We think the Big Bang was the beginning of time and space itself. But there are problems with this story. The energy of empty space – known as the cosmological constant – poses one major problem. The cosmological constant is 120 orders of magnitude smaller than the standard Big Bang theory suggests it should be, a finding that scientists have called "the largest discrepancy between theory and experiment in all of science”. A solution is found in the idea of the cyclical universe. The cosmological constant has been winding down over a cycle of multiple Big Bangs and Big Crunches.

A cyclic universe is a universe which follows an infinite self-sustaining cycle. In the 1930s, Einstein came up with the idea that the universe could go through an infinite cycle of Big Bangs and Big Crunches. The expansion of our universe could have been caused by the collapse of a previous universe – it sort of bounced back from the contraction of the universe before it. You could say our universe was reborn from the death of the universe before it. If this is true, then our Big Bang was not a unique event; it was one insignificant bang among an infinite number of other bangs. The cyclic universe theory does not necessarily replace the Big Bang theory, it just sheds some light on some more questions, such as what was before the Big Bang and why the Big Bang led to a period of rapid expansion.

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You could say our universe was reborn from the death of the universe before it.

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