Cosmologists are pressing rewind on the first instant after the Big Bang by simulating 4,000 versions of the universe on a massive supercomputer. 

The goal is to paint a picture of the immediate aftermath of the Big Bang, when the observable universe suddenly expanded 1 trillion trillion times in size in the tiniest sliver of a microsecond. By applying the method used for the simulations to real observations of today’s universe, researchers hope to arrive at an accurate understanding of what this inflationary period looked like.