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TrickyDicky
TrickyDicky is offline
#19
Feb23-12, 04:39 AM
P: 2,892
An interstellar medium enriched by stellar ejecta would be anything but static. A universe without entropy would be not even wrong, but, I naively suspect it would remain in its original state. A universe without BB nuclosynthesis still needs a source of hydrogen for primordial stars to form. Once the stellar formation process began, the ISM would be continuously enriched by stellar ejecta. I fail to see how that could ever achieve equilibrium. It would merely continue to be enriched until so heavily metallized it could no longer support stellar fusion. The answer seems to be stars would not form in a universe without entropy.
Quote Quote by mathal View Post
Exactly. This is merely a thought experiment. Objects like stars from our universe are not static- they age, things change, proportions of elements change with time. They couldn't exist in the form they have here. I find it hard to conceive of such a universe, the interrelationship of the laws that govern this universe are not workable without entropy. It is not that it is a physical law, merely that it is a consequence of the laws we operate under (in particular gravity).

You are thinking of primordial stars- our universe. The static universe TrickyDicky is presenting requires they just be here timelessly. An impossible requirement from my understanding of physics.
mathal
Of course it is just a thought experiment, like the many that are used in science to get a better understanding of things, when Einstein imagines he is riding a photon no-one thinks about the practical impossibility of doing that. Many things are explained in physics thru thought experiment or ideal models that are known not to exist in reality.
Anyway a static universe doesn't imply there is no "local" change, it is just the global cosmological parameters as a whole that don't change wrt time.
Otherwise it would have been plain silly from Einstein and the physicist of their time to even consider static spacetimes as models for our universe knowing as it is obvious that locally things change.