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M or String theory

First, let's get one thing straight. String theory and M-theory are not pseudoscience. They make predictions that can be tested. They are perfectly good theoretical science. They will be tested over the next few years at the LHC and possibly the Tevatron, and later hopefully at the ILC. Claims that they are not real science are simply utter bollocks. It doesn't really matter if they can be post-fitted to the data, all that matters is whether they can acturately model reality. If a theory can be found that does better than current theories it makes no difference if it is right first time or if we spend 50 years altering the theory to make it fit.

On the other hand, string theory is actually obsolete since it has been replaced by M-theory, so it makes no sense to discuss it any more than is makes sense to discuss the orbits of the planets being related to platonic solids. As for M-theory, personally I think it is unlikely to be correct, and I think it is a shame that there are many pseudo-scientific claims made in relation to it and various multiple worlds ideas. However, the only way to have any meaningful discussion about it is to wait until there is data that can confirm on deny it's predictions. Since we don't have that yet, any discussion on whether it is true or not can only relate to abstract mathematics and will have nothing to do with the real world.
 
a_unique_person said:
Which is why I think SETI is doomed to fail. Any advanced civilisation won't be using light speed communications.
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Light has broken LS. Quantum tunneling, Gisin's "teleportation" (really bad choice of a label), collapsing superposition between entangled particles have all broken LS but there is no way to transmit information faster than LS. Experiments have been made that show LS is a limit in regards to information transfer. If you have a method please share it with us.
 
~enigma~ said:
Well there is FTL travel as far as light goes as can be seen in the experiment by Wang here

The experiment has been duplicated and done with different gases.
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That's phase velocity. The phase velocity of light is irrelevant when trying to transmit information, and this phenomenon is essentially just a curiosity. Group velocity is what matters, and group velocity has never exceeded c.

others (most notably Gisin) have done other experiments that show entangled particles transfer "information" at speeds that dwarf light speed.
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That's not actually transmitting information at all, though. It's demonstrating that reality is non-local (a technical term which is widely misunderstood), which isn't the same thing. It is not possible to transmit actual information with this technique.
 
Ziggurat said:
That's phase velocity. The phase velocity of light is irrelevant when trying to transmit information, and this phenomenon is essentially just a curiosity. Group velocity is what matters, and group velocity has never exceeded c.



That's not actually transmitting information at all, though. It's demonstrating that reality is non-local (a technical term which is widely misunderstood), which isn't the same thing. It is not possible to transmit actual information with this technique.
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You misread me. My response was to a unique person who claims that SETI would fail because aliens would use FTL communication. Reread the second to last sentence please. I am the one who says information can't be sent faster than LS.

ETA - notice the quotation marks surrounding the word information in regards to Gisin?
 
Ziggurat said:
That's phase velocity. The phase velocity of light is irrelevant when trying to transmit information, and this phenomenon is essentially just a curiosity. Group velocity is what matters, and group velocity has never exceeded c.
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Actually, from the article:

In a vacuum all the phase velocities and the group velocity are the same. In a dispersive medium, however, they are different because the refractive index is a function of wavelength, which means that the different wavelengths travel at different speeds. Wang and colleagues report evidence for a negative group velocity of -310c, where c (=300 million metres per second) is the speed of light in vacuum.
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In regions of anomalous dispersion the group velocity can exceed c or become negative, but in those cases it is not a useful concept (in the sense of information transfer, for example), so there is no problem for relativity. This happens near the medium's resonance frequency, where the wave train is completely distorted. If anyone is interested, they can check any book that talks about dispersion of light. Two very famous examples are Jackson's Classical Electrodynamics (chapter 7 in the third edition) or Born and Wolf's Principles of Optics (chapter 2).
 
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More to the point, John Baez has just posted the latest edition of This Week's Finds in Mathematical Physics at the n Category Café, where he comments on the String Theory controversy. There's an interesting discussion at the blog.
 
~enigma~ said:
You misread me. My response was to a unique person who claims that SETI would fail because aliens would use FTL communication. Reread the second to last sentence please. I am the one who says information can't be sent faster than LS.

ETA - notice the quotation marks surrounding the word information in regards to Gisin?
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It'll happen. Maybe not in that form.
 
a_unique_person said:
Pure pie in the sky wishful thinking. One of the other dimensions in quantum theory. SETI has been pretty quiet so far.
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Wishful thinking doesn't make anything scientifically possible when there are experimental results that show otherwise. If you don't have experimental evidence to back your claim it is just as you call it - wishful thinking - but it has no base in science whatsoever.
 
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