redshift vs. blueshift

redshift

[ red-shift ]show ipa

noun

1. a shift toward longer wavelengths of the spectral lines emitted by a celestial object that is caused by the object moving away from the earth.

blueshift

[ bloo-shift ]show ipa

noun

1. a shift toward shorter wavelengths of the spectral lines of a celestial object, caused by the motion of the object toward the observer.