When you buy through links on our articles, Future and its syndication partners may earn a commission. The universe started with a bang, but how will it end? Scientists have a few theories. | Credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images Scientists have a pretty good idea of how our universe began: According to the Big Bang theory, an infinitely small, dense point rapidly expanded 13.8 billion years ago, and the universe has been experiencing accelerating expansion ever since.