See http://physics.stackexchange.com/questions/214950/if-dark-matter-only-intera...

		okket on Aug 26, 2016 \| parent \| context \| favorite \| on: New class of galaxy has been discovered, made almo... See http://physics.stackexchange.com/questions/214950/if-dark-ma... TL;DR: Dark Matter doesn't clump because of missing "friction" from the other forces, esp. electromagnetic/weak.