[CraigS]

I think we're roughly on the same page here .. its very interesting this ..

Originally Posted by renormalised

A forest doesn't have the same morphology as the trees which make it up. What is happening, is that the patterns of morphology at the micro and meso scales, when taken as a whole, drive other patterns at the macro scale which may bear little resemblance to those smaller scale patterns.

I don't think there is a need to invoke a "driving process" between the various levels of scale. If there is no evidence of one in nature and the pattern spontaneously forms in the simulation, I don't think we can say that this is happening.

Originally Posted by renormalised

Their combined effect creates the spiral patterns of the galaxies and in turn the megascale patterns also influence the others at the smaller scales.

I can see that there is iteration at the lower-scale level, (the outputs from one step in time feed back, as inputs to the next), that's actually the function the computer performs in the model.
Maybe there's also a natural feedback process at this same level of scale in the real thing, also.
But once again, I can't see a need for invoking feedback between this level, and say, the next one up, when the simulation forms the pattern without such a mechanism.

Originally Posted by renormalised

In order to study how the spiral density wave creates and drives the spiral structures in galaxies, you must know how the stars form within them and what other processes/patterns occur within them.

I really don't think there is any such thing as a "driving spiral density wave". I think the fact that the spiral shape appears spontaneously without any cause, suggests that it is nothing more than an illusion, which our pattern-recognition sensors pick up. There is not necessarily any "driving force" (of nature) behind it. The structure merely self-assembles in this pattern, because of the behaviours of the individual parts, at the lower scale.

Originally Posted by renormalised

And, in order to understand how the stars form and the clouds of dust and gas are related to this process (and others), you must also know how the spiral structures of these galaxies work. It can't be escaped.

Once again, I don't think there are any "workings" we can attribute as being at cause in creating the spiral structure .. there is no need for any such mechanism, as it appears purely because of interactions between the 'standard' behaviours, of the lower scale components.

Originally Posted by renormalised

The problem with being overly reductionist is that you lose sight of the interrelationships between the apparently disparate pieces of the whole. That is a big problem with science...this over reliance on reductionism and pigeon holing of everything. In many cases, more knowledge can be gained by considering the whole, rather than the parts.

I whole-heartedly agree !

Cheers