking in and of itself. There is actually a lot less nonverbal communication to take into account, and therefore less stuff they have to sort through mentally, when talking on the phone. But, with calling someone, you never know if the person will be there, whether you are interrupting, what their mood will be, etc.. Similar, if someone calls, you don't know who it will be (unless you have Caller ID, what they want, and so on.

So, is it just talking on the phone, or is it instead the anticipation of receiving/making a call that troubles those with Asperger's?209.244.187.155 (talk) 14:45, 10 November 2008 (UTC)

Where did you read that??? No, anxiety about talking on the phone is not one of the symptoms for Asperger's syndrome, and not even a common characteristic. However, somebody with Asperger's could have trouble understanding the "unwritten rules" of talking on the phone, and develop an anxiety. Lova Falk (talk) 15:10, 10 November 2008 (UTC)

Aspergers (and it's big brother: Autism) is a 'spectrum' condition. There are people to be found on all points along the line between normality and autism. Hence, people (such as myself) with Aspergers have a reasonably wide range of issues and it's impossible to speak for everyone who is on that spectrum.

But we can make some generalizations: Interpersonal communication of all kinds is more difficult for aspies than for normal people. Picking up non-verbal cues is the hardest thing for all of us. Hence, on the telephone we are at least on an equal footing to other people - which means that for some of us, using the phone is easier than face-to-face - and using things like eMail and IRC is yet easier (because even tricky things like comprehending the tone of voice is eliminated). However, some Asperger's (myself included) find phone conversations more stressful than face-to-face. In my case, this is because I still don't have an innate mental model of what the other person is feeling or thinking - and the few tricks I've been taught about body posture and facial cues are useless too. So I dislike phone conversations slightly more than I dislike face-to-face conversations - but both are basically unpleasant. Email/forums/IRC is easiest for me. SteveBaker (talk) 16:46, 10 November 2008 (UTC)

Is this compound acidic or basic?

A student has asked me whether acetylcholine is acidic or basic. Acetylcholine is a quaternary ammonium cation, and as such, has a permanent + charge on the N. So I believe this means that it won't gain or lose a proton, regardless of the pH of its environment, and consequently is neither acidic nor basic. But this sort of thing has always confused me, so please let me know if this is wrong before I give out bad information. ike9898 (talk) 14:52, 10 November 2008 (UTC)

Things can be acidic in ways other than the Brønsted–Lowry acid-base theory ("acid is something that loses H+"). If you put this N+ thing in water, how might it interact (remember water exists partially as a mixture of "H+ and OH-")? If you change the balance of H+ and OH-, you're changing the pH of the solution. DMacks (talk) 17:52, 10 November 2008 (UTC)

I suppose it will either remove some free OH- from solution, consequently increasing the ratio of H+ in solution and lowering pH, or it will have no effect at all. How would you describe acidity/basicity of this molecule, short of being quantitative about it? Would you simply call it a weak acid, or it there something more precise you can say? ike9898 (talk) 18:06, 10 November 2008 (UTC)

Asuming that the -NH₃⁺ bit is the most acidic bit, it will have some measurable pKa value. Any solution that has a pH above this number will result in deprotonation of the molecule. According to this page, the Ka of acetylcholine is 1.8e-5, which means the pKa is 4.74. So any solution of a pH greater than 4.74 will deprotonate the -NH₃⁺. In other words, in a pure water solution (pH = 7.00) acetylcholine will be acidic. Cheers. --Jayron32.talk.contribs 17:59, 10 November 2008 (UTC)

The N doesn't have a proton to lose. It has 4 substituets. ike9898 (talk) 18:06, 10 November 2008 (UTC)

You're right. I misread the article. But the pKa of the molecule is measured, so it really is a weak acid. It doesn't matter WHERE the proton comes from. Looking at the structure, the base form of Acetylcholine is likely to be a zwitterion of the form CH3COOCH^-CH2N⁺(CH3)3 or maybe on the next carbon to the right... --Jayron32.talk.contribs 18:13, 10 November 2008 (UTC)

What about the effect cited by DMacks above? Is the + charge going to pull OH- ions out of solution? ike9898 (talk) 18:19, 10 November 2008 (UTC)

I don't see why that would work. After all, Na⁺ ions aren't acidic in any way; they don't "pull" OH^- ions out of water at all... --Jayron32.talk.contribs 18:25, 10 November 2008 (UTC)

Wrong on both counts. That paper is talking about the dissociation constant of a complex with a receptor, not a pKa. Na+ is indeed acidic, although very weak. Acetylcholine is also a very weak acid; you can deprotonate a carbon next to the nitrogen to form a nitrogen ylide, or the carbon next to the ester carbonyl to form an enolate. But both pKa's are greater than 14, which means that the deprotonation will be largely negligible in water. Acetylcholine could also act as a Lewis acid and react with water as RNMe3+ + H2O -> RNMe2 + MeOH + H+, but that's probably not what the OP had in mind because it "destroys" the molecule rather than simply deprotonating it. --Itub (talk) 20:22, 10 November 2008 (UTC)

Good call, Itub. Yes, I was lazy in not fully reading the article. After looking over the structure, there's no reason to assume that ANY of the C-H bonds is particulatly acidic; they certainly don't look much more acidic than, say, the C-H bonds in acetylacetone, which, while being more acidic than alkyl C-H bonds, really doesn't compare to classically defined "acids". --Jayron32.talk.contribs 21:13, 10 November 2008 (UTC)

Bodily fluids in the wash

If i put something in the washing machine with some sort of bodily fluid on it, it feel like im just making a solution of bodily fluids and soaking my clothes in them and this will then rub off on things - i guess my question is to what extent is the true. thanks. 143karbkaz (talk) 15:10, 10 November 2008 (UTC)

143karbkaz, I think we already answered this question here when originally asked by zakbrak341. I like how your user name is the just the reverse of the original. Laenir (talk) 15:44, 10 November 2008 (UTC)

I forget the password for that account, and its a different question - the question for that was do the enzymes in detergent break down the protiens in semen. This is a different question :( 143karbkaz (talk) 15:56, 10 November 2008 (UTC)

When something with stains from bodily fluids is put into a washing machine (note that name - bit of a clue there!) the washing powder will break down the protein of the stain and allow it to become a suspension in the water. Now here comes the cunning bit, the machine then empties all that water away and rinses the clothes twice more so ensuring that no stains or particulate matter is left in the clothes or linen. Semen, saliva and urine are particularly easy stains to remove and in theory the washing machine does make a 'soup' of bodily fluids but it then proceeds to flush it all away and rinse out the clothes thoroughly. I would bet a wad of cash that it would not be possible to detect semen, saliva or urine in washing after a full hot cycle. This is the same system they use in modern hospitals to clean linen. Dang, this modern technology is good! 86.4.187.55 (talk) 16:09, 10 November 2008 (UTC)

I suppose its probably possible to work it out, such a tiny amount and thats dissolved in what 40L of water, work out the concentration of that, then work out how much water the clothes hold after they have been spun, then work out how much solute would be in that, then when thats all dissolved in the next rinse cycle ect. it would be pretty small. But do you think the solute would rub off on things once its dried? —Preceding unsigned comment added by 143karbkaz (talk • contribs) 16:18, 10 November 2008 (UTC)

It's just as well I don't believe in homeopathy...all of that dilution making things more powerful...Urgh! SteveBaker (talk) 16:48, 10 November 2008 (UTC)

I just knew when I saw your name and "dilution" in the edit summary that you were going to make a comment about homeopathy... you're getting predictable! --Tango (talk) 16:56, 10 November 2008 (UTC)

OK. For the sake of thoroughness, lets ACTUALLY see how much spooge is left on your clothes after your last nocturnal emission and if you wash it in a typical washing machine. Lets make some spherical cow-type assumptions. Lets say that the ejaculate is completely and evenly dissolved in the wash water each time the washing machine fills, and lets assume that you do the "double rinse" option on your washing machine. According to Ejaculation, the average event produces 1.5 - 5.0 mL of spunk. Lets just take the high end of that volume. According to this page, a modern "energy star" compliant washer uses 18-25 gallons per load. Doing a quick conversion, and this time lets use the smaller end, so we can maximize the amount of jizz in the washing machine, for our "worst case scenario" wash, we get a metric volume of 68 liters, or 68,000 mL. 5/68,000 means that after the wash cycle, we have .000735 % of our cum left in the wash. After one rinse cycle this reduces to .000000108 % left, and after 2 rinse cycles, that leaves us with .000000000000159 % of our original stain left in the machine. Considering that the average ejaculation features, according to our article on Semen analysis, 60,000,000 sperm per milliliter, or 300,000,000 sperm in our 5 mL test case. Multiplying this by our dilution factor gives us .0000047; which means that there is a 1 in 200,000 (roughly) chance that a single sperm is left in your washing machine after a standard wash cycle, with the double rinse option. And this is ignoring any effect that soap may have on denaturing or destroying the components of the semen. I don't think you have anything to worry about. --Jayron32.talk.contribs 17:50, 10 November 2008 (UTC)

That's got to win some kind of award for the largest quantity of synonyms for sperm used in one paragraph. —Cyclonenim (talk · contribs · email) 18:08, 10 November 2008 (UTC)

I don't follow your calculations. You seem to be assuming that there will be 5ml of liquid left in the washing machine after it drains each time, I expect it is considerably higher. --Tango (talk) 18:10, 10 November 2008 (UTC)

Hense the spherical cow reference. OK. Lets assume that there is really 500 mL of water left after each wash, so I was off by a factor of 10,000. That's still a 1 in 20 chance of finding a single spermatazoa in the wash. I am not concerned... --Jayron32.talk.contribs 18:19, 10 November 2008 (UTC)

There are 3 drainings, so wouldn't you be off by a factor of 1,000,000? That would give an expectation of 5 sperm after the wash. I think your cow is a little too spherical. I think the fact that any sperm would almost certainly be killed by the heat (and perhaps the soap) is more important than the dilution (which is far too difficult to calculate reliably). --Tango (talk) 19:14, 10 November 2008 (UTC)

Actually, the three dilutions I did would be the 5/68,000 500/68,000 500/68,000, to get the 1/20 number. --Jayron32.talk.contribs 19:19, 10 November 2008 (UTC)

What if the machine does not have a special spunk cycle? Edison (talk) 19:59, 10 November 2008 (UTC)

The point of the calculations is to show the rediculousness of the premise of the original question. The idea that when you wash and entire washload of clothes, some of which has a trivial amount of semen on it, that that semen could somehow cover all of the clothes in the wash, "contaminating" them. The idea that you could somehow "coat" an entire washload of clothes with semen (well, using a washing machine. If you and a bunch of friends were REALLY dedicated...) by simply washing clothes is just silly. --Jayron32.talk.contribs 20:39, 10 November 2008 (UTC)

Well, yeah, but our concepts of filth aren't necessarily dictated by logic. Here's a little experiment my roommate showed me back in uni: take a small cup of water, like the little Dixie cup you use at the dentist. Drink a little of the water. Everything okay? Now spit into the cup, as much as you can without actually horking up anything nasty. No need for phlegm, just mouth saliva. See if you can refill the cup to replace what you drank. Okay, now drink the spit water. You know the water is okay because you just drank it and you know the spit is okay because it's yours and it just came from your mouth, yet most people have a very hard time gulping down the mixture and even many that can do it, can only do it as a "dare" type thing. There's nothing in the cup that wouldn't be in your mouth the second you take a swig, but one is filthy while the other is not. No logic there. Matt Deres (talk) 17:45, 11 November 2008 (UTC)

VCR tape to DVD

How do I copy one to the other please?--212.139.78.231 (talk) 17:48, 10 November 2008 (UTC)

Probably better suited for the computing reference desk, but here's a little article which gives you some hints at how to do it. Basically, it requires hardware: Linky —Cyclonenim (talk · contribs · email) 18:05, 10 November 2008 (UTC)

Buy a DVD recorder. My computer came with one installed. --Jayron32.talk.contribs 18:06, 10 November 2008 (UTC)

Do you have a DVD player for your TV that can burn DVDs? If so, just connect your VCR player to the DVD player's input and follow the instructions for burning DVDs. If you don't, and want to use a computer DVD burner you will need a TV tuner card to connect the VCR player into. If you want more details, there are loads of tutorials online, try google. --Tango (talk) 18:07, 10 November 2008 (UTC)

Don't use a standalone DVD recorder. They usually make proprietary discs that are not readable by other machines. I've had two and neither made DVDs that any other machine could view, even the DVD-ROM on my 'puter. Matt Deres (talk) 17:47, 11 November 2008 (UTC)

I agree with Matt..I purchased a standalone and was quite upset to find out the discs would not work in any other player. cheers, 10draftsdeep (talk) 18:26, 11 November 2008 (UTC)

You have a few options here, you can use a dedicated vhs dvd combo recorder, you can connect a player and a dvd recorder, you can buy an external device (pinnacle supply a few) or you can get an internal video capture card and the related software. First is the easiest but least flexible, the last is the hardest but gives you all the options. Alternatively, you can use a specialist company who can either put the video onto DVDs for you or provide as video files and help you edit them. One such Company is Vinyl to Digital and they can convert vhs to dvd or to any other format and provide help and support for whatever you want to do. 17:35, 26 May 2009 (GMT)

water clock from 2008

http://www.alibaba.com/showroom/Water_Clock/------------15--------------.html

Where would I find an explanation on how these work? —Preceding unsigned comment added by 12.213.224.56 (talk) 18:21, 10 November 2008 (UTC)

Maybe in the article Water clock? --Jayron32.talk.contribs 19:14, 10 November 2008 (UTC)

That article is about old-fashioned mechanical clocks, with gravity driven water as the power source. This questioner is asking about electrically powered digital clocks that use an open container of water as a primitive cell. Possibly a Daniell cell, but I'm not sure. APL (talk) 19:48, 10 November 2008 (UTC)

They run on saltwater batteries. Digital clocks require so little energy that even a "homemade" battery can work. You may also be interested in two potato clocks The Amazing Two Potato Clock. See the brief paragraph here : List_of_battery_types#Homemade_cells. APL (talk) 19:13, 10 November 2008 (UTC)

Please note - the power doesn't come from the water - it comes from the dissimilar metals in the two electrodes reacting with each other via the water. Hence the claims for "potato powered clock" or "lemon powered clock" or (god forbid) "water powered clock" are all just a tad inaccurate. SteveBaker (talk) 21:30, 10 November 2008 (UTC)

Indeed, as Steve notes, the power provided is from the difference in reduction potential between the two dissimilar metals. These set ups are functionally equivalent to ANY other battery, like good old double-a cells, and the salt water/lemon/potato provides NO electromotive force themselves; they only provide the medium in which the required spontaneous chemical reactions happen. --Jayron32.talk.contribs 22:12, 10 November 2008 (UTC)

Galaxy flow

If the galaxies are moving in the same direction, isn't that the same as saying they aren't moving at all? If there was a supermassive object beyond the visible universe, wouldn't it be impossible to receive any effects from it, including gravity? Before any of you mention it: xkcd. — DanielLC 18:23, 10 November 2008 (UTC)

If it were due to a massive object then the galaxies nearer it would presumably be moving faster than those further away, that difference would be meaningful value (as you say, the actual movement of a given galaxy is meaningless since there is no universal frame of reference - in fact, it's the tidal force that has the measurable effect rather than the gravitational force itself). As for it being beyond the observable universe, I agree, if we're observing its gravitational effects then we are observing it so it must be within the observable universe. It could be something more fundamental than just a lot of matter, though, perhaps something to do with the global structure of spacetime? I think we're probably in the unfortunately common situation of a journalist not knowing what they're talking about (New Scientist is generally better than mainstream journalism, but it's far from perfect).--Tango (talk) 18:31, 10 November 2008 (UTC)

The cosmic microwave background defines a privileged state of motion everywhere in the universe, called the Hubble flow: it's only if you're moving with the Hubble flow that the CMB is isotropic. The large-scale net movement (which may not be real) is with respect to that. The part about its being a pull from beyond the observable universe is just speculation (only circumstantially supported by the data), but it makes sense once you understand the ambiguity in the definition of "observable universe". The part of the universe we can actually observe with telescopes is limited to a past light cone extending back to 400,000 (0.0004 billion) years "after the big bang", which is when the primordial soup cooled down enough to become transparent. (See Age of the universe#Explanation for what "after the big bang" means.) If you extend the light cone another 400,000 years back in a naive way, assuming matter/radiation dominance, then the size is not much different—either way you get about 46 billion light years (comoving) in every direction, which is the value in our observable universe article. But most cosmologists think that there was an inflationary epoch a small fraction of a second "after the big bang" during which the growth was dominated not by matter or radiation but by a cosmological-constant-like quantum field and the universe expanded by a factor of 10^{something large} in a very short time. If you extend the past light cone through that, it covers an enormously larger (comoving) area. So the idea is that the net motion is due to something from the pre-inflationary era which is inside our past light cone but well outside the part of the universe that we can actually see. -- BenRG (talk) 20:51, 10 November 2008 (UTC)

I've never heard of "observable universe" being used to mean anything other than the light cone going all the way back to t=0, is it common to define it to stop at the moment of last scattering? --Tango (talk) 21:58, 10 November 2008 (UTC)

It is fairly common, if somewhat inaccurate, to use "observable universe" to mean "visible universe" (i.e. the universe as probed by light). Dragons flight (talk) 22:12, 10 November 2008 (UTC)

I noticed that too.. if we're seeing the gravitational effects of an object, we must be seeing the object itself. Unless, as said above, it's some weird phenomenon independent from the laws of physics as we know them. which is a pretty unreasonable assumption. 72.236.192.238 (talk) 22:34, 11 November 2008 (UTC)

is my scientific methodology sound?

i'd like to test whether a wikipedia article is being suppressed.

my methodology is:

1. identify a control page that
   1. is approximately the same length as the test article
   2. has an inadequate lead section
2. the test article is international law and the arab-israeli conflict, which has an inadequate lead section
3. my hypothesis is that the reason it doesn't meet our wikipedia:lead_section guideline is it's being suppressed
4. to make the test blind, i will pay a paper mill to read both articles and produce a lead section for each that
   1. meets the guidelines of wikipedia:lead_section
   2. incorporate as much of the current lead as possible (to minimize the chances of reversion)
   3. is in line with lead sections of good articles of the same length
5. from two different net cafes i will
   1. create a new wikipedia account
   2. from each account change one of the page's intro to the intro produced by the paper mill
6. if the improved control intro is not reverted/obfuscated but the improved test intro is, i will conclude that the wikipedia article is being suppressed

what do you think of my scientific methodology —Preceding unsigned comment added by 82.124.214.224 (talk) 19:30, 10 November 2008 (UTC)

If you're serious about the scientific aspect, some obvious problems are that two data points don't mean much, and that two encyclopedia articles are different enough that one is not a good control for the other. If you're more interested in improving article content, forget this science experiment and just bring up your concerns on the talk page. There's no need to resort to sockpuppetry or subterfuge- in fact you'll find that doing so makes your work here more difficult rather than easier. Friday (talk) 19:52, 10 November 2008 (UTC)

I'm not interested in doing work here, and I'm not interested in the article I linked -- that's why I've never made an edit. I am interested in (knowing--not changing) whether Wikipedia articles are suppressed! That is useful and good information to know... I'll think about your specific concerns, but please tell me if you have an easy way to improve my test algorithm. —Preceding unsigned comment added by 82.124.214.224 (talk) 20:14, 10 November 2008 (UTC)

Actually: do you have an easy way for me to divine whether Wikipedia articles (such as the one I linked) are being linked, and in a way that is scientific? I don't understand your point that two Wikipedia articles are "different enough" that if the intro paragraph of one is reverted to two short sentences (the latter of which doesn't even make sense) and the control articles aren't, it wouldn't imply that the control article was being suppressed?? The only reason for the control, is to show that reverting a good, obvious improvement doesn't normally go on. How would you feel if the control group were, say, twenty articles?

You haven't defined what suppression is. You're experiment wouldn't prove suppression in any way, because that would mean reading the intent of people who are removing information from the article. There are many good faith reasons to remove text from an article, or to prevent new text from being added, and not all of them imply "preventing people from hearing the TRUTH!". --Jayron32.talk.contribs 21:08, 10 November 2008 (UTC)

Nice attempt to paint me as a conspiracy nut ("the TRUTH"). How about you read what I wrote and come up with a single good faith reason to remove the lead the paper mill would produce from the article itself and based directly on our lead guideline? —Preceding unsigned comment added by 82.124.214.224 (talk) 21:41, 10 November 2008 (UTC)

The use of the word "suppression" is itself perjorative, and implies a deliberate attempt to deceive. I see no evidence of that here, and I also see no evidence that the methodology would test for that. --Jayron32.talk.contribs 22:09, 10 November 2008 (UTC)

Who said anything about deception? I mentioned suppression. If you don't think there's any reason to even suspect it, why don't you take 30 seconds and change the lead paragraph to something sensible, after reading the rest of the article. I am genuinely interested in whether your good-faith attempt will get reverted, and I don't know if it will. Try it! If it does get reverted, we can discuss why, if you still won't think it's suppression...

Removal != suppression. There are many reasons to remove verbage from an article, and suppressing it, which is basically the intentional act of preventing information from becoming public knowledge, is only one of them... --Jayron32.talk.contribs 23:52, 10 November 2008 (UTC)

What is suppression? When one viewpoint surpasses another and thus oppresses the lesser? Wikipedia is built on this. It's the collective ideology of capitalism, the industrial revolution, and Web 2.0: Putting something out there for others to shamelessly improve on. Mac Davis (talk) 23:12, 10 November 2008 (UTC)

No, I mean suppression literally: pushing things down into the bucket. I would like to test whether the mentioned article does this by not having a lead paragraph.

"Pushing things down into the bucket?" As I understood what you meant, I would say the same thing Jayron32 did. Often elimination of words is the best writing technique. Mac Davis (talk) 23:26, 10 November 2008 (UTC)

You're normally absolutely right, and the first thing I do after typing something is cut, cut, cut. In this case however the lead paragraph hasn't just been pruned -- it doesn't exist at all! Look at the "introduction" to international_law_and_the_Arab–Israeli_conflict and you'll see the lead paragraph doesn't exist. For comparison you can read our guideline, and then read the intro section of some good or featured articles. Now do you see why I am interested in whether the missing lead is an act of suppression or not, and would like to test it? I'm not saying it is, or isn't -- here at the reference desk, my question is about the methodology for testing this.... If you'd like to be my volunteer, please, make some improvements to the lead section so I can see if they'll be reverted. To make the study blind, I don't want to make changes myself... —Preceding unsigned comment added by 82.124.214.224 (talk) 23:49, 10 November 2008 (UTC)

How do you intend to control for the different levels of attention the two articles receive? I suspect that any article relating to conflicts in the Middle East will have a large number of unique editors, a large number of edits per day, and appear on a large number of editors' watchlists compared to the typical Wikipedia article. Edits to sensitive topics are also often more successful if they are discussed in advance on the article talk page — a precaution that is often unnecessary for less contentious areas.

In other words, I can think of quite a few confounding factors for your study. Instead of wasting your time and money to generate a meaningless result, perhaps you should try discussing the matter calmly and politely on the relevant talk pages. Accusing editors of 'suppressing' topics (whatever that means) isn't likely to result in the sort of collaborative consensus-building that allows us to create great articles. TenOfAllTrades(talk) 00:01, 11 November 2008 (UTC)

You're right about all that. Let's try it and see how it goes (see my comment below) 82.124.214.224 (talk) 00:23, 11 November 2008 (UTC)

Here's a test: dig into the fossil record and see if there has been any dispute over the contents of the lead. In this case, considering that over the past year there has been only one minor change to that header section, the prior probability of your hypothetical (and amorphous) "suppression" is low. — Scientizzle 00:10, 11 November 2008 (UTC)

I like that test, it proves that no one is digging up the suppressed information. I guess I'll be the first! :) I'm going to do the edit myself and see what happens. I'll post my version here first and you suggest improvement, then I'll post it there. See ya', I'm off to read the article and lead paragraph guideline carefully!—Preceding unsigned comment added by 82.124.214.224 (talk • contribs)

How is something "suppressed" if it's never before been added? The assumption that any reversion of a new addition is an attempt at censorship violates Wikipedia's core behavioral policies, too... If you can improve the article, please do so...but don't disrupt Wikipedia to make a point, okay? — Scientizzle 00:35, 11 November 2008 (UTC)

Okay, I was bold and added this:

The resolutions of major institutions of international law, such as the International Court of Justice, are rejected in the case of the Arab-Israeli conflict by both Israel, the principal state involved in the conflict (there is no Palestinian state), and the United States, another country supporting Israel's decision to do so. This rejection is possible because international laws, unlike the more familiar laws of local and national governments, are neither legislated nor enforced by a sovereign government having jurisdiction and law enforcement powers: there are local and national governments in the world, but no "international government" of the same kind. Instead, countries exercise sovereignty in international affairs, and are bound by the findings of international institutions only insofar as they submit themselves to their authority. At times, nations cooperate easily, and international institutions, as the manifestation of this cooperation, wield considerable power. At other times, such as in the case of the Arab-Israeli conflict, international institutions are less powerful.

with the edit summary "improved lead. Please refer to Wikipedia:Lead_section and make further improvements". We'll see what happens...

Don't post your version here, this is the science ref desk. We're good at science, we're not necessary good with international affairs. The article's talk page is the place to get opinions on changes. Alternatively, you could just update the article and just see if anyone reverts, if they do you can go to the talk page to discuss it then (see WP:BRD). --Tango (talk) 00:42, 11 November 2008 (UTC)

No. I do not think it is sound at all. Not even close.

