On Sunday, October 18, 2020 at 6:09:39 AM UTC-6, John Clark wrote: > > On Sun, Oct 18, 2020 Alan Grayson <[email protected] <javascript:>> > wrote: > > *> If the very early universe is a hot photon gas, wouldn't that be a very >> high entropy initial condition?* > > > That would be true if gravity was not an important factor as is the case > for most experiments we can produce in the lab where gravity can be safely > ignored, but in the very early universe gravity was enormously important > and can not be ignored. >
*In Boltzmann's formula for entropy, gravity isn't a parameter. I think entropy only depends on the number of possible microstates, and therefore on the volume. AG * The early universe was very smooth but, due to random quantum variations, > not perfectly smooth. So some parts of the universe had very slightly more > mass/energy than other parts. As time progressed, because of gravity, the > slightly denser regions pulled in slightly more particles into themselves > than the slightly less dense regions did, and so those tiny variations > started to grow larger. As a result of that growth of variations entropy > increased and the Universe never again reached the very low entropy level > it had when it was young. > > *> For a given volume, the entropy is what it is, related to the possible >> microstates as given by Boltzmann's formula. If the volume increases, the >> entropy increases, and it starts at a maximum level depending on the volume >> of the very early universe. So I see no distinguishing the Actual Entropy >> from the Maximum Possible Entropy. AG* > > > The point is that if the universe is expanding (and accelerating) then > there is no such thing as the universe having a Maximum Possible Entropy, > whatever entropy value you give me no matter how large I can show you a > time when the universe will have an even larger entropy. > *The concept of Maximum Possible Entropy was introduced by Jason, via his reference, and shown schematically in his diagram. Supposedly it can be compared with actual entropy at any time. I have no idea what this means. AG * > > John K Clark > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/198293d3-75a7-48c9-9dd6-c7bc31e328aao%40googlegroups.com.
