Red Shift

Red Shift - When the wavelength of light recieved has moved to the right.

The visible spectrum of light has patterns of dark lines. If these are red-shifted, the star is moving away from us. The further the lines are shifted, the faster the star is moving relative to us.

If the star is moving towards us, the wavelength of the light waves become shorter and so the pattern of lines moves towards the blue end of the spectrum.