Say I'm holding a rod composed of an incomprehensible solid, and this solid rod is 1 light second long. Then say I poke you with the rod and at the same time I flash a light on you. If light is the universal speed limit, then you should see the light before you feel the annoying poke. But if the rod is incompressible, where is the delay?

  • $\begingroup$ Sorry in bad with with search engines. Well close this question $\endgroup$ Mar 31 '16 at 23:19
  • $\begingroup$ An incomprehensible solid can only exist in a universe where there are no laws of physics, because the laws of physics make things comprehensible. $\endgroup$ Mar 31 '16 at 23:59
  • $\begingroup$ Hence why incompressible substances do not exist... $\endgroup$
    – Jared
    Apr 1 '16 at 0:10

There is no such material as "Non-compressible" to that extent -

Even in a "least-compressible" rod, the push itself would be carried by electromagnetic forces from atom to atom. These forces also can not travel faster than light. So, the poke can not reach before light.

The delay is inside the rod. Meaning the movement does not reach the other end faster than light. Or you can say, there is no such material.


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