Cold Dark Matter Is Heated Up By Stars, Even Though It Cannot ‘Feel’ Them
If dark matter doesn’t interact with normal matter or light, how can it be heated up?
One of the great cosmic mysteries of our time is the presence and existence of dark matter. Unlike normal matter, which is made of known particles that can emit, absorb, or otherwise interact with light and the other known particles, dark matter simply passes through both itself and everything else. It is completely invisible, as far as we can tell, except for one effect: it appears to have a gravitational mass. It affects the curvature of spacetime, and holds galaxies, clusters of galaxies, and the great cosmic web together.
When we run our simulations, however, we get very specific predictions for the structures that dark matter should form. The cosmic web lines up, but the smaller, galactic scales don’t. Long touted as the biggest problem for cold dark matter, scientists have uncovered the solution: dark matter gets heated up by stars. Here’s the story of how that happens.
Imagine the Universe as it might have been in the earliest stages after the Big Bang…