How Comets Revealed Dark Matter's Secret ⚡ экспресс

The Oort Cloud is a swarm of trillions of icy boulders at the very edge of the Solar System. They are nearly motionless until something disturbs them. Vera Rubin proved back in the 1970s that galaxies spin far too fast — as if wrapped in an invisible framework. This hidden mass was named dark matter. If it's made of ancient black holes roaming our Milky Way, then they, passing through the cloud, scatter comets like a bowling ball knocking down pins.

But astronomers don't see that many comets coming from the Oort Cloud. So massive black holes are only a tiny fraction of dark matter, no more than 0.2%. On the other hand, lightweight black holes with the mass of an asteroid leave almost no trace — they slip through the cloud unnoticed. So the invisible world might be teeming with such minnows, and we have no idea.