On 18-Aug-02, Tim May wrote: > Hal has brought up Huw Price's book, "Time's Arrow and > Arhimedes' Point," and especially the > thermodynamic/entropy arguments related to recurrence a la > Poincare, Boltzmann, and others.
> A point Price makes several times is th > "..though it needs to be borne in mind that not everyone > had a clear grasp of the fact that the low-entropy past is > itself in need of explanation." (p 37) > "In sum, the puzzle is not about how the universe reaches > a state of high entropy, but about how it comes to be > starting from a low one." (p 40) > "For all their intrinsic interest, then, the new methods > of nonlinear dynamics do not throw new light on the > asymmetry of thermodynamics. Writers who suggest otherwise > have failed to grasp the real puzzle of > thermodynamics--Why is entropy low in the past?--and to > see that no symmetric theory could possibly yield the kind > of conclusions they claim to draw." (p 44) > "There is no separate problem as to why entropy in branch > systems always increases towards the future, in other > words: only the big problem was in the bottle in the first > place." (p 45) > And so on. Price repeatedly bases many arguments on his > dissatisfaction with assuming a state of high order. (To > be fair, his book is an interesting romp through many > theories of time asymmetry, touching on Feynman-Wheeler > absorber theories, delayed choice experiments in quantum > mechanics, psychology, etc. Not a bad place to get exposed > to a lot of the current issues. Just don't take his > particular "crotchet" too seriously, is my advice.) > Frankly, I don't worry how the beer got in the bottle (one > of his example, about gas expanding out of a beer > bottle...Price worries that the analysts of time are not > asking proper questions about how the beer came to be in > the bottle in the first place...most of us, dullards that > we are, assume that a bottling company _put_ the beer in > the bottle!. > I'm not being flip. It's an observed fact of our universe, > and likely derivable from anthropic arguments, that > there's a lot of "free energy" around: a lot of unfused > hydrogen, a lot of gravitational potential energy, a lot > of stored chemical energy, etc. How this came to be from > "first principles" from an initial singularity is of > course unknown at this time. Have a look at Vic Stenger's work-in-progress http://spot.colorado.edu/~vstenger/Nothing/06After.pdf He argues that the net energy in the universe is zero; not an original idea, many GR theorists think this is the case. Since the net energy is zero the universe could have come from nothing. Then he makes a plausibility argument that more symmetric states are unstable relative to symmetric ones (Frank Wilczek has made the same observation) and hence the void (as he calls it) being completely symmetric is unstable. The universe arises from a spontaneous Planck scale fluctuation that breaks the symmetry and produces a de Sitter (empty, exponentially expanding) universe. Then further symmetry breaking causes matter to condense out of the de Sitter space (as proposed by Guth) and produces the universe we see. In this model the initial low entropy comes about because the initial Planck fluctuation *has as much entropy as it can possibly have* - it's not low entropy for its size - but the expansion of the universe increases the *possible maximum entropy* much faster than the actual entropy increases. So we find the universe very far from equilibrium and structures like galaxies and ourselves can form. I don't think any part of this model is original with Vic, although maybe putting it altogether in one place is. Each part has been around awhile and has stood up to theoretical scrutiny - which is not to say it's true. It was on the basis of this model that I proposed that new universes will pop into existence as this universe thins out into an empty space = void again. As I understand it, this kind of event is suppressed in the presence of interaction with a mass producing field like the Higgs field - which is why the universe must thin out to essential emptiness before new universes can spontaneously expand. ... > I don't _know_ where the free energy or high initial order > of the universe came from. But I sure don't believe that > 10^80 or more particles in the Universe, following > 10^10^10^10^10^.....10 different ballistic > trajectories--not even counting Planck-scale effects, will > "every now and then fluctuate into this low entropy > configuration that is us." (my phrasing, not Price's) > But there are other interesting things in the book, more > so than in many other books on time and time asymmetry. As > I said, a good read. I'm about half way through H. D. Zeh's "The Physcial Basis of Time". It's fairly mathematical and pretty rough going for me, but it's very good. Brent Meeker The universe is not tuned to life. Life is tuned to the universe. --- Vic Stenger