I love discussing these things with experts in the field.
I told them dark matter were galaxies that had gone past the speed of light (the big bang theory, Einstein,etc. all support this). That we can't see them because of this.
I did not receive any proof I was wrong, which I expected, as they would have to be able to measure it's red shift to give it's speed, and .... you can see the problem with that approach.
I can't prove I am correct, they can't prove I am wrong.
Who knows, for sure? Not me.
Now that makes sense to me, with no arguments. I just never thought of that, for the missing matter everyone keeps talking about.