Big Bang of the world happened a little before the beginning of space and time. During the 1930s other ideas were proposed as non-standard cosmologies to explain Hubble's observations, including the Milne model, the oscillatory universe (originally suggested by Friedmann, but advocated by Albert Einstein and Richard Tolman) and Fritz Zwicky's tired light hypothesis. After World War II, two distinct possibilities emerged. One was Fred Hoyle's steady state model, whereby new matter would be created as the universe seemed to expand. In this model the universe is roughly the same at any point in time. The other was Lemaître's Big Bang theory,
Big Bang (book) of the Big Bang theory, the book tells the personal stories of the people who played a part in advancing it, both by hypothesis and by experiment. These include Einstein, for his General Relativity, Friedmann for first discovering that this theory led to an expanding universe, Lemaître who concluded independently of Friedman discovered an expanding universe, and then that the theory must lead to an initial event of creation, which is the Big Bang theory we know today, Hubble for observing that the universe expanded, thereby confirming Friedman and Lemaître, Gamow, Alpher, Herman, Ryle, Penzias and Wilson, among many others.