Why Doesn't Dark Matter Fall Into Black Holes?

Imagine a busy highway where cars (stars) drive quickly and crash into each other occasionally. Now imagine ghosts (dark matter) floating through the same highway at nearly the same speed but passing right through the cars without touching them.

Stars often fall toward the center of a galaxy, eventually crashing into the big black hole there. But dark matter is different because its particles are collisionless. They do not bump into each other like gas atoms or stars. Instead, they pass right through one another freely.

For dark matter to fall into a black hole, it needs to lose energy, much like a car braking before entering a parking spot. Stars lose energy by colliding with other stars or gas clouds. Dark matter has no such friction. It zooms past the center and swings back out again in an elliptical path, forever orbiting but never settling into the black hole.

This is why we see dark matter forming large 'halos' around galaxies rather than sitting tightly inside the black holes.