Elasticity and light speed vibrations

[snorkack]

Special relativity requires any substance to be compressible.
Indeed, if an item were made of a perfectly rigid substance, then move one end of it, and the other end must move at the same moment - the movement must be transmitted instantly, faster than light.
Thus, the special relativity sets lower limit to compressibility - by requiring that mechanical vibrations must not be transmitted faster than light.
BUT while special relativity does forbid transmission of information faster than light, it does not forbid transmission of information at exactly the speed of light.
So... If there is an imaginary substance, with nonzero rest mass density, which has the property that it can transmit mechanical vibrations at precisely the speed of light... what would be its further properties?

 

[ZapperZ]

Special relativity requires any substance to be compressible.
Indeed, if an item were made of a perfectly rigid substance, then move one end of it, and the other end must move at the same moment - the movement must be transmitted instantly, faster than light.
Thus, the special relativity sets lower limit to compressibility - by requiring that mechanical vibrations must not be transmitted faster than light.
BUT while special relativity does forbid transmission of information faster than light, it does not forbid transmission of information at exactly the speed of light.
So... If there is an imaginary substance, with nonzero rest mass density, which has the property that it can transmit mechanical vibrations at precisely the speed of light... what would be its further properties?

This scenario is self-contradictory.

A solid is formed by atoms and molecules forming BONDS with one another. These bonds are EM interactions. So AT BEST, things can only be transmitted at the speed of light, IF you ignore that these atoms and molecules have masses. But they do have masses, and unless one wants to turn off inertia, these masses do not react in an instant. After all, we have seen how retarded effects of the lattice ions resulted in an "overscreening" region in a superconductor that essentially causes an attractive interaction between two electrons. So this inertia of the lattice ions is very real.

This means that mechanical vibrations (essentially the speed of phonons) can never be the speed of light in vacuum, even under an ideal scenario!

Zz.

 

[Greg Bernhardt]

This is posted in the Sci-Fi Writing and World Building forum but I don't see any relation to a story. Closing.