It seems that an important question in physics is "why did the universe start in a state of low entropy?".
I'd like to ask a related question: given an expanding universe, is there a relationship between density and entropy?
The early universe was in a state of high density and high temperature. What I'm asking is, given expansion doesn't that necessarily imply low entropy?
As the universe expands it will necessarily cool off. That's very similar, as I see it, to a state where there is a high temperature region with a low temperature region near-by, such that energy can flow from the region of high to low temperature.
In this case we have a high temperature system that will evolve into a low temperature system over time (due to expansion). Without expansion that wouldn't happen: the average temperature would just remain the same.
So, my question is, does that evolution from high to low temperature imply an evolution from low to high entropy?
If so it seems odd, but entropy becomes dependent not just on the current state of the system but on possible future states.
To make my point perhaps more clear: isn't it necessarily the case the there are more possible states for a system to take post-expansion than pre-expansion?
Or to take another tack: say I have a model universe that's finite in size. I start it in a low entropy state and let it evolve for a while until it reaches thermal equilibrium. It's now in a high entropy state. Then we turn on expansion. It seems to me that I've just opened up the possibility for higher entropy and my system can go on evolving in interesting ways (rather than just having random thermal fluctuations).
But maybe I'm just rambling incoherently here.
I'd like to ask a related question: given an expanding universe, is there a relationship between density and entropy?
The early universe was in a state of high density and high temperature. What I'm asking is, given expansion doesn't that necessarily imply low entropy?
As the universe expands it will necessarily cool off. That's very similar, as I see it, to a state where there is a high temperature region with a low temperature region near-by, such that energy can flow from the region of high to low temperature.
In this case we have a high temperature system that will evolve into a low temperature system over time (due to expansion). Without expansion that wouldn't happen: the average temperature would just remain the same.
So, my question is, does that evolution from high to low temperature imply an evolution from low to high entropy?
If so it seems odd, but entropy becomes dependent not just on the current state of the system but on possible future states.
To make my point perhaps more clear: isn't it necessarily the case the there are more possible states for a system to take post-expansion than pre-expansion?
Or to take another tack: say I have a model universe that's finite in size. I start it in a low entropy state and let it evolve for a while until it reaches thermal equilibrium. It's now in a high entropy state. Then we turn on expansion. It seems to me that I've just opened up the possibility for higher entropy and my system can go on evolving in interesting ways (rather than just having random thermal fluctuations).
But maybe I'm just rambling incoherently here.
via International Skeptics Forum http://ift.tt/2fWc6XO
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