"If a ball is put in a spin in space it will spin forever right. But the law of physics says for every action there is an equal and opposite reaction. What is the reaction in this case? Black matter?"

As long as you are on the way to "put" the ball in a spin, you exert a force on the ball, increasing its torque. The inert mass of the ball _re-acts_ with a force against your force. Have you ever accelerated a merry-go-round with children on it? You can _feel_ the resistant force of the mass of the apparatus plus the children.

After having stopped exerting the force on the ball – and assuming there are not _other_ influences (e.g. from gravitation) –, the ball remains in its current state, i.e. spins forever. This is a basic principle of classical physics, invented (some say: discovered) by Isaac Newton.

In modern physics, of course, it's a little bit different. After certain periods of time there will be some radioactive decay of some elementary particles in the ball, and there will be some quantum fluctuations too. This will change the torque of the ball a little bit.

If a ball is put in a spin in space it will spin forever right. But the law of physics says for every action there is an equal and opposite reaction. What is the reaction in this case? Black matter?

1) How would the dark matter have been condensed into the appropriate concentrations in early stars?

2) What would have propped up the dark matter from gravitational collapse into black holes long enough for them to annihilate?

it's obvious. dark energy????

Dark Matter – existance proven but unkown
WIMPs – unproven existance

These are the basis of their statements?

How are we to believe these conclusions??

Good question. Astrophysicists say, that most of the time stars built out of normal matter are in an equilibrium between gravity – which tries to compress the star – and radiation pressure – which tries to expand the star. Dark matter, by definition, does not react to radiation (electro-magnetic interaction). So what does the dark matter inside a star – where these particles are near to each other already – keep from collapsing more and more rather rapidly?

A similar question comes to mind: What does a neutron star keep from collapsing? As far as I know, electro-magnetic interaction is not needed for the stability of a neutron star. I have read something about "configuration pressure", which has to do with quantum physics.

1) How would the dark matter have been condensed into the appropriate concentrations in early stars?

2) What would have propped up the dark matter from gravitational collapse into black holes long enough for them to annihilate?

When it comes to DM, I think the issue is less clear. Yes, there does appear to be a large source of gravity out there that we can not account for yet, at least on very large scales. Since we can not see it, it makes sense to call it DM. Whatever it is, be it matter or energy, about the only thing we know for sure about it is that it exerts and is affected by gravity. I think that Olaf confuses the above examples that were/are on firm ground with DM which is on much more shaky ground.

That is not to say that those doing the research shouldn't be stretching themselves and pushing the limits of their intellects and imaginations. They should. Perhaps papers such as the article talks about can serve an important function as thought experiments. Remember, Einstein never conducted a single experiment. The problem with research into DM that I see is this. The field is very important and very high visibility. I would be willing to bet a lot of money that whoever definitively proves what DM is will be guaranteed a Nobel prize. So the stakes are high. I expect we will see a high noise to signal ratio when it comes to DM papers and that will make it difficult to cull out the helpful thought experiments from the chaff. I don't think that improper comparisons help with the winnowing process.

On a different point, the idea that DM is its own anti-particle seems like a rube goldberg contrivance. Given the amount and densities that we think we are seeing now, then there must have been a unbelievably huge quantity of the stuff in the early universe. That would imply very different conditions than appeared to have existed. Just think of the resulting gravity, heat, and mass through which other particles would have to move. It makes sense that DM has an anti-particle, but it defies logic that it is its own. Of course, the universe has a way of surprising us just about every day.

I take the ideas of dark matter and dark energy and WIMPs as useful working models that will allow today's astronomers and other scientists to develop further what has come to be known about everything else in the universe. Will we ever really finish learning? Probably not.

It's simple logic. If one does not calculate the consequences, one is not able to falsify the concept. Considerations of this kind should not be presented to the public as scientific research, at best as science fiction – which can be amazing.

And how, pray tell, does one falsify the concept of WIMPs, if one does not calculate the consequences of their comprising DM?

Ok please at least tell us why you call this bullshit? I am interested in the reasoning why this is all bullshit.

Perhaps not. Matter and anti-matter would annihilate each other before being able to gravitate together to form a star. But then wouldn't dark matter do the same?

Or perhaps, if we endow this imaginary stuff (dark matter) with the properties of weakly interacting only through gravity and interacting even more weakly in the self-annihilation reaction, then we can get it to do exactly what we imagine it should have done.

Ow – I just broke my brain.

Some time ago other planets were theoretical, now we see them everywhere.

At this point the highs particle is still theoretical, but soon we migth be able to confirm it's existance or not with the LHC.

At this point additional dimensions are theoretical but with any luck and the LHC we might confirm it's existance or not.

And so far I now, the properties of dark matter are very well known, it is just that up untill now we have no confirmation about its existance so time and many experiments will tell.

The WIMPs are believed to be their own antiparticles, like neutrinos and photons, wich means that if 2 of them gets to close they annihilate eahother. In high concentration areas then more annihilation would occur than in sparse areas.

Whether WIMPs exist or not remains to be seen.