Expanding universe, conceptual illustration. A timeline of the universe's evolution is shown from the Big Bang at bottom left to the present day at upper right. Matter formed after the Big Bang, the initial expansion of the universe from an infinitely compact state 13.8 billion years ago. In 1917 the physicist Albert Einstein applied his general theory of relativity to the whole universe and proposed that it was static. However he had to include a 'cosmological constant' in his equations to ensure the correct results. In 1929, Edwin Hubble showed that galaxies were moving apart and the further away they were the faster they were separating, key evidence for the expansion of the universe. This lead to Einstein abandoning his static model and accepting an expanding model of the universe.