1. You're going to need to define "suppressed" much better than you've already done.
   1. What does "Suppressed" mean?
   2. Why would this "suppression" manifest itself in the lead of the article?
   3. Are you expecting a particular point of view to be pushed? Or just a general resistance to change?
      1. If the former, which? If the latter why would the Israel article be more susceptible to it?
2. You would need a lot more than two pages to draw any significant conclusions.
3. You would also need your "control" articles to be as heavily watched and edited as your test articles
   1. If the control articles are intended to be non-controversial, this may be very difficult.
   2. How would you measure page watched-ness?
4. You would need your "Essay mill" students to be completely unbiased, and familiar with WP's style.
   1. I bet they'll figure out where you got the articles from.
   2. It would not be a blind study if you copy-edit their leads at all. Even just going through and adding the wikilinking could taint the experiment.
5. You've only described a single-blind experiment. The measurement criteria had better be very well defined ahead of time.
6. You've just now told us, some of the subjects in your experiment, that you intend to run an experiment.

APL (talk) 01:36, 11 November 2008 (UTC)

I was thinking that I shouldn't ask you guys, but I thought it wouldn't really matter, it's a very different circle of people. That's why I didn't ask on the article's talk page though... How important are double-blind studies versus single-blind? Are researchers really that bad when they know what effect they're evaluating?

Yes - in some cases, it makes a big difference. In a drug study where half the people get placebo and the other half get real drugs, it's very hard indeed for the doctor who is handing out the drugs not to say something that will clue the patient in to what's really going on and thereby destroy the placebo effect. Double-blind is the only scientific way to do this kind of study. SteveBaker (talk) 03:26, 11 November 2008 (UTC)

I've made the edit, as you can see. I think it's pretty clear now. Am I wrong to conclude that if it stays (isn't reverted) then the lead had NOT been totally inadequate before my edit BECAUSE of a group of people suppressing the article -- making sure the lead didn't say what's in it -- but for some other reason? Or is this also a wrong conclusion on my part?

The edit in question is here.

So, after discussing your scientific methodology, finding it inadequate, you elect to not even follow your own inadequate procedure? Regardless of what happens here, nothing will be proved, no experiment has been conducted. "Experiment" does not mean "try random stuff and see what happens.".

Incidentally, the lead you added to that article doesn't really seem to be a good summary of the article. It seems more like a brief rant on the implications of the topics of the article, but not really a summary. I don't know enough about the topic to give a fair assessment of that, though. APL (talk) 04:58, 11 November 2008 (UTC)

It would be REALLY tough to suppress an article here on Wikipedia. Remember that all of your changes - and everyone else's are stored in the article's history. If someone "suppressed" something - you can look to your last version - see exactly who changed it, how they changed it and when they changed it. You can go to their Talk: page and ask them why they did that - your question and their answer also remains in the edit history for all eternity. To remove an entire article or do something 'special' to wipe out some editing history would require the decisions of a whole committee of people...fiercely independent people...getting them to agree to suppress something would be all but impossible...and all of those discussions are retained in 'history' pages forever. The paper-trail is very complete and all-but-impossible to alter. Given all of that - it would take a lot of nerve for someone to start methodically suppressing stuff, you could easily create an unbelievable stink (because you can easily prove everything that happened) - and if you're right, people will flock to your side. However, I wish I had a dollar for every time I reverted someone's crappy editing, poor grammar, unreferenced facts, violations of policy/guidelines...and ended up being accused of "suppression". So if you feel something has been inappropriately removed - you've got to go to the talk: page - and ask why. If you disagree with the reasons - then seek to get a consensus of users who agree with your points - if you succeed, you can restore your version and people will defend you if it gets removed again. But if you fail - you'll have a lot of people patiently explaining WHY you're wrong...and you'll simply have to swallow your pride and admit that you're wrong. SteveBaker (talk) 03:26, 11 November 2008 (UTC)

thank you for that... but nothing of mine was removed. can you also explain given that it's not possible to suppress information, why some articles are heinously biased?

Since this whole thing is pretty bankrupt as far as 'science' and experimentation, and, I can't find it right now, but I'm almost positive that there's a WP policy that specifically forbids this sort of experimentation, perhaps this discussion should be brought up in the talk page of the article in question? APL (talk) 05:04, 11 November 2008 (UTC)

(edit conflict) You don't understand NPOV and consider something biased even though it follows it? You're biased and assume anything without the same bias isn't? The articles in question were only written by one or two people and have not been edited for NPOV? The articles in question are the subject of an ongoing edit war and have been locked on The Wrong Version? Making an article NPOV is harder than you think? Making an article NPOV is impossible? There are over a million articles on Wikipedia, so some will be biased? I think people can add to this.

Who said anything about bias? I didn't. Who was that directed to? APL (talk)

APL, I think Wikipedia is only against experimentation that damages it, such as inserting false information. The OP's experiment involves improving Wikipedia. — DanielLC 05:15, 11 November 2008 (UTC)

Fair enough. That may be what I'm thinking of. APL (talk) 05:50, 11 November 2008 (UTC)

Bias (even serious bias) or incompleteness or other defects in a Wikipedia article may be due to the inexperience of the person who created the article, or to "inadequate attention" from other editors, or both. It is not necessarily the result of "suppression". Some articles get little if any attention after they are created. I think a stroll through Wikipedia using the "random article" link will demonstrate that. CBHA (talk) 06:45, 11 November 2008 (UTC)

Bias is a tough thing to judge. What happens is that opinion lies on a line between one extreme and the other - you always regard your own position as being in the middle of the line - so if the article is to the left of where you are - it's biassed. However, for someone who's opinion is to the left of yours - it's balanced. Who's right? Dunno. The solution to bias in Wikipedia is simple - we don't choose the facts - we find references and write what they say in our own words. The opinions of the authors SHOULDN'T matter (although it obviously does sometimes). But if you find an article (especially one with a lot of authors that's been around for a long time) - and you think it's biassed - you should probably take a deep breath and realise that your opinion is not in the center of the spectrum of opinions. For new-ish articles with just a couple of authors - bias can certainly creep in - and it's your responsibility to get in there - talk it out on the discussion page and use FACT with REFERENCES to bring the article into balance and harmony. When you consider the amount of hate and resentment flung around in the articles about John McCain and Barrack Obama - then look at the beautiful pair of articles that were simultaneously brought to featured status in time for the US election day - you've got a pretty good idea of how to do this. You WILL end up agreeing to text that you don't personally approve of - but you'll also have the chance to get the facts in there. Wikipedia is actually a shining beacon of conflict resolution in this regard. SteveBaker (talk) 14:15, 11 November 2008 (UTC)

Speed of Electricity.

http://en.wikipedia.org/wiki/List_of_common_misconceptions states that "Electricity" is fast, but the electrons inside move slow. However I have yet to see an article/document stating the research behind this and blah blah blah. I wanted to know if I could get more accurate sources. I myself have found http://www.eskimo.com/~billb/miscon/speed.html

but I wanted to know if there was a more scientific article on it...

In retrospect the whole list_of_common_misconceptions page has alot of unsourced material but that's not my point. 70.89.49.205 (talk) 19:34, 10 November 2008 (UTC)

Have you looked at the electric current article, particularly the section on drift speed?

List of common misconceptions is actually fairly well sourced, as articles of that class go. In cases where references are not cited, other Wikipedia articles linked in the article have the appropriate citations. If you can contribute sources where needed, please do. ~Amatulić (talk) 19:51, 10 November 2008 (UTC)

See Speed of electricity, which says that the electrons carrying current flow a t a typical rate of millimeters per second, while the impulse when current is switched on travels through copper at almost the speed of light. Electrons start entering one end of the conductor at about the same time they start flowing out the other, but the electrons are not travelling all the way through the wire that fast, because there are so many of the charge carriers present in any small section of wire. The article Drift velocity gives a mathematical explanation of the slow rate with which electrons drift through a conductor. Edison (talk) 19:55, 10 November 2008 (UTC)

Ahh, Thank you for the results, I appreciate your time looking 70.89.49.205 (talk) 20:29, 10 November 2008 (UTC)

It's not such a difficult concept. Imagine a garden hose that's been running for a while. You turn it off, wait a bit, then turn it on again. The instant you turn it on, the water starts flowing out of the other end. Even if the hose is 100' long - the water comes out almost instantly - the delay between turning the water on and getting water out of the end is probably something like the speed of sound in water. Yet the water flow itself is nothing like that fast - a few feet per second probably. It's the same deal with the electrons and the wire. The wire is already "full" of electrons - so when you push one into the wire at the battery end - there is a knock-on effect that pushes one out of the other end at about the speed of light in copper...but the individual electron meanders very slowly along the wire. I read somewhere that there was a good chance that when you put a new battery into a flashlight - there is a good chance that not one of the electrons would make it out of the battery, all the way around the circuit and back into the battery before the battery went dead. I'm not sure that's really true - but as Edison says - at a couple of millimeters per second, it's an amazingly slow process. SteveBaker (talk) 21:17, 10 November 2008 (UTC)

These explanations are still a bit misleading since they suggest that the electrical energy goes in the same direction as the charge carriers, just faster. Actually it's just as happy to go in the opposite direction. When you initially insert a battery into a circuit, it pulls charge carriers from the wire connected to one of its terminals and pushes them into the other. That leads to a cascading effect that travels around the circuit in both directions from the battery, meeting up at the far end of the circuit (the halfway point). If you're modulating the current/voltage to send a message, as with a telegraph or broadband over power lines, the signal travels from sender to receiver along both wires. (I think. There's no reason for it not to, anyway.) -- BenRG (talk) 22:55, 10 November 2008 (UTC)

A very good and profound question, regarding an issue or phenomenon that isn't covered in classical textbooks, either at high-school level or higher, introductory ones. This issue was raised during a course I gave about half a year ago, and drove changing the usual syllabus of the course. SteveBaker's explanation is a very good simplified demonstration. However, the phenomenon of electric current is far more complex. In brief, at least two phenomena are involved here. The 1st of which is the actual motion of free electrons, which is typically very small, as already mentioned before. The 2nd is a result of the appearance of a potential difference or voltage along the conducting wire, which acts as a source of disturbance. This disturbance spreads through a potential gradient in a wavelike manner, namely a pulse (physics). As all waves do, they carry energy delivered to the mettalic atoms of the conductor, thus heating it. The pulse has nothing to do with the actual free electros motion, but manifests itself as a momentary repeated change in their rate of oscillations, propagating along the conductor in approx. 70% of the speed of light. There are differences between the dynamics related to DC & AC, and other phenomena related exclusively to the latter.

To elaborate in depth on the subject, you're invited to look up at: (1) Solid State Physics, (2) Solid State Physics, by Ashcroft & Mermin, (3) Introduction to Solid State Physics, by Kittel. BentzyCo (talk) 23:15, 10 November 2008 (UTC)

Square seconds

According to the article on acceleration, SI measures it in terms of meters per square second (m/s²). What does a square second look like? --67.185.190.46 (talk) 22:31, 10 November 2008 (UTC)

It probably looks similar to what a second looks like. Mac Davis (talk) 22:46, 10 November 2008 (UTC)

Think of it in words. Velocity/speed is in meters per second - how many meters can be covered in one second's time. That is, the change in displacement/distance with respect to time. Acceleration is the change of velocity with respect to time, so it should have units of "meters per second per second." If the velocity changes by 5 m/s in one second, it's acceleration is 5 meters per second, per second. This works out to m/s² (take m/s and divide by s) --Bennybp (talk) 22:47, 10 November 2008 (UTC)

What does a second look like while we're at it? Acceleration is the rate of change of speed - its units are "meters per second, per second" (ie if you are accelerating at 2 ms^-2, your speed will have increased by 4 ms^-1 after 2 seconds), and (ms^-1)^-1 becomes ms^-2. (ec: wow, beaten to the punch - twice.) 81.102.34.92 (talk) 22:50, 10 November 2008 (UTC)

If units are used to describe physical quantities, the "derived unit" of ms^-2 describes how distance and time might be related in this situation. Mac Davis (talk) 23:03, 10 November 2008 (UTC)

Seconds squared by itself is a meaningless unit. However, meters PER second squared is acceleration. One cannot arbitrarily pull part of the unit out of the definition and make it meaningful. For example, let's say your name was John Joseph Smith, and I were to ask "what does ephsmi mean?" That's essentially what the OP's question does to the units; though I admit that it looks like seconds squared is an "operative" part of the unit, it's REALLY just a mathematical convenience. The real physical quantity is (meters PER second) PER second which is mathematically identical to meters PER second squared. --Jayron32.talk.contribs 23:48, 10 November 2008 (UTC)

I chalk it up to either my own personal density or my poor education that I only figured out as an adult that all it means is that for each second the thing is falling, it adds X meters per second to its velocity. --Sean/76.182.94.172 (talk) 00:00, 11 November 2008 (UTC)

Occasionally (rarely) it is pronounced "Meters per second per second", if that helps you at all. APL (talk) 01:38, 11 November 2008 (UTC)

The significance of the exponent is that it implies the distance travelled has a linear relationship with the square of the elapsed time. The fact that the units are in the form distance/time^2 is not a coincidence; it means that the two quantities are related. --Bowlhover (talk) 02:57, 11 November 2008 (UTC)

It's really only a notational convenience. We square (and cube and more) all sorts of peculiar units. The 'volt' and the 'watt' (for example) both have seconds-cubed in their expansions - the units of 'permittivity' have seconds to the fourth power. If your rate of acceleration is changing - you might have seconds-cubed - if the rate at which your rate of acceleration is also changing you have seconds-to-the-fourth power. It's just notation. SteveBaker (talk) 03:12, 11 November 2008 (UTC)

Calling the unit "metres per square second" raises the question: what on earth is a "square second"? It sounds very strange!

In my experience with the terminology, I have never before heard it called that. "Metres per second squared" is usual IME, and (as noted above) that is simply an abbreviated way of saying "metres per second per second". CBHA (talk) 06:59, 11 November 2008 (UTC)

Yeah - I've never heard "meters per square second" either. I suppose that when some people are talking about units of (for example) density, we could talk about kg.m^-3 as "kilograms per cubic meter" rather than "kilograms per meter cubed" - but scientists don't often do that unless they are talking casually to laymen - and they certainly only do it that way when it makes physical sense (which it doesn't with 'squared seconds'). But we need this kind of nomenclature. Saying "meters per second per second" is easier for the layman to understand than "meters per second squared", but when we get into some units, that convention quickly becomes unwieldy. An "ohm" for example would be a "meter meter kilogram per second per second per second per ampere per ampere" - or a "farad" would be an "ampere ampere second second second second per meter per meter per kilogram"! You simply have to use the mathematical convention of calling an object that's multiplied by itself a "square" and an object that's multiplied by itself three times a "cube". We do that just to make the words easier to understand. It doesn't have a physical meaning - but this is math - so it doesn't have to have physical meaning. It all relates back to Dimensional analysis - in which the units can be treated like variables in an equation and can be multiplied and divided - cancelled out or raised to some power as needed. SteveBaker (talk) 13:55, 11 November 2008 (UTC)

Nuclear reactor efficiency numbers

I'm looking for some numbers on nuclear power plant efficiency and I'm having a hard time getting them. Any help? I'd like to compare them to solar, wind, coal, and oil. Mac Davis (talk) 22:45, 10 November 2008 (UTC)

Can you define more precisely what you want? There are different ways to look at it. Fuel is not totally depleted, heat is not totally converted to electricity, capacity is not fully utilized, etc. Dragons flight (talk) 22:59, 10 November 2008 (UTC)

Heat not totally converted to electricity. What is the word for this? Thanks. Mac Davis (talk) 23:04, 10 November 2008 (UTC)

Thermodynamic efficiency, I guess, but I don't see how you can meaningfully compare different types of power plant this way. The important differences are in things like the construction cost, the cost and availability of the fuel, the environmental impact, and the risk of serious accidents, not the amount of waste heat they produce (unless it's enough to be a pollutant, I guess). All else being equal a power plant that produces less waste heat is better, but all else is rarely equal. -- BenRG (talk) 23:27, 10 November 2008 (UTC)

I was thinking economically, a major factor would be how much of the produced heat could be turned into electricity. Might the about the same 30%-50% for all of them? Mac Davis (talk) 00:15, 11 November 2008 (UTC)

It's probably not a big factor economically. Think about it—if the cost of a unit of heat is really different between technologies, then one could be far less efficient and be still be really profitable. What you want from an economic point of view is cost per kWh and things like that. --98.217.8.46 (talk) 01:09, 11 November 2008 (UTC)

I would imagine it would convert heat to electricity identically to coal - the turbine arrangement ought to be pretty similar. Maybe the operating steam temperatures are different - but I kinda doubt it matters. But I'd echo what others have said - the problems with nuclear are not to do with generating the heat...you've got heat to spare...so efficiency isn't really the issue. It's all about cost-of-ownership, safety and waste disposal. But coal also generates low level radioactive waste - and it's worst waste product (the CO2) is still untrappable. The worst that a nuclear plant has ever done (Chernobyl) when criminally badly operated - with all of it's safety gear disabled - didn't really cause any more problems than coal plants do when they are operating ordinarily. SteveBaker (talk) 03:03, 11 November 2008 (UTC)

SteveBaker, very well said. Mac Davis (talk) 22:53, 11 November 2008 (UTC)

I suspect the 100,000+ permanently displaced people would consider the Chernobyl event rather different than what "coal plants do when they are operating ordinarily". Dragons flight (talk) 04:56, 11 November 2008 (UTC)

Um, well, Chernobyl did make a huge area of land uninhabitable and dispersed pretty radioactive materials over a large area. I would consider that qualitatively different than the sorts of ills caused by coal. But it's not really the point, and using Chernobyl to discount all nuclear technology is extremely short-sighted, I am sure we would agree... --98.217.8.46 (talk) 03:13, 11 November 2008 (UTC)

Have you ever flown over Wyoming or Kentuky? Coal mining has rendered huge areas effectively uninhabitable also, and the health effects in these areas (mostly black lung disease but also mining disasters) are much worse overall than those from Chernobyl. Nuclear has a dramatically lower overall impact that coal, even when you count in the criminal negligence of the designers and operators of the Chernobyl plant. -Arch dude (talk) 15:22, 11 November 2008 (UTC)

As SteveBaker said, if the steam turbine technology is comparable between nuclear and coal plants then it can be ignored if all you're doing is comparing those two technologies. What matters for the comparison is the differences between the heat sources, including the plant designs and whether one heat source has a much different cost than the other. If you're trying to get a single efficiency number then you'll have to define what you mean by efficiency. Nuclear fuels can produce more fuel from what is otherwise waste, and can generate electricity without a steam cycle. One can also generate heat with uranium by exploding it, or by stacking it a mile high on geothermal piping. -- SEWilco (talk) 04:06, 11 November 2008 (UTC)

(unindent) A sea level rise of just 20cm could create 740,000 homeless people in Nigeria alone. If you buy into the theory that the unprecedented force of hurricanes in the USA over the past few years is related to global warming - then if even ONE of them was caused by CO2 from coal-fired power stations - then Chernobyl is like a damp squib. Most major hurricanes cause 1000+ deaths (many have caused over 8,000) - Chernobyl caused only 47 immediate deaths (although the increased cancer risk will ultimately have shortened the lives of thousands more). If they hit a major city - hurricanes can easily temporarily displace a million people (Chernobyl displaced only 300,000). Well over 300,000 did not return to New Orleans after Katerina which certainly trumps Chernobyl's 100,000 'permanently displaced' people. The Chernobyl disaster has actually benefitted local wildlife - there are species of wild donkey previously thought to be extinct that are now florishing in the depopulated area. Now think about Polar bears...(no, the cute baby ones...yeah - that's it!). SteveBaker (talk) 15:29, 11 November 2008 (UTC)

geting back to the original question, "Power plants employing saturated or only weakly superheated steam have a thermodynamic efficiency of 35% or less. Such power plants include nuclear power " from the google summary of http://www.freepatentsonline.com/3992884.html although i can't find it on the site now, and "35% to 45%" from http://wiki.answers.com/Q/What_is_the_thermal_efficiency_of_the_nuclear_process_for_generating_electricity_and_how_does_it_matter&src=ansTT. seems in the right ballpark, offhand. Gzuckier (talk) 20:04, 11 November 2008 (UTC)

November 11

How to move energy faster than the speed of light

Imagine you have a easily pliable ring millions of miles in diameter. What if one were to stand in the exact center of this ring with a garden hose and release a perfectly even stream of water for one second while doing a 360. The water would then hit the ring causing it to move in a wave that would cover millions and millions of miles (or whatever circumference you would like) in one second. Is this possible?

Thanks--UhOhFeeling (talk) 06:23, 11 November 2008 (UTC)

Only if you are standing in Philadelphia. CBHA (talk) 07:03, 11 November 2008 (UTC)

Since a ring with a diameter (2xr) of about 2 million miles (1,911,200 miles) is already at a distance (r) of 4 times the average distance of the Moon from earth (238,900 miles) all sorts of factors come into play, including what keeps your pliable ring taut, at what speed it is rotating, the fact that neither a garden hose as delivery system nor water as a liquid would have much chance of meeting your "perfectly even stream" requirement. And that's just for starters. Having someone hop up and down on the surface of the ring might have a better theoretical chance of producing a wave, but nowhere near any speed of light. 76.97.245.5 (talk) 08:01, 11 November 2008 (UTC)

Hypothetical example, assume ideal conditions.--UhOhFeeling (talk) 09:28, 11 November 2008 (UTC)

Doing this with a light beam is much more reliable than with water. Just shine a torch away from you, and quickly rotate so the torch shines in all directions. At long distances from you, the torch beam is moving much faster than light. I thought we had an article mentioning this, and why it is not normally considered to count as FTL (because it doesn't allow superluminal information transmission), but I can't find it. Algebraist 09:54, 11 November 2008 (UTC)

Indeed. Or replace the water with raido waves and you have a pulsar. Suppose pulsar is at A and sweeps its beam between B and C, many light years apart, in a fraction of a second. Then energy is transferred from A to B (or to C) at the speed of light - but no energy is transferred from B to C. Gandalf61 (talk) 10:01, 11 November 2008 (UTC)

I guess it's similar to how the group velocity of light can exceed the "speed of light". The key point, as has been said, is that no information is travelling faster that light speed. --Tango (talk) 11:52, 11 November 2008 (UTC)

That is why you need water (or whatever you want, Hypothetical Example) to impart a force on the pliable strip between B and C creating a physical wave moving faster than the speed of light. Under ideal conditions would this hypothetical work?--UhOhFeeling (talk) 19:58, 11 November 2008 (UTC)

Why bother? Light can push stuff, so you can probably get a wave going with that if you want to. You still won't have superluminal information transfer. Algebraist 20:00, 11 November 2008 (UTC)

Sure Light is fine, Hypothetical. Why won't you have superluminal information transfer is my question. Thanks.--UhOhFeeling (talk) 20:04, 11 November 2008 (UTC)

Because as you stand at A swinging your spotlight (at FTL speeds) from B to C, there's no way that events at B at the time the light hits can influence what you're doing (said events are still way in the future at this point). Thus events at B can't influence C FTL through this mechanism. Algebraist 20:11, 11 November 2008 (UTC)

The "wave" isn't propagating along the ring, it's being caused separately at each point when the beam of water or light hits it, so there is no information going along the ring (well, there will probably be a wave propagating as well, but that will follow along behind at a slower speed). The only information moving if from the centre of the ring to the ring itself, which travels at sub-light speeds (for water) of light speed (for light) but never faster. --Tango (talk) 20:13, 11 November 2008 (UTC)

Why would the wave be following along at a slower speed if the energy hit it in such a way that the wall was being pushed in a way that would create a wave faster than light. Couldn't this wave continue after it's initial trip around on it's own? --UhOhFeeling (talk) 01:27, 12 November 2008 (UTC)

Of course not, any more than dropping a thousand rocks into a pond in a line will create some sort of supersonic ripple that arrives at the other end of the pond immediately. Each rock creates a wave (really a set of waves) that spreads out from its point of impact at a fixed speed, and the presence of other waves is irrelevant. (This isn't very precise for waves on the surface of water, but the idea is correct.) Given that you're trying to make a faster wave, you must be dropping the rocks into the pond with very little time between them: so little time, in fact, that the first rock's waves haven't reached the last rock when it hits! This means that the rest of the pond (in the direction of the line of rocks) will see the wave from the last rock before any of the others have had any effect on it. This is what is meant by the lack of superluminal information: the first rock can't affect the last rock because information about its impact on the water can't get to the last rock's impact.

With the speed of light, the "can't affect" becomes an absolute statement that encompasses all kinds of effects, so it is simply irrelevant to each part of your ring that you have already doused some other part, since the other parts are all too far away to have affected it (yet). At the moment your last bit of water hits the ring, that part of the ring is aware only of that last bit of water, so we can't expect that part of the ring to do anything special like maintain the ludicrous speed of the "wave". (Put differently, there is no single object that we may call "the wave", because it's not causally connected.) Moreover, assuming all the miniwaves propagate at the same speed, no previous part of the wave will ever catch up to the leading edge (where the water hit last), so there won't even be interference at that edge to make anything interesting happen.

In short, the answer is Yes, it's possible, but so what?. The fact that the water was once all in the center with you does not make it one object when it hits the ring, because it too has become causally disconnected. The various events of bits of water striking bits of ring are unrelated, and any "speed" you assign them as a group (by considering the change in position with respect to time of "the most recent place where water has hit") is entirely a construct of your perception.

