On Sun, Oct 18, 2020, 6:53 PM Bruce Kellett <[email protected]> wrote:
> On Mon, Oct 19, 2020 at 3:33 AM Jason Resch <[email protected]> wrote: > >> On Fri, Oct 16, 2020 at 6:19 AM Bruce Kellett <[email protected]> >> wrote: >> >>> On Fri, Oct 16, 2020 at 5:49 PM Jason Resch <[email protected]> >>> wrote: >>> >>>> On Thu, Oct 15, 2020 at 6:07 PM Bruce Kellett <[email protected]> >>>> wrote: >>>> >>>>> On Fri, Oct 16, 2020 at 9:51 AM Jason Resch <[email protected]> >>>>> wrote: >>>>> >>>>>> I noticed that Victor Stenger's position on entropy, as described >>>>>> here: https://arxiv.org/pdf/1202.4359.pdf on page 7, appears to be >>>>>> the same as described by the cosmologist David Layzer in a 1975 issue of >>>>>> Scientific American: >>>>>> https://static.scientificamerican.com/sciam/assets/media/pdf/2008-05-21_1975-carroll-story.pdf >>>>>> >>>>>> The basic idea, which is described graphically here: >>>>>> https://www.informationphilosopher.com/solutions/scientists/layzer/arrow_of_time.html >>>>>> >>>>>> It is a counter-argument to the commonly expressed idea that the >>>>>> universe began in a low entropy state. Rather, it explains how the >>>>>> expansion of the universe increases the state of maximum possible >>>>>> entropy. >>>>>> If the universe expands more quickly than an equilibrium can be reached, >>>>>> then there is room for complexity (information / negative entropy) to >>>>>> increase. >>>>>> >>>>>> Why is it that the "low entropy" myth is so persistent, and this >>>>>> alternate explanation is so little known? Some physicists, such as >>>>>> Penrose >>>>>> are still looking for alternate explanations for the special low entropy >>>>>> state. What fraction of physicists are aware of Stenger's/Layzer's view? >>>>>> Does it appear in any physics textbooks? Has it been refuted? >>>>>> >>>>> >>>>> It is refuted by the idea of unitary evolution in QM. Unitary >>>>> evolution means that everything is reversible, If new microstates are >>>>> created as the universe expands, then this expansion cannot be reversed: >>>>> the creation of such microstates gives an absolute arrow of time. This is >>>>> generally rejected, because physicists tend to believe in unitary >>>>> dynamics. >>>>> If dynamics are not unitary, then the universe is not governed by the >>>>> Schrodinger equation, and arguments for the multiverse collapse. >>>>> >>>> >>>> I understand unitarity for a fixed physical system with certain finite >>>> boundaries. But how does that work for the case of an expanding universe? >>>> If you define the wave function for the observable universe at time 1, what >>>> is the wave function for time 2? Doesn't the number of possible states in >>>> time 2 not increase beyond what it was in time 1, given new information has >>>> entered the system from the cosmological horizon? >>>> >>> >>> If there is a unitary operator that takes the wave function at time 1 to >>> time 2, the the evolution is unitary and reversible. Horizons play no part >>> in this. >>> >>>> Also, I think we can borrow a lesson from quantum computing to shed >>>> some light on the problem of irreversibility and entropy. Quantum computers >>>> need to use reversible logic gates to prevent premature decoherence. >>>> Reversible circuits generate garbage (ancilla) bits as a result of the >>>> continued operation of the computation. (see >>>> https://en.wikipedia.org/wiki/Ancilla_bit and >>>> https://quantumcomputing.stackexchange.com/questions/1185/why-is-it-important-to-eliminate-the-garbage-qubits >>>> ). >>>> >>>> If we extend this analogy to the universe, can we envision the rise of >>>> complexity/macroscopic order in a similar way to the locally growing order >>>> of a reversible computation, which must generate waste heat >>>> ("garbage/ancilla bits") leading to global rise in entropy? So long as >>>> there are enough places to dump these ancilla bits (such as into the low >>>> temperature, non-equalized environment), then there is space for growth of >>>> local order through the process of reversible computations. >>>> >>> >>> The quantum process of generating the ancilla bits is unitary, hence >>> reversible. If these bits are treated as garbage and thrown away, then the >>> result is irreversibility. No new space for bits is created. >>> >>> >> But according to the Bekenstein bound, the maximum possible entropy of a >> system is bound by its mass/enegy AND its volume. Two particles by >> themselves can encode an infinite amount of information if given infinite >> space to place them. >> >> Wouldn't expanding the available volume for a system increase the number >> of bit-combinations you can work with? >> > > > The maximum entropy state for a given mass-energy occurs when the entire > system forms a black hole. Increasing the volume of space around this BH > does not affect the entropy -- it is already at its maximum. The only way > to increase this maximum is to increase the amount of mass-energy available > -- and simply expanding the universe (available volume) does not do this! > I think it's the other way around, a black hole is the maximum entropy for a given volume, not for a given mass-energy. At least that's what Bernstein's equation implies: Entropy is bounded by (Radius * Energy * (a constant)) https://en.m.wikipedia.org/wiki/Bekenstein_bound Jason > Bruce > > -- > 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/CAFxXSLT1QdG1326SD0KCTAM9x4nBQ-brjw4ifqt1h_w_N0z2Rw%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAFxXSLT1QdG1326SD0KCTAM9x4nBQ-brjw4ifqt1h_w_N0z2Rw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- 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]. 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