Thanks Simon,

My question to myself is: if there is so much of this dark matter, even if we can't see it, why aren't the gravitational effects of it bending light visible?

The thought of attributing 70% or whatever of the mass of the universe to something completely undetectable goes against all the laws of the scientific method. You construct your theory around observable phenomena, you do not construct your phenomena around theories, then claim that 70% of it is invisible....

So any theory that can work without invisible stuff has got to be better.

Dave L