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

Gravitational waves - second question

  1. Jan 30, 2009 #1
    Gravitational "waves" - second question

    Assuming our concept of the universe expanding (perhaps) and that the fabric of space time is expanding at the same rate as our galaxy and solar system (velocity equal, so relatively motionless), would we still be able to detect gravitational waves when a planet (Earth, for example) accelerates around the Sun?
  2. jcsd
  3. Jan 31, 2009 #2
    Re: Gravitational "waves" - second question

    Your question includes internal inconsistencies and I have no idea what "velocity equal so relatively motionless" means.

    Our galaxy is NOT expanding to any appreciable nor measureable degree. Only at (great) cosmological distances is dark energy (the cosmological constant) large enough to over come gravity and enable spacetime to expand. At ginormous distances from us, galaxies are receding at greater than the speed of light and hence gravitational waves from those galaxies will never reach us., nor will anything else; locally gravitational waves should always reach us unless the cosmological contant grows in the future to such a degree that, say, the sun and earth move away from each other at greater than light speed.

    If that doesn't not make enough sense try wikipedia at


    and note other wiki sources to the right under the box PHYSICAL COSMOLOGY. Beware "horizons" in cosmology are not immediately obvious.
  4. Jan 31, 2009 #3
    Re: Gravitational "waves" - second question

    While I personally like the idea of an ether, most say the "fabric of space" is just a metric. I would think the influence of gravity is present from any matter in the observable universe but in most cases would be too small to detect. Naty1 did well pointing out if you can't see the light, you will not feel the gravity.
  5. Jan 31, 2009 #4
    Re: Gravitational "waves" - second question

    Sincere thanks for overcoming the naive challenge of my question (I was having a hard time knowing how to word it). Your explanation, though, did answer what I was trying to get at. I'll also look on wikipedia as suggested...thanks...
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Gravitational waves - second question
  1. Gravitational Waves (Replies: 15)