Blue Shift is an occurrence whereby a moving object (galaxy) emits light in such a way that the waves of light actually posses a higher frequency than when emitted, the higher frequency of the light results in a shift towards the blue-end of the visible light spectrum. This is a method used in astronomy to determine that a visible object is moving towards the Earth. The only known galaxy exhibiting blue shift is the ANDROMEDA GALAXY. Its light is blue shifted because the galaxy is approaching ours.