How Black Holes Help Us See the Invisible ✛ ✎ ✦
The Universe is filled with invisible dark matter. Fritz Zwicky first suspected its existence, and Vera Rubin confirmed: galaxies rotate as if embraced by an unseen mass. The orbital calculation methods pioneered by James Jeans helped prove that this mass must be many times greater than the visible one. Dark matter particles pass through us by the billions every second, without touching atoms. But there is a way to spot them.
At the center of our Galaxy, around the supermassive black hole, a swarm of smaller black holes whirls. These compact objects work like a giant slingshot. When a dark matter particle comes close, gravity spins and flings it out, accelerating it to 25,000 km/s. Calculations using James Jeans' methods show that this stream of fast dark matter surpasses all other sources in the Galaxy.
For underground detectors, this is a breakthrough: now even ultra-light particles can be caught. Thus, black holes transform from matter devourers into a key to the mystery of dark matter.
Only a tiny fraction of dark matter particles fall into the gravitational slingshot of black holes, but it's these ejected particles that can reach Earth and give themselves away.
In the movie 'Interstellar,' the characters use the gravity of a black hole to accelerate their ship — much like black holes at the center of the Galaxy launch dark matter, like a stone from a slingshot.