Dark matter galaxy, not many stars:

Originally posted by Metal Brain
"What if there aren't enough black holes to find to explain dark matter?"

That has not been determined yet. I doubt that is the case.

We have explained before, small black holes blow up after some time goes by, so it is totally unlikely black holes explain dark matter. They would have effects on our own gravity field in our solar system, because dark matter should be present most anywhere in our galaxy.

We only suss out dark matter by how it affects light going by them, deflecting the light.

There would be too much deflection of light around black holes which we would detect.

Black holes are not the answer.

Originally posted by sonhouse
We have explained before, small black holes blow up after some time goes by, so it is totally unlikely black holes explain dark matter.

And I have explained before that that only applies to very small primordial black holes and is thus a very poor argument for black holes being unlikely.

They would have effects on our own gravity field in our solar system, because dark matter should be present most anywhere in our galaxy.

We only suss out dark matter by how it affects light going by them, deflecting the light.

There would be too much deflection of light around black holes which we would detect.
Not true.
A lot of black holes do exist and we have largely not detected them. The very few we have detected were not by deflection of light.
Deflection on a large scale such as the one used to detect dark matter would be no different if the dark matter was black holes.

I fully admit that there are significant problems with black holes being the explanation for dark matter, but your reasons are not good ones.

Originally posted by twhitehead
And I have explained before that that only applies to very small primordial black holes and is thus a very poor argument for black holes being unlikely.

[b]They would have effects on our own gravity field in our solar system, because dark matter should be present most anywhere in our galaxy.

We only suss out dark matter by how it affects light going ...[text shortened]... lems with black holes being the explanation for dark matter, but your reasons are not good ones.

I just think they would be rather easy to spot, to tell from some kind of non interacting matter. The stuff is just too evenly spread to be miniature black holes IMHO.

For one thing, if all this was black holes, why wouldn't they have converged on each other and make a noticable gravity well through collisions?

I think we will know a lot more when LIGO and its buddies get going to full sensitivity.

Originally posted by sonhouse
I just think they would be rather easy to spot, to tell from some kind of non interacting matter.

But you need more than just hand waving. What is your actual evidence / argument that they would be easy to spot? What easily spotted black holes can you name? Black holes exists and are probably fairly common, yet we do not easily spot them.

The stuff is just too evenly spread to be miniature black holes IMHO.
Who says they must be miniature?
And where is your reference or evidence for your belief that dark matter is evenly spread?

For one thing, if all this was black holes, why wouldn't they have converged on each other and make a noticable gravity well through collisions?
For the same reason that non-black hole matter hasn't.

I think we will know a lot more when LIGO and its buddies get going to full sensitivity.
Yes, that will certainly be one way to estimate the prevalence of black holes. But it is notable that that really will be the very first good measurement of the prevalence of black holes and your claims to the contrary are totally unfounded in actual astronomy.