Dark matter galaxy, not many stars:

http://www.mnn.com/earth-matters/space/stories/scientists-discover-galaxy-made-almost-entirely-dark-matter

I guess it's inevitable that somewhere in the universe in a universe filled with majority dark matter V our kind of matter, it was bound to happen, a whole galaxy of the stuff with not much of our kind of matter in it.

So the next question obviously will be, how many more will they find like it?

Originally posted by sonhouse
So the next question obviously will be, how many more will they find like it?

That question has no answer unless a time limit is given.

I wonder to what extent they can distinguish between black holes and other types of dark matter.

Originally posted by twhitehead
That question has no answer unless a time limit is given.

I wonder to what extent they can distinguish between black holes and other types of dark matter.

If they are close enough, black holes have a certain pattern of orbiting material, velocities and such.

The dark matter is much more homogenous, basically a big blob of stuff, whatever that stuff is. The main and possibly the only way to suss out dark matter blobs is the effects of its gravity on nearby objects but on a much larger scale than most black holes.

Search for another explanation, because dark matter doesn't exist.

Seriously. Some apes at the bottom of a gravity well built some decent math. That doesn't mean the entire universe must conform to that math.

Originally posted by apathist
Search for another explanation, because dark matter doesn't exist.

Seriously. Some apes at the bottom of a gravity well built some decent math. That doesn't mean the entire universe must conform to that math.

No, but the evidence is pretty strong. It may be that the explanation for the effect is from parallel universes (in the Everett sense or in some other multiverse sense) where their normal matter interacts with our universe to produce dark matter effects, and lighter universes, with less matter, produce the "dark energy" effect through some sort of expansion drag effect. So that dark matter and dark energy don't exist as such but are effects associated with parallel universes. But that is an explanation for dark matter, not a denial of its existence.

Originally posted by sonhouse
http://www.mnn.com/earth-matters/space/stories/scientists-discover-galaxy-made-almost-entirely-dark-matter

I guess it's inevitable that somewhere in the universe in a universe filled with majority dark matter V our kind of matter, it was bound to happen, a whole galaxy of the stuff with not much of our kind of matter in it.

So the next question obviously will be, how many more will they find like it?

Black holes are the dark matter. The amount and size of the black holes is simply underestimated.

Originally posted by DeepThought
No, but the evidence is pretty strong.

Evidence needs to be interpreted. There is a program in place to interpret the evidence so that our current theories about the laws of gravity are not violated.

I hear you though. I would not be surprised to learn I am wrong and that dark matter exists. And I will not be surprised to learn that it doesn't.

Originally posted by Metal Brain
Black holes are the dark matter. The amount and size of the black holes is simply underestimated.

That is total BS. Black holes have jets shooting out the poles for one thing, these dark matter blobs have no such thing.

There is intermittant Gamma radiation, X-rays, UV, visible light coming off black holes when they digest some planet, gas or star, these blobs CAN'T do that, they emit NOTHING.

We only know of the presence of these objects by the gravity, the way they influence nearby masses. They don't control individual star movements like black holes which are an extremely concentrated mass that bends the hell out of space/time, you go inside a black hole and 1 second can stretch to a million years.

There is no such effect inside a dark matter cloud. It is an amorphous cloud of non interacting stuff, and just what stuff it is is unknown.

Originally posted by sonhouse
That is total BS. Black holes have jets shooting out the poles for one thing, these dark matter blobs have no such thing.

There is intermittant Gamma radiation, X-rays, UV, visible light coming off black holes when they digest some planet, gas or star, these blobs CAN'T do that, they emit NOTHING.

We only know of the presence of these objects by the ...[text shortened]... cloud. It is an amorphous cloud of non interacting stuff, and just what stuff it is is unknown.

Not BS. Leave your personal feelings about me out of it.

http://phys.org/news/2016-05-scientist-link-primordial-black-holes.html

Originally posted by sonhouse
That is total BS. Black holes have jets shooting out the poles for one thing, these dark matter blobs have no such thing.

There is intermittant Gamma radiation, X-rays, UV, visible light coming off black holes when they digest some planet, gas or star, these blobs CAN'T do that, they emit NOTHING.

We only know of the presence of these objects by the ...[text shortened]... cloud. It is an amorphous cloud of non interacting stuff, and just what stuff it is is unknown.

Actually none of that is correct.
There may be other reasons why black holes cannot account for dark matter but nothing of what you said is such a reason and most of it is wrong, or only true in some circumstances.
Most black holes are largely invisible to us - and even more so in distant galaxies.

Originally posted by Metal Brain
Not BS. Leave your personal feelings about me out of it.

http://phys.org/news/2016-05-scientist-link-primordial-black-holes.html

Well, ok., but this isn't proved, it's a theory with some evidence to support it and the particle based theories shouldn't be ruled out yet.

I would go as far as to say that black holes would be a perfectly legitimate for the dark galaxies even if dark matter in other forms is real, ie there could be galaxies in which black holes are as common as stars are in our galaxy, and stars are rare. Of course the difficulty is explaining how they formed, but that is not a difficulty in the observations but rather in theory.

Originally posted by twhitehead
Actually none of that is correct.
There may be other reasons why black holes cannot account for dark matter but nothing of what you said is such a reason and most of it is wrong, or only true in some circumstances.
Most black holes are largely invisible to us - and even more so in distant galaxies.

The only way for black holes to be dark matter is if there are literal clouds of them but very small ones, googles of them but Hawking radiation would ensure a very short lifetime so in order for black holes to be dark matter there would have to be a permanent replacement of them in our universe because the smaller the black hole the less stable they are.

Originally posted by sonhouse
The only way for black holes to be dark matter is if there are literal clouds of them but very small ones, googles of them

Explain your reasoning behind this because at face value it doesn't make any sense.

but Hawking radiation would ensure a very short lifetime
How short. Give us a figure for black holes the size of the sun or the size of Jupiter. But first justify your claim that they must be small.

Assuming dark matter makes up 95% of our Galaxy (as per Wikipedia), then for every star there would be 19 times as much mass in black holes. LIGO has so far only observed one event as far as I know and it found two black hole with masses 29 and 36 times the mass of the sun. (which I believe, merged to form one about 62 solar masses loosing 3 solar masses in the merger).

So lets just assume that for every star there is one black hole 19 times its size. Why is this not possible?