Red shift

The red shift of the light coming from fast moving galaxies is an example of the Doppler effect. The light from the galaxy looks redder than it would be if the galaxy was still.

(See: Doppler effect)

The diagrams show a greater and greater red shift as the star (or galaxy) moves away from the observer at greater and greater speeds. In the last diagram one of the absorption lines had been moved into the infrared region of the spectrum. By measuring the amount of red shift for a certain line we can calculate how fast a star (or a galaxy) is moving towards or away from us.