Dark Matter May Have Left Its Fingerprint in a Gravitational Wave.

Dark matter makes up roughly 85 percent of all the matter in the universe. We have never directly detected a single particle of it. But a new method developed by physicists at MIT and across Europe may have just opened a door we didn’t know existed. When two black holes collide and merge, they send ripples through the fabric of spacetime, these are known as gravitational waves and if those black holes happened to spiral through a dense cloud of dark matter on their way in, those waves carry an imprint of it. For the first time, scientists have a technique to read that imprint and one signal in the existing data is already raising eyebrows.