Redshift

The redshift of a given object is a measure of the amount that the wavelength of its emitted or reflected electromagnetic radiation has increased. This increase in wavelength is due to the relative motion of a source with respect to an observer; a light emitting source moving away from an observer will have its spectrum shifted toward longer (in optical light, redder) wavelengths. In practice this is analogous to the Doppler shifting of sound waves emitted from a moving source. Light emitted from a source moving towards an observer will experience a blueshift.

Support For the Big Bang Theory

The red shift in atomic spectra of distance cosmic objects is a source of evidence for the big bang theory. The red shift, the expanded wavelength of light due to the Doppler Effect of faraway objects, suggests that these objects are moving away from earth. This is a phenomenon predicted by the Big Bang Theory.