tomatoherd wrote:As I've said in the past, something is wrong with the physics, age, or understanding of cluster theory.
Which "cluster theory" would that be? We don't have a good theory about the
formation of globular clusters. But their
behavior is accurately described by orbital mechanics.
If gravity exists (ha!), then after 13 billion years this cluster would have condensed into a massive black hole. It appears to have little "centrifugal" momentum to counteract gravity, as do disc shaped solar systems or galaxies.
There's no such thing as centrifugal momentum. There's no mechanism that would cause a cluster to collapse. Why do you think that gravity needs some counteracting force? Our solar system is 5 billion years old, and it hasn't collapsed. Like a star system, or a galaxy, a globular cluster is a collection of largely independently orbiting bodies. Orbits don't normally decay. The only reason a globular cluster could collapse would be if the individual stars in it lost angular momentum. Since there are no viscous processes, there is nothing to remove energy from the stars. They interact gravitationally, which simply transfers angular momentum. Stars that lose a little move into closer orbits; stars that gain it move outwards, and may be lost to the cluster. That's why clusters evaporate, they don't condense.
Someone answers, "oh, well each individual star has its own 'tangential velocity', but they are randomly oriented, hence no disc formation". But if the cluster's origin was a one-time event from a shared gas cloud, how could there have been individual, random, and no doubt even opposing momentums / orbits generated? Someone else says, "well, even with gravity, all motion is not uniformly 'inward': by close encounters, some stars are even ejected from the cluster". But forget not: in those encounters, the remaining star LOSES momentum, and hence SHOULD fall further towards the common center of gravity.
What difference does it make if the structure is a disk or a sphere? The dynamics of individual stars is no different. Even in disk galaxies, the majority of mass is found in the bulge, where the orbits are largely at random inclinations. Clusters may not have formed from a shared gas cloud. And even if they did, and started out as disks, there's no reason for them to stay that way. Disks aren't stable. Galaxies, too, evolve into ellipticals. When you perturb rotating disk structures, you gradually randomize the orbital inclinations of the members.
If a star loses ALL angular momentum, it will fall into the center. But that takes far longer on average than a few tens of billions of years for a structure like a globular cluster. In fact, the cluster evaporates faster, which just reduces the perturbations over time.
These clusters as described I believe defy Newtonian physics. But I don't think it's Newton who is wrong.....
Clusters demonstrate Newtonian physics. And you need nothing more than Newtonian physics to numerically model them, and the models behave just like what we observe.
Hubble's Messier 5
...lots better....
. It was their donut shapes that particularly caught my interest. Mmmmm, I fancy a 
or two now.