Finally, note that non-physical speeds such as that of the water-ring contact point are not well defined given the existence of other observers; for an observer moving at an appropriate relativistic velocity, the wetting of the ring may be happening in more than one place at once and be moving in the opposite direction you say it is! --Tardis (talk) 17:11, 12 November 2008 (UTC)

See also Superluminal Scissors (wot, no article?); here, then. --Sean/76.182.94.172 (talk) 13:36, 11 November 2008 (UTC)

Cool article, I'm not sure if it applies here as the information would be directly impacting the surface rather than traveling the length of the scissor edge.--UhOhFeeling (talk) 20:02, 11 November 2008 (UTC)

Is concussion or neck injury common in horned animals?

Or, at least, the ones attacked to their heads?

I suppose the answer is kind of straightforward - the ones who would suffer them were sorted out long ago because they didn't survive - but it's one of those questions I have if I awaken in the middle of the night.

Reading about sheep (redirected from rams), I didn't even find much about their horns, though considering that the article says injuries are one of the main causes of death for them, maybe it does still happen.

I would also think that perhaps said horns are so incredibly thick that the constant head butting never gets through to their skulls. However, I also wonder if that doesn't increase the chance of neck injuries.

Thanks.Somebody or his brother (talk) 13:06, 11 November 2008 (UTC)

See the comments here for some thoughts on the relative resistance of head-butting animals to traumatic brain injury. - Nunh-huh 16:04, 11 November 2008 (UTC)

Which begs the question, if a sheep is concussed, or suffers cognitive impairment, how does one know? It isn't like the sheep was writing novels or working out differential calculus before the injury... --Jayron32.talk.contribs 19:31, 11 November 2008 (UTC)

You could devise some simple tests for the sheep to compare cognition before and after. Even measuring pupil reactivity or something. Plasticup ^T/C 23:48, 11 November 2008 (UTC)

The force of the collision can't "stay" in the horns (unless they deform but that is besides the point...) The force has to dissipate somewhere, which is down the horns, across the head, down the neck, into the body and to whatever is anchoring the animal in place ( In this case the hooves). Here is some info as it related to woodpeckers (http://web.cornell.edu/blogs/theessentials/?p=395) I bet some of it carries over... 152.16.15.23 (talk) 19:48, 11 November 2008 (UTC)

How many cells are in an embryo when it splits into twins?

I understand that identical twins are formed when an embryo splits very early on. How many cells are in the embryo when it splits? Is it always the very first split that results in two embryos? —Preceding unsigned comment added by JeremyStein (talk • contribs) 15:07, 11 November 2008 (UTC)

The article you link to answers yoru question in the first paragraph and the start of the second: "If the zygote splits very early (in the first two days after fertilization), each cell may develop separately its own placenta (chorion) and its own sac (amnion). These are called dichorionic diamniotic (di/di) twins, which occurs 18–36% of the time.[15] Most of the time in MZ twins the zygote will split after two days, resulting in a shared placenta, but two separate sacs. These are called monochorionic diamniotic (mono/di) twins, occuring 60-70% of the time[15]. In about 1-2% of MZ twinning the splitting occurs late enough to result in both a shared placenta and a shared sac called monochorionic monoamniotic (mono/mono) twins.[15] Finally, the zygote may split extremely late, resulting in conjoined twins."

I'm not sure how many cells the earliest splitting equates to, but it's clear that splitting is possible at almost any point in the pregnancy. 137.108.145.10 (talk) 15:35, 11 November 2008 (UTC)

well, i'm not sure that conjoined twins are split later on, so much as twins which have fused later on. the requirement for splitting the embryo is that it must happen early enough so that each cell is totipotent i.e. can take off and start an embryo on its own. this is a handy property for lab tinkering; you take an early embryo, gently take the cells apart, and you have a bunch of identical embryos. repeat as desired. according to our article, this stops at about 4 days. i'm not expert, so i'll accept that. doesn't sound unreasonable. at this point the cells begin to become increasingly specialized; for instance, the first thing is that cells become to think of themselves as one end of the embryo or the other. from fruitfly work, if you then transplant cells from one end to the other things go haywire, but if you move the cells at each end around on the same end, no problem. the specialization then gets more specific from there downhill, like at one point you can swap the future leg and antenna and each will switch to the correct item for where it now is, but the next day it won't. this implies that it's the neighboring cells that somehow tell the developing cells what they're supposed to be, and as each part develops the cells within tell each other what they're supposed to be doing. it's fascinating stuff. caveat: i haven't read anything about it in a decade or so, so this represents state of the art for the end of the last millenium. Gzuckier (talk) 15:53, 11 November 2008 (UTC)

Totipotent cells are present in the morula up to the 16-cell stage. At 32 cells, the morula begins to differentiate. So it isn't necessarily the first split that leads to identical twins. A split anywhere up to 16 cells can lead to identical twins. Axl ¤ [Talk] 11:30, 12 November 2008 (UTC)

basic anatomy

why do you taste eyedrops after applying them to your eyeballs? —Preceding unsigned comment added by 69.246.63.171 (talk) 18:53, 11 November 2008 (UTC)

It's because the drops travel down the nasolacrimal duct into your nasal cavity and from there down onto the back of your tongue. Fribbler (talk) 19:01, 11 November 2008 (UTC)

That's awesome!! Mac Davis (talk) 22:55, 11 November 2008 (UTC)

I wonder if it goes in reverse: i.e. spicy foods causing one's eyes to burn. I still figure the majority of the cause of that is airborn molecules but now I wonder... 152.16.15.23 (talk) 23:58, 11 November 2008 (UTC)

A dentist once injected novocaine into the inside of my cheek and it went up into my eye, which went numb. The tears that came out and ran down my cheek from the stinging tasted of novocaine. She said "oops". --Sean 01:03, 12 November 2008 (UTC)

How does the exchange of virtual photons mediate attractive vs. repulsive coulomb force?

I understand that, in QED, it is the exchange of virtual photons that mediates that coulomb force via the transfer of momentum. However, what I am having difficulty tracking down is how the charge information is carried. (I.e. whether the transfer should function as attractive or repulsive force.) I'm willing to work my way through the technical details if I can just be pointed toward a good online source, such as some scientific journal articles. (The virtual particle FAQ didn't prove useful for me, unfortunately.) Any suggestions? Thank you.—RJH (talk) 20:11, 11 November 2008 (UTC)

Hmm, no help here then.—RJH (talk) 16:54, 14 November 2008 (UTC)

pain

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glass recycling projects third world

We live in the Namib desert in Namibia and require information about recycling glass for a community project. Is there a way of reusing the glass bottles to manufacture glass tiles or beads or any other product to either sell to tourists or reuse in a sustainable way? Your advise will be much appreciated.

Johan Raubenheimer <email redacted> —Preceding unsigned comment added by 41.198.48.196 (talk) 21:53, 11 November 2008 (UTC)

Glass is a pretty recyclable material - you just need a sufficiently hot furnace - and people with the right skills to reform the liquid glass into new shapes. I guess in the Namib, the problem will be finding fuel for the furnace. I wonder if it would be possible to make a solar furnace with enough power to do the job? Making glass animals is a pretty easy skill to learn - you can do that with a small propane torch - you don't even need a furnace. If you have someone with the imagination to produce something unique, then you would have something to sell to tourists. The trick will be in finding a compelling and unique art style. If you can find the talent - you could sell the product on the Internet too. Small, high value product that don't have high shipping costs are a great choice for Internet marketting. SteveBaker (talk) 00:06, 12 November 2008 (UTC)

Also see Bottle wall for one use not requiring melting/furnaces. There are others. We used to make vases by coating and/or cutting glass bottles. Get a bunch of people together and brainstorm. 76.97.245.5 (talk) 07:33, 12 November 2008 (UTC)

surface of last scattering

Cosmic_background_radiation#Features says:

Accordingly, the radiation from the sky we measure today comes from a spherical surface, called the surface of last scattering. This represents the collection of points in space (currently around 46 billion light-years from the Earth—see observable universe) at which the decoupling event happened long enough ago (less than 400,000 years after the Big Bang, (13.7 billion years ago)) that the light from that part of space is just reaching observers.

If the event occurred 14 billion years ago in that space, shouldn't it only be 14 billion light-years away instead of 46 billion ly? At first I was thinking that we're moving away so fast that it takes 4 times as long for the light to reach us, but that violates special relativity, right? So how can both those numbers be right? Thanks 72.236.192.238 (talk) 22:44, 11 November 2008 (UTC)

It doesn't violate special relativity because there isn't actually any movement involved, it's just the space inbetween expanding. When we talk about the universe expanding that doesn't mean everything in it is moving outwards it means the actual spacetime itself is expanding. The standard analogy is to think of a balloon. Before you blow up the balloon, draw some dots on it. Now as you blow it up those dots get further and further apart, but none of them has actually moved relative to the balloon. --Tango (talk) 22:56, 11 November 2008 (UTC)

See Metric expansion of space#Understanding the expansion of space. The pictures illustrate a nearly identical situation (light from 12–13 billion years ago, instead of 13.7, from an object that's now 28 billion light years away, instead of 46). -- BenRG (talk) 23:10, 11 November 2008 (UTC)

It is really quite simple (simpler than the above answers make it sound). The thing we see as the surface of last scattering is moving rapidly away from us (Hubble expansion). Today we can see light from it that was emitted 13 billion years ago, and we infer from where it was then and how fast it has been moving that it should now be 46 billion light years away. In other words, it is simply a matter that the separation is believed to have increased a lot during the time it took the initial light to reach us. Dragons flight (talk) 23:40, 11 November 2008 (UTC)

Black knees

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If you are concerned about unusual symptoms you experience after physical exertion, you should speak to a medical expert. TenOfAllTrades(talk) 23:24, 11 November 2008 (UTC)

I'm not concerned about the symptoms; it's a physiological question. Not worth a wasting the Doctors time. So I'll ask agin, why do my knees look like they are bruised when I come back from a long run, but it isn't a bruise as it goes away a couple of hours later. --TrogWoolley (talk) 00:21, 14 November 2008 (UTC)

any way to guess how long it took someone to write something?

Resolved

I'm wondering if there is any way to come up with an approximate guess as to how long it took someone to write something. in particular, how could I go about guessing how long it may have taken to write these paragraphs in particular? What about a more general way to guess? —Preceding unsigned comment added by 83.199.126.76 (talk) 23:07, 11 November 2008 (UTC)

Probably the wrong place. Touch typists can manage up to 1k per minute, although 400 characters per minute is more typical. --Stephan Schulz (talk) 23:21, 11 November 2008 (UTC)

Wikipedia on this article cites it at 50-70 words per minute. I guess I'd use that as a baseline but obviously it's going to depend on the individual. —Cyclonenim (talk · contribs · email) 23:25, 11 November 2008 (UTC)

Two things: one, what does "probably the wrong place" mean? Two: why do you both talk about typing speed, when I mean writing speed. We're not talking about chatting (or how I'm writing now), but composition as well....surely it's less than blind typing, especially when we're talking about references as well... Can anyone give me a minute estimate for my above link specifically, and how you made that guess? Thank you!

You're in the wrong place because this problem is not well enough defined to have a useful scientific answer. I gave you a lower limit. Composition speed is often considered half of typing speed, but that of course depends on how well the writer is familiar with the topic and if they know what they actually want to say. You might get some anecdotal evidence at the language or humanities desk. --Stephan Schulz (talk) 00:10, 12 November 2008 (UTC)

Okay, so I cut and paste the paragraphs into a character counter and divided by five, because hte typing speed article says every five characters counts as a word (regardless of actual space locations), and got 1022. So if the guy composed it continuously, and was able to type all that at 60 words per minute, then if composition is half of typing speed (30 wpm) it took him 34 minutes. If he was very thoughtful and typed half as slowly, it took him 68 minutes. And the upper limit is about 15 hours, because that's how long there was between when what he's replying to appeared, and his reply.... So... anywhere from 34 minutes to 15 hours. Can we do ANY better than that?

I think it's pretty clear that the answer is "No". We know the time when the edit was committed - but we don't know when the person started to type it. It's certainly not just a matter of typing speed - thinking speed matters too. Also, if they proof-read and then go back and fix up errors or decide to expand upon a particular thought...there is truly no way to put a number on it. SteveBaker (talk) 23:49, 11 November 2008 (UTC)

Do you agree with my reasoning of between 34 minutes and 15 hours? Can you find a trick to improve it by a TAD? (such as a way to figure out that it's almost certainly less than ten hours -- ALL of us know this intuitively!)

No - I certainly don't agree. We have no idea whether this was bulk cut/pasted from other sources - or whether this was a synthesis of some other document written in advance - or whether this is a very thoughtful piece composed by someone with many interruptions who goes through many drafts before hitting that 'Send' button. Heck, he may have been thinking about this for a year and only just now decided to put his words into print. There is quite simply no way to know - and any kind of speculation is just that: "speculation". SteveBaker (talk) 04:49, 12 November 2008 (UTC)

Thank you. You have me convinced. I realize I can't even have an upper limit of even the lifetime of the poster, since the paragraphs could include cut-and-paste from deceased people as well! :( I guess the conclusion is exactly what you first said, no way to know even approximately. You can put a green checkmak, resolved, next to this question (I don't know how to do it). Thanks!

FYI: You add {{resolved}} just under the title of the question. SteveBaker (talk) 18:11, 12 November 2008 (UTC)

May I ask why it has to be less than 10 hours? And on a second note, sometimes people leave their computer in the middle of typing, so really even 10 hours is possible. —Preceding unsigned comment added by 76.69.241.185 (talk) 00:56, 12 November 2008 (UTC)

I understand that Flaubert wrote Madame Bovary at a rate of about 1 sentence per day. --Sean 01:12, 12 November 2008 (UTC)

At the other end of the spectrum, Anthony Trollope wrote 1000 words an hour, day in, day out for years, according to Brittanica Concise Encyclopedia. Clarityfiend (talk) 04:13, 12 November 2008 (UTC)

Leonhard Euler likely more than that. Mac Davis (talk) 22:22, 12 November 2008 (UTC)

November 12

What shape is this?

I was thinking about this some time ago. Imagine a small room that has a door on each of its six faces. On the center is a flower pot and some clothes that I discarded. If I open and enter any of the doors in this room, I will enter a room with the flower pot and the same clothes that I discarded earlier. My question is, what is the shape of the room? I'm pretty sure it is not 3 dimensional. --Lenticel ^(talk) 00:37, 12 November 2008 (UTC)

I think you have been trapped in a game. In many old 2D games when you went off one side of the screen you reappeared at the other side. Obviously they have upgraded your game to ake advantage of a graphics processor to do 3D. On the other hand you might like to read the bit at the end of Shape of the Universe,we may be in something far weirder. 01:10, 12 November 2008 (UTC)

A room with 4 walls, a floor, and a ceiling could be considered as a cube with six faces. CBHA (talk) 02:43, 12 November 2008 (UTC)

This reminds me of a hemicube. Anyway, I'd say either the room is three dimensional, but the geometry isn't Euclidean, or you're on a three-dimensional analogue of a torus. That is, the surface is three-dimensional. — DanielLC 01:22, 12 November 2008 (UTC)

Topologically speaking, if the room has six walls in addition to floor and ceiling, the floor of the room could be a sphere, a torus, or a projective plane, for example. If it has four walls + floor and ceiling, then the room could be a three-torus or any number of weirder manifolds. Algebraist 01:31, 12 November 2008 (UTC)

Wow, this weirder than I thought. --Lenticel ^(talk) 01:37, 12 November 2008 (UTC)

We could narrow it down further if we knew whether or not going through any of the doors changes you from being right-handed to left-handed, or vice versa (or, equivalently, makes everything else in the room turn into its mirror image, but changing you sounds more fun!). --Tango (talk) 01:46, 12 November 2008 (UTC)

We also want to know whether going through a door changes your "up". —Tamfang (talk) 07:56, 14 November 2008 (UTC)

I wonder whether you got this idea from Cube 2: Hypercube which has similarities (but limited logic). PrimeHunter (talk) 01:56, 12 November 2008 (UTC)

Well I got the idea while I was taking a bath earlier today. The cramp bathroom inspired the idea. By the way, the movie seems to be cool. Maybe I'll try to find a DVD version later.--Lenticel ^(talk) 02:18, 12 November 2008 (UTC)

If the answer is "not 3 dimensional", then the word you're looking for is "Hexagon". APL (talk) 14:03, 12 November 2008 (UTC)

It's not a tesseract is it? It's a non-3-dimensional shape which is connected in ways I don't understand. AlmostReadytoFly (talk) 16:35, 12 November 2008 (UTC)

A tesseract is 4D, I don't think we have any reason to believe we're working in 4 dimensions. --Tango (talk) 16:42, 12 November 2008 (UTC)

Potential Energy

For the sake of simplicity, let's consider gravity. Now I understand why the gravitational potential energy of an object has to be negative (as it approaches the source of gravity its potential energy must decrease in order to allow its kinetic energy to increase), but isn't energy the ability of an object to do work? And so it seems odd that an object could have negative energy (when its, say, lying on a table). How would one resolve this apparent contradiction? Thanks. —Preceding unsigned comment added by 76.69.241.185 (talk) 00:46, 12 November 2008 (UTC)

It doesn't have to be negative, you can set the zero of potential energy to be anywhere you like. The maths is often easier if you set the zero to be at infinite distance and thus have it always negative, but it doesn't really matter. All that matters is the change in energy. For an object on a table it would probably make sense to set the zero to be when the object is on the ground, since that's the lowest it can get. If you do that, then when it's on the table it has positive energy and can do work as you would expect. --Tango (talk) 01:04, 12 November 2008 (UTC)

For an object A in a gravitational field of another object B, it makes sense to define a zero of potential energy at very large (infinite) distance between the objects, and to measure the velocity relative to the center of mass (CM) of the system of the two objects. Then, if the TOTAL energy of A is negative, then it is on the bound orbit around CM ; and if the TOTAL energy of A is positive, then it is on the open orbit. Gravitational potential energy of A is always negative. If A performs work, its total energy decreases, but its instant potential and kinetic energy may either increase or decrease, provided their SUM (the total energy) decreases and provided the potential energy stays negative. Now, for the AVERAGE potential and kinetic energies of A in the BOUND orbit, you can apply a so-called virial theorem. For a classical gravitating system, it states that AVERAGE kinetic energy Ekin equals minus half the AVERAGE potential energy, Ekin = -Epot/2 ; or, equivalently, Etot = Ekin + Epot = -Ekin = Epot/2 < 0 . In a two-body system the AVERAGE is determined over a closed orbit; in a many-body gravitational system the strict average is over an infinite time, but for a "very large" finite time the result holds with high accuracy, too. Anyway, since E = Epot/2, body A performing work DE > 0 changes E to E - DE, so makes Epot "more negative" (thta is, larger in its absolute value). That means that Ekin also becomes larger in its absolute value! What happens is, the body A, having lost some energy, moves to a tighter orbit where its total energy is indeed lower (larger in absolute value, and negative) but its mean-square speed is higher. Hope this helps. --Dr Dima (talk) 01:47, 12 November 2008 (UTC)

Camera red eye and white eye

I've noticed that my new camera often causes people to have one red pupil and one white pupil instead of the standard camera red eye. I thought that the red eye was caused by reflection of the red on the back of the eye. So, that doesn't explain how the white eye effect is produced. It never happened with any of my older cameras. So, I am left wondering if it is the camera. Has anyone else here had a camera do this? Is there a fix to make it stop doing it? It is a pain because the auto-removal of red eye doesn't work if the pupil is white. -- kainaw™ 01:41, 12 November 2008 (UTC)

Could it be some weird anti-red eye feature going horribly wrong? Try turning off any weird anti-red eye features and see if it stops happening. --Tango (talk) 01:50, 12 November 2008 (UTC)

Also, have you tried it with different subjects? Maybe the person you are photographing has a strange eye (in which case, they should probably see a doctor!). --Tango (talk) 01:51, 12 November 2008 (UTC)

I have noticed it with more than one person. About 90% of the times I've seen are with my son. But, about 99% of the photos I take are of him. So, there is no reason to think he is more prone to it. I've tried to turn off all weird functions on the camera. It isn't easy to use because it is designed to be so easy to use that it decides what you want and does it for you - refusing to let you decide what you want. Something I did got it to stop blinking the flash 4-5 times before snapping a photo - which often meant that the cool photo of my son would end up being him covering his eyes and turning away from the evil flashing light. -- kainaw™ 02:08, 12 November 2008 (UTC)

This site has any explanation of camera red eye and one reason for white eyes: [7] Rmhermen (talk) 02:11, 12 November 2008 (UTC)

Thanks. It commented on the reflection being common when the pupil is angled away from the camera, towards the nose. Looking back at the photos I didn't manually correct, I can see that the people with one white eye are looking away from the camera and towards their nose. -- kainaw™ 02:40, 12 November 2008 (UTC)

I suppose it's worth asking whether your son is cross-eyed? If the two eyes were not pointing in the same direction - then the reflection off the retina of one, would not occur on the other eye. It's hard to imagine any other reason. SteveBaker (talk) 04:41, 12 November 2008 (UTC)

It's also possible if the camera is close to the person's face, but they're looking at something well behind the camera. I don't know how close the camera would need to be for this. --67.185.190.46 (talk) 06:36, 12 November 2008 (UTC)

My understanding is that if the eye is looking straight at the camera the flash will produce a reflection of the vascular, and thus red, back of the retina. However if the eye is not directly aligned with the camera the reflection is of the less vascular parts of the retina producing a white reflection. I believe the phenomenon of 'red-eye' is a human problem associated with the particular vascular anatomy of the human retina. Perhaps it occurs in other primates. Richard Avery (talk) 08:13, 12 November 2008 (UTC)

Since this is occurring with photos of several people, a medical cause is unlikely. However retinoblastoma can give this appearance. Axl ¤ [Talk] 12:05, 12 November 2008 (UTC)

Now that I had some search terms for Google (thanks), I understand. This happens with children and isn't very uncommon. If a child is looking away from the camera (by about 15 degrees), the eye that is looking towards the nose will turn white. The other will be dim red - not a complete red-eye, but not white either. If you look at eye, you can see the main optic nerve is not dead center in the back of the eye. It is about 15 degrees off center. So, if the child is looking away at just the right angle, you get reflection off the optic nerve, not the nice red part of the eye. Further explanation that I've found from tons of Google hits is that this is limited to children because the size of the whitish area around the optic nerve is larger in relation to the size of the eye than it is in adults. Also, adults tend to look at the camera, not slightly away - so they don't even get in position for this sort of reflection. Since I've been mainly photographing my 1-year old son and his friends, I've been picking up a lot of kids at just the right angle to get the white-eye reflection. -- kainaw™ 13:41, 12 November 2008 (UTC)

Light Has Intelligence?

I saw a "documentary" recently in which a "scientist" stated that light has shown to anticipate experiments in which it is involved. The guy did not seem like a crack pot. What in the world could he be referring to? —Preceding unsigned comment added by 75.67.217.220 (talk) 01:52, 12 November 2008 (UTC)

Perhaps retrocausality? Jkasd 02:16, 12 November 2008 (UTC)

See also, freebasing and crack cocaine. Plasticup ^T/C 02:50, 12 November 2008 (UTC)

I suspect you're thinking of things like the "wave-particle duality" effect and quantum mechanics. Because of the wave–particle duality of light, the results of certain experiments seem to depend on how you are measuring the results - which leads one to kinda imagine that the light in the experiment "knew" how you were ultimately going to measure it - and changed it's behavior beforehand.

I recommend reading Double-slit experiment - and Quantum eraser experiment.

Suffice to say, the light isn't "intelligent" - but it does behave in ways that seem so far from our normal experience that it's almost impossible to get your head around the implications. This stuff leads us into the ideas of parallel universes and all manner of other weirdnesses.

SteveBaker (talk) 04:37, 12 November 2008 (UTC)

I'd guess the Elitzur-Vaidman bomb-tester is closest to what he might have been thinking of Dmcq (talk) 09:04, 12 November 2008 (UTC)

The deal with light is that it is not a particle or a wave, it is its own thing. Its just "light". We have models that treat it like a particle; and those models work to explain some of the behaviors of light. We also have models that treat it like a wave; and those models work to explain some of the behaviors of light. The deal is, that both models fall apart roughly 50% of the time; that is for any set of conditions in which light behaves as a particle, the wave model looks like it doesn't work, and visa-versa. The reality of light is that it doesn't have an analog in the "big" world. You can't say light is like _blank_, where _blank_ is any thing you have the ability to manipulate with your hands. Any "contradictions" in lights behavior, which make it, for example, appear "intelligent" as described (such as the aforementioned Double-slit experiment), are just the result of the faultiness of our models. Its our problem, not light's... --Jayron32.talk.contribs 17:24, 12 November 2008 (UTC)

The trouble is that this is simultaneously a correct - but also intensely frustrating - answer! You're absolutely right - light is something for which we have no analogs - which leaves us no way to explain it that does not tempt us into dangerous extrapolation-from-experience. Ordinary 'stuff' has a mass and you can stop it moving. Then you can stick it on a weighing machine and you know it's mass. When you push ordinary stuff towards light-speed, it gets heavier and heavier - and if you could somehow get it up to light speed, it's mass would be infinite. So the mass of normal 'stuff' is infinite at the speed of light and something reasonable all the rest of the time. Photons, however can only move at the speed of light - but yet they have actual sane, finite masses. Time is similarly warped - so for the photon, time doesn't exist...neither does distance. It's no wonder that it 'misbehaves' in every way imaginable compared to normal 'stuff'. The very nature of the zeroes and infinities that pop up at the speed of light in relativistic calculations pretty much guarantees that light is going to be weird. SteveBaker (talk) 22:05, 12 November 2008 (UTC)

How come garbage explodes only when it's buried?

