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The Sun, Electromagnetic Waves, and Gravitational Waves

  1. Oct 10, 2012 #1
    This is a question about electromagnetic waves and gravitational waves.

    Let's say we're on the Earth and we're looking up at the sun (safely).
    If the sun were --for some reason-- to violently and dramatically jerk from its position, how would we first find out?

    Would we first *see* the sun move?
    Or would we first detect a change in our orbit?

    Would the light, the electromagnetic wave, reach us first, or would the gravitational wave reach us first? Would they happen at the same time?
     
  2. jcsd
  3. Oct 10, 2012 #2
    I don't know a situation where the sun would jerk from its position but I'm fairly sure that it takes around 8 minutes and 20 seconds for light to travel from the sun to Earth, so you probably wouldn't notice anything until that time had elapsed.
     
  4. Oct 10, 2012 #3

    Drakkith

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    Changes in both gravity and electromagnetism travel at c.
     
  5. Oct 10, 2012 #4
    Same.
     
  6. Oct 10, 2012 #5
    Electromagnetic waves have an electric field component and a magnetic field component that are orthogonal to each other.
    Is there something analogous to this with gravitational waves?
     
  7. Oct 10, 2012 #6

    Drakkith

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    Not to my knowledge. I believe the wave is in the metric and only has one "component" if you will.
     
  8. Oct 10, 2012 #7

    Matterwave

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    Gravitational waves have 2 independent components of the metric corresponding to the 2 possible polarizations.
     
  9. Oct 11, 2012 #8

    Drakkith

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    I assume this is different than the electric and magnetic components of an EM wave?
     
  10. Oct 11, 2012 #9

    mfb

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    It is different - but you can compare it to two orthogonal polarizations of light.
     
  11. Oct 11, 2012 #10

    Drakkith

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    Got it.
     
  12. Oct 11, 2012 #11
    LIGO (Laser Interferometer Gravitational Wave Observatory) was built to detect such waves....but as far as I know, they have not found anything. So at this point gravity waves are still theoretical....right?
     
  13. Oct 11, 2012 #12

    Drakkith

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    I'd say so. We expect to find them as GR has been right about most observed effects so far, but we just haven't been able to locate the suckers yet!
     
  14. Oct 12, 2012 #13

    Physicist50

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    Wouldn't the speed of a gravitational wave depend on the mass of the object, (in this case, the sun) and the warpage of space-time?
     
  15. Oct 12, 2012 #14

    Drakkith

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    No, gravitational waves travel at c. They are in the metric itself and not affected by it. Kind of how light isn't affected by electric and magnetic fields, it just goes right through them.
     
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