Back in 1998, astronomers made a curious discovery. By studying the behavior of distant supernovas, they concluded that the universe is not just expanding, but that this expansion is accelerating. The cosmos, they concluded, is exploding.
The discovery rocked cosmology. It implied that the universe would probably experience a long cold death as its components raced inexorably away from each other. It also raised the question of what was causing this acceleration. Cosmologists eventually decided that the expansion was being driven by a force they called dark energy and began to develop a cosmological model that could account for it, called the Lambda-Cold Dark Matter (ΛCDM) model.
The story reached a climax in 2011 when the astronomers behind the discovery were awarded the Nobel Prize for physics. But important questions remain and understanding this enigmatic phenomenon has since been a central challenge for modern cosmology.
