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Cosmic Radiation - how is our sun's speed calculated?

  1. Oct 26, 2010 #1
    From the anisotropic dipole of the CMB, they are able to calculate our velocity through space relative to this radiation. How exactly is this done - in general terms. What assumptions are they needing to make ab out this radiation to deduce our speed from it?

    I don't understand the connection between observing the radiation and identifying our speed relative to it.

  2. jcsd
  3. Oct 26, 2010 #2


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    The connection is basically just the Doppler effect. The radiation will appear blueshifted in the direction of motion and redshifted in the opposite direction. That's why there is a dipole in the first place. This can tell you the velocity relative to a frame of reference in which the radiation appears isotropic (down to a level of one part in 105 of course :wink:)
  4. Oct 26, 2010 #3
    Oh.... I think I'm getting it now. It sounds like you mean they are comparing the frequency of the dipole radiation to the frequency of the non-dipole radiation. The difference in frequency represents the speed at which we are travelling (ie, based on the doppler shift of this frequency that is)?

    Thanks for the explanation.
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