Why would large quantities of dark matter not stick together ?

[mikenovice]

Does dark matter form orbits around stars ? Why would dark matter and "regular" matter, say, a dust belt not mingle and stick together?

Just with black holes, with d.matter we are positing new objects with complex properties instead of simply admitting imperfection in gravity. Since it is difficult to show how gravity is mediated (as opposed to showing its effects, which are clear)...to me, Occham's razor is best applied by modifying gravity rules locally instead of inventing new substances.
Of course, it is inelegant to make exceptions to gravity, which works well. On the other hand, gravity is so strange as to be suspicious: something leaves a mass at lightspeed, collides with other objects: the effect of this collision is to suck the object against the direction of the impact, and it does not weaken from use, and penetrates any type of element ?

While gravity generally applies, it is so strange that one should be willing to think about exceptions.

 

[LURCH]

The problem is that Dark Matter is known to exist. Every time we develope some new isntrument with greater sensitivity, we see new things that we could not see before. Untill that moment, those things were Dark Matter.

...gravity is so strange as to be suspicious: something leaves a mass at lightspeed, collides with other objects: the effect of this collision is to suck the object against the direction of the impact, and it does not weaken from use, and penetrates any type of element...

Since the development of GR, this is not the way gravity has been understood to function. It is not a form of radiated energy, but a geometric condition of spacetime.

 

[brightmatter]

Does dark matter form orbits around stars ? Why would dark matter and "regular" matter, say, a dust belt not mingle and stick together?

Just with black holes, with d.matter we are positing new objects with complex properties instead of simply admitting imperfection in gravity. Since it is difficult to show how gravity is mediated (as opposed to showing its effects, which are clear)...to me, Occham's razor is best applied by modifying gravity rules locally instead of inventing new substances.
Of course, it is inelegant to make exceptions to gravity, which works well. On the other hand, gravity is so strange as to be suspicious: something leaves a mass at lightspeed, collides with other objects: the effect of this collision is to suck the object against the direction of the impact, and it does not weaken from use, and penetrates any type of element ?

While gravity generally applies, it is so strange that one should be willing to think about exceptions.

The problem is that Dark Matter is known to exist. Every time we develope some new isntrument with greater sensitivity, we see new things that we could not see before. Untill that moment, those things were Dark Matter.

Since the development of GR, this is not the way gravity has been understood to function. It is not a form of radiated energy, but a geometric condition of spacetime.

dark matter is not dark because scientists have seen dark matter and will see dark matter.

 

[Chronos]

Dark matter, as conventionally defined, does not compact like ordinary matter. The particles simply pass through each other. They interact as weakly with one another as they do with ordinary matter.