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Gravity Field of earth ?

  1. Mar 24, 2010 #1
    This may be a dumb question , but as light travels from the sun to earth , each photon has its own gravitational field , so when the light hits earth does the gravitational field of earth become stronger.
  2. jcsd
  3. Mar 24, 2010 #2

    D H

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    No. For one thing, the effect would be tiny. For another, it doesn't exist. The Earth is more-or-less in thermal equilibrium. In fact, the Earth as a whole is still cooling off from its formation 4.5 billion years ago.
  4. Mar 24, 2010 #3
    DH... did you post in the right thread?

    And cragar: I am pretty sure to have a gravitational field, you need mass. Photons don't have mass, so they don't have the field, and therefore can't contribute to earth's gravity field.

    of course, even if they had mass, you have to assume that all photons impinging upon the Earth actually stay on the earth, leading to a buildup of mass.

    Seems weird, no? o_O
  5. Mar 24, 2010 #4
  6. Mar 24, 2010 #5
    You dont need mass , to create a gravitational field , In relativity mass or energy bends space time , and if the field associated with the photon goes away where does the field go or the energy , doesn't the energy from the photon still create a field .
  7. Mar 24, 2010 #6

    D H

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    Yes. You already get the gist of it:
    The Earth is in thermal equilibrium. The incoming solar radiation is balanced by outgoing radiation, mostly thermal. Think of the Earth as an energy-neutral frequency converter.

    Photons carry energy. Energy, like mass, curves space-time. (Mass is energy.)
  8. Mar 24, 2010 #7
    i see , incoming energy= outgoing energy
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