The old lady told me to take out the garbage earlier (always naggin') so I jokingly said I'll chuck it in the backyard. Then she said "You can't throw it in the backyard, ass-h*le, it'll draw rats!" Then I said, "Fine, I'll bury it! That way I wont have to pay a goddam garbage bill!" Many colorful obscenities later she told me that garbage will explode if buried for a short time. I didnt want to agree with her at the time, but I vaguely remember hearing that's why landfills are vented and have flames shootin out of factory whistle lookin thingamajigs. My neighbor 3 trailers down has had garbage all over his yard for years that wasnt buried and he hasnt had no problems. Not even rats. What gives?Sunburned Baby (talk) 02:28, 12 November 2008 (UTC)

Maybe it explodes on Wednesdays while your friend is at work? —Preceding unsigned comment added by 83.199.126.76 (talk) 02:32, 12 November 2008 (UTC)

Much of our garbage tends to produce methane when it decomposes. When sitting in the open, the gas just floats away. When buried, it builds up in pockets. If, for some reason, the pocket of gas is ignited, it can make a small explosion. Venting natural gas from landfills isn't done just for safety. There are people who buy natural gas, so the landfill companies bottle up the byproduct for profit. So, why not bury your garbage, stick a hose down in it, and funnel off the gas into some empty wine boxes you have laying around. You might make enough to pay for a whole week's worth of lottery tickets. -- kainaw™ 03:06, 12 November 2008 (UTC)

The "some reason" for the gas igniting Kainaw mentioned is often an exothermic reaction in the decomposition process. I tried to find a nice link for you. Although several sites including our Composting page mention the fact that decomposition by anerobic bacteria generates heat, I've failed to find a nice concise description of the process. Anaerobic respiration holds some clues, but not much context. What you get is spontaneous combustion which has a dead end link to Fermentation (biochemistry). Don't get you hopes up for not getting rats when you bury the stuff. I used to live next to a former dump and the critters had no problem burrowing to the larder. You'd just get a chance to ignore what you don't see. Your neighbor who didn't get any might have had a local ecosystem (e.g. snakes, cats, owls etc.) that kept the rat population down to an unnoticeable/non existent size. The amount of biogas you get out of your household waste is not likely to reach marketable amounts unless you wish to build a Mount Trashmore in your back yard. The volume of easily digestible biomass in proportion to stuff that takes decades to break down is likely not very high. To reduce the volume of trash you put out you could deliver glass, plastics, metals and paper to a local recycling center and pepper your back yard with compost barrels (no access for rats) to use the compostable portion of your biodegradable trash. Depending on gas prices and local garbage collection policies and prices you might come out ahead or not. 76.97.245.5 (talk) 07:17, 12 November 2008 (UTC)

Methane as cause of global warming

Im looking for references that Methane in the atmosphere causes much more global warming than co2 and therefore that burning natural gas is good for the earth.--GreenSpigot (talk) 02:58, 12 November 2008 (UTC)

Woooaahh...be very VERY careful how you say that!!

Our Methane article does indeed say (correctly) that "Methane is a relatively potent greenhouse gas with a high global warming potential of 72 (averaged over 20 years) or 25 (averaged over 100 years)." (and there is a reference for that). CO2 has a 'global warming potential' of 1 - so clearly Methane in the atmosphere is a REALLY bad thing.

HOWEVER it is most certainly NOT a good idea to drill for natural gas and burn it in order to save the planet! It's far better to leave it underground where it belongs! Methane deep underground where it's been safely buried for millions of years - is just fine where it is! The only (exceedingly special) time when what you say is correct is if the natural gas is already in the atmosphere - then converting it to CO2 is better than waiting for many decades for it to degrade by itself.

So please don't go around saying "we should all be using natural gas because it's good for the atmosphere" - because nothing could be further from the truth! The kinds of situation we're talking about is when (for example) you have a herd of dairy cows and their poop would normally produce a bunch of methane that would do terrible things to the planet - then it is much better to use that methane as a fuel (both extracting some useful energy - and converting it into much safer CO2 in the process).

SteveBaker (talk) 04:22, 12 November 2008 (UTC)

Methane is more potent per molecule; however, in absolute terms we've added much more CO2 to the atmosphere than methane, so methane has had less of a global warming impact than co2. Dragons flight (talk) 05:53, 12 November 2008 (UTC)

Yes - I agree. This may change as the methane clathrate deposits in the deep oceans begin to melt. There has been some evidence that this exceedingly nasty situation is starting to occur - and (reluctantly) one has to say that burning the stuff as fuel (converting it to CO2) before it can ramp up the greenhouse effect (with the potency of methane) might be a last-ditch way to survive that situation. However, it's a decidedly "non-trivial" problem to do that - and we'd want to be very sure that the runaway melting of these deposits was really going to happen before we took such a drastic step. SteveBaker (talk) 14:57, 12 November 2008 (UTC)

Full moon on birthdays

Over the course of a lifetime of, say, 85 years, how often could one expect their birthday to coincide with the full moon? -- JackofOz (talk) 05:34, 12 November 2008 (UTC)

Three times on average. Dragons flight (talk) 05:54, 12 November 2008 (UTC)

Thanks. How did you work that out? -- JackofOz (talk) 07:29, 12 November 2008 (UTC)

A full moon occurs once every 29.5 days according to its article, so a birthday has one chance in 29.5 of coinciding with one. 85 is almost three times 29.5. (Something for werewolves to look forward to?) Clarityfiend (talk) 07:58, 12 November 2008 (UTC)

Yep, that's what I originally figured. It just felt way too low, so I thought I must have gone wrong somewhere. Depending on where the birthday falls, you might only manage 2 birthday full moons in an 85-year lifetime. Is there any way to work out, for any particular birthday and a given starting year, when the birthday full moons will occur, or do you have to use an ephemeris and do it "manually"? -- JackofOz (talk) 08:22, 12 November 2008 (UTC)

It probably sounds low because the moon changes size quite slowly and appears full to the naked eye (at least mine) for several nights a month. Algebraist 08:25, 12 November 2008 (UTC)

You probably would need an ephemeris; the 29.5 days varies a bit. However, there may be astrological software that can tell you when a solar return (birthday) coincides with a sun-moon opposition (full moon). You would also need to know the place of birth so that you could reduce the time to UT, the time used in most ephemerides.--Shantavira|^{feed me} 08:43, 12 November 2008 (UTC)

Pneumonia

What is the survival rate for untreated bacterial pneumonia if the victim is an otherwise-healthy young adult? --67.185.190.46 (talk) 06:28, 12 November 2008 (UTC)

Untreated, bacterial pneumonia kills ~30% of the afflicted [8]. Dragons flight (talk) 06:45, 12 November 2008 (UTC)

But it's occurrence and observation is, I assume, much higher in the sick and elderly. Being in good physical condition and having a robust immune system bacterial pneumonia may manifest itself as only a cough and I may not even go to the doctor. Any measurements (short of those from controlled experiments) is going to suffer monstrous selection bias. Plasticup ^T/C 15:05, 12 November 2008 (UTC)

Pneumonia describes an illness that necessarily has certain symptoms, i.e. fluid in the lungs, almost always accompanied by fever and some degree of difficulty breathing. If you only have a cough, then you might have an infection, but you do not have pneumonia. Dragons flight (talk) 16:22, 12 November 2008 (UTC)

It's certainly possible that a person whose only symptom is a cough has pneumonia. It's especially possible in the elderly or others with immune dysfunction, but not what you'd expect in the young: I think Darongs flight's point is that those with vigorous immune responses fight off infection before it becomes pneumonia. Since the question asks specifically about the young, we can't give a reasonable answer if the population studied includes the elderly and we don't have the data to correct for age. 30% is certainly high for a young population. - Nunh-huh 17:26, 12 November 2008 (UTC)

Lots of folks (especially kids) get so called walking pneumonia, otherwise identified as atypical pneumonia, often with mycoplasma as the causative agent. As a result of the slow growth rate of this organism, a generally healthy patient can exhibit nothing more than a nagging cough and certain degree of lethargy as they go about their daily business, which doesn't clear up after a long period of time. Most parents I know (who are reasonably frequent consumers of healthcare) are quite familiar with it. I'm not sure how it resolves itself if untreated, what I see is parents who see those symptoms in their kid for a couple of weeks, go to the doc and get the diagnosis, and get it treated with specific antibiotics. But if you're the type of person who avoids doctors unless absolutely necessary, for whatever reason, you probably wouldn't be worried enough to seek attention.Gzuckier (talk) 17:45, 12 November 2008 (UTC)

Query about today's featured picture.

What a fantastic picture, but that apart can anyone explain the blue/green light circle at the rotor tips. I understand that it is caused by lights but what is the purpose of the lights, surely they are not decorative. Are they part of some safety system that shows the position of the rotors at night to prevent..um.. unpleasant accidents? Richard Avery (talk) 08:23, 12 November 2008 (UTC)

Link to the image. Just in case this will not be answered today.--Lenticel ^(talk) 09:32, 12 November 2008 (UTC)

That's definitely an amazing photograph! This pdf linked from the V-22 Osprey talk page mentions "upgrading rotor tip lights & formation lights for improved night vision goggle (NVG) compatibility" and this page also mentions that the "prop-rotors have lights in the rotor tips for night safety." --LarryMac | Talk 14:23, 12 November 2008 (UTC)

See these pictures 1 and 2 of the B-25 Mitchell, an American bomber during the Second World War: it's long been a common practice to have something light at the edges of blades, although as you can see, 60+ years ago they simply painted the propellor tips rather than having lights at the edge. Nyttend (talk) 14:42, 12 November 2008 (UTC)

Certainly it's so that the pilot can visualise where the rotor tips are - that's especially important in this aircraft because it's a tilt-rotor craft - those engine nacelles swivel through roughly 90 degrees between hovering and forward flight. When hovering in confined areas - it's really useful to be able to see that your rotor tip is just about to whack into a tree limb or a lighting pole or something. I strongly suspect that they only turn them on in those specific circumstances because military aircraft don't generally want to be seen at night. SteveBaker (talk) 14:50, 12 November 2008 (UTC)

Thanks guys and gals, kind of what I thought but you have collectively sourced and expressed it so well. Richard Avery (talk) 15:21, 12 November 2008 (UTC)

Mars

How long could an unprotected human survive on the surface of Mars? —Preceding unsigned comment added by 195.188.208.251 (talk) 12:35, 12 November 2008 (UTC)

According to drowning, lack of oxygen takes about six minutes to cause brain death, so at most that long. I think that'll kill you before the cold does, but I don't know for sure. Algebraist 12:57, 12 November 2008 (UTC)

I'm not sure drowning is a fair comparison.

In any case the article on Time of Useful Consciousness, says for altitudes over 50,000ft, you've only got 9 to 12 seconds before you lose the capacity for rational thought. The surface of Mars would be similar or worse. So, you'd want to get back inside pretty quickly. APL (talk) 13:59, 12 November 2008 (UTC)

The atmospheric pressure on the surface of Mars is a shade less than one percent of the air pressure at Earth's sea level. For the purposes of sustaining life, it's better described as a low-quality vacuum than an atmosphere. In that vein, you'll probably be interested in our articles on the Armstrong limit, Human adaptation to space#Unprotected effects, and space exposure. Briefly, you would expect somewhere in the neighbourhood of 10 seconds of useful consciousness. Based on animal experiments, if your friends dragged you into the airlock and repressurized you within about 90 seconds, you'd probably survive without permanent injury. Beyond that threshold, you're probably toast. (I would expect rapid, serious damage to the lungs.) TenOfAllTrades(talk) 15:53, 12 November 2008 (UTC)

What would cause that damage? If you survive the initial decompression (most importantly, don't try and hold your breath), the barotrauma from a difference of (effectively) one atmosphere shouldn't be too extreme. I think it's hypoxia that would kill you by damaging the brain (it important to note that hypoxia is worse in hard vacuum than when drowning - the oxygen is kind of sucked out of you rather than just being used up, hence 90 seconds rather than the 6 minutes Algebraist mentioned). Since the Martian atmosphere isn't much of a thermal conductor (there simply isn't enough of it), the cold would take longer to affect you so we can probably ignore it. --Tango (talk) 16:10, 12 November 2008 (UTC)

From Space exposure : "But severe symptoms such as loss of oxygen in tissue (anoxia) and multiplicative increase of body volume occur within 10 seconds, followed by circulatory failure and flaccid paralysis in about 30 seconds.[1] The lungs also collapse (atelectasis) in this process, but will continue to release water vapour leading to cooling and ice formation in the respiratory tract." APL (talk) 22:13, 12 November 2008 (UTC)

Leaves changing color at different rates

Here in Beaver Falls, Pennsylvania, most leaves have fallen, but there's a large maple with large leaves (I'm guessing Norway Maple) behind my house. Reading Autumn leaf color, I note that the article says that "Often the veins will still be green after the tissues between them have almost completely changed color." However, this tree is odd, with leaves that are more extreme than this: some of its leaves are totally yellow, while leaves farther up the branch are almost totally green still. Is it simply because these leaves are closer to the trunk, or because they're (most of the time) shaded by the leaves at the edge of the tree, or some other reason? And is this an unusual phenomenon, or is it common and I've really not been paying attention all my life? I checked last night, by the way: they really are on the same branch, so it's not as if there are leaves from two trees intermingled. Nyttend (talk) 14:36, 12 November 2008 (UTC)

Leaves change color because the sap is "running", as they say in the maple sugaring industry. Basically, all of the sap (i.e. sugary water) is drained out of the tree into storage in the roots. This makes sense because the roots are insulated by the ground, where as the leaves are basically big heat-dissipators, and so are VERY suceptible to freezing. The process is relatively slow; it can take several days to weeks to complete, depending on the size of the tree. For very large trees, the leaves at the periphery (i.e. farthest from the trunk) are "drained" first, so the leaves there die off earlier. For very large trees, the leaves at the tippy-top can have changed and fallen before those near the bottom and close to the trunk have even begun to start changing. --Jayron32.talk.contribs 17:37, 12 November 2008 (UTC)

Not sure where there's stuff about this but the colour in those leaves is put there to protect the leaf from sunlight whilst the tree absorbs back anything useful. Putting in that golden colour costs the tree. So the outermost leaves and those facing south will be coloured most. You might notice leaf buds are often brown or red too to protect them whilst developing. Dmcq (talk) 18:02, 12 November 2008 (UTC)

human fat

in Volume how does a pound of human fat compere to lard —Preceding unsigned comment added by Seanbaguley (talk • contribs) 15:30, 12 November 2008 (UTC)

Both are slightly more than 0.9g/c^3, a little less than water. Lard is slightly denser. SDY (talk) 15:35, 12 November 2008 (UTC)

length of Vibrio cholerae

What's the typical size, i.e. length of a cholera bacterium? --Ayacop (talk) 16:21, 12 November 2008 (UTC)

2-3 microns in length, 0.5 microns in width. - Nunh-huh 17:15, 12 November 2008 (UTC)

Could you add that to the article Vibrio cholerae? Rmhermen (talk) 23:18, 12 November 2008 (UTC)

yeast need salt?

In order for yeast dough to rise does it need to contain salt? RJFJR (talk) 17:04, 12 November 2008 (UTC)

No. See fermentation. 93.132.179.55 (talk) 17:14, 12 November 2008 (UTC)

Salt is used in baking to control the rate of fermentation, but is not strictly necessary for fermentation proper. However, "without salt, the yeast acts very rapidly and peters out too quickly. Too much salt will stunt yeast activity" [9]. "Salt controls yeast activity to achieve a slow, steady rise and it strengthens the dough structure; eliminating salt can result in a baked bread that has collapsed." [10] - Nunh-huh 17:17, 12 November 2008 (UTC)

Thank you! RJFJR (talk) 18:22, 12 November 2008 (UTC)

Just as an aside, bread made with no salt tastes terrible. Robinh 21:53, 12 November 2008 (UTC)

The Tuscans would probably disagree with you. (Classic Tuscan bread is made without salt.) -- 128.104.112.72 (talk) 23:32, 13 November 2008 (UTC)

Strength difference men-woman

What is the strength difference between men and woman?--Mr.K. (talk) 18:52, 12 November 2008 (UTC)

Estimates vary, particularly based on how you define "strength". this USMC report suggests the average woman's strength is 40%-70% of her male counterpart's. This report (with a higher average age) notes 50%, and then proceeds to note that males are also heavier and that strength-per-weight (if you elect to use that sort of "strength" definition) has a completely different result -- they find that males and females are effectively equal in terms of strength-per-muscle-mass. — Lomn 19:41, 12 November 2008 (UTC)

No surprise there, though, right? I don't think it's headline news to announce that folks with bigger muscles tend to be stronger... Matt Deres (talk) 17:29, 13 November 2008 (UTC)

Animal abuse

Wikipedia is preventing me from linking directly to the image I'm talking about. But on that site, encyclopedia dramatica, when you search "Animal Abuse", at the bottom you see an animated gif of a cat in some terrible device that shoots some liquid from the bottom into a chamber that the cat is in. What is that device that the poor cat is in? 98.221.85.188 (talk) 21:06, 12 November 2008 (UTC)

Encyclopedia dramatica is basically a joke site; I would not judge anything I read there too seriously. --Jayron32.talk.contribs 21:12, 12 November 2008 (UTC)

The Pet Spa [11]. Hydromassage, bath, and blowdry machine for dogs and cats. Edison (talk) 21:23, 12 November 2008 (UTC)

That's kind of a relief. But why was the cat so upset when it was in there? Was the water too hot? Was the machine being misused? 98.221.85.188 (talk) 22:04, 12 November 2008 (UTC)

Most house cats can't stand getting their fur wet. There are exceptions to this rule, of course, but I have a hard time imagining your average house cat enjoying a "hydromassage". APL (talk) 22:09, 12 November 2008 (UTC)

What's the problem with linking to Encyclopedia Dramatica? —Preceding unsigned comment added by 83.199.126.76 (talk) 21:51, 12 November 2008 (UTC)

If I'm reading the spam black and whitelists right, you can't link anywhere on ED except the Main Page, because (a) it's a haven for anti-Wikipedia trolls, and (b) it's a haven for trolls in general, and has tended to be linked only to harass someone or to act as a shock site. I may be wrong, but I suspect Main Page was whitelisted only after the actual article on the site finally passed its 1000th deletion review. Confusing Manifestation(Say hi!) 22:33, 12 November 2008 (UTC)

Why is 350°F the standard for cooking food?

Almost every recipe I see wants to be cooked in an oven that is 350°F. Some call for temps up to 450°F. But I've never seen any recipe that calls for a temp outside of these extremes. (I'm sure there are exceptions) What's so special about this temperature range and cooking food? --70.167.58.6 (talk) 22:21, 12 November 2008 (UTC)

Related article or place to start deduction from: Temperature (meat). Mac Davis (talk) 22:30, 12 November 2008 (UTC)

Actually, that article doesn't help.

I think the temperature has more to do with the smoke point or flash point of fats and oils. Lard, for example, has a smoke point of about 370°F. Vegetable shortening smokes around 360°F. You don't want all the fat burning away while the food cooks.

Higher temperatures are useful for different cooking techniques, such as searing the outside of a piece of meat so that the inside continues to cook after it is removed from the oven. ~Amatulić (talk) 22:48, 12 November 2008 (UTC)

Note the temperatures in the Temperature (meat) article are the meat temperatures when cooked, not the oven temperatures.

When oven cooking foods of any significant thickness (such as cakes, pies, roasts of meat, puddings, large potatoes) using too low a temperature will not cook them through to the middle, or will take an unnecessarily long time to do so. Using too high a temperature is likely to result in the outside being dried out or burnt before the centre is cooked. The recommended temperatures are compromises between these two problems. CBHA (talk) 23:04, 12 November 2008 (UTC)

If you'd like to use different temperature settings, try a convection oven. NB Acrylamide is produced in increasing amounts at temperatures exceeding 350 F. The temperature settings of ovens are not a reliable indicator of actual temperatures inside (and those tend to vary significantly from one point in your oven to the other). You may find recipes for conventional ovens that tell you on what rack / distance from the heating element to place your food. To be sure your food is cooked properly use a meat thermometer. To make sure baked goods are done, the traditional method is to stick a knitting needle in and declare it done when no dough sticks to the needle anymore. (OR by my granny :-) 76.97.245.5 (talk) 00:26, 13 November 2008 (UTC)

Generally, 350 deg F is a temperature which is hot enough to encourage the Maillard reaction to occur (aka "browning"), without causing substantial burning to also occur. If you get up into the 500 deg F range, the food will char or burn (i.e. produce ash) which imparts a bitter and unpalatable flavor. Below probably 325-350 deg F, and there is likely not enough heat for the vital Maillard reactions to occur; it's these reactions that produce those brown tasty bits that form when meat is properly cooked. Its also why most slow-cooking methods, such as "crock-pot" cooking, require you to brown the meat seperately before adding to the crock pot. The crock pot gets hot enough to cook the meat (generally up to around 180-190) but never gets hot enough to brown it; which means you miss an entire flavor component of the food. --Jayron32.talk.contribs 03:15, 13 November 2008 (UTC)

November 13

anaerobic motor /propulsion

i would like to know whether an anaerobic motor /propulsion really exists. To me anaerobic refers to organisms. furthermore: the described process releases oxygen besides heat . can such a process/reaction called anaerobic? clear question: can an oxygen producing reaction be called anaerobic or what can it be caled instead?

finds in wikipedia: http://en.wikipedia.org/w/index.php?title=Special%3ASearch&search=%22anaerobic+propulsion%22&ns0=1&fulltext=Search

http://en.wikipedia.org/wiki/Ictineo#Ictineo_II

http://en.wikipedia.org/wiki/Ictineo_II

thanks--Stefanbcn (talk) 00:38, 13 November 2008 (UTC)

Anaerobic - means "not needing air" (basically) - so any motor that doesn't need air (like an electric motor - or a clockwork motor) is "anaerobic". A coal fired steam engine - or a gasoline powered car is "Aerobic"...it needs oxygen from the air to work. A motor that used some chemical process to produce oxygen and burned that to make motion would probably be called "anaerobic" too. SteveBaker (talk) 00:51, 13 November 2008 (UTC)

Artificial holographic sun

Using sulfur lamps and rotating mirrors, would it be possible to create a false window with a nice holographic landscape, with a completely realistic rectangle of direct false "sunlight" striking the floor/walls? (this is for people with just a brick wall to look at and no direct sunlight) and could mirrors make it plane parallel? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 04:34, 13 November 2008 (UTC)

Well, it has been done - some really expensive flight simulators have used laser-projected displays that are bright enough to simulate natural sunlight at real-world candela values - and I've worked on them.

However, it's freakishly expensive and insanely dangerous. Remember that if you stare into the real sun - it's so bright that you will damage your eyes if you don't look away within a few seconds. Now consider a display device (a projection TV or something) that put out enough light to produce that same effect - plus enough to project all of the rest of the world at natural brightness levels too. In fact, it would need more energy even than that because it would have to scan over the scene at least 60 times a second - and the screen itself would not be perfectly, 100% reflective - so the display is putting out a lot more energy than the sun - within the small range of angles that covers the scene. If you think for a moment about the amount of heat that the sun puts out as it shines onto your skin - the display would probably have to chuck out that much heat too!

The result would have to be an amazingly powerful laser or something very similar. If you were to happen to catch a glimpse of the light from the laser itself (rather than it's dispersed, reflected image) - you'd be blinded instantly...no chance to blink or look away. When I worked with such a system a few years ago - everyone who entered the room when it was turned on had to go through a 30 hour laser safety course - the doors had to have automatic locking devices to stop people coming in when the laser was turned on - and there were all manner of handrails and such stopping people from going where the laser was operating. We nicknamed the gigantic water-cooled laser "The Death Ray of Ming the Merciless" because it looked exactly like something from the lair of a 1950's SciFi super-villain.

There is another issue here - which is for an outdoor scene to look completely real (ie not like a super-high-def TV screen) - the light has to appear such as to cause your eyes to focus at the correct depth. For an outdoor scene where nothing comes within (say) about 30 feet of the viewer, it's enough to 'collimate' the light so it appears to come from a source that's infinitely far away. This is tough to do. You either need a dome to project it onto that's at least 30' away - or a curved mirror such that the path from the laser projector to the eye is at least 30 feet - or you need some large, expensive glass lenses that are the size of your window to perform the same task. The difficulty with all of those things is that the scene only looks truly real when your head is at the "designed eyepoint" of the system - if you step a few feet to the side, the illusion is destroyed. It's kinda possible to correct for that - but the viewer needs to be wearing some kind of tracking device - and only one viewer gets a perfect view at a time.

So, yes - it's certainly possible - I've seen it done and the result is highly realistic and extremely compelling. But I don't think we'll see it happening as an entertainment device anytime soon.

SteveBaker (talk) 15:23, 13 November 2008 (UTC)

I don't mean to bring the topic back up, but what if replaced with a projector, it was an LED array. LED don't emit heat, just light I thought. 66.216.163.92 (talk) 23:37, 13 November 2008 (UTC)

They aren't really bright enough to create the effect of sunlight. Even packed tightly together...I don't think it would work. SteveBaker (talk) 16:04, 14 November 2008 (UTC)

Suphur lamps give the full spectrum of sunlight, LED's can't and have nowhere near the efficency. I have not heard of the laser device, it sounds fascinating. My idea would be have a pane of rapidly rotating tapered interleaved reflective spirals with a plasmonic projector changing the image on the turn of the spirals to create the hologram. That way your head would be torn off like putting it into an industrial dough mixer well before you managed to blind yourself looking into the projectors at the top and bottom of the machine. Another method would be projecting on to translucent hemispheres over a hole on a spinning washing machine cylinder. I will get this second hand, though I will have to be careful not to get too close to it.

