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Merged Puzzling results from CERN

Hilarious that it's a lead story on Google news now, with screaming "Einstein turned on his head!" headlines.
 
sol invictus said:
I thought GPS always worked by phase. Isn't that why you need at least four (instead of three) satellites in view at any one time?
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No; for large enough distances, you don't need to look at phase information. The frequencies are between around 1 and 1.5 GHz. About 5 cm.

OK, so this is an ideal, and there are multiple satellites in different directions, so phase information can help. Still, once you get to a couple of meters, who cares?
 
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Quantum tunneling
Quantum Tunnelling is the quantum mechanical effect that permits a particle to pass through a barrier when it does not have enough energy to do so classically. You can do a calculation of the time it takes a particle to tunnel through such a barrier. The answer you get can come out less than the time it takes light to cover the distance at speed c. Does this provide a means of FTL communication?
Ref: T. E. Hartman, J. Appl. Phys. 33, 3427 (1962).

The answer must surely be "No!"—otherwise our understanding of QED is very suspect. Yet a group of physicists have performed experiments that seem to suggest that FTL communication by quantum tunneling is possible. They claim to have transmitted Mozart's 40th Symphony through a barrier 11.4cm wide at a speed of 4.7c. Their interpretation is, of course, very controversial. Most physicists say this is a quantum effect where no information can actually be passed at FTL speeds. If the effect is real it is difficult to see why it should not be possible to transmit signals into the past by placing the apparatus in a fast-moving frame of reference.
Refs:
W. Heitmann and G. Nimtz, Phys. Lett. A196, 154 (1994);
A. Enders and G. Nimtz, Phys. Rev. E48, 632 (1993).

Terence Tao has pointed out that apparent FTL transmission of an audio signal over such a short distance is not very impressive. The signal takes less than 0.4 ns to travel the 11.4 cm at light speed, but it is quite easy to anticipate an audio signal ahead of time by up to 1000 ns simply by extrapolating the signal waveform. Although this is not what is being done in the above experiments, it does illustrate that the experimenters will need to use a much higher frequency random signal, or transmit over much larger distances, if they are to demonstrate FTL information transfer convincingly.

The likely conclusion is that there is no real FTL communication taking place, and that the effect is another manifestation of the Heisenberg Uncertainty Principle.
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However, I heard a rebuttal to this where music was transmitted faster than light as evidence communication could indeed be transmitted. It was on NOVA or something.

Beyond that exposure to the information, I know nothing. :)
 
epepke said:
No; for large enough distances, you don't need to look at phase information. The frequencies are between around 1 and 1.5 GHz. About 5 cm.
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That's the carrier frequency. The phase info GPS uses under normal operation isn't of the carrier wave.

OK, so this is an ideal, and there are multiple satellites in different directions, so phase information can help. Still, once you get to a couple of meters, who cares?
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I don't think so. I'm pretty sure GPS always uses phase (just not carrier phase). According to wiki, the frequency of the embedded signal is around a MHz for the civilian band, which translates into ~meter accuracies. But you always need four satellites - if GPS used roundtrip timing instead, you'd only need three.
 
Skeptic Ginger said:
Quantum tunnelingHowever, I heard a rebuttal to this where music was transmitted faster than light as evidence communication could indeed be transmitted. It was on NOVA or something.

Beyond that exposure to the information, I know nothing. :)
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According to the known laws of physics, quantum effects cannot transmit information of any kind faster than light, full stop.
 
sol invictus said:
How exactly to you measure a distance of 732km through the earth to an accuracy of a few meters.... other than by the travel time of neutrinos?
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Military GPS can do that for you. And can measure the expansion and contraction of the planet from day to night.

ETA: I should have read on before replying.
 
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sol invictus said:
To 50cm accuracy, over 700km of Alps?
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Probably. Didn't old-school transits do at least that well over hundreds of miles? How accurate were mountain heights measured bit by bit all the way from the ocean via water leveling hoses?
 
Clearly this explains why Michelson and Morley failed to find the luminiferous ether:- they didn't look for it underground!;)

I read about this on the BBC an hour ago . My own thought was exactly that of Sol Invictus- how do we measure a straight line through the mountains? Obviously they must feel confident about this, but I'd like to see a second run at right angles to the existing one. (Hey, it's only money!). I guess a crosscheck is more or less what the team involved would like too.
 
BenBurch said:
With good instruments and great care you can get wonderful accuracy. Distant targets are a problem because of air refraction, however.
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GPS has a roughly analogous problem with ionosphere/troposphere effects. There are ways to deal with it (using both the L1 and L2 signals is a good start), but it's still a significant term in the error budget.
 
Could a significantly dense enough mass within the mountain, (metal vein etc) significantly alter the result enough to perhaps produce such a result?
 
No, this was posted today but went back to yesterday to compensate for some quantum echo effect.
 
Hoppy said:
Pardon my ignorance. What are the implications if this is indeed true?
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It's impossible under the known laws of physics. So, if it's true, those laws are wrong. And not wrong in a small way - faster than light propagation, even if only by a little, means that the particle is propagating back in time in someone's reference frame.

There are ways you might be able to modify physics to make this possible and not cause everything to melt down - but no one has ever come up with a theory that allows that and is also consistent with everything else we know.

In short, one of the best-tested features of nature says this is impossible.
 
That's why I think this is so interesting. Odds are pretty heavy it's just a measurement error hidden away somewhere. But I like entertaining the idea that maybe it isn't. Neutrinos do have mass, correct? What would going faster than the speed of light do to that mass? I'm pretty sure their mass hasn't become infinite simply because we're still here.
 
How are all the gravitational effects calculated, especially with the Alps sitting above the path?
 
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