Edwin Hubble usually gets top billing for the Big Bang Theory, which suggests that the universe was born in a massive explosion, roughly 13.8 billion years ago. According to the Big Bang Theory, all of the matter that exists now came from this cataclysmic expansion, and most scientists believe that the expansion of the universe continues today. The first scientist with this intergalactic view was actually Georges Lemaître, a Belgian mathematician and Catholic priest who called his hypothesis the Cosmic Egg in 1927.
In 1929 at the Mt. Wilson Observatory in California, Hubble -- unaware of Lemaître’s writings -- discovered that galaxies were moving away at high speeds, in essence confirming Lemaître’s theory with some degree of observational certainty.
The day that started with a bang:
- Lemaître described the beginning of the universe as a shower of fireworks, comparing galaxies to burning embers spreading out in a growing sphere from the center of the blast.
- He believed this explosion from a “primordial atom” was the beginning of time, taking place on what he called "a day without yesterday."
- Hubble received the lion’s share of credit, though. Scientists talk in terms of Hubble’s Law, and his description of matter flowing from the Big Bang is known as Hubble Flow.