A laser projector is actually three lasers, one red, one green and one blue - the light from them is combined into one colored beam with some mirrors and the resulting light is aimed into a pair of spinning hexagonal prisms - with mirrors on each of the 6 facets. One mirror spins horizontally at (say) 60/6 = 10 rotations per second - and that causes the lasers to scan vertically downwards and then jump back 60 times a second. The second mirror spins at 1000 times that speed(!) and causes the lasers to scan from left to right and then jump back one thousand times in every 1/60th second. Modulating the light from the lasers can be managed in a variety of ways. The result is that the laser scans a rectangular area exactly like the electron beam in a TV set and produces a very bright, full-color picture. Aiming that onto the inside of a large dome which is 'painted' with microscopic spherical glass beads results in a really compelling image of whatever TV/video picture you care to provide.

But as I said - such systems are huge, hideously costly, and vastly too dangerous to be "consumer" equipment. SteveBaker (talk) 16:04, 14 November 2008 (UTC)

Bird identification

Hello, I was at Taronga Zoo today and I took a photo of this little sparrow-ish thing. I would be very grateful if someone could help me with identifying its species. Thanks! 122.106.197.159 (talk) 04:43, 13 November 2008 (UTC)

That looks a bit like a silvereye to me. Tonyrex (talk) 06:02, 13 November 2008 (UTC)

rectilinear perspective

Do people actually see in rectilinear perspective, or is this just a convention of western art? For example, I've seen Looney Toons cartoons in which when viewing a tall rectangular building from the bottom, the lines start curving together at the top (rather than pointing straight at the vanishing point). --VectorField (talk) 06:11, 13 November 2008 (UTC) I guess an example of what this would look like can be found at fisheye lens. --VectorField (talk) 06:18, 13 November 2008 (UTC)

See also Perspective (visual) and for Cartesian rectilinear perspectives and variations on this see Perspective (graphical). In traditional Japanese and Chinese art, the perspective is constructed differently, more like parallel perspective. Julia Rossi (talk) 10:05, 13 November 2008 (UTC)

It's more than just convention. The idea is that the canvas should be like a window through which you can see the three-dimensional scene, and if you work that out in detail for a flat canvas (as described in Perspective (graphical)) you get the rules of perspective. It's the flatness of the canvas that matters, not anything going on inside the eye or brain. I don't think that people see in rectilinear perspective (I don't think the idea even makes sense—I think it's an instance of the homunculus fallacy) but the theory of perspective makes no such assumption. It does, however, assume that you stand in the correct location and have only one eye.

If you work out the rules for a cylindrical canvas instead, you get cylindrical perspective. (More precisely, if you follow the correct perspective rules for a cylindrical canvas with the viewer in the center and then unroll it, you get what's normally called cylindrical perspective.) The advantage of a cylindrical canvas is that you can get a wider field of view. A flat canvas is limited to a 180° FOV, and as you approach that limit the canvas size goes to infinity or the distance from canvas to viewer goes to zero, both of which are inconvenient. If you stand at the wrong distance from a large-FOV flat image (and any convenient distance will be wrong) it will look very distorted. A cylinder doesn't have that problem. Any small enough part of a cylinder is roughly flat, and so an unrolled cylindrical perspective is suitable for a very wide image that's meant to be looked at only a bit at a time (walking from side to side). A wide or tall background in a cel-animated TV show will normally be drawn in cylindrical perspective since it's designed to be panned over. -- BenRG (talk) 14:45, 13 November 2008 (UTC)

Oooh! Good question!

Perspective of some kind is a necessary part of any practical visual system. We really do see things that way. The different kinds of perspective come about through the shape of the 'screen' onto which the scene is projected - and the nature of the lens and how it gathers the light.

• In an idealised 'pin-hole' camera, the film (or digital imaging device) is flat - and since light travels in straight lines through a notional zero-sized pin-hole at the front of the camera - and then onto the flat surface inside, all straight lines in the world outside project into straight lines in the image - and we have perfect rectilinear perspective.
• In a practical camera - the lens isn't a pinhole and it has to bend the light to make it focus properly - that results in a non-linear mapping of real world onto the flat film plate - and depending on how much the light is bent, straight edges turn into curves and you no longer have rectilinear perspective.
• In our eyes, the imaging surface (the retina) isn't flat - so straight lines in the real world (like the sides of a tall building) don't project into straight lines on the retina. However, our visual system isn't a matter of a bunch of pixels on the retina being "absorbed" somehow by the brain. It's MUCH more complicated than that. One of the things our visual system does is to compensate for those complicated curves so that we "see" straight lines where the lines are straight...we're not aware of the weird mapping that goes on because of a non-zero pupil diameter and a non-flat retina. We are aware at some level that things seem "smaller" the further they are away - but we're also unconsciously correcting for that - so we don't think that a car is tiny because it's further away. The mathematical fact of perspective has been converted by our visual system into something that takes on different meanings depending on the context about which we are considering them. There are several optical illusions that play on that to demonstrate that we don't "see" what is really there.
• In art, the painting itself is generally flat - and artists generally want to give the impression that the rectangular frame of the painting is like a hole cut into the wall and the art is like an image coming through that hole - which is then percieved by our eyes. So then the mathematically "correct" thing for the artist to do is to pretend that the painting is a pinhole camera image and use rectilinear perspective - and then let our eyes process that image as if it were really light coming through a hole in the wall. Because that image then enters the eye in the same way that the light from a real object would - and the painting "looks real" to us (well, not quite because of issues of depth of focus and "collimation" of the resulting light).
• In 3D computer graphics, (my speciality - I'm a graphics programmer for the games industry) no matter how wide-angle the "virtual camera" becomes - since the screen is flat - and we use rectilinear perspective because the math is simplest that way. Especially - we want to map straight lines onto straight lines - because our graphics algorithms are much simpler that way. And (fortunately) it all looks right for the same reason that art looks right. But we do see "fish-eye distortion" in computer graphics - and this is true even though the computer is translating straight lines into straight lines (actually, the graphics hardware is incapable of directly drawing curved edges - rectilinear perspective is built into the 3D circuitry at a fundamental level!). We perceive wide field-of-view images as distorted (and some people will even go so far as to claim that everything is curved even when that is a physical/electronic impossiblity!) The reason for that is that we are taking an image from a 'virtual camera' with a wide field of view (say 120 degrees) and presenting it on a screen that only subtends (perhaps) 30 degrees at your eye. This is not a natural thing - and our brains have to somehow interpret this as if the image were being seen through a distorting "fish eye" lens when all it's really seeing is through an idealised pin-hole camera. Our mental compensation for that imagined distortion (which is not present in the mathematically "correct" rectilinear perspective) results in a strong impression of curvature.

A similar problem occurs with narrow-angle images (eg taken with a telephoto lens) where the relative lack of perspective foreshortening leaves us with a wrecked sense of distance. Film makers love to use this. In a romantic scene with the moon in the background, they'll pull their camera WAY back from the actors - then zoom WAY into them - and the resulting screwup of our mental idea of perspective makes the moon look HUGE. This is used in action shots too - when the hero is running away from the burning car - which explodes behind him hurling him towards the camera...you place the camera WAY back from the car - put the actor fairly close to the camera and a VERY safe distance from the car...then the telephoto lens screws up the perspective for us - and we think the car is really close. It's still very close to being strictly rectilinear perspective - but our brain's inability to compensate for the distortion that results from the mismatch of the field of view means that we see things in way that they really are not.

SteveBaker (talk) 15:03, 13 November 2008 (UTC)

I think it's interesting that how we see things is generally governed by how we expect to see them. We know what size a car is, so we see it as being that size regardless of how far away it is (to use your example). However, if you're in an unusual situation, for example seeing cars on a road when looking out of the window of a plane, your brain doesn't really know what to expect and you need to consciously work out what you're seeing and you do notice the fact that cars are all so tiny (the standard cliché is to compare them to ants). --Tango (talk) 15:33, 13 November 2008 (UTC)

I'm going to take issue with the idea that our brains "compensate" for the curved shape of the retina. There's no one in there looking at the image projected on the retina. All the brain gets is a bunch of electrical signals down the optic nerve. If the retina were flat and the distribution of cones and rods were tweaked accordingly (to keep the visual acuity fixed), you'd get exactly the same collection of signals going to the brain (except in slightly different focus). I don't think the brain "knows" the shape of the retina—it doesn't need to know.

To put it another way, once you've projected onto one canvas you can re-project onto any other without needing the original scene as a reference. Fisheye Quake and PanQuake take advantage of that to produce realtime 3D in a mathematically accurate fisheye/cylindrical projection, by first rendering to a cube map and then rearranging the pixels. You could do the same thing in hardware these days (using one big rectangle and a pixel shader for the second pass). So, although modern graphics cards aren't designed for non-rectilinear projections, they can certainly produce them, probably at full frame rate, and it would be a pretty neat gimmick to have in a new game. So get cracking, Steve. :-) -- BenRG (talk) 21:22, 13 November 2008 (UTC)

To put this simply, our eyes use elliptic geometry and a flat canvas uses Euclidean geometry. Trying to put the same picture on both will require some warping. — DanielLC 15:56, 13 November 2008 (UTC)

The extent to which rectilinear perspective correctly replicates a 3D view, at least for a fixed observer and small field of view, can be judged by the success of trompe-l'oeil illusions. Gandalf61 (talk) 16:02, 13 November 2008 (UTC)

Recent coverage of drawing on curved canvases here. —Preceding unsigned comment added by 190.220.104.35 (talk) 19:21, 13 November 2008 (UTC)

Some painters used "Chinese perspective" where things are higher in the picture to indicate distance,or which are more axonometric and others used "landscape perspective" where distant objects are in more subdued hues, without the mathematical device of our modern geometric perspective. It is a modern mathematical invention. Edison (talk) 19:54, 13 November 2008 (UTC)

And, of course, painters like Picasso don't bother much about the rules of perspective at all. That's how it is with geniuses - they break the rules and sometimes make new ones. —Preceding unsigned comment added by 98.17.34.3 (talk) 01:10, 14 November 2008 (UTC)

Ceiling fan

Hello. If a Ceiling fan is switched on at the wall but it is actually off then does it still use electricity? Sorry if its a stupid question. ```` —Preceding unsigned comment added by AreDeeCue (talk • contribs) 13:49, 13 November 2008 (UTC)

No. The circuit has to be closed to use any noticeable amount of electricity (I'm ignoring cases such as worn out wires sparking against nails in the attic and such). Any switch anywhere in the line that opens the circuit will cause the flow of electricity to stop. -- kainaw™ 13:58, 13 November 2008 (UTC)

Your question implies that there are two (serial) switches to operate the fan? If this is the case, both switches must be on for the fan to work. Therefore the fan is not using electricity. Sometimes the wall-mounted control has an LED to indicate that it is on. However this LED uses a trivial amount of electricity. Axl ¤ [Talk] 14:01, 13 November 2008 (UTC)

The ceiling fans that use an infrared remote (to avoid the need to add house-wiring for houses that don't have a second switch and circuit) DO use a tiny amount of electricity when they're turned on at the wall but off using the remote. Some piece of circuitry has to be powered in order to pay attention to the InfraRed receiver. It's pretty tiny - but with a bajillion appliances around the home all eating small amounts like that - it does add up. The kind of ceiling fan that has a pull-cord to turn it on and off shouldn't be consuming any electricity at all when it's turned off there instead of at the wall. SteveBaker (talk) 14:26, 13 November 2008 (UTC)

The OP might also consider reading Standby power.--Lenticel ^(talk) 00:34, 14 November 2008 (UTC)

Echinoderm diversity

Estimations of the diversity of extants echinoderms vary widely, from 6,000 to 10,000 species, and even reliable sources differ a lot. Which is the most authoritative source on echinoderms, and what figure does it give? Thanks. Leptictidium (mt) 14:56, 13 November 2008 (UTC)

dangerous situation arising from killing germs?

If you kill all the germs in a place germs like to live, won't it just create natural evolutionary pressure toward germs that aren't affected by death? —Preceding unsigned comment added by 83.199.126.76 (talk) 15:22, 13 November 2008 (UTC)

Not being affected by death is tricky, but antibiotic resistance certainly arises in this way. Algebraist 15:47, 13 November 2008 (UTC)

Well - I don't think they can be "unaffected by death" - that's kinda silly! But I guess what you mean is that these critters are not killed by whatever means you've been using to kill off the others. If so - then yes! This happens all the time. In hospitals particularly, there are antibiotics everywhere - in the air and on all of the surfaces. Bacteria are mostly killed by this stuff being everywhere - but one in a trillion (maybe) survives - and this causes an evolutionary effect that results in types of bacteria that are immune to all of the common antibiotics. It is therefore necessary for the drug companies to continually come up with new antibiotics that the bacteria has not yet been exposed to - and which can therefore kill them...until a few more years have gone by. Doctors also recognise this and they don't prescribe the newest and most powerful antibiotics until they know that the older (and by now, better-resisted) have failed. This is an attempt to keep the newer kinds of treatment in reserve for the most resistant bugs. It's not just 'germs' either - strains of rats and mice that are immune to the common kinds of rat and mouse poisons are also appearing. There is no doubt that evolution does this all the time. SteveBaker (talk) 16:52, 13 November 2008 (UTC)

Also, it depends on just how you kill them. For example, very few living things can survive a good autoclaving. Naturally, a hospital bug that could stand it would have an enormous evolutionary advantage — but that matters little if there are no bugs that would stand even a chance of doing that in the first place. Simple broad-spectrum disinfectants like hypochlorite or hydrogen peroxide are similar: some organisms do resist them better than other, but in sufficient concentrations and quantities they kill pretty much everything indiscriminately.

A common trait of such non-specific disinfection methods is that they can only be used on non-living objects, or at best can only be applied externally to e.g. localized areas of skin. That's because, if they were applied e.g. to the entire human body in concentrations sufficient to kill bacteria, they'd kill the human too. Antibiotics, on the hand, can be administered internally, because they specifically kill bacteria while not being toxic to humans. However, this very specificity also allows bacteria to develop resistance to them: since a useful antibiotic must target some biochemical feature specific to bacteria, rather than indiscriminately killing every living cell, it's usually possible for bacteria to develop mutations such that the specific features the antibiotic attacks are no longer present.

Mind you, it is possible for organisms to develop resistance to even non-specific poisons, at least to some extent, over sufficiently long timescales. For example, ethanol is toxic to most living cells at sufficient concentrations, but most species, including humans, have developed some degree of resistance to it, since it's so commonly found in nature e.g. as a product of fermentation. An even more striking example is free diatomic oxygen: to anaerobic organisms, it's as deadly as ozone or fluorine, but over the 3 billion years since the evolution of photosynthesis, most living things have developed elaborate mechanisms for tolerating and, eventually, even making use of it. Even so, oxidative stress remains a significant source of cellular damage in organisms, including humans, that are exposed to high concentrations of oxygen. —Ilmari Karonen (talk) 20:02, 15 November 2008 (UTC)

What do you call this camera trick?

OK, I'm not sure how to describe something visual in words, but I will try. In movies and TV shows, they have this camera trick where the object in the forefront (usually a person) stays stationary but the background somehow moves. It seems like some sort of trick of perspective. This technique is usually used to convey shock, something unexpected or when the person makes a sudden realization. Sorry I can't give a better description, but this technique is used enough that hopefully someone will know what this is named. 216.239.234.196 (talk) 15:32, 13 November 2008 (UTC)

Dolly zoom APL (talk) 15:45, 13 November 2008 (UTC)

Yep, that's it! Thank you. (Comment: So they actually move the camera? Wow.) 216.239.234.196 (talk) 15:58, 13 November 2008 (UTC)

I've always heard it called a "Hitchcock zoom" because he was the one who first popularized it. It requires zooming the camera either in or out and simultaneously moving the camera either backwards or forwards. Done correctly (which is tough), the person in the foreground stays at exactly the same size - but the background zooms in or out. It has the effect of separating the character from their surroundings - which Hitchcock used to great effect to get across emotional state and such. Adding 'rim lighting' or other inconsistent lighting for the character is another way to separate a character from the background that Hitchcock used effectively. SteveBaker (talk) 16:57, 13 November 2008 (UTC)

Specifically, Hitchcock developed it for the movie Vertigo to illustrate Jimmy Stewart's character's acrophobia. I think I remember reading in Truffaut's book on Hitchcock that he conceived it in connection with one of his earlier films but was then told it could not be done. --Anonymous, 23:03 UTC, November 13, 2008.

Yep - in an era before computer-controlled cameras and dollies it would have required great skill (and possibly MANY retakes!) to pull off the effect - the dolly would have been pushed by a bunch of guys while the cameraman adjusted the zoom...coordinating those actions to the required degree of accuracy would be nightmarish! You can see why some people would say it was impossible. These days, you could just as easily cheat by standing the actor in front of a blue-screen and zoom into the background with a separate camera - but we have had computer controlled cameras that could do it since about the time of the first StarWars movie. SteveBaker (talk) 15:51, 14 November 2008 (UTC)

You could do it with an all-mechanical system. One option would be a zoom lens with a custom-cut thread (rather than the standard helical thread) so that a constant-speed rotation of the zoom ring produces the needed zoom rate, at which point a pair of electric motors (one to move the camera around, and one to drive the zoom lens) will give you the effect you want. If you don't have electric motors, you could move the camera on a rack-and-pinion track with the rack driving the zoom lens. I'm sure there are a number of other ways to set up a mechanical linkage between the zoom and the camera motion. --Carnildo (talk) 22:07, 14 November 2008 (UTC)

Sure - I'm sure it could be done - but it wasn't. I believe they also had to coordinate refocussing the camera while zooming and dollying. SteveBaker (talk) 05:45, 15 November 2008 (UTC)

Energy drink ingredients

Do any ingredients in energy drinks other than sugar and caffeine have proven desirable short-term effects? NeonMerlin 15:43, 13 November 2008 (UTC)

You're probably best to just run through the list of ingredients in your favourite energy drink and check the Wikipedia articles. The major active ingredient in guarana is caffeine. Taurine has been shown to axiolytic effects in some animal studies, but no effect on human beings has been observed. The NIH has reported that supplements containing gingko biloba have no measurable benefit when taken as directed. The list goes on, but you can probably find what you're looking for by following the links from Red Bull, Rockstar, and the others. TenOfAllTrades(talk) 16:25, 13 November 2008 (UTC)

Visual acuity of hawk's eye: why/how?

Hi, is there an article that explains why the hawk's eye has such great visual acuity? I can't find any info on WP on such a fascinating subject. Kreachure (talk) 16:52, 13 November 2008 (UTC)

Maybe you should read the article you linked to, then. Matt Deres (talk) 17:41, 13 November 2008 (UTC)

Yeah, thanks, but I was looking for more information, like the one provided by the bird vision article which I just found. Kreachure (talk) 18:09, 13 November 2008 (UTC

I think visual acuity is provided by the number of cone cells in the fovea, and presumably by how other bits of the eye work. Hawks presumably have a higher percentage of cones in the fovea than other species. This is just complete assumption. —Cyclonenim (talk · contribs · email) 18:54, 13 November 2008 (UTC)

I understand that some hawks and falcons actually have a slight concavity in the retina which allows for greater focus on distant objects and more visual cells than there would normally be, although I can't remember the details. 137.151.174.128 (talk) 21:56, 13 November 2008 (UTC)

resistors

today i encountered with a resistor named 3k9,4k7,and 100R.can any body plz tell me what values of these resistance and what is the type of these resistors . -- 116.71.186.13 (talk) 17:36, 13 November 2008 (UTC)

3900 ohm, 4700 ohm and 100 ohm. It's a funny bit of notation that is standard in the industry, but makes sense easily enough. They're just bog standard resistors as far as I can tell from that information. 137.108.145.10 (talk) 18:56, 13 November 2008 (UTC)

Is there a ref for that notation? It seems a bit uninformative, lacking an indicator of the precision rating like the color coding on resistors has. Edison (talk) 19:49, 13 November 2008 (UTC)

It is mentioned in the Resistor article briefly and also at Electronic color code#Other schemes. The notation used seems to follow BS 1852. Nanonic (talk) 19:56, 13 November 2008 (UTC)

BS 1852 now superseded by BS EN 60062. Latest version seems to be 2005.--GreenSpigot (talk) 13:09, 15 November 2008 (UTC)

Fructose Malabsorption

Disclaimer: I have no intend to ask for medical advice here. If you think you cannot answer without giving medical advice please just ignore my questions. If you feel obliged to tell me to see a doctor please give me name and address, too, as I have seen many doctors and none of them has even mentioned fructose malabsorption.

The one section of the fructose article (fructose malabsorption#Fructose Metabolism) states that fructose is absorbed using GLUT-2, the rest of the article states it is absorbed by GLUT-5. This seems to be a bit of a contradiction, or can GLUT-2 absorb fructose, too, but GLUT-5 is specialized on it?

It is not clear to me from the articles if fructose is normally (without f.m.) absorbed in the small intestine, the large intestine, or both, and if f.m. affects only the absorption in one of those or both. Fructose#Malabsorption gives the medical advice that Exercise can exacerbate these symptoms by decreasing transit time in the small intestine, resulting in a greater amount of fructose being emptied into the large intestine which I know is not true from my own experiences. Fructose not being absorbed and rotting in the large intestine as well as in the small would account for this experience.

Are ther many different forms of f.m. and is the absorption via GLUT-2/5 totally absent or only reduced?

Fructose is a small molecule, isn't it absorbed by pinocytosis or is it that the pinocytosed amount is too small? Thanks 93.132.177.64 (talk) 19:24, 13 November 2008 (UTC)

As our fructose article states, "The mechanism of fructose absorption in the small intestine is not completely understood. Some evidence suggests active transport, because fructose uptake has been shown to occur against a concentration gradient. However, the majority of research supports the claim that fructose absorption occurs on the mucosal membrane via facilitated transport involving GLUT5 transport proteins. Since the concentration of fructose is higher in the lumen, fructose is able to flow down a concentration gradient into the enterocytes, assisted by transport proteins. Fructose may be transported out of the enterocyte across the basolateral membrane by either GLUT2 or GLUT5, although the GLUT2 transporter has a greater capacity for transporting fructose and therefore the majority of fructose is transported out of the enterocyte through GLUT2." In case this isn't clear, it's essentially saying that fructose is primarily transported from the lumen of the small intestine into the cells lining it by GLUT5, and transported out of those same cells into the bloodstream by GLUT2. - Nunh-huh 19:43, 13 November 2008 (UTC)

Poisoning through the ear

(This is merely a question of curiosity with no intended "medical" application.) Is it actually possible to poison someone, as King Hamlet was killed, by pouring poison into their ear? If so, what poisons are effective that way and how, physiologically, does the poisoning take place? Was it a common belief in Shakespeare's time that someone could be poisoned through the ear, and would Shakespeare have known if this depiction of poisoning was accurate or not? 137.151.174.176 (talk) 20:33, 13 November 2008 (UTC)

There was a long discussion on this very topic on here last February. --140.247.249.93 (talk) 20:52, 13 November 2008 (UTC)

Thanks for the link. The interpretation that it's symbolic (poison in the ear representing evil words) instead of based on medical knowledge is quite plausible-- the result of the poison, in which the King suddenly becomes covered in leprous scabs, certainly doesn't seem like a literal description of something that could really happen. 137.151.174.128 (talk) 21:51, 13 November 2008 (UTC)

Also see eustacian tube. A good read on this topic. --Jayron32.talk.contribs 21:08, 13 November 2008 (UTC)

Though I agree with the symbolism interpretation discussed previously, I would also point out that perforated eardrums would have been much more common in Shakespeare's day than they are now. Someone with a perforated eardrum would be quite susceptible to poison poured into the ear, because it would pass right through the middle ear and into the throat. --Scray (talk) 03:31, 14 November 2008 (UTC)

I realize this is wandering off topic. Would perforated eardrums have been more common in Shakespeare's day than they are now because a) they could not be treated or b) eardrums were more often damaged or c) both? Thanks, CBHA (talk) 03:51, 14 November 2008 (UTC)

I'm not sure you;d need a perforated ear drum for the poison to work. The poison, after all, doesn't have to reach the digestive tract; just the blood stream. While your digestive tract provides a relatively easy way to reach the blood stream, other venues (the lungs, the nose, the eyes, and yes the ears themselves) may provide a relatively easy means by which to get the poison into the blood. Indeed, the poison may not have to even get past the ears; it could probably be absorbed directly through them straight to the blood stream... --Jayron32.talk.contribs 04:16, 14 November 2008 (UTC)

While there are poisons that can pass through intact skin (including external ear), much more permeable are the mucous membranes (like the linings of lungs, nose, eyes). A nightshade poison like the one employed in Hamlet would not cross intact stratified squamous epithelia (such as skin or intact external ear) efficiently, but would be absorbed through a mucous membrane (such as nasopharynx after passing through a perforated eardrum). @CBHA: Perforated eardrums are associated with untreated middle ear infections, which can result in spontaneous rupture and release of "pus under pressure". In addition, I don't know when European physicians started puncturing eardrums to provide relief, but my guess is that the practice has been around for a very long time. --Scray (talk) 04:47, 14 November 2008 (UTC)

spider-silk 'stronger' than steel. What does that mean?

