How do we know the Universe hasn’t always existed? © Getty Images

How do we know the Universe hasn’t always existed?

What existed before the Big Bang is a question as old as the Universe itself.

Asked by: Pete Sears, Australia

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There’s a wealth of evidence that the Universe began in a Big Bang around 14 billion years ago. We can see distant galaxies racing away from each other, and the space around them is filled with cosmic radiation whose intensity and spread are consistent with that expected from the aftermath of the Big Bang. But none of this rules out the possibility that there was another universe before ours.

According to some theorists, when Einstein’s theory of gravity is combined with quantum theory, the Big Bang could really be part of a Big Bounce, in which the collapse of a previous, and perhaps very different, universe is followed by the creation of our own. While speculative, these theories do at least resolve the otherwise tricky question of what existed before the Big Bang.


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