Information transfer that is faster than c?

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Discussion Overview

The discussion revolves around the concept of information transfer through a rigid material and whether such transfer could occur faster than the speed of light. Participants explore the nature of pressure waves, the properties of materials, and the implications of compressibility in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether poking a long rigid material would result in an instantaneous response at the other end, suggesting that the response would be limited by the speed of light due to the nature of pressure waves.
  • Another participant agrees that the electromagnetic processes involved in transferring information would not allow for an incompressible material, challenging the initial assumption.
  • A participant inquires about the observable effects when the material is poked, proposing that a compression wave would propagate through the material, similar to a sound wave in air.
  • One participant asserts that the wave propagating through the material is indeed a sound wave.
  • Another participant confirms that the speed of this wave corresponds to the speed of sound in the material, implying it is dependent on the material's properties.

Areas of Agreement / Disagreement

Participants generally agree that the response in the material is not instantaneous and is limited by the speed of sound. However, there is some debate regarding the concept of incompressibility and the nature of the wave propagation.

Contextual Notes

The discussion does not resolve the implications of compressibility or the exact nature of the wave propagation in different materials, leaving these aspects open for further exploration.

Puma24
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If I were to have some material, that was rigid, and was also say, 300,000,000 metres long. If I were to poke it at one end, would another observer see an instantaneous response at the other end? Ie, would the information I put into one end of the material travel faster than the speed of light to the other end?

I guess it woudln't be so easy. I assume that poking it counts as a sort of pressure wave that would have to be transferred through all the electrostatic processes along the way, which would be limited by c? Then I guess, can you argue that there is such thing as an incompressible material? (at least in regards to the force of my jabbing finger)
 
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Puma24 said:
I guess it woudln't be so easy. I assume that poking it counts as a sort of pressure wave that would have to be transferred through all the electrostatic processes along the way, which would be limited by c? Then I guess, can you argue that there is such thing as an incompressible material? (at least in regards to the force of my jabbing finger)

Correct, the electromagnetic processes have to carry the information the whole way, and no, by your previous thought process, you can't have an incompressible material.
 
Alright then. So if we had the power to observe the material, would we see the side I poke move slightly, and then a sort of compression wave propagate through the material (like you could imagine a sound wave compressing air), warping the dimensions as it goes? Do you know if the speed of this wave has a speed that is constant, or is a consequence of the materials properties, like density I guess?
 
Puma24 said:
and then a sort of compression wave propagate through the material (like you could imagine a sound wave compressing air),
I believe it literally is a sound wave.
 
Hurkyl said:
I believe it literally is a sound wave.
Yes. And the speed at which the wave propogates is the speed of sound in that material.
 

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