"That guy must have been f*cking Brilliant! Especially since Darwin wasn't even a physicist and didn't have access to microwave telescopes that led to the discovery of the back ground radiation that made scientists realize that the big bang happened."
<nitpick>
It wasn't the discovery of the Cosmic Microwave Background that led to the Big Bang theory. The BBT was around before the discovery of the CMB -- the CMB just added good supporting evidence for the BBT.
Eddwin Hubble came up with the notion of a Big Bang due to a curious phenomenon called the universal redshift. Because of the Doppler Effect, objects in space moving toward us have their spectra shifted toward higher frequencies ("blue shifted"), while objects in space moving away from us have their spectra shifted toward lower frequencies ("red shifted").
Hubble was doing galactic astronomy, estimating how far away galaxies were based on how dim they appeared and how intrinsically bright less-distant galaxies of the same type should be. He was also measuring the Doppler shift for each of these galaxies. What he discovered was that, on average, the more distant a cluster of galaxies was from the Earth, the more red-shifted its spectrum was -- as though the entire universe were flying apart with the Earth at its center.
(Later, more complex cosmological models explain this appearent Earth-centered universe as being due to expansion in 4 dimensions, as though the universe is the surface of an inflating balloon.)
Hubble guessed, based on how far the most distant galaxies were and how fast they were expanding, that at some point several billion years ago, all the galaxies would have all been together in the same place, and would have "exploded" outward to end up with the positions and velocities we see today.
Hence, a really really big "bang".
