Redshift. Animation illustrating the effect of redshift. This is a form of the Doppler effect, seen as an increase in the wavelength of light during its journey to Earth. In this animation, light blue wave is emitted from a galaxy, and in the time it takes to travel to Earth, the expansion of the universe causes its wavelength to increase, changing its colour through green and yellow to red. The discovery of redshift, and the fact that more distant galaxies were more shifted, was important evidence backing up the expanding universe and Big Bang model of cosmology.