Big Bang Theory:
In 1927, following Albert Einstein's announcement of the theory of relativity, Georges Lemaître proposed that nearly 20 billion years ago, the universe was a single, tiny atomic particle, and that in one cataclysmic flash, it expanded outwards to become the universe we know today. Edwin Hubble later helped support this theory by proving that the universe was indeed expanding. In 1964, Arno Penzias and Robert Wilson discovered Cold cosmic microwave radiation, which they believed to be the Remnants of of the Big Bang. This discovery earned them the Nobel Prize.