Picture of Edwin Hubble. Photo courtesy of Wikimedia.
universe is changing, and even give us clues as to how the universe formed.
Hubble combined his measurements of the distances to galaxies with other astronomers' measurements about redshift (the movement of stars and galaxies away from us). He noticed a relationship, which is now called Hubble's Law.Hubble's lawstates:the farther away a galaxy is, the faster it is moving away from us. In other words, the universe is expanding!
You can see an Example of Hubble's Law on the graph below. The X-axis shows distance and the Y-axis shows velocity. You'll notice that the galaxies that are farthest away in distance are traveling at the highest velocity.
Graph showing that galaxies farther away are moving faster. Graph courtesy of NASA/MSU. Public domain.
http://ck12.org/flexr/assemble/?fid=732 (CC BY-SA)