Comment Re:This whole concept has always bothered me. (Score 1) 61
Gravity tends to clump stuff up.
But not the same way luminous matter (the "standard" stuff) clumps up. The mass distribution needed to explain spiral galaxies assumes that this "dark matter" remains at the periphery of the galaxy, keeping the rotational velocities constant as one moves away from the galactic center. So now, dark matter has to be something that doesn't interact with gravity (or curved space-time) the same way normal matter does. It curves space-time like normal matter does. But it isn't pulled into the gravity well (space time curve) toward the center of a galaxy the way other matter is.
Or, our model of gravity/space-time isn't quite right.