Re: the universe is ~6kyo
Posted by Southern Man on Jul 04, 2002 at 09:43
Re: the universe is ~6kyo (DA Morgan)
I’ll skip your switching of who said what since you restated your position and moved on.
“My point was and is that it will crunch or become cold and dead whether entropy exists or not.”
Yes, that is what I have always understood you to be saying. It is just wrong. Let’s come at this from another direction. Energy does not warp space and appear to attract energy as mass appears to attract mass. Therefore if the universe consisted of only energy there would be nothing to halt the expansion. Now entropy states that the organization of energy declines over time. A glass of ice in warm water always turns into a glass of cool water. If we extrapolate this to the universe full of different atoms, ultimately the result will be a universe full of only iron atoms since iron contains the most binding energy per nucleon (highest mass/energy ratio). Now if the density of the iron atoms left at the end is high enough to overcome the remaining expansion then the universe will collapse. Otherwise it will continue to expand.
BUT what if entropy were different? What if a glass of cool water could become a glass of warm water with ice cubes in it with no outside influence? Now there is nothing to say whether we end in iron or in hydrogen and atomic sized black hole stuff. It might not matter how much mass we start with because the end could be unstoppable hydrogen traveling outward at near the speed of light. Without entropy to maximize the mass/energy ratio the mass could be quite different.
“ Assume entropy didn't exist. Would gravity behave differently?”
Yep. Not in the context of the apparent attraction between two atoms but in the context of a universe of changing mass and energy. When the mass changes because of entropy so does gravity.
“To me you are confusing cause and effect. Gravity does not depend on entropy. Entropy, however, may well be a consequence of gravity.”
At this point I am not willing to say that entropy is or is NOT a consequence of gravity. But assuming it was, then a difference in entropy would REQUIRE a difference in gravity which would affect the end. You are making my point for me. But as I said, I’m not willing to base my argument on that solid foundation just yet. I would rather just point out that entropy determines the ratio of energy to mass and that determines the end.
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