I heard that spider-silk is stronger than steel. What exactly does that mean, and if it's true, why don't we spin spider-silk into threads, then strands, then long thick cables, coat them in something to keep the weather out and make ****in suspension bridges and ***t out of em... —Preceding unsigned comment added by 83.199.126.76 (talk) 20:33, 13 November 2008 (UTC)

It generally means that, pound for pound, spider silk has a higher tensile strength than steel. Its just that if you made steel threads as small as spider silk, the silk would be stronger, or alternately if you made cables of spider silk, those would be stronger than similarly weighted steel cables. However, getting enough spider silk together to build a suspension bridge is likely impossible. --Jayron32.talk.contribs 21:07, 13 November 2008 (UTC)

The fact we're not doing it (yet) is not for want of trying [12] [13]. As our page spider silk points out there are several different types of spider silk, all with their unique properties. At least for capture-spiral silk some of its resilience comes from lengths of silk that are coiled up in the glue drops and sort of act like giving a lassoed animal some rope when it pulls. The extra silk uncoils while the spider prey is decelerated when it gets caught; that absorbs some of the kinetic energy. Although the material of spider silk itself is already amazingly strong, see BioSteel, the real stuff is not just strands of the material spun into threads etc. but a complex construct of interlinked strands and bits. It's probably going to be a while till the process of producing steel cables has become as expensive as that of manufacturing spider silk. A cautionary note, though, before you start heading for a future in spider silk bridge construction: being based on organic chemistry, evolution has so far only produced very few critters with a special appetite for iron [14] that could pose a risk to steel bridges, but protein is a whole different matter. Apart from critters that would already consider a tall protein structure delectable, it's a very small evolutionary step for lots of species to specialize on protein bridge cables. Scientists would have to run hard to stay ahead of the game to keep your bridges from getting eaten as fast as you could build them. 76.97.245.5 (talk) 22:59, 13 November 2008 (UTC)

Thanks! I didn't even consider the delicious aspect... —Preceding unsigned comment added by 83.199.126.76 (talk) 23:02, 13 November 2008 (UTC)

Note that steel is widely used as a construction material not just for its tensile strength, but also for its high compressive strength and high Young's modulus (stiffness). Even if we could make suspension bridge cables from spider silk, we would still need to use steel for the towers (where compressive strength is required) and decks (where stiffness is required). Gandalf61 (talk) 10:21, 14 November 2008 (UTC)

Polar deserts

Is it possible for a hypothetical planet to have polar deserts instead of ice caps? As in - not in the sense Antarctica is a rainless desert, but rather a hot Gobi-esque desert. Lady BlahDeBlah (talk) 21:10, 13 November 2008 (UTC)

If it was tilted over like Uranus and tidally locked to its star so that one of the poles always faced the star, then that would probably be a polar desert. For a normally tilted planet, the poles are always going to be colder than the equator because the sunlight hits them at a shallower angle. --Tango (talk) 21:12, 13 November 2008 (UTC)

The first case is impossible. It the planet does rotate, none of its poles can always point to the star. Preservation of angular momentum ensures that the axis of rotation is stable. If one of the poles would always point to the sun, the axis of rotation would rotate itself. And in particular, if the planet is tidally locked, the axis of rotation (one per planetary year) is necessarily perpendicular to the orbital plane. --Stephan Schulz (talk) 21:55, 13 November 2008 (UTC)

Stephan is right (as usual) that you can't have a pole tidally locked to a star. However, if a planet is tilted more than ~60 degrees, then one expects that the poles have a higher annual average temperature than the equator because they spend more time in direct sunlight than any equatorial location. In fact, a highly tilted planet should form an equatorial ice cap instead of a polar one. Of course the poles will still get cold during the half of the year they are pointed away from the star, but just not cold enough to offset being pointed directly at the star for half the year. Dragons flight (talk) 23:48, 13 November 2008 (UTC)

I heard once that the critical angle, where the poles and equator are equally insolated, is 54°; but I never did get around to working it out. —Tamfang (talk) 08:17, 14 November 2008 (UTC)

Of course it's impossible... in my defence, I was suffering from a 24 hour stomach bug yesterday... The best you could get would be the poles going between hot desert and cold desert as the planet orbits the star. --Tango (talk) 10:50, 14 November 2008 (UTC)

So a planet with a tilt of more than 54 degrees would do it, kinda? Lady BlahDeBlah (talk) 13:55, 14 November 2008 (UTC)

...or of course, a planet that's devoid of water and closer to its star - even though the poles would still be colder than its equator, the poles could be hot and dry by our standards. I bet the poles on Venus are pretty hot and dry. But I like Tango's answer better. SteveBaker (talk) 21:43, 13 November 2008 (UTC)

I was working under the assumption that the whole planet being a desert doesn't count - it is something of a trivial solution! --Tango (talk) 10:50, 14 November 2008 (UTC)

I'm altogether in favor of trivial solutions! SteveBaker (talk) 15:33, 14 November 2008 (UTC)

Newton and the travel time of light from the Sun

I read last night that Sir Isaac Newton estimated that it took 10 minutes for light to travel from the Sun to the Earth...the true number is around 8 minutes - so that was a pretty good estimate for the era. The trouble is that he didn't know the speed of light (not even approximately) - and he didn't know how far the Sun is from the Earth either.

So how the heck did he come up with a number that's so accurate?

I'm scratching my head trying to come up with any way he could have estimated this time at all...let alone being so amazingly accurate about it.

SteveBaker (talk) 21:48, 13 November 2008 (UTC)

Ole Rømer made the first reasonably-accurate measurements of the speed of light in 1676. Newton lived until 1726/7, and he would have had access to Rømer's result. The method is described at Ole Rømer#Rømer and the speed of light, and there's a history of speed-of-light measurements at Speed of light#Measurement of the speed of light. TenOfAllTrades(talk) 21:57, 13 November 2008 (UTC)

I think knowing Kepler's laws did the rest. T^2 = D^3. where T is the Earth's orbital period and D is the planet's mean distance from the Sun. (I am not sure of the units to use... 152.16.15.23 (talk) 05:45, 14 November 2008 (UTC)

T^2 is proportional to D^3. Determining the proportionality constant (and thus, the scale of the solar system) was a major problem in astronomy for a long time. --Carnildo (talk) 22:17, 14 November 2008 (UTC)

Rømer calculated the speed of light compared to the speed of the earth in its orbit. This gives the time for light to reach the earth with a little maths without needing to know the distance to the sun. Dmcq (talk) 11:40, 14 November 2008 (UTC)

Indeed. Our Ole Rømer article says that, prior to Rømer's more accurate measurements, Cassini used observations of Jupiter's satellites to conclude in 1675 that "light seems to take about ten to eleven minutes to cross a distance equal to the half-diameter of the terrestrial orbit". The calculation is based on the apparent variation in the satellites' periods depending on whether the Earth is approaching or receding from Jupiter - essentially, it is a Doppler effect measurement. Gandalf61 (talk) 11:57, 14 November 2008 (UTC)

LHC

Does the Large Hadron Collider only operate at night? 99.226.138.202 (talk) 23:31, 13 November 2008 (UTC)

No. Dragons flight (talk) 23:51, 13 November 2008 (UTC)

Is there any reason to suspect that the LHC only operates at night? --98.114.98.124 (talk) 13:15, 14 November 2008 (UTC)

If you run it at night, fewer people in Europe will notice when the black hole sucks them up, because they'll be asleep. It's purely pragmatic. --98.217.8.46 (talk) 01:51, 15 November 2008 (UTC)

One of the large colliders only opperates in Summer when the power consumption is lower. In Winter the Electricity is needed for heating... This might be the case to work in the night, although I never heared of that.--Stone (talk) 13:52, 14 November 2008 (UTC)

There is too much involved in operating a large accelerator to be able to power it up and down every day. In general, large colliders run 24-7 and the people who work on/with them get scheduled in shifts that run around the clock. Dragons flight (talk) 15:38, 14 November 2008 (UTC)

Actually - it doesn't operate at all right now because it's broken and is going to take many more months to fix. It's possible that they might want to operate it at night in order to place the bulk of the earth between the machine and the sun in order to shield it in some way - but that wouldn't be true for all of the experiments it does. SteveBaker (talk) 15:31, 14 November 2008 (UTC)

November 14

non-enzymatic catalyst

I was justing thinking, some biological enzymes like lysosome catalyze the substrate conversion to product by preferentially binding to the transition state. This transition state binding lowers the Gibbs free energy of TS, therefore speeding up the reaction. My question is why is it UNLIKELY that non-enzymatic catalysts operate by this fashion? —Preceding unsigned comment added by 128.252.173.86 (talk) 01:16, 14 November 2008 (UTC)

See Enzyme#"Lock and key" model. It has to do with the complexity of enzymes as molecules. Consider the difference between an enzyme, which is basically structured to recognize a SINGLE transition state based on its peculiar protein structure, versus "non-specific" catalysts, such as MnO₂ or suface catalysts like Platinum or Paladium. Enyzmes are the only molecules even CLOSE to the complexity necessary to "recognize" a specific transition state. Non-organic catalysts just aren't that "picky". --Jayron32.talk.contribs 03:35, 14 November 2008 (UTC)

Neem oil as insecticide

I find references for Neem used as an insecticide. Plus some pharmaceutical company had a patent lawsuit going, so there's evidence it works. But how does it kill the bugs? Inhibit reproduction? Glomm up their breathing mechanism? Damage their organs? Other? 76.97.245.5 (talk) 01:40, 14 November 2008 (UTC)

creatively, how heavy might I make pure heat (historical caloric) in liquid form?

Resolved

Hi guys. Last time I asked about the temperature of pure heat and got very good responses, including historical things like caloric, etc. This time I would like a creative answer to how much, hypothetically, caloric might weigh, even though the whole idea is at complete odds with about two hundred years of detailed observations. Thinking back before then, to the seventeen hundreds and before, what might be a plausible weight scientists could have given to heat? Thank you. —Preceding unsigned comment added by 83.199.126.76 (talk) 03:53, 14 November 2008 (UTC)

Um, heat is not a substance... I thought we went over this. Heat is just a form of motion. Motion doesn't have a temperature, or a weight. --Jayron32.talk.contribs 03:55, 14 November 2008 (UTC)

I suppose you could apply Einstein's Energy = mass*(speed of light^2) equation to figure out how much mass an object's thermal energy would be equivalent too. This has no bearing on reality: adding energy to a system via heat does not increase the system's mass at all. (except perhaps in the world of freaky-particle physics that I know nothing about and assuming we are staying within classical velocities). You can calculate the amount of thermal energy has been added to a system by knowing how much the temperature changed (Celcius) and the object-you-are-heating's heat capacity. Then you can find out how much mass has an equivalent amount of energy by using E = mc^2. If you keep your units straight you should wind up with a rather unimpressive small number (or if you find small numbers astounding an impressively small number). 152.16.15.23 (talk) 04:31, 14 November 2008 (UTC)

Adding heat certainly adds mass; see my post below. --Tardis (talk) 15:28, 14 November 2008 (UTC)

When did this become Wikipedia:Reference desk/Nonsense? 24.76.161.28 (talk) 04:18, 14 November 2008 (UTC)

Seriously dude, if you are writing a fictional story ANYWAYS, well, just make it up. Are you really just asking people to give you ideas for your story? I mean, if you aren't interested in writing a story where the laws of nature bears any resemblence to reality, why bother even asking us?!? Just make it up yourself! --Jayron32.talk.contribs 04:21, 14 November 2008 (UTC)

I didn't say it shouldn't bear any resemblance to reality. If scientists never had any instruments, science would still be in the dark ages... And caloric isn't from the dark ages, but much later. :)

Please follow-up at pseudoscience refdesk, not here. --Scray (talk) 04:22, 14 November 2008 (UTC)

Where can I find the pseudoscience refdesk? 216.239.234.196 (talk) 13:56, 14 November 2008 (UTC)

haha, but obviously of the actual refdesks science is the closest :)

Yikes, 24.76 please don't get so grumpy (the internet does not transmit emotions well). While you may have intended to come off differently, it seemed like you were ranting, which isn't going to make people want to answer your question. (Just to be sure I'm trying to be friendly myself so imagine a calm soothing voice with this text) Some friendly advice from someone who has asked many off the wall questions here myself, it would help to phrase "odd" questions like this so refdeskers people know you want a creative answer rather than a scientific one. I realize you tried by posting pseudoscience in the header, but it may have also been useful to ask in a more hypothetical manner like "How might I be able to express heat as mass? I know that doesn't make any sense realistically but hypothetically can anyone think of some way to do it?" 152.16.15.23 (talk) 05:00, 14 November 2008 (UTC)

Thank you, you're an angel (even though they don't exist). I'm deleting my 'rant' and changing the subject. I love you very much.

Why would energy have mass? 216.239.234.196 (talk) 13:56, 14 November 2008 (UTC)

It doesn't I think, they're just interchangable per E=MC². A bit of mass is lost when atoms are formed from protons and neutrons because they need energy for the strong nuclear force to hold them together. That's the basic gist of it, anyway. To the OP, please understand, you cannot ask for a real world answer to something that bears no resemblence to real life. We can't weigh heat, we can only describe it as moving particles. —Cyclonenim (talk · contribs · email) 14:36, 14 November 2008 (UTC)

You have a couple of things backwards there. Nuclear fusion releases energy, rather than requiring it from the incoming nucleons. (In general, it doesn't take energy to hold things together; instead, the fact that they are held together implies that it would take energy to pry them apart, so they must have less energy when together than when apart.) The energy that is released was potential energy before the particles combined; that the result has less mass than the sum of the constituents implies that the now-absent potential energy had — or was — mass. The same applies to all forms of energy; a hot brick has more mass than a cold brick, and a charged battery has more mass than a discharged one. With mass (perhaps "as mass"?) comes inertia and gravity; even light gravitates (it has to; otherwise gravitational lensing would violate conservation of momentum).

I find it next to useless to try to partition the "amount" of something into "mass" and "energy"; energy is just a term that implies certain behavior (like being transferrable) for some portion of the "stuff" present. You can consider them different "currencies" with an exchange rate of $c^{2}$ if you like, but then considering an object's amount of each is much like asking how much of the worth of a computer should be measured in euros and how much in yen. The answer depends on where it is and what you're doing with it and is clearly unrelated to the intrinsic value of the object. --Tardis (talk) 15:28, 14 November 2008 (UTC)

Dear OP: The last time you asked (essentially) the same question, we tried to tell you - as politely as possible - that this is a bloody stupid question and consequently it can't be answered. You pigheadedly insisted that we still try to answer it - lacing it with caveats to the point of meaninglessness. So this time - I'll just come right out and say it: It's a bloody stupid question and it STILL can't be answered. There is no such thing - nor can there ever be such a thing as "liquid heat" - I don't know how you got this concept wedged into your brain - but you need to get it un-wedged. As for everyone else - please don't feed the troll. SteveBaker (talk) 15:25, 14 November 2008 (UTC)

SteveBaker, I'm at a complete loss. I like your answers here and at other reference desks, they're highly informative and well-reasoned. But I just don't understand why this question (or the previous one) bothers you. Would it bother you as much if I were asking about astrological signs, making it clear that I wasn't looking for a scientific answer, which is that astrology == nonsense? If I said "to those who believe in astrology, which would be good signs for a Gemini's partner"? It might be "essentially" the same question as coming back and asking "okay, other than the people who told me to go **** myself because of how unscientific astrology is, I got very good responses, and now would like to ask about who good partners are for a Libra.". Seriously, I don't see how you can consider me a troll for asking for something whimsical. Do you think I believe in liquid heat? No. Do you think I'm pretending to believe in liquid heat? No. If one day I asked about spiderman's powers, and a few days later I asked about superman's powers, making clear that I meant my quesiton "in-universe" style and not from the point of view of an actually, really existing spiderman or superman, would you call me a troll? No. In this case my question has been answered below, "caloric was also thought of as a weightless gas". If the spiderman article told me that he is able to stick to buildings through tiny, sharp hairs that come out of his fingertips, would you deny me this information just because it's nonsense? Of course not. so be nice. you might have a point if I pretended to believe in this stuff, or if my question wasn't very clear on the point that I'm asking for pseudoscientific answers...

_{Then what the hell is this? Matt Deres (talk) 20:45, 14 November 2008 (UTC)}

Anti-freeze with a stupid brand name? --Tango (talk) 21:21, 14 November 2008 (UTC)

Perhaps you would be interested in reading Caloric theory. Here is a quote from the very first line (emphasis added) : "Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids.". So there's your answer. Even back when scientists thought heat was a liquid, they thought it was weightless. I'm sure they came to this conclusion by noticing that hot objects do not get lighter as they cool off. APL (talk) 04:24, 15 November 2008 (UTC)

Thank you for the answer. I had indeed missed that part of the article! I'm marking this question resolved.

CONTRADICTION TO RELATIVITY

question accidentally deleted by new question poster. Restored by 152.16.15.23 (talk) Harshagg (talk) 03:57, 14 November 2008 (UTC)harshagg

Hello,

question is something tricky pls. try to understand it

Question :-

Consider 2 persons A and B .A is at rest wrt earth and B is moving with velocity of light wrt earth.

• I A observe B then time for B will be infinity wrt A.
• And if B observe A then for A time will be infinity wrt B.

According to this time for A and B will increase wrt each other and time increase will be same so time cannot be infinity for either A or B wrt each other. Which actually contradict relativity.

Is this concept true if yes then relativity doesn't exit and if not what is wrong in this???

(Email removed to protect from spam; answers will be provided here. --Bowlhover (talk) 04:05, 14 November 2008 (UTC))

Not a contradiction. This was answered about 3-4 days ago; look above or at the archives. Basically, in order for A and B to "compare notes" one or the other must accelerate to reach each other's frame of reference, and this acceleration brings them into the same frame of reference, and removes the paradox. I am sure SteveBaker will be along shortly to give you the right answer, and tell you how wrong I am, but I am pretty sure I have the basic idea here... --Jayron32.talk.contribs 04:11, 14 November 2008 (UTC)

The main problem is that the theory of relativity says no object with mass can move at the speed of light. PrimeHunter (talk) 04:28, 14 November 2008 (UTC)

Sorry for being pigheaded about this but it can create all kinds of confusion if people leave out "speed of light in a vacuum". The experts are going to say "of course" but ordinary folks might spend years trying to figure some phenomena out till they get a "now they tell me" revelation. This doesn't affect OP's question though. 76.97.245.5 (talk) 09:41, 14 November 2008 (UTC)

And massless objects going at the speed of light cannot be decelerated to sublight speeds, so there's never a chance to 'compare notes'. Algebraist 11:58, 14 November 2008 (UTC)

Retrocausal information transfer.

File:Pixspike2.jpg

Trevor Loughlin (talk) 04:54, 14 November 2008 If a certain device dramatically cut the low frequency component of consecutive incorrect predictions of a one bit random event generator (or deterministic and chaotic events for that matter) over billions of results, turning a bell shaped curve into a spike with rarely more than three incorrect predictions, would it be fair to call this process a form of intelligible faster than light signaling? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 04:51, 14 November 2008 (UTC)

Hi Trevor, you accidentally deleted someone's question when you posted yours. Don't worry, I fixed it! These refdesk pages are really active so it is easy to accidentally overwrite someone else's questions. You can avoid this by clicking the ask new question link at the top of the page which creates a separate little section all for you. If you want to edit it later, scroll down to where you asked the question and click the edit button on the right hand side of your subject header rather than click the edit this page tab on the top of your screen. It cuts down on edit conflicts that way... 152.16.15.23 (talk)

I'm not sure if I understand your question entirely. (I don't know what the "low frequency component of consecutive incorrect predictions" is specifically) If you are asking if hypothetically we could predict the outcome of a random 2 state event better than chance will we have succeeded in superluminal information transmission? For that to be the case, some form of information needs to be transmitted at superluminal speeds. I am trying to think of a way to exploit this to create a superluminal situation, but I am not having any luck so far. Can you clarify when hypothetically during this process of random generation and subsequent transmission, the value of the bit is being correctly guessed at? 152.16.15.23 (talk) 05:23, 14 November 2008 (UTC)

As long as the value of the bit can only be predicted after it has been generated (i.e. you can't see the future), and it moves at slower than light speeds then no. 152.16.15.23 (talk) 05:39, 14 November 2008 (UTC)

And a warning that a low pass filter cannot work in real time, but can only produced a delayed result. Graeme Bartlett (talk) 06:00, 14 November 2008 (UTC)

Clearly if any device predicted the future, even to the slightest extent, by increasing th accuracy of predictions, it have immense practical effects. I would install a bank of them and bleed the Las Vegas casinos dry by predicting the roulette wheel outcomes, while making a jillian dollars on Wall Street. Edison (talk) 06:15, 14 November 2008 (UTC)

I have, though not quite on that scale (yet) because you have to start with a reasonably low bet and not be greedy even with this device, or in the short term you could still lose your bankroll. I turned £2 into £85 at 1 pence per go on a casino which is now closed (due to loss of American business, not me.) It took a week and got boring in the end. Beating the lottery would be more fun. My main aim is to increase the accuracy still further to predict and prevent (as in minority report ,but without the precogs) abductions and terrorist attacks before they happen(multiple universe theory gets rid of any paradox)-but only for nations that respect basic human rights! A sort of terrorism in reverse. The device works by sorting randomness a bit like Maxwell's Demon sorts atoms, but after 27 years work I will make a bit of money and rule the world for a while before I give more details! Of course the most intriguing aspect would be to send ASCII code from a future wikipedia page to bring transhuman technology from the far future to right now, eliminating inconvenience like aging and death. The device can be considered an infinite improbability drive. It alters probability enough to reverse the arrow of time on a macroscopic scale, and i wonder, though this is pure speculation, whether this could be enhanced enough to reverse the thermodynamic arrow for physical objects. I will leave you to think about the implications of this. Incidentally the device is not a filter in the common sense of the word, I am talking about the result of the predictions. This device DOES work in real time. The low pass cut-off refers to the analysis of the previous results (a histogram of how many incorrect predictions there were in a row, and the fact that the distribution is non-random. The device waits until it has made its prediction and then waits for the user to enter the predicted binary result via two form buttons, and in the process it compares the input to the past prediction (more often correct than not) and makes a line graph and frequency polygon from these results. It can also work in continuous test mode, using a separate electronic true random number generator plugged into the computer. The device uses its own true random number generator to provide the bits for the forced synchronicity mathematical (negentropy) software I have developed. User:Trevor Loughlin|Trevor Loughlin]] (talk) 14:03, 14 November 2008 (UTC)

This is incredible! CBHA (talk) 14:19, 14 November 2008 (UTC)

Excellent use of definition #1. — Lomn 14:33, 14 November 2008 (UTC)

I think this proves that the visual basic 6.0 programming language is not for dummies after all. The enormous complexity of the mathematics such as designing software logic gates that have not been thought of before, such as the "analogue XOR gate" in the quantum neural network would not have been possible without the ease of the VB6 programming environment. I can program visual c++ with MFC but if I had to use a less intuitive compiler I would have got nowhere. Bring back classic VB6.0!Trevor Loughlin (talk) 14:42, 14 November 2008 (UTC)

At this point I think it best to remind you that the Reference Desk's core purpose is to provide referenced answers to questions, not serve as a soapbox or venue for promoting original research. You seem to be drifting pretty far from the original "superluminal information" concept. — Lomn 16:07, 14 November 2008 (UTC)

I'm not sure this filter will work at all like you want it to. Even though you can plot the number of times you guess wrong consecutively, you won't improve your guessing rate from 50-50 (over a large number of guesses). If you think about it, that same curve also applies for the number of times you guess correctly consecutively. With enough guesses, I bet if you plot them they will be exactly the same, indicating you have roughly the same number of right answers as wrong answers. 152.16.15.23 (talk) 16:18, 14 November 2008 (UTC)

Yes it is entirely possible to cheat an online casino by predicting their random number generator. [15] No it does not count as superluminal communication, even if the casino is on Mars. APL (talk) 04:16, 15 November 2008 (UTC)

Also, Yes it is possible to constantly come out ahead at online poker against stupid humans, simply by playing the odds. People make bots for this all the time. No prediction needed. APL (talk) 04:18, 15 November 2008 (UTC)

WRONG ON BOTH COUNTS. First if a casino uses a psuedo-random number generator OF COURSE they are asking for trouble, because NO finite computer program can EVER produce truly unpredictable numbers,which is why nearly every sensible casino now uses totally unpredictable electronic quantum random number generators-look this up to understand the difference. Secondly it is true that a good robot will beat a novice player because poker has an element of skill and the robot never misses a trick or gets tired, but that is an entirely different issue.No amount of skill will predict true random events. Also some robots actually HACK into the system, there is no prediction involved in this, just cheating, and the security flaw has already been corrected. By the way, if anyone sells or gives you a robot to play online roulette you will lose money. Unlike poker bot's they cannot work in the long term. If they did work the people who wrote the software would keep it to themselves.

