On Thu, Nov 20, 2014 at 10:43 AM, Bruno Marchal <[email protected]> wrote:
> > On 19 Nov 2014, at 19:43, Richard Ruquist wrote: > > In MWI it is rather difficult to reverse time and unsplit the universe. > > > The "mutiverse" is only the quantum configuration space taken seriously. > The SWE describe all quantum evolution as a rotation (a unitary > transformation) of a state vector in the Hilbert space. I can hardly > imagine something more reversible. > > > It's not Hermitian > > > It is unitary. > Well it lacks enough energy to go forward in time, going backwards cannot be that hard. > > Bruno > > > > > Richard > > On Wed, Nov 19, 2014 at 1:40 PM, John Clark <[email protected]> wrote: > >> On Tue, Nov 18, 2014 at 12:06 AM, Russell Standish <[email protected] >> > wrote: >> >> >> I'd say that by about 1850 when people started to have a understanding >>>> of what Entropy was physicists had all they needed to have known that the >>>> universe must have started out in a very very low entropy state, that is to >>>> say they could have predicted the Big Bang in the early to mid 19th >>>> century; and they wouldn't