If there was a huge rod the length of a light-year in space and someone pulled one end of it, when would the other end move?
1 Answer
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The signal would travel down the rod at the speed of sound in whatever material the rod is made from. When exactly the other end would move depends on what the rod is made of.
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$\begingroup$ Would that change the shape of the material then? $\endgroup$– VdubceacCommented Feb 24, 2020 at 19:53
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1$\begingroup$ Yes, more or less depending how hard you push it. A lightyear long rod made of just about anything is going to have an enormous mass. It would feel like pushing against a wall made of whatever the material was. $\endgroup$– CharlieCommented Feb 24, 2020 at 19:55