Dark Matter

From this thread on Reddit:

Basically all we know about dark matter is that it is responsible for binding galaxies together despite their high rate of rotation. If it were just the gravity from visible matter holding galaxies together, they would fly apart at their current rate of rotation. There’s simply not enough stuff. But galaxies don’t fly apart. So somethingis going on.

There are a number of possibilities. It could be that our theory of gravity is wrong. It just works differently at galactic scales for some reason. It could be that there are a bunch of blackholes whizzing around that we’re missing. It could be that there is a repulsive force out in the void between galaxies pushing things inwards.

I pay attention to dark matter stuff because (rightly or wrongly) I’ve used dark matter as a metaphor for the unconscious.