Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Gravity waves

  1. Oct 28, 2005 #1


    User Avatar
    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?
  2. jcsd
  3. Oct 28, 2005 #2


    User Avatar
    Science Advisor

    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.
  4. Oct 28, 2005 #3
    How can it not be altered permanently if it's giving off heat?
  5. Oct 29, 2005 #4


    User Avatar
    Gold Member

    Is that why the heat is so important?
  6. Nov 1, 2005 #5
    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.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook