Imagine we had somehow filmed the whole history of the universe and you could play the movie in reverse. It would start off much as things stand today: a vast and elegant web of galaxies and nebulae.

In the beginning, the world was empty and cold. Prior to the Big Bang — yes, before the Big Bang — the universe underwent a breathtaking cosmic expansion, doubling in size at least 80 times in a ...

For decades, scientists have relied on a popular idea referred to as cosmic inflation to explain how the universe began and why it looks the way it does today. This theory suggests the universe ...