Gravity waves

  • Thread starter daniel_i_l
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  • #1
daniel_i_l
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I read that one of the most accepted proofs that gravity waves have energy is Richard Feymann's : imagine beads on a rod, gravity waves can move the beads creating friction and heat so they must have energy.

Why does the heat creation make this such a great proof? Isn't it obvious that if they can accelerate mass than they must at least have potantial energy? I know that I must be missing something here. Can someone please explain?
 

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  • #2
Ich
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One might otherwise argue that the passing of a GW will not alter the rod permanently and therefore the GW doesn´t lose energy. Or so.
 
  • #3
Ich said:
One might otherwise argue that the passing of a GW will not alter the rod permanently and therefore the GW doesn´t lose energy. Or so.
How can it not be altered permanently if it's giving off heat?
 
  • #4
daniel_i_l
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Is that why the heat is so important?
 
  • #5
daniel_i_l said:
Is that why the heat is so important?
It is important since it is thermodynamically impossible to convert all work to heat, so if a gravity wave does some work W for some time T, then does no more work, and an amount of heat Q is given off, the entropy of the rod has increased.
 

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