A Mysterious Force is Ripping The Cosmos Apart
Something big dominates the Universe. We have absolutely no idea what it is.
Back in 1998, astronomers discovered something puzzling about the universe. It was, the motion of distant supernova seemed to show, not only expanding — something well established for decades — but accelerating, growing bigger at an ever faster rate. The discovery was utterly unexpected; something quite at odds with what we thought we knew about the universe.
Until that time, astronomers believed the expansion of the universe, set in motion by the big bang, should be slowing over time. After all, the universe is filled with stuff — planets, stars, galaxies — that all exert a gravitational pull on each other. This pull should act as a kind of drag on the expansion, slowing the rate at which things move apart.
For it to be expanding instead seemed to fly in the face of all logic. Gravity — the only force known to act on cosmic scales — is purely attractive. It can pull stars and planets together, weave them into galaxies and thus shape the night sky — but it can never force things apart.
To explain the acceleration, then, science needed a counterpart to gravity. Some unknown fifth force that, over vast distances, acts to push things apart. Even weirder, this…
