On Sun, Oct 18, 2020, 7:31 PM Bruce Kellett <[email protected]> wrote:
> On Mon, Oct 19, 2020 at 11:21 AM Jason Resch <[email protected]> wrote: > >> 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 >> > > > Nah. You have interpreted that wrongly. If you compress a given amount of > mass-energy into a smaller and smaller volume, when the radius reaches the > Schwarzschild radius, a black hole will form. This then represents the > maximum entropy state for that fixed amount of mass energy. Do not forget > that entropy works rather differently in GR. > You're contradicting the equation. R can increase arbitrarily which increases the bound arbitrarily high. > The Bekenstein bound merely limits the amount of mass-energy (hence > entropy) in a given volume (or the minimum volume that a fixed amount of > mass-energy can be squeezed into). The only way to increase that minimum > volume is to increase the mass-energy. The volume of the surrounding space > is irrelevant. > The black hole entropy equation is different from the bernstein bound. The black hole is an edge case of the equation, which in its most general form relates volume and energy to a maximum entropy. 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/CAFxXSLR6iMBOymkL0FbuYqRbZq35XozrXcGi141qvG9_2o3n9Q%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAFxXSLR6iMBOymkL0FbuYqRbZq35XozrXcGi141qvG9_2o3n9Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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