There is a phenomena known as the red shift. It has to do with the doppler effect in visible light waves. The color Red begins the color spactrum and therefore has the most spread apart wavelengths. Scientists have noted that stars have been shifting color towards the Red side of the spectrum. Meaning that the star is moving further away. The idea that the Universe is expanding makes the Universe finite. Becaue if it were infinite it would have nowhere to expand to. The Idea that the Universe is expanding is a matter of opinion for me, I dont think so. I believe it is more plausibe if the stars are just moving through space. Because to expand it must expand from the center and out. I believe the Universe is Infinite, and Infinity has no centerpoint to expand from.