Before 1998, models of the universe’s future leaned towards gravitational slowing, perhaps culminating in collapse. After the discovery, new scenarios came to the fore. If dark energy remains constant, the universe may continue expanding indefinitely, growing colder and darker in a ‘Big Freeze’. If its strength changes over time, more dramatic outcomes are possible, including a ‘Big Rip’ where galaxies, stars, and eventually atoms themselves are torn apart.
