View Full Version : Dark natter is said not to intereact with itself, except gravitationally, but....

2019-Jan-13, 05:09 AM
..could the physical interaction just be very very small?

Or would that still lead to clumping of dark matter?

Ken G
2019-Jan-13, 06:26 AM
There can always be a very small interaction, perhaps like neutrinos have. But we have to explain things like the Bullet cluster, where we can see that the dark matter has passed right through while the gas has collided. So that puts a limit on how small the interaction must be. If it never interacts at all, we won't be able to isolate it in the laboratory.