Non-scientific versions of the answer have invoked many gods and have been the basis of all religions and most philosophy since the beginning of recorded time.
Now a team of mathematicians from Canada and Egypt have used cutting edge scientific theory and a mind-boggling set of equations to work out what preceded the universe in which we live.
In (very) simple terms they applied the theories of the very small – the world of quantum mechanics – to the whole universe - explained by general theory of relativity, and discovered the universe basically goes though four different phases.
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