My device does not have any internal model of what it is going to predict, because it does not predict, rather it TRANSMITS data from the future to the present by modulating probabilty waves. Thus it is capable of "predicting" things that no amount of skill could predict, such as things with no or virtally no previous history like the twin towers attack. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 06:08, 15 November 2008 (UTC)

Do you mean to tell us, Trevor, that you can make a 100,000 binary predictions of random events that have 50:50 odds of going one way or another, and be right even just 50,700 times (ie 0.7% better than pure luck)? I hereby bet you $58,000 to your $460 that you can't. —Preceding unsigned comment added by 83.199.126.76 (talk) 14:21, 15 November 2008 (UTC)

I will make a web page with a client program linked to my device, and then you can test the device before you want to take on such a bet! —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 16:01, 15 November 2008 (UTC)

Listen, if you want to rule the world with your device, you'd better NOT make any sort of public interface, otherwise you may lose your competitive advantage. I suggest you take only my private bet, and make the interface available only to me, since I will not be asking any questions about your device (so you don't lose your competitive advantage), and $58,000 will certainly help you start ruling the world. The bet is, you get $58,000 if you make 50,700 correct predictions out of 100,000 guesses -- ie a 0.7% advantage over blind luck -- as to which of two possibilities my next random number will be (you don't even have to show me your device or tell me anything about it) against your $460 if you lose. I am more than happy to test this using a web interface you make available only to me (again, I don't suggest you make it public) if you can allow me to use it to predict the results of my own hardware random number generator. I hereby take your bet on these terms.

first we'll try your web interface, which will fail to predict my result at least 50,700 times out of 100,000 guesses (ie fail to have even a 0.7% advantage over blind luck), and then we'll talk about how to show you that I'm really using a random number generator and that you're really failing to guess its results better than 50,700 times in a 100,000, ie any better than 0.7% better than blind luck. Then you can pay up. Alternatively, I am happy to send you $58,000 within a fixed number of days if you are able to guess correctly even 50,700 times out of 100,000 guesses, ie if you show even a 0.7% advantage over pure luck) -- no questions asked about your device. —Preceding unsigned comment added by 83.199.126.76 (talk) 17:14, 15 November 2008 (UTC)

I recommend hurrying up and collecting the JREF prize while it's still being offered. APL (talk) 17:45, 15 November 2008 (UTC)

Just so you know, Travor, the JREF prize is a scam. It will NOT pay out money if you do something supernatural in a scientific, repeatable way. It will just say "well, since it's so repeatable under rigorous, controlled experiments, it's just part of science now, whether we understand it or not. sorry...not paranormal.... but thanks for advancing science! We have hard work ahead now, because what you showed is really ****ing weird, so please, let us get to work. Don't let the door hit you on the way out. We might call you back for even more experiments, though -- this thing has us completely puzzled, it's not supposed to be possible! We have to revise all our rules." That's right. Revise all their rules. After the fact. In reaction to your demonstration. And their rules will include the possibility of whatever you just did, since it's now part of the empirical record (or will be once Harvard, Princeton, etc.... scientists are through with their even more detailed experiments on you.) You'll note that this extra step is part of the protocol. Of course, Harvard, Princeton, Yale scientists won't be there at the preliminary step, but only after you've "passed" that step. They will be there to make sure whatever you can do is now part of official, accredited science, and that therefore you will not get one penny of your million.

I might as well say : "I'll give you $1,000,000 if you get half of America to use a non-word at all levels of speech and writing, and get the non-word into all the dictionaries". This is fraud, a scam, because if you succeed they will just say "thanks for the effort, but since half of America is using it in all levels of speech and writing and it's in all the dictionaries, it certainly is a word, regardless of the fact that you are its coiner. The million dollars is for doing it with a nonword. Go ahead: we are so firm in our belief that Americans use only real words, and that the dictionaries have only real words, that if you can show half of America using a nonword in all levels of speech and writing and in all the dictionaries, we'll pay you ONE MILLION DOLLARS". It's a fraud. It's a scam. It's not a real challenge. It's a shell game, where you're told that you can win money by pointing to the proper one of the three cards. It's a lie, because you can't win money by pointing to any of the cards. This is a scam in the EXACT SAME WAY: you're told you'll win a million dollars by doing something paranormal in a scientifically rigorous way, but that is by definition impossible, just as through the trickery of the dealer it is IMPOSSIBLE to point at the king. Not impossible because you couldn't have done anything paranormal, impossible because EVEN IF YOU DID YOU DON'T WIN. The reason it's a fraud is because EVEN IF you point at the proper card you don't get the money. EVEN IF you do something paranormal you don't get a million. By the way, just so you know, James Randi used to be a MAGICIAN. It's why he knows how to develop fraud protocols such as his challenge.

There is no CHALLENGE, they are just ripping people off. He says : "if you demonstrate something supernatural in a scientifically rigorous way"... Look, there are plenty of things that science is surprised by, doesn't understand at all. If you had said you would do any of them before science produced that result, scientists would have said "no way! that's supernatural". but now that they know the results, they call it a part of science, even if unexplained. So there is no way to win with James Randi. You could clap your nude arms and have a perfect gold sphere with a diameter the size of your head fall out from your hands every time you did that, as many times as you did that, after you went nude through a metal detector into a room surrounded by a thousand scientists, and stood on a scale brought by them, to show you're not even carrying any extra weight, and clap and have gold spheres fall out as many times as you wanted, and they wouldn't pay out: as soon as you've proved that this effect is part of the universe in a rigorous, reproduceable, scientific way, they will say "well, damn is that unexplained, but now that we have so much evidence, it's not paranormal anymore. It's just an unexplained part of nature." STAY AWAY FROM THAT FRAUD, JAMES RANDI.

I, on the other hand, bet you $58,000 to your $460 without a scam protocol. You make that interface, I go on it, and if you predict even 50,700 of my random results out of 100,000 guesses I pay you $58,000, no questions asked. you don't have to show me your device. there is no second step. there is no fraud protocol. there ain't nothin but the money, which I will transfer to you within a specified number of days. But that won't happen: what will actually happen is that your device will fail to be right even 0.7% of the time, even 50,700 times out of 100,000, and once I show this to you as well, you will have to pay up $460. Do we have a deal? —Preceding unsigned comment added by 83.199.126.76 (talk) 19:29, 15 November 2008 (UTC)

At risk of answering the question and avoiding all this side-talk about predicting random-number generators...

Simplify this to a common analogy. I have two boxes. I place a left-hand glove in one and seal it. I place a right-hand glove in the other and seal it. I give one box to Julian and one box to Adaline. Julian hops on a spaceship and travels to Pluto (let's assume he has a real cool ship so can get there at the speed of light). Now, he tries to predict what is in Adaline's box - not his. He has two choices. It could be a right-hand glove or a left-hand glove. Statistically, if this is repeated millions of times, he will be correct 50% of the time. But, we assume he has some magic way of being correct 75% of the time - as the question states, the wrong answers are avoided more often. Does this mean that Julian has created superluminal transfer of information? No. The information is in the box. He took it with him at the speed of light. When he guesses, no information is being transferred. He is just guessing. When he opens the box, he sees in the time it takes light to get from the box to his eyes what he has. That information travelled with him at the speed of light to his destination. From that, he deduces what is in Adaline's box - he does not see Adaline's box at superluminal speeds. From here, you can expand this scenario to include 3 options in the box, 4 options in the box, 5 options in the box... as many as you like. Anything you do will show that the only information transfer is what it is in Julian's box, which travels with him at the speed he travels, which is not faster than the speed of light. -- kainaw™ 20:01, 15 November 2008 (UTC)

bronchitis/passing out - need information

My friend was diagonised with bronchitis 3 months ago. he was passing out every time he coughed. he was treated after one month and was discharged. he has started coughing and getting the feeling he's going to pass out. Is this normal? what is the cause of the passing out? please advise. —Preceding unsigned comment added by Njmagondu (talk • contribs) 09:46, 14 November 2008 (UTC)

We cannot give medical advice on the Reference Desk GaryReggae (talk) 10:08, 14 November 2008 (UTC)

Your friend needs to see a doctor. Axl ¤ [Talk] 10:49, 14 November 2008 (UTC)

Try looking at passing out and bronchitis. 152.16.15.23 (talk) 16:25, 14 November 2008 (UTC)

Cure for AIDS by giving him transplanted blood stem cells

Recently, doctors have reported that they could cure at least one man of AIDS using a rare treatment. See the full story [here]. The case has been reported first in the Wall Street Journal.

Why did they choose a non-scientific publication to describe the case? Mr.K. (talk) 12:20, 14 November 2008 (UTC)

It is not uncommon for authors to announce their findings in popular media before the findings are formally published in peer-reviewed literature. --98.114.98.124 (talk) 13:12, 14 November 2008 (UTC)

The key phrase here is "peer-reviewed literature". The Wall Street Journal will print anything that sells papers. It doesn't have to be true. A real medical journal will require review by experts in the field before agreeing to publish an article. So, when a story such as this comes out in the press before the medical journals, there is a very high probability that it will fail peer review. -- kainaw™ 13:36, 14 November 2008 (UTC)

A more generous viewpoint would be that peer review takes a long time and they wanted to publish quickly and the peer reviewed version will follow later. I wouldn't be that generous though... --Tango (talk) 13:44, 14 November 2008 (UTC)

They didn't choose the WSJ. The case was presented at the Conference on Retroviruses and Opportunistic Infections in February and a special meeting convened by the Foundation for AIDS Research in September. The case was discussed again at a recent HIV conference and this time the mainstream noticed. Dragons flight (talk) 15:54, 14 November 2008 (UTC)

While I'd normally offer a similar answer to Kainaw's, I'm inclined to give the benefit of the doubt here. Hütter and Thiel seem to have a respectable publication track record, and the mechanism they propose for this cure seems reasonable. Bone marrow transplants have a high rate of morbidity and mortality, so this isn't a silver bullet treatment. (This therapy is only worth the risk if the patient also needs treatment for leukemia.) Donors carrying suitable mutations are relatively rare, meaning that even among patients who need a bone marrow transplant, a suitable donor will be difficult to find.

In other words, scientifically speaking, this story isn't that huge. It isn't going to directly help more than a very small fraction of HIV-positive individuals, and it operates by a mechanism that was already essentially known to work. The mainstream media have picked it up because of the OMG they CURED teh AIDS1!!!! factor; it's roughly akin to the Scientists cure cancer stories that we see every couple of months, whenever someone has a promising result in an in vitro trial. To summarize: these guys did cure an HIV-positive patient; it's pretty cool from a technical standpoint; the method is only applicable to a tiny subset of infected individuals; we've still got a long way to go for a generally-applicable cure; this proof-of-principle lends (further) credence to some gene-therapeutic approaches which are in the works. TenOfAllTrades(talk) 14:34, 14 November 2008 (UTC)

I agree with much of this, but it may be premature to say "these guys did cure an HIV-positive patient", because only time will tell. I recall when some thought nef-deleted virus would be a vaccine strain for HIV, until people infected with this strain of HIV progressed to AIDS. I've given other reasons to take a deep breath before cheering too loudly here: Talk:AIDS#Cure_Cases. It is an interesting report, no doubt, but "cure" should be used carefully. --Scray (talk) 05:28, 15 November 2008 (UTC)

Supposing it was possible to find a few uninfected bone marrow stems cell in an AIDS infected patient. Could these not be cultured without the need for a foreign donor, and then re-injected?Trevor Loughlin (talk) 15:42, 14 November 2008 (UTC)

I'm not sure if that will work for two reasons. First is the transplanted marrow from the article came from an HIV resistant patient. Second, I'm not sure if there is a method that can surely locate bone marrow with uncompromised cells. Maybe you could remove the marrow cells, treat them, then culture them... I dunno though. I've heard from someone that donating bone marrow feels like your soul is being sucked out. Can anyone corroborate that description? 152.16.15.23 (talk) 16:42, 14 November 2008 (UTC)

Marrow donation really is not that bad for most donors, but isn't generally necessary now, anyway. Stem cells can be obtained by treating with factors like G-CSF then drawing blood, isolating the uncommon stem cells using antibodies like anti-CD34. BTW, simple treatment of stem cells with antiretrovirals won't do the trick, because of HIV latency. --Scray (talk) 05:23, 15 November 2008 (UTC)

RNAi in flatworms

What species of flatworms have been used in RNAi studies? I know of S. mansoni, S. japonicum and F. hepatica. Does anyone know about monogenea or planaria being used in RNAi? Thanks Donek (talk) 13:58, 14 November 2008 (UTC)

Isn't species an artificial distinction?

OK, I'm not exactly sure how best to phrase this question, but I'll do the best I can. Isn't species an artificial distinction? That is to say that evolution is constantly happening, that life is always evolving, and that one species doesn't magically evolving to a completely new species. Everything is in a state of transition and usually very slowly, like the hour hands on a clock. 216.239.234.196 (talk) 14:04, 14 November 2008 (UTC)

Not quite sure where you are going with this, but you might be interested in our species problem article. Gandalf61 (talk) 14:07, 14 November 2008 (UTC)

The clock is a very good example. If you imagine each tick of the second hand as a genetic mutation, then every movement of the minute hand might represent different strains of a species (e.g. MRSA) and, as in your example, every hour a new species is formed. Whether the distinction is artificial or natural depends upon whether the definition of species is shared characteristics between two organisms or the ability of two organisms to successfully reproduce, respectively (I think). Donek (talk) 15:11, 14 November 2008 (UTC)

Yes - "species" is an extremely arbitary distinction - and the precise point when two sets of gene-lines have split far enough to call them "different species" is horribly vague and certainly inconsistently used.

However, like a lot of things it's very convenient.

We know that there is no distinction between a Zebra and a Lion that's materially different than the distinction between this Lion over here - and that other identical-looking Lion over there...or that cockroach or that bacterium. The two lions, the zebra, the cockroach and the bacterium are all related back in history - they have a common ancestor - they are all (including the two lions) genetically different...it's just a matter of degree.

Even using genetic similarity is a bit tricky because there is more genetic similarity between a male human and a male chimpanzee than there is between a male human and a female human (a fact which explains a lot about interpersonal relationships!). But having to call everything from a bacterium to a bactrian by the same name for the sake of some kind of linguistic purity is simply not productive. So we use this artificial distinction - in the full knowledge that it's arbitary and that there will be tricky 'corner cases' where the distinction is hard to nail down.

SteveBaker (talk) 15:16, 14 November 2008 (UTC)

The term "species" is not arbitrary. It has a very specific meaning: Any animals that can procreate and produce fertile offspring are in the same species. If mutations cause an offspring to be unable to procreate and produce fertile offspring, then it has mutated into a new species. The problem is that people who do not comprehend the definition of species use it for whatever they want it to mean. Then, a word with a specific meaning suddenly has dozens of possible meanings and nobody knows what anybody is talking about. So, ignorant use of "species" may be arbitrary, but proper use is not. -- kainaw™ 15:20, 14 November 2008 (UTC)

Sorry, but this is not exactly true. There are actually very intense and ongoing debates within the scientific community as to the reality and definition of the species concept, all of which revolve on the inability of a simple linguistic construct to take into account the mind-boggling diversity in nature. Ability-to-interbreed seems to work sometimes but not always as a way of determining things. There are many examples that don't fit well into the above definition, in part because biology is, well, complicated. Darwin himself recognized that under his theory, "species" was to some extent necessarily an arbitrary marker of genetic differentiation—the lack of a fixity of species guarantees this fact. The "can it interbeed" is a useful heuristic for talking about species, but for those who are really dealing with the fuzzy borders between species, and for those engaged in the philosophy of biology, it is insufficient... --98.217.8.46 (talk) 15:37, 14 November 2008 (UTC)

The "problem" is when the interbreeding concept is applied to asexual or bacterial things. For animals, interbreeding is well-accepted as the primary indicator of species. Difficulty identifying the species of a bacteria has no bearing on identification of the species of an animal. Attempting to mix up and confuse the two is rather misleading. For Darwin, he did not take the time to grab up two similar birds and see if they could breed. He just assumed that since they were very similar, they probably can breed, and went from there. Using Darwin's lack of time to perform experiments to claim that he didn't understand what an animal species was is also misleading. -- kainaw™ 16:17, 14 November 2008 (UTC)

(edit conflict) Is this relation "being in the same species" transitive, though? If animal X and animal Y can interbreed successfully, and animal Y and animal Z can interbreed successfully, is it always and necessarily true that animals X and Z will be able to interbreed successfully? Maelin (Talk | Contribs) 15:40, 14 November 2008 (UTC)

No, it is not transitive, and so does not give rise to well-defined equivalence classes (i.e. species). See ring species. Algebraist 16:14, 14 November 2008 (UTC)

Excellent question. I was about to ask that myself. As a layman, my response would be no, otherwise evolution wouldn't progress.

Ring species are used as an example of demonstrating that species are not discrete. You cannot assume that because two different animals procreate they are in a unique species. One of them may be in a species that the other doesn't belong to. The inability to discretely map every animal to a unique species causes problems for people who need to put each animal in its own little box. But, that is a problem for the person doing the classifications, not the animals. -- kainaw™ 16:23, 14 November 2008 (UTC)

216.239.234.196 (talk) 16:16, 14 November 2008 (UTC) (Outdent) I'm the OP. If it helps, what I was referring to was species within a single branch of the evolutionary tree. So, I'm not necessarily talking about a frog versus a tiger, but rather all the previous versions of frogs and all the previous versions tigers. 216.239.234.196 (talk) 16:09, 14 November 2008 (UTC)

That doesn't really affect anything. How do you know your separate species aren't the start of two branches? Dmcq (talk) 18:57, 14 November 2008 (UTC)

There are many attempts to draw trees that show how different organisms relate to one another. It is required as common homework and tests in biology (especially bioinformatics). But, any respectable professor will explain that the trees are only for the benefit of those trying to do research on some specific evolutionary trait. As explained above, an organism may bridge other species. I've used geometry since I work in bioinformatics and the students have a lot of math background. Consider the "species" of all shapes with all sides equal. An equilateral triangle and square fit that species. Now, consider the "species" of all shapes with four sides. A rectangle and a square fit that species. So, you have a square that bridges two species. You can see that species overlap. That happens with real organisms (not just abstract shapes). Trying to divide up the species so there is no overlap will lead to many false assumptions and artificial distinctions. -- kainaw™ 19:20, 14 November 2008 (UTC)

I think the poster is actually commenting on a related but slighty different issue. Take a tiger. It is descended from millions of other animals that we would call "tigers", and before that millions of other "cats", and before that other "mammals", and so on. Within that continuous chain of descendancy we insert names for different species, however the gradiations are often gradual rather than abrupt so choosing when a cat becomes a tiger is rather arbitrary. Dragons flight (talk) 19:32, 14 November 2008 (UTC)

There are 3-D models that I've seen. They are rather useless in my opinion. But, they show evolution over time and the speciation fades in - showing how a single species can evolve into multiple species. It isn't supposed to be arbitrary though. The term "mule" used to refer specifically to any offspring between two animals that was not fertile. That indicated that there was the start of a separation of species since animals in the same species must have fertile offspring. As evolution progresses, the two groups of animals may have DNA drift that causes procreation to fail. So, as time progresses, there is supposed to be a point where a single species separates into two groups - with possible overlap. -- kainaw™ 19:44, 14 November 2008 (UTC)

Then again, there are things like Ligers which are not necessarily impotent. A species can be defined based on biological capability of reproduction, but there are barriers other than biology to consider. A saint bernard and a chihuahua may be the same species, but a wolf is different? Behavior and ecology are the barriers between wolves and dogs, not anatomy. The concept of a species is a useful tool, but there are lumpers and splitters and the idea that there is a single ironclad definition of the word is a gross oversimplification. SDY (talk) 01:05, 15 November 2008 (UTC)

heat and static transfer through extension cables

i have an extension cable that when in use and it has not been fully extended it blows the socket it uses and i was also wandering about static electricity being in the extension cable if that also causes the problem? —Preceding unsigned comment added by Kendo23 (talk • contribs) 15:26, 14 November 2008 (UTC)

An undamaged extension cable should have no appreciable external effects. If you've got a cable that is blowing fuses, tripping circuit breakers, accumulating static charge, getting hot, or doing anything else abnormal, stop using it. Replacements are cheap. — Lomn 16:01, 14 November 2008 (UTC)

A coiled up extension cord can't shed heat as quickly as an extended one. Most extension cords that come wrapped up inside a reel of some kind either say in big letters that you can only pull such-and-such number of amps of current through it - or they tell you that the cord must be fully extended before it can be used safely. So I'm guessing that you're trying to run something that needs far to much current (like a room heater or something) - or that your extension cord has to be unreeled before use. There should be something written on the reel telling you what the restrictions are. Failing that - it might be damaged and shorting out against the casing or something - if so, then as Lomn says...get it fixed or throw it away! (It's definitely not static electricity by the way.) SteveBaker (talk) 16:14, 14 November 2008 (UTC)

Agree with Lomn. A hot e-cord will allow fewer amps to flow than a cold one. There appears to be a short circuit in the cord that allows a high current flow and "blows the socket" (trips the circuit breaker?). Toss it! "Replacements are cheap" (which may also be the problem hear). Static is not the problem. Saintrain (talk) 17:30, 14 November 2008 (UTC)

I've seen cords that specify different maximum currents for coiled and uncoiled use, so it could be a combination of the two. Whatever the instructions are, it's important to follow them (unless you are a qualified electrician and know when it's safe not to). --Tango (talk) 18:26, 14 November 2008 (UTC)

If it's blowing the fuse or circuit breaker, it's not due to heat accumulation. There's probably a fault in the cord's internal insulation at some point along its length. When the cord is coiled, the two conductors are brought into contact, causing a short circuit and blowing the fuse. When the cord is extended, the two wires are held apart and everything appears to work. (Until someone wiggles the cord, or steps on it, or picks it up, or...and brings the conductors together again.) I concur with all the above comments — if an extension cord is behaving oddly, stop using it. (It's possible that the cord could have been damaged by overloading it while it was coiled; the heat buildup could have melted some of the internal insulation, causing this intermittent fault.) TenOfAllTrades(talk) 18:44, 14 November 2008 (UTC)

Being infected and sweating

When I have been close to somebody with a cold, for instance when my face got showered when a young child with a cold had a sneeze, I think it is good to sweat a bit to get rid of some of the virus. I checked common cold, transpiration, perspiration and sweat therapy, and didn't find anything, but the article on sauna said: "The skin of our bodies is in effect another eliminatory organ so even when other organs are compromised in chronic illnesses or contamination, the skin through sweating can rid the body of such chemicals and toxins." And this is basically my idea about why sweating would help to prevent a cold. Is this true or is this nonsense???
(I know that maybe strictly speaking some could call this asking for medical advice, but I disagree, because I don't ask if sweating is good for curing a cold, just about if the mechanism of sweating leads to getting rid of some of the virus, possibly helping in preventing getting a cold.)
Lova Falk (talk) 16:53, 14 November 2008 (UTC)

Well, I think an important issue here is a question of scope -- can we expect sweating to operate on a scale large enough to be useful? It's entirely plausible that some amount of virus is sweated out; that much is true. But even if you sweat 1% of your body moisture (a level I would expect to be dangerously high), you'd also likely have sweated out just 1% of whatever virus concerns you (a level that can be dismissed as meaningless). If a child sneezes on your face, the most efficacious response is to promptly wipe your face. As for the sauna article, it is heavily referenced -- but it's not specifically referenced. I'm quite skeptical of three paragraphs that drop 40 references at the very end with no indication as to what relevance any of them have to the material presented. Long story short, I think it's nonsense. — Lomn 17:47, 14 November 2008 (UTC)

It is common for an active athlete to lose 2-3% of their water per hour to sweat. Dragons flight (talk) 18:00, 14 November 2008 (UTC)

There is no evidence that sweating per se improves outcome. However fever has a beneficial effect in recovery from many infections. Axl ¤ [Talk] 23:38, 14 November 2008 (UTC)

Here's a rule of thumb for you... If any process, product, or comprehensive lifestyle uses the word "toxin", it is total bullshit. Real, tested, curative processes are targeted at real chemical compounds made of real atoms, or real biological agents with real DNA and genetics and stuff like that. Anything which supposedly rids your body of "toxins" is just snake oil. --Jayron32.talk.contribs 23:54, 14 November 2008 (UTC)

Well, the liver is not made of snake oil, and it could broadly be said to remove "toxins" as one of its functions. Pharmacokinetics might be of interest to anyone looking to clear "toxins" from the body, though the article on Wikipedia is pretty general and I've yet to see any good "layman's introduction" to the subject. SDY (talk) 00:27, 15 November 2008 (UTC)

The liver removes specific compounds and infectious agents from the body, which can be named and identified and given chemical formulas, and the mechanisms for their removal can be explained using chemistry and biology. If any advertisement for anything tells you it removes "toxins" from the body, but does not name those "toxins" it is bullshit. --Jayron32.talk.contribs 00:46, 15 November 2008 (UTC)

While I agree with your implication generally, IMHO you're stating the "BS" case too strongly. For instance, hemodialysis is frequently said to work (in part) by removing "toxins", the vast majority of which we cannot name. We don't even know which are the most important in mediating uremia. --Scray (talk) 05:36, 15 November 2008 (UTC)

(After edit conflict higher up in the queue) I'm not expert. However the mechanism you are describing looks highly unlikely for preventing an infection. Cold viruses attack the Mucous membranes of your upper respiratory tract. There are no sweat glands in those. So you'd either have to get rid of the virus before it gets into your respiratory tract, for which washing would be more effective than sweating it seems; or you'd have to wait till enough of the little blighters have multiplied to be present in your sweat. (At this point you'd likely be quite sick and even the ones you loose with the water you sweat wouldn't make that big a difference.) What might work, though is that sweating is a "symptom" of a whole range of processes in your body. Since sweating is the body's cooling system it is likely that your body temperature is increased, creating an inhospitable environment for the viruses. If your body is cooling itself by sweating then your respiration rate may also be increased, that should reduce the number of viruses per volume of air. (Think hurricane vs. light breeze.) More importantly blood flow throughout your body is probably higher. This helps getting components of your Immune system to the site where the viruses are trying to get a foothold. If we are talking sauna, the higher air humidity also makes for an unfriendly environment for cold viruses. It helps keep your mucous membranes moist and flush infectious agents into your acidic stomach. The cells lining your mucous membranes are also "happier" in a moist environment and won't be as easy to attack as stressed cells. To what extent the salt that gets excreted in sweat is also excreted in mucous secretions by association I don't know. Saltwater is however more effective in nasal lavage than plain water. (see Osmotic pressure). And just to boot when you sweat your feet are likely warm: cold feet cause the blood vessels in the nose to constrict, which makes the nose colder and reduces the blood circulation, inhibiting the body's immune response. [16]  :-)Lisa4edit (talk) 00:57, 15 November 2008 (UTC)

Thank you all! Next time I get close to a child with a cold, I'll wash my hands and face, and make sure to stay warm - but not by running or biking when it's cold outside.Lova Falk (talk) 18:02, 15 November 2008 (UTC)

searching for the name of a old device with large glass discs

im serching for the name of a device the has a serie of large glass discs that turn in opposite directions and generate sparks from static electricity , i saw it in a documentory about the victorian era —Preceding unsigned comment added by 216.113.44.180 (talk) 18:43, 14 November 2008 (UTC)

Are you looking for a Wimshurst machine? TenOfAllTrades(talk) 18:46, 14 November 2008 (UTC)

yes thats it , thanks , there is just one thing i cant figure out , im not sure if the charge in this machine is generated by the disc itself or metal fixed to it and if the type of material used influences the amount of electricity generated —Preceding unsigned comment added by 216.113.44.180 (talk) 20:28, 14 November 2008 (UTC)

The discs have to be an insulator and the metal affixed to it has to be conductive. The insulating quality or dielectric strength and breakdown voltage of the insulators as well as the geometry determine the maximum voltage and current produced for a given speed of rotation. The charges are produced by electrostatic induction in the wedges of tinfoil pasted on the rotating glass discs. a 1903 encyclopedia explains it in some detail and says the discs might be made out of rubber. A good machine could produce a 1 foot (30 cm) spark. The glass was likely to be varnished to reduce moisture on the surface which would drain off the charge.Edison (talk) 22:36, 14 November 2008 (UTC)

oxyfuel combustion engine( IC engine)

out of quriosity i am posting this question, what happens, what load is applied on the piston, how much is engine efficiency when; 1) the 78% of nitrogen in the air that is supplied to the combustion chamber is replaced by oxygen ie. there will be 100% oxygen plus fuel for combustion. 2) the 78% nitrogen is removed and there is only 21% oxygen and fule in the combustion chamber of the same size as in the above case. please answer with an equation to prove it. thanx in advance. —Preceding unsigned comment added by Sharath.sgh (talk • contribs) 18:53, 14 November 2008 (UTC)

See Oxy-fuel, which while a short article, leads to several OTHER articles which may be helpful. --Jayron32.talk.contribs 23:50, 14 November 2008 (UTC)

How does water put out a fire?

Is it through cooling or does it smother the fire? —Preceding unsigned comment added by 64.234.6.82 (talk) 23:29, 14 November 2008 (UTC)

From our article on fire, "Fire extinguishing by the application of water acts by removing heat from the fuel faster than combustion generates it." Jkasd 00:36, 15 November 2008 (UTC)

Cooling, I believe. See Fire triangle. --Tango (talk) 00:38, 15 November 2008 (UTC)

Doesnt the application of water all over the burning mass also starve the fuel of oxygen?--GreenSpigot (talk) 01:42, 15 November 2008 (UTC)

If that were the case little children around the world would be suffocated as they played in water sprays. --Trieste (talk) 01:56, 15 November 2008 (UTC)

I didnt say sprays of water. I meant a mass of water. Any way, a spray of water will reduce the available oxygen content around the fire wont it?--GreenSpigot (talk) 02:02, 15 November 2008 (UTC)

Fire fighting#Use of water says that both factors (cooling and asphyxiation) come into play. Rather than the water itself, it is the water vapour that reduces the supply of oxygen to the fire - so more of a sauna effect than a shower. Gandalf61 (talk) 11:24, 15 November 2008 (UTC)

So, shouldnt the article on Fire state that fact?--GreenSpigot (talk) 13:00, 15 November 2008 (UTC)

You should mention it on the Talk:Fire page - but they're going to want a reference to show that this is true. SteveBaker (talk) 18:18, 15 November 2008 (UTC)

November 15

Vapor pressure

If I understand the subject at hand correctly (which, not having taken a chemistry course, I probably don't), all substances, including solids, have a vapor pressure, and if atmospheric pressure is reduced to below this vapor pressure, the substance at hand will evaporate/sublimate away. If so, why can solid objects exist in space (a complete vacuum)? Shouldn't they have sublimated away long since? 69.177.191.60 (talk) 00:54, 15 November 2008 (UTC)

From Vapor pressure#vapor pressure of solids, "due to their often extremely low values, measurement can be rather difficult". Outer space isn't actually a complete vacuum. Objects that are sent into space (spacecraft, satellites, etc.) are designed to have even lower vapor pressures than everyday objects. Axl ¤ [Talk] 01:04, 15 November 2008 (UTC)

Does gravity hold things in space together? Even small objects have gravity, which may be great enough to prevent the escape of atoms on their surface. It is theorized that the atmosphere of the earth's moon, and other rather small objects in space, has gradually escaped the gravitational pull. But atoms of a solid material may be unable to escape the gravitional pull of the parent body. —Preceding unsigned comment added by 98.17.34.3 (talk) 14:28, 15 November 2008 (UTC)

In order to change state from solid to gas, energy is required, see phase transition. There is very little heat in the 'vacuum' of space and no energy to cause the sublimation. Everyday objects also not not sublime when in a vacuum chamber for example. Most everyday objects are pretty stable, it is only when objects are heated close to their melting / boiling temperature that the most energetic particles close to the surface of the material will begin to vapourise. Of course a vacuum will lower these temperatures but if you do not supply energy to a system it cannot gain the energy suuficient for vapourisation. Jdrewitt (talk) 14:50, 15 November 2008 (UTC)

Frameshift mutation.

Would a frame shift mutation affect the building of only one protein, or does the frame shift extend beyond the first stop codon? Can the entire chromosome be read as codons in groups of three, or can the codons start at positions offset from a multiple of three from the very first nucleotide at the 5' end? Basically I'm sure that if a point mutation occurs, it presumably it doesn't affect the entire chromosome, but I'm not sure how. Jooler (talk) 01:06, 15 November 2008 (UTC)

Think about what nucleic acid is used by the ribosome to generate protein. How is that nucleic acid formed? Is it a complete chromosome copy, or some smaller unit? --Scray (talk) 05:05, 15 November 2008 (UTC)

General equation for two bases (or metal hydroxides) reacting

Hi guys, just doing some basic chemistry and the general equation (i.e. Acid + Base -> Water + Salt) for when two bases (or metal hydroxides) react has eluded me. Specifically, I am looking for the gener equation that would help me determine the below reaction:

$KOH+Fe(OH)_{3}\rightarrow$

Thanks. Foxy Loxy ^Pounce! 02:01, 15 November 2008 (UTC)al

Hydroxide, beside being a Bronsted base is also a good Lewis base and thus often forms complex ions with transition metals. My best guess is some form of iron(III)hydroxyl ion:

Fe(OH)_x^(3-x)

it probably depends on the coordination number of Iron(III) as to the specific formula, but my guess is that this forms a complex ion of some sort. See [17], especially the description of Reactions of iron ions in solution and the following section Reactions of the iron ions with hydroxide ions. Good luck! --Jayron32.talk.contribs 02:20, 15 November 2008 (UTC)

Actually, I am probably wrong there. It looks like no reaction will occur in this case, the article I cite makes the claim that iron does not form soluble hydroxide complexes, and this page: [18] also states: "Another reaction type frequent seen is the formation of a hydroxide followed by the formation of a soluble hydroxide complex ion. Fe(OH)3 and Mg(OH)2 do not form soluble complexes, but aluminum and zinc do". Looks like no reaction will occur given those reactants! --Jayron32.talk.contribs 02:30, 15 November 2008 (UTC)

Well that explains why I could not think of the equation! Thank you very much. Foxy Loxy ^Pounce! 03:40, 15 November 2008 (UTC)

Fuller's formuls

This is a civil engineering question.Do anybody help by providing the proof of the Fuller's formula that is used in getting densest mix out of various fractions of construction aggregates?The formula is as follows:

      p=(d/D)^n
      where p-fraction of the material passing a certain seive of size d
      d-maximum size of the aggregate
      n-gradation coefficient usually equals 0.45 or 0.5 

202.70.74.136 (talk) 02:12, 15 November 2008 (UTC)

Well, you obviously want a function that gives p=0 when d=0 and p=1 when d=D. And scale invariance suggests a power law. So that just leaves the question of the correct exponent n. I think the value of 0.45 or 0.5 is reached empirically - this text book says Fuller's original value of 0.5 was "based on wide scale experiments"; this source says "Why 0.45 exponent in Aggregates Gradiation ? The typical answer is: "that's the way we've always done it"". Gandalf61 (talk) 11:14, 15 November 2008 (UTC)

Would an organism that could successfully repair all cellular damage be theoretically immortal?

The general consensus seems to be yes, and many think it even attainable. I’m open to be convinced and would like healthy immortality as much as anyone. But my objection is that there is more to an organism than its component cells. Aren’t there general effects which work on the ENTIRE system? For example, over many decades, gravity bends the spine, and causes breasts to sag, and so on. Could it be that these effects work on levels ABOVE the cellular one, on the body as a machine?

If you had a wooden bridge that gradually bowed under the weight of traffic, would you make that bridge healthy just by replacing it splinter by splinter? Aren’t there cracks BETWEEN the splinters, even between molecules, that mean that the replacement of an organism’s cells, one at a time, will not entirely negate the effects of aging? Myles325a (talk) 06:44, 15 November 2008 (UTC)

Hmm, this is suspiciously like a homework question. However I'll assume good faith and give you a couple of pointers. See biological immortality. Partly it depends on how you define "immortality". The "goal" of all organisms is to reproduce. Most unicellular organisms undergo asexual reproduction, provided they live long enough with favourable circumstances. The "daughter" organisms have identical DNA to the parent. Perhaps this is a form of immortality? Or has the organism foregone immortality in favour of reproduction? With multicellular organisms (including humans), the intervening connecting tissue between cells needs to be maintained as well as the cells themselves. However in many complex organisms, cells often undergo apoptosis. Axl ¤ [Talk] 07:25, 15 November 2008 (UTC)

Would it be the same organism? Julia Rossi (talk) 08:31, 15 November 2008 (UTC)

Aha! The good old Ship of Theseus paradox. SteveBaker (talk) 15:06, 15 November 2008 (UTC)

"We both step and do not step in the same rivers. We are and are not."

— Heraclitus

Axl ¤ [Talk] 10:08, 15 November 2008 (UTC)

You are defining a situation where the hardware of the body is somehow kept in perfect repair. That doesn't cover the "software"...our brains. I don't think it's clear whether or not our brains could continue to function indefinitely - even though the hardware is OK - would the software keep running. To pick an example - a Windows PC will gradually run more and more slowly over years of use if you don't periodically "defragment" the hard drive. Perhaps our minds have similar problems - but maybe there is no built-in "defrag" because we have not evolved to live long enough for it to matter. We know it'll run for 100 years or more - and it seems that the changes in mental acuity that come with age are related to structural matters that your magic cell repair gizmo would prevent. So I don't think we know whether the mind (as opposed to the brain) would continue to work indefinitely. SteveBaker (talk) 15:06, 15 November 2008 (UTC)

Maybe God was smart enough to install Linux (ext3) instead of Windows (ntfs) and avoid the disk defrag problem. Heehee. Oh no - me brain is open source! -- kainaw™ 16:26, 15 November 2008 (UTC)

Maybe...I'm pretty sure I got given Sinclair BASIC! SteveBaker (talk) 18:11, 15 November 2008 (UTC)

I thought of a better analogy for those who don't understand PC's (or who use a sensible operating system and have never defragged anything in their lives!). Imagine a large library. When they built the library, they filled it full of books and put them all in Dewey-decimal ordering with books in alphabetical order within each group. The library contains a million books - but only a couple of librarians - who are meticulous about fixing broken bindings and stopping people from dog-earing the books - they clean and polish the shelves and keep the book-worms at bay. But they never re-organize the shelves. When the library is new - you can find books really easily - you go to the right category - then you zip along the shelves to the right place in the alphabet - and there is your book. But over the years, visitors to the library pull out books and sometimes they put them back onto the shelves in the wrong order. After decades, centuries or millennia, the library gets further and further from its original state of order. The books, the shelves and the card indices are all kept in perfect repair - but things get harder and harder to find. Eventually, there are a million books in random order on the shelves and the library stops working - nobody goes there anymore and it "dies". This kind of "software" disorder could conceivably affect our minds and kill us - even if the 'hardware' of our bodies were immortal. SteveBaker (talk) 18:11, 15 November 2008 (UTC)

publishing thesis

how i can publish my pHD thesis in wikipedia. its title is Electron and light microscopical studies on the lung of one humped camel(camelus dromedarious).Dr doaa (talk) 07:04, 15 November 2008 (UTC)

You cannot publish your PhD thesis in Wikipedia. Wikipedia does not allow original research. A good way to publish elements of your thesis is to discuss with your supervisor and submit an article to a peer-reviewed journal. Axl ¤ [Talk] 07:08, 15 November 2008 (UTC)

If you want to publish original research online you could take a look at arXiv. Mr.K. (talk) 11:31, 15 November 2008 (UTC)

There are a LOT of peer-reviewed journals out there; one is likely to accept your work for publication so long as it is really novel work. It might not make it into Nature or Science, but there is probably someone that will accept it. Talk to your advisor, and see what he recommends. --Jayron32.talk.contribs 17:10, 15 November 2008 (UTC)

You could create your own website, publish your thesis and put a link to it on your wikipedia user page. Lova Falk (talk) 18:07, 15 November 2008 (UTC)

air compressors - energy required.

I want to know the energy(electricity,KW-H) usage rate for air compressors. Compressor: Centrifugal, Displacement = 1000 CFm, output pressure rating = 100psi. Suppose, the out put flow required is 500 CF per Minute. Then, what would be the power consumed in an hour. The compressor motor rating is 250 HP. Is there any thump rule or simple formula to find it out..? Whether the equation, P1.V1 = P2.V2 is applicable here..?(P1 = Atmos. pressure, P2 = 100psi. and, V1, V2 are volumes). —Preceding unsigned comment added by Ajivg1 (talk • contribs) 12:39, 15 November 2008 (UTC)

This depends on its efficiency, but 50 percent is probably a reasonable guess. 250 HP would correspond to 500 HP *(0.746 kilowatts/HP) = 370 kilowatts. That is, every hour it would use 370 kilowatt-hours. -User: Nightvid (unregistered) —Preceding unsigned comment added by 129.2.43.42 (talk) 15:10, 15 November 2008 (UTC)

Neurotransmitters

This came up recently in class and not even the PhD qualified teacher could think of an answer - why do we have so many different neurotransmitters? Apart from having different receptors which is a cop-out answer, we got so far as to say it was probably just an evolutionary mid-stage? RHB - Talk 15:49, 15 November 2008 (UTC)

What do you mean by "evolutionary mid-stage"? There is no destination in evolution, so I can't see how it's meaningful to talk about being half-way there. --Tango (talk) 16:57, 15 November 2008 (UTC)

The best answer I can think of is that we don't want any "bleed though" between the different functions of the brain. If we had only one neurotransmitter, then it could possibly "leak" into synaptic junctions where it would cause all sorts of havoc. With a wide array of neurotransmitters, each localized to a certain set of cells in the nervous system, there is less chance of "cross contamination." Although, the better answer is "because it works"; remember that evolution is not an intelligent process. Stuff gets preserved in the system only because it doesn't self-eliminate. Anything which does not cause insta-death is likely to be preserved by the system, not because it is the best possible way to do it, but because it works. --Jayron32.talk.contribs 17:07, 15 November 2008 (UTC)

My guess (maybe a bit like Jayron32's idea) is that at every single moment there is an extremely complicated activity going on in the brain, with lots and lots of processes simultaneously that influence each other. Every single movement, every single sensation, every single thought (and each thought also elicits some memory, some emotion), the arcadian rhythms, just to name some examples, all have their neural base. I think to have different neurotransmitters is far more efficient for the brain than to have only one.
As a metaphor, you could compare with colors. All information that colors contain can be expressed in binary codes, but it is far more efficient for us to see the color red, green, yellow or blue than to process 001001, 010001, 110111, or 100011.Lova Falk (talk) 19:39, 15 November 2008 (UTC)

in theory, could a discovery about reality invalidate the possibility of physics as a field of science?

In theory, though it's ridiculously unlikely, the entire field of mathematics could be invalidated by the discovery that no system of axioms could fail to be inconsistent, and that for any set of mathematical assumptions, there exists no p such that p can be proven using those assumptions, but not p cannot be also be proven.

Does the same thing exist in physics? Could any results (however ridiculously unlikely) completely invalidate for physicists the very possibility of physics as a science?

I'm thinking, if Einstein or Maxwell, or any other scientist, were in a coma, and for whatever reason on a long opium trip (a la Kublai Khan), living in a dream-world much like anyone's who dreams, then if they decide to do experiments in their dream, or any other rigorous analysis of their new world, they would soon conclude that whatever has happened to reality, it has invalidated the pursuit of physics forever. Outside of dreams, however, could reality (though this is ridiculously unlikely) produce any experimental results that completely invalidate the very idea of physics? —Preceding unsigned comment added by 83.199.126.76 (talk) 16:35, 15 November 2008 (UTC)

Physics (and the rest of science, by extension) is based on the assumption that the universe can be explained. That is, there is a fixed set a physical laws that govern how the universe behaves. If it turns out that that isn't the case, and the universe just makes things up as it goes along, then the whole of science goes to pot. However, all our observations so far seem to support the assumption, so it's extremely unlikely. --Tango (talk) 16:55, 15 November 2008 (UTC)

There's not a single "lynch-pin" that holds up all of science which, if shown to be incorrect, would bring the whole thing down like a house of cards. It just doesn't work that way. Sure, individual ideas are constantly being refined, but none of those ideas is SO important and SO key to the entire process would be rendered wrong. Science is descriptive not prescriptive and as such, it doesn't depend on being "right" all the time. If God came to earth and said "Look guys, I was just kidding with all those laws of physics, here's a new set of laws. Work it out!!!", it would not invalidate all of the old laws, since they worked very well to describe the universe as it existed at that time. Science would adapt to take in the new set of data. --Jayron32.talk.contribs 17:03, 15 November 2008 (UTC)

Then phsyics is in direct contrast with mathematics, in which when an old result is overturned, it is not the case that this does "not invalidate the old result, since it worked very well to describe the truth as it existed at that time." —Preceding unsigned comment added by 83.199.126.76 (talk) 17:31, 15 November 2008 (UTC)

Old results in mathematics aren't overturned, they're just built upon. Once something has been proven, that's it, it's not going to suddenly turn out to be false after all. (There is always a chance the proof will be incorrect, but once it's been checked by a decent number of mathematicians you can be pretty sure it isn't, and there is always the standard caveat from Godel, but that makes no difference to day-to-day mathematics.) --Tango (talk) 18:02, 15 November 2008 (UTC)

(ec) The most fundamental idea of physics is that is there are fundamental laws of nature that can be discovered through application of the scientific method. New laws are discovered, or old laws modified, when new data is provided by experiment. The important feature of a law of nature is that it universally true at all places and in all conditions. More extreme experiments test the boundaries of the applicability of what we believe the laws to be and occasionally they have to be updated as a result. An example is Newtons law of gravity being modified by Einstein's general relativity. But always a new set of laws is put in place that is now universally true in the new set of data. The foundation of science requires that such a set of laws exist - it is the unprovable act of faith in science if you like. It is logically possible that a discovery could be made that showed that such a set of laws, however formulated, could not exist in all circumstances. This would certainly invalidate the basis of physics, but I would be hard pressed to think of any way such an experiment could ever be performed. SpinningSpark 17:09, 15 November 2008 (UTC)

I think the point is best made by talking about what happened to Newton's laws of motion when Einstein proved them "wrong" with relativity. Physics can't be completely wrong because they predict reality with such great precision - but they certainly can (as happened with Newton's laws) be shown to be missing some important terms that only show up under conditions that we have not yet fully explored (in that case - it was the fact that Newton had not explored the nature of light adequately). There were times in past history (eg with Aristotle's laws of motion) where the laws were simply wrong (certainly true with Aristotle's stuff) - but those were always in times when the modern scientific method was not being employed. The ancient Greeks actually frowned upon the idea of doing experiments and making measurements. Modern science really doesn't allow us to make such gross errors. Once we have a law that explains a large swath of phenomena - and which makes predictions that actually come true - it's exceedingly unlikely that the law can be utterly wrong - except in realms of mass, speed, size, temperature - that we have not carefully explored.

The situation is actually rather similar in mathematics. Godel showed that any sufficiently powerful logical system will allow theorems that can neither be proven nor disproven. This is a profound (and disheartening) conclusion - but mathematics didn't end on that day - neither did very much of the theoretical or practical applications of mathematics collapse. It works too well for that kind of major collapse to happen.

And in physics - we discover that at it's heart, quantum theory says "it's all just random anyway" - and that devastating blow to the idea of the "clockwork universe" didn't really make a dent in other areas of physics. Sure, we know that in principle a massively unlikely quantum event could cause a grand piano to spontaneously materialise in the middle of my subtle experiment to find an extrasolar planet - but that fact doesn't alter the validity of that experiment in any important way - so it can be neglected. If string theory were proven true (or false...either would be profound) - our fundamental understanding of absolutely everything would change - but Hooke's law of spring stiffness wouldn't change - we could still rely on Ohm's law. That's because whatever this new theory is, it has to explain WHY voltage, current and resistance behave as they evidently do. The new theory can't say that for "normal" conditions Ohms law is wrong - because we've shown (and continue to show) that it must be correct because our computers are working OK.

Physics (and science in general) is about two things: "HOW things behave" and "WHY they behave like that". The "WHY" part certainly can (and does) change...but the HOW part can only change in such a way that's consistent with all of the 'HOW' laws we already have. We can say that what we thought were quarks and photons and electrons and such are really only vibrating 26-dimensional strings...but that change to our understanding of "WHY" can't take away the indisputable fact that HOW "electricity" flows along copper wires is according to I=V/R. Of course it's possible that the string theory might produce the discovery that Ohms law should really be: I=V/R+0.00000000000000000000000000000000000000001xP/L where 'P' is the charge on the electron and L is the amount of time elapsed since the big bang - but this would hardly be a profound 'HOW' change - only a profound 'WHY' consequence - and most people would not do physics much differently as a result. That's what happened to Newton's laws of motion. We discovered this bizzaro thing about the speed of light and that space-time is distorted by gravity fields and the changes to Newton's laws all end up being modified by this factor of (1-v²/c²) - but since for almost all practical purposes, v²/c² is just about zero - so the 'modification' is essentially nothing. Physics changed radically - but it made absolutely zero difference to all of that beautiful victorian science that taught us how to make steam engines and such.

SteveBaker (talk) 17:41, 15 November 2008 (UTC)

I think SteveBaker has most of this correctly, but I firmly but respectfully disagree with his assessment of the difference between "why" and "how". All physics describes is the "How's". For example, one can describe "how" light is generated from a heated object blackbody radiation and also "how" photons and electrons interact to produce that light and also "how" the way the universe organized itself after the big bang led to the creation of photons and electrons. However, the big "why" questions, such as WHY the laws of the universe work the way they do, WHY it was created in the first place, WHY humans exist to study it; etc. etc. are entirely unanswerable via science. Which is OK. Science is not equipped to answer these questions, and never has and never will be. But that does not make science invalid; rather science is the best system we have to answer the "how" and "what" questions. See the works of Stephen J. Gould especially Rocks of Ages and The Hedgehog, the Fox, and the Magister's Pox for more on these ideas... --Jayron32.talk.contribs 20:15, 15 November 2008 (UTC)

I disagree - Science does have two parts, the hows and the whys. The scientific method involves making some observations, finding a law to describe those observations (a "how") and then coming up with a theory to explain that law (a "why") and predict further laws which you can then test. --Tango (talk) 20:31, 15 November 2008 (UTC)

Another one for the bird psychologists here...

What's going on with the parrot here? Anger thing or sex thing would be my guess. --Kurt Shaped Box (talk) 16:56, 15 November 2008 (UTC)

It could have just been trained to do it for some strange reason. --Tango (talk) 17:09, 15 November 2008 (UTC)

Conservation of momentum

Okay, let's say you were hanging off a cliff, attached to a rope which is wrapped around a pulley attached to the edge of the cliff, and the rope is connected to a large rock (there's also no gravity). If you were to pull on the rope, obviously you would start rising and the rock would start moving. But how would momentum be conserved? The magnitude of your momentum is the same as the magnitude of the rock's momentum, but their in different directions.

The planet to which the pulley is firmly bolted is a part of the 'system'. It moves in the opposite direction to you and the rock...albeit rather slowly! (And this is true whether or not we are ignoring gravity) SteveBaker (talk) 20:02, 15 November 2008 (UTC)

transistor configuration116.71.178.160 (talk) 20:33, 15 November 2008 (UTC)

i am going to make this http://www.redcircuits.com/Page38.htm project .but i dont know that how the transistor Q3 being used in the circuit is baised and why it could control the amplitude of louder sound in a limit while allowing all little sound fully amplified. plz.plz.plz.plz.plz.plz.help me]