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Let's imagine that doing research for the space elevator someone manages to build a very strong wire. But instead of using it for the space elevator a wire several millions of kilometers long is attached to 2 satellites and put in orbit around the sun.

These two satellites might work as a radio bridge, but instead of sending electric signals along the wire they take turns to apply small pulls to the wire. The satellite on the other side would detect the pull with an accelerometer (or using two wires it could measure angle variations).

Assuming there would be no elastic effect, could we have faster than light communication?

FluidCode
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    It would be helpful to you if you note that mechanical disturbances propagate at the speed of sound through a given media. –  Mar 07 '20 at 13:52
  • Assuming there would be no elastic effect What material do you suggest? (Hint: there is none.) – garyp Mar 07 '20 at 13:54

2 Answers2

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Of course not. Thanks to the theory of relativity we know that nothing goes faster than light, except for the possibility of spacetime to expand faster than the speed of light, but that's another question.

Vibrations in a solid propagate with a certain velocity which in turns depends on how you excite the atoms in the solid and the type of vibration: optical or acoustic. I would imagine that a thug on a rope would excite only the acoustic modes of a solid which are in the order of $10^4$ m/s.

The theory of propagation in solids is well treated by quantum theory of matter, and condensed matter. More details can be found in the following book

  • Solid state physics, Ashcroft
Davide Morgante
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Assuming there would be no elastic effect, doesn't make sense. There is always an elastic effect. Thus the mechanical communication through the wire will happen with the speed of sound of the metal.

Assuming there would be no elastic effect, would mean that the speed of sound is infinite. This is impossible by the theory of relativity.

Thomas Fritsch
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