Although nearly a century has passed since an astronomer first used the term “dark matter” in the 1930s, the elusive substance still defies explanation. Physicists can measure its effects on the movements of galaxies and other celestial objects, but what it’s made of remains a mystery.
In order to solve it, physicists have come up with myriad possibilities, plus a unique way to find each one. Some ideas for dark matter particles arose out of attempts to solve other problems in physics. Others are pushing the boundaries of what we understand dark matter to be.
“You don’t know which experiment is going to ultimately show it,” says Neal Weiner, a New York University physics professor. “And if you don’t think of the right experiment, then you might not find it. It’s not just going to hit you in the face, because it’s dark matter.”