Why do scientists believe that the universe is expanding? In 1929, the American astronomer Edwin Hubble (after whom the famous telescope is named) discovered that galaxies are moving apart from each other at high speed. This led to the conclusion that the universe is expanding like an inflating balloon. The further apart the galaxies are, the faster they move. For instance, a galaxy 10 million light years away gets 300 km further from us every second. A galaxy 10 times further off moves ten times faster, and so on.