# Gravity waves

Gold Member
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?

Ich
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.

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?

Gold Member
Is that why the heat is so important?

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.