The Big Crunch

Before dark energy was discovered in 1998, many physicists favored the Big Crunch. With enough matter, gravity would halt the expansion and pull everything back together. Galaxies would rush inward, the background radiation would heat up, and the universe would collapse into a singularity — a mirror image of the Big Bang. Some even imagined the collapse sparking a new Big Bang, a cyclic universe bouncing forever. Then observations of distant supernovae showed expansion is accelerating, not slowing. Dark energy is pushing galaxies apart faster every year.