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Imagine you are one lightyear away from a photon sensitive (light sensitive) switch. So it is obvious that light would take one year to reach to the switch. Now I have a one lightyear long plank. I simply point the plank towards the switch and press it. Now I just did work which light would take 1 year to do in a matter of seconds.

Now the question is, did I break the laws of physics?

Please do not give an answer like " it is impossible to make a plank this long ". Just think about it. Even I am thinking about this question right now.

Brandon Enright
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Rohinb97
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1 Answers1

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when you push the plank, it will take a year for your push to be felt by the other end. In the meantime (assuming you had the strength), the plank will just compress as it moves. The reason is that although it is rigid, it still takes a minimum of a year for the atoms in the plank to communicate down the line (one giant game of telephone) that there was a push at all.

This is not a relativistic effect, it works on short scales too, but the communication speed is near light (assuming a perfectly rigid material in an ideal universe), so you do not notice the compression.

BTW, the physics police probably would pull you over if your trick worked the way you described

Jim
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