Galileo is famous for observing and proving his heliocentric model of the universe. After his observation the existing model of the universe was slowly phased out.
Somebody else would probably have made the same discoveries, eventually.
An observation is a review of what happened. A conclusion is the reselts.
Disney Universe happened in 360.
Entropia Universe happened in 2003.
Lego Universe happened in 2010.
It happened in the center of the universe, for which it is still expanding on the universe.
Mega Man Universe happened in 360.
Phantasy Star Universe happened in 2006.
Bust-a-Move Universe happened in 2011.
Dancing Stage Universe happened in 2007.
DC Universe Online happened in 2011.
The Big Bang theory states that the Universe started with all currently existing matter, concentrated in an extremely small, space - in an extremely hot and dense state. It is not clear what happened before that, or whether there even was a "before".