This is my first question. Hope it's in respect of quality standards.

Let's suppose to have a "long" rigid almost unbreakable bar of fixed negligible diameter . (we can imagine it as a rigid wire) Lets suppose that the "bar" goes from Earth to Sun (8 light minute distance) but not consider the masses/gravity of Sun and Earth.

1. If I pull the bar 1 meter , what's the relativistic analisys ? Since the info that "I pull the bar" travels at light speed , in the 8 minutes the info reach the Sun is the Bar one meter longer ?

2.The cosmological question: If the bar goes from one galaxy to another , how the universe expansion reflects on it?

  • $\begingroup$ Concerning 1. I would even say: it travels with the speed of sound in your material, probably much slower than $c$. $\endgroup$ Commented Jun 12, 2015 at 11:54
  • $\begingroup$ Concerning 2: 8 light minutes is not long enough for any significant effects of expansion to manifest in it; the structural strength would overpower expansion by many orders of magnitude. $\endgroup$
    – Jim
    Commented Jun 12, 2015 at 14:46


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