A Russian physicist and mathematician, Friedmann made two assumptions about the universe in 1922: first, that is looks roughly the same in every direction, and second, this should be true from wherever one looks. These ideas suggested that the universe is not static, as Albert Einstein was arguing at the time. He predicted what Edwin Hubble later found—that the universe is expanding. Even so, Friedmann’s work was not widely known in the West until the 1930s. Arno Penzias and Robert Wilson’s discovery of the homogeneity of background microwave radiation throughout the universe proved Friedmann’s ideas. Later, Friedmann models were used to explore what the universe might have looked like in its early stages.