On 15 April 2015 at 04:39, Telmo Menezes <te...@telmomenezes.com> wrote:
> Hi Liz, > > >> Ok. I have an idea about that, it is probably not original. Tell me what >>> you think: >>> The universe was not created. All possible states just exist. The moment >>> of the big bang is one of the many possible states. What we call the past >>> is a sequence of steps in the state graph that are coherent predecessor of >>> each other, in the sense that they contain less and less information. Given >>> that the moment of the big bang is the lowest entropy state conceivable, >>> all history lines will originate there. >>> >>> My problem with any view based on entropy is that entropy doesn't appear >> to be fundamental to physics; it is the statistically likely result when >> objects are put in a certain configuration and allowed to evolve randomly. >> > > There is, however, an interesting parallel to be made with Shannon's > entropy, which is a measure of information content and not just a > statistical effect. Once in the realm of digital physics, it becomes > questionable if physical entropy and information entropy are separate > things. > Yes, and there is also black hole entropy. It's POSSIBLE that Boltzmann stumbled on something fundamental via a route that doesn't lead via fundamental physics (B's entropy is only apparent to macroscopic beings) I don't know if the jury has come down in favour of entropy being in some way fundamental to the universe, but it's certainly possible. (Though not the thermodynamic sort.) > > >> However the laws of physics are (mainly) time-symmetric, with the >> definite exception of neutral kaon decay and the possible exception of >> wave-function collapse, and an ordered state could evolve to become more >> disordered towards the past (although that would make the past appear the >> future for any beings created within that ordered state). Yet we never see >> that happening, and there is an elephant in the cosmic room, namely the >> expansion of the universe, which (istm) must always proceed in the >> direction of the AOT. >> > > What if the AOT is a purely 1p phenomena? > Well, it's clearly a 3p phenomenon in that we all agree that things age etc. But it's perhaps purely a "macroscopic creature phenomenon" > >> Hence the appeal to boundary conditions. If something forces the universe >> to have zero (or very low) radius at one time extremity but not at the >> other, this asymmetry could be sufficient to drive the arrow of time in a >> particular direction. >> >> I've (as it were) expanded on this idea before, however, so I won't go on >> at length about it again. >> > > I'll search the archives when I have a bit of time. > Briefly, the boundary condition on the universe appears to be that it has a big bang at one time extremity (or something like one) but not a corresponding crunch at the other. This alone means that the density of the contents of the universe is constrained to decrease globally along the time axis as you move away from the BB, and my contention is that this is probably enough to create an AOT even with the laws of physics operating - by assumption - time-symmetrically, when you look at the various processes that result from a decrease in density (and temperature, effectively, since particles tend to move until they reach a patch of the background fluid which is moving at their speed). Such outcomes include the formation of nuclei, atoms, and eventually gravitationally bound states like galactic clusters etc. -- 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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
