how is empty space expanding?

Originally posted by @humy
One of the first things many cosmologists did when dark matter theory was proposed is to estimate the amount of mass of black holes to see if that could account for the apparent rotation of galaxies; it didn't even come close. If there were that many black holes, we should be seeing vastly more gravitational lensing cases (from black holes) than we do observe.

Skip Black Holes.
What about Wimps?

Originally posted by @metal-brain
No. I said dark matter was likely to be mostly black holes.

That's not consistent with our observations.

Originally posted by @kazetnagorra
That's not consistent with our observations.

I don't observe many bats at night, but I'm sure they are there and very numerous.
Find a better way to observe and you might find the black holes you cannot now.

Originally posted by @metal-brain
I don't observe many bats at night, but I'm sure they are there and very numerous.
Find a better way to observe and you might find the black holes you cannot now.

Do you think we might be able to find faeries if we use better ways to observe?

Originally posted by @kazetnagorra
Do you think we might be able to find faeries if we use better ways to observe?

We know black holes and bats exist.

Originally posted by @metal-brain
We know black holes and bats exist.

But not in the same place and time🙂