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What? Scientist observe SOUND trabeling FASTER than the speed of light....

So you're saying we should just yell really loud to aliens instead of trying to visit them becuase it'll be faster?
 
Originally posted by: KDOG
Originally posted by: chuckywang
Theory of Relativity says no.
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According to the article, this has been done! Somehow it doesn't violate any of einstiens laws.
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The experement basicly measures the 'peak' of a wave. With interfeence, the peak jumps around. if you cna make it jump in the same direction, the peak moves faster than light, but the energy itself doesn't.
 
In their experiment, the researchers achieved superluminal sound velocity by rephasing the spectral components of the sound pulses, which later recombine to form an identical-looking part of the pulse much further along within the pulse. So it?s not the actual sound waves that exceed c, but the waves? ?group velocity,? or the ?length of the sample divided by the time taken for the peak of a pulse to traverse the sample.?
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Can anyone expand on this? Or simplify?

Edit: nevermind, thanks Evadman!
 
I think I know how this works. I believe this is possible because the wave group isn't a singular material object. It's really just a coincidental collection of independent objects that look like a single object.
 
Originally posted by: Fritzo
So you're saying we should just yell really loud to aliens instead of trying to visit them becuase it'll be faster?
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..only if sound wave particle can travel far enough to reach them without enviromental disturbance. :disgust:
 
Originally posted by: marulee
Originally posted by: Fritzo
So you're saying we should just yell really loud to aliens instead of trying to visit them becuase it'll be faster?
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..only if sound wave particle can travel far enough to reach them without enviromental disturbance. :disgust:
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so you're saying... yes
 
For the first time, scientists have experimentally demonstrated that sound pulses can travel at velocities faster than the speed of light, c. William Robertson?s team from Middle Tennessee State University also showed that the group velocity of sound waves can become infinite, and even negative.

So if the speed can be negative then we would hear the sound before it was emitted? yeah, right.
 
The article first denies that information traveled at a speed in excess c, but then it seems to suggest that at least some information did travel in excess of c. 😕
 
You have to understand that what is being said: the group velocity is faster than light, the individual waves are not traveling faster than light. Basically, it's just a mathematical trick that uses phase to make it appear as if things are traveling faster than light; there is nothing earth shattering going on here.
 
Originally posted by: RaynorWolfcastle
You have to understand that what is being said: the group velocity is faster than light, the individual waves are not traveling faster than light. Basically, it's just a mathematical trick that uses phase to make it appear as if things are traveling faster than light; there is nothing earth shattering going on here.
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Do you mean something like, the sound doesn't actually propagate faster than light, just that by nature of a wave being well, wave shaped, the vector of both the horizontal and vertical motion at a certain point along the wave is greater than that of C.

If it's that, I'd have to agree that this is nothing too astounding.
 
perhaps it was jsut that sound traveled faster than light in a certain material? The speed of light is only equal to c in a vaccuum, in a a material it is 1 over the square root of the magentic permeability and the electric permitivity.
 
"So if the speed can be negative then we would hear the sound before it was emitted? yeah, right. "

A sound requires a phase change before it becomes a sound, so no you wouldn't hear it, but for the sake of simplicity, yes the sound would be there before it was emitted.

This has already been done with light, it's not all that far fetched to believe it can be done with sound too. The universe isn't quite as simple as being limited only to what makes sense.

Originally posted by: BrownTown
perhaps it was jsut that sound traveled faster than light in a certain material? The speed of light is only equal to c in a vaccuum, in a a material it is the square root of the magentic permeability and the electric permitivity.
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That's another way to go about it, but this isn't the idea in the article. They actually did make sound travel faster than c, to the extent described in the article of course.
 
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