The same thing happens to light. As a star speeds away from us, its light shifts towards the longer red wavelength. If it moves towards us, the light shifts towards the shorter blue wavelength. Having already discovered that our galaxy was not special but just one of many, Edwin Hubble turned his attention in 1929 to analysing the light from these galaxies to see how they were moving relative to our own. To his surprise, the light from distant stars in the galaxies he observed were all shifted towards the red. Nothing seemed to be coming towards us.
