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The Dot in .mars
Skynet writes "CNN has a really cool interview with Chad Edwards, manager of the Mars Network Office, about NASA's desire to improve telecommunications to and from Mars. They plan to get a 1MBps link up by 2007. They also discuss the possibility of multiple Internets spread throughout solar system, all interconnected. Very interesting discussion."
This is actually quite an insightful question.
The problem is that when you tug on a rope what you actually do is send a "wave" of compression and stretching down the rope, and it takes time for the wave to reach the other end and be felt.
The same happens if you push on a rod.
The speed of this wave is determined by the stiffness and mass of the rope or rod. The stiffer and lighter, the faster it travels. So, you say, make your rod or rope stiff enough and light enough and it should travel faster than light!
In fact you can't do that. The stiffness of a rope or rod is determined by the strength of the forces between the atoms that make it up, which are determined by electromagnetic effects (same as light). The fact that these effects only transmit information between the atoms at the speed of light puts an absolute limit of how stiff a rope or rod you can make, and ensures that the waves always travel slower than light.
Chad Edwards, when asked about the possibility of online gaming to Mars, said that they were concerned about high ping times. Edwards did say that they are confident, however, that their ping times will be lower than those currently enjoyed by players on Blizzard's battle.net service.
You have probably read something somewhere about the EPR paradox and the Aspect experiments, which are key ingredients in discussions about the interpretation of quantum mechanics. This is a delicate subject, even many physicists will make errors when trying to explain it. I will also, I am sure, but I count someone will correct me (I actually hope somebody skilled in foundations of QM will comment on this, I am only an experimental nuclear physicist).
EPR (Einstein, Podolsky and Rosen) considered a correlated pair of particles with spin. E.g. when a neutral pion (spin zero) decays into two photons, the spins of the two photons must be opposite (conservation of angular momentum). Spin is always measured along a polarization axis, with only two possible answers, say + and -.
In the case where both spins are measured along the same axis you know what the measurement will read as soon as you know one of them, namely the opposite. If the two axes are under an angle, quantum mechanics gives a simple formula for the probability that the measurements will give opposite answers (cos^2 of half the angle between the axes, or so).
If you would assume that the actual direction of the polarization was already determined in the middle (when the pion decayed), then you can show that this probability distribution must have a certain property (the illustrious 'Bell inequality'), which is *not* fulfilled by the quantum mechanical prediction. Then Aspect actually tried it out (and it is a very difficult experiment) and lo & behold, QM was right and hence the 'actual spins' (which is a vague concept) are *not* determined in the middle but at the moment of the measurement, and hence the information about the *other* measurement travels faster than light, instantaneous even.
The sad point to note for your superluminal lasercommunication is that you cannot *influence* the information. It is Nature who decides the direction of the spins. So the answer to your question is 'No, in that fashion you cannot communicate faster than light'. Information can be superluminal, influence cannot. For communication you need to be able to influence the information.
With your measurement you can predict what the other would measure if the polarization axis there would be chosen (anti)parallel to yours. You cannot tell from your (measurements) the direction of the other polarization axis, which is what you were suggesting. If, for instance, one (the sender) would keep its polaxis constant and the other (the receiver) would do a series of measurements with the (wrong) idea that due to the correlation you should see an angular dependence; well then, pity, you would measure in any angle + and - equally often (with some random deviations). The QM correlation only tells you whether the other one will measure the same or the opposite, if you would *already*know* the other axis.