Dipole anisotropy
Dipole anisotropy is a form of anisotropy and the progressive difference in the frequency of radiation from opposite directions due to the motion of the observer relative to the source. As a result of that motion, one end of the 360-degree spectrum is redshifted, whereas the other end is blueshifted. That effect is notable in measurements of the cosmic microwave background radiation, due to the motion of the Earth.

Physical cosmology