[math-fun] Brief "golden era" aka "flowering period" for universe. Enjoy it while can.
It is well known that the entropy of the universe increases. However, the entropy of the observable portion of the universe (within the de Sitter horizon) can and will decrease. Indeed, in about 1000 gigayears, the part of the universe observable from point X will, for all but an extremely small-measure-fraction of X, contain only a few bits of entropy and be almost empty, containing zero atoms and only a few very cold photons. This is due to the exponential expansion of the (Lambda-dominated) future universe with e-folding time of about 14 gigayears. There will however remain a few "islands" e.g. gravitationally bound agglomerations such as our galaxy (unaffected by the overall expansion), that will continue to be interesting for well beyond that time, e.g. the smallest red dwarf stars are forecast to continue shining for 10000 gigayears. But these places will be exponentially rare. So if we plot on a horizontal axis, time, and on the vertical axis, entropy of the observable part of the universe viewed from typical point, the curve will increase at first, reach a max, then decrease. Let me call the max-info point, the "golden era" when the universe is "most interesting." I estimate that this golden era is happening approximately now. More precisely, somewhere between 5 Gyr and 30 Gyr of age (present age is 13.8 Gyr). I have not seen this whole remark before. Why now? Basically because Lambda-domination began at age 9 Gyr and the entropy-increasing processes such as star formation & shining, black hole formation & mergers, etc, are increasing entropy at approximately a linear rate, which cannot compete with the exponential decrease that sets in once Lambda-domination gets rolling. (The observable portion of the universe has a fixed radius of about 14 giga light years, which will remain approximately constant forevermore, say the mathematics of de Sitter space.) It indeed has been estimated that over 90% of the stars that will ever form, have already, and presumably the same is true for black holes (since they arise only from very short-lived stars). -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
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Warren D Smith