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Does gravity affect to wavelengths?

  1. Jul 7, 2013 #1
    My question is... Does the wavelength of light (in vaccum space, of course) suffer changes as it approaches to a gravity field, or simply stays the same?
  2. jcsd
  3. Jul 7, 2013 #2


    Staff: Mentor

    Wavelengths are frame variant, so they depend on the reference frame used to measure them. So you need to specify the frames before your question can be answered. Also, different gravity fields have different properties, so you need to specify that also.

    If you consider the gravity field around a spherical non-rotating planet and the reference frame of observers which are stationary wrt the planet then the wavelength will be shorter for observers lower down.
  4. Jul 7, 2013 #3
    It changes. As a simple example, if you are standing on the surface of the earth and shine a flashlight into outer space, the energy of that light beam will become progressively red-shifted the farther it travels out into space. Conversely, if you were in outer space shining a flashlight towards the Earth, the energy of the light beam would become progressively blue-shifted as it approached the Earth.
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