Classically communicate information faster then light?

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Discussion Overview

The discussion revolves around the concept of whether information can be communicated faster than the speed of light through a thought experiment involving a pipe filled with tightly arranged balls. Participants explore the implications of pushing one ball and the resulting movement of another ball at the opposite end of the pipe, questioning the role of relativity in this scenario.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes a thought experiment involving a pipe filled with balls, suggesting that pushing one ball could result in the instantaneous movement of another ball at the opposite end, raising questions about the nature of information transfer.
  • Another participant references an external source discussing the possibility of sending signals faster than light by pushing a rigid rod, indicating that this concept has been previously explored.
  • A later reply implies that the initial participant may have answered their own question regarding the instantaneous movement of the ball, suggesting a potential misunderstanding of the underlying physics.
  • There is a challenge to clarify the speed of longitudinal pressure waves through a material, indicating a need for deeper exploration of wave propagation versus instantaneous movement.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are competing views regarding the implications of the thought experiment and the nature of wave propagation versus instantaneous movement.

Contextual Notes

The discussion highlights limitations in understanding the propagation of forces and the role of relativity, with unresolved questions about the assumptions underlying the thought experiment.

Philip Land
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Where in this though-experiment do I get it wrong?

Even though no mass can travel faster then c, maybe information can? And I'm not talking about quantum entanglement etc.

Consider a pipe, filled with balls that are very tightly arranged. If I push the outermost ball on one side of the pipe, the ball on the outermost other side of the pipe will fall out, outside the pipe.

Now let's mak this pipe longer, and disregard friction.

This mean, that if I want to move the ball on the other end of the pipe. I can simply push the ball on the side of the pipe close to me.

So my push has now been propagated throughout the balls in the pipe. Like a longitudinell wave if you like.

Now, If we make this pipe ##6*10^8## m It will take light 2 s to travel through the pipe, but the ball in the end of the pipe gets moved instantaneously as I push the ball in the start of the pipe?

Is this correctly thought or where does relativity prevent this from happening? Because we actually don't have quick velocities here, just propagation (I know that sounded strange).

Or is this a cheat thought-experiment because the pipe with the balls inside acts like an extension of my pushing finger?
 
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Philip Land said:
So my push has now been propagated throughout the balls in the pipe. Like a longitudinal wave if you like.

... the end of the pipe gets moved instantaneously as I push the ball in the start of the pipe?
You kind of answered your own question, before you asked it.
 
Philip Land said:
Like a longitudinell wave if you like.
And what do we call the speed of longitudinal pressure waves through a material?
 
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