Joe Fitzsimons
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 Jan 18 comment Is there any thing other than time that “triggers” a radioactive atom to decay? @dmckee: I said it was -not- an intrinsic property, and I had hidden variables specifically in mind. As regards the increased probability, your point is exactly the reason for the disclaimer immediately following it. To explain it properly would require quite a technical discussion about nuclear structure and interaction cross-sections. Jan 18 revised Is there any thing other than time that “triggers” a radioactive atom to decay? added 516 characters in body Jan 18 answered Is there any thing other than time that “triggers” a radioactive atom to decay? Jan 18 comment Home experiments to derive the speed of light? I would imagine it simply uses the falloff in illumination to measure distance. That seems far easier than timing pulses. Dec 11 awarded Quorum Nov 18 comment Home experiments to derive the speed of light? @Frédéric: At each hop there is routing overhead. When a packet expires at that hop the processing is different. Nov 18 comment Home experiments to derive the speed of light? @Frédéric: I'm not sure you can simply take the difference of two times in traceroute. It neglects the processing overhead which may be substantially different at each node. Nov 18 comment Home experiments to derive the speed of light? @Frédéric: Yes, I guessed it wouldn't be much. I just can't figure out where he got the numbers from. Nov 18 comment Home experiments to derive the speed of light? @sigoldberg1: The speed of light is approximately $3\times 10^8 m s^{-1}$. Thus it takes only $10^{-7} s$ to travel through 30m, unless the speed is orders of magnitude lower in the fiber. This is 100 nanoseconds, not 10 microseconds. For a 10 microsecond delay you need 3km. Nov 12 comment Home experiments to derive the speed of light? Well, I don't know about you, but I don't have 30000 km of optical fiber in my kitchen cabinets. Nov 12 comment Home experiments to derive the speed of light? Even if you used the retroreflector left on the moon (which is never more than 406000 km from us, the time delay between sending and recieving a reflected signal is only a little over a second. For a signal bounced off the ISS (assuming you could even achieve this) the time delay would be roughly 1ms. It would be extremely hard to measure this accurately using 'common household tools', not to mention the difficulty of actually distinguishing the signal from the background noise. Nov 12 comment Home experiments to derive the speed of light? Yes. Fortunately it is usually written on them. Nov 11 comment Physics and Computer Science I'm not so sure about this. It is not particularly hard to learn the background for an undergrad course, even if it is not particularly in your area, provided you have a sufficiently numerate background. Nov 9 awarded Beta Nov 8 answered Home experiments to derive the speed of light? Nov 8 comment Physics and Computer Science Physicists usually use mathematical equations to model the world, not algorithms. This is not the same thing as algorithms, and indeed the existence of an algorithm to solve these systems of equations is not a prerequisite. Nov 8 awarded Commentator Nov 8 comment The Many Body problem @Tobias: Simulation of either is at least BQP-complete, so it makes little difference which you use. Nov 8 comment Velocity of Object from electromagnetic field I believe the fastest rail gun speed achieved is about 10 km/s. I don't, however, understand why you have given a magnetic field strength as an EMF. The units simply don't make sense. Even if they did, this is simply not enough information. Is the projectile charged, magnetic, etc? The maximum velocity will be limited by conservation of energy as already pointed out, but without knowing how the system you have in mind works, we have no way to calculate the initial potential energy and any driving force etc. Nov 8 comment Physics and Computer Science So, why are people voting to close without leaving a comment?