[CraigS]

Originally Posted by CraigS

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

Now, that's where you're going right out on a limb and stretching quite a few physical laws...spontaneous generation with no causative mechanism. That's tantamount to creation from nothing, which is one reason why laypeople find digesting what scientist say about the BB rather difficult and gives the looney tunes brigade their ammunition to go on with what they do. The reason why scientists say things like the BB (or in this case the spiral pattern in galaxies) has no cause is that they don't understand the mechanisms behind it very well, if at all. You can't have laws of physics saying one thing and then totally disregard one of the underlying principles behind them (cause and effect) just because you can't fathom why something happens, given your present state of understanding. There's quite a bit we do understand, make no bones about that, but we do waffle on too much and dig our own graves when it comes to making pronouncements on areas of knowledge we've barely begun to even figure out, let alone know what's happening.

Yes Carl … fair enough, too. My words may have been misleading.
There is clearly a cause .. that would be the non-linear behaviours which take on a life of their own, once the smaller scales interact with eachother, within the simulation. So I guess one can point to this as the 'cause'.

What I meant to say, is that it is not caused by something external which takes on the form in our thinking of a physical "spiral density wave".
If we give such a thing the ontological status of say a primitive entity that can be demonstrated by experiment, then it should be able to be described separately from its constituents ... and I don't think we can do this for "a spiral density wave" .

Also, there are systems which have feedback operating between dissimilar levels of scale … which produce a verfiable cause and effect on the components. Eg: I can kill off a few thousand brain cells by having a few drinks, eh ? This would be a different system from the ones simulated in the model we're talking about here, though.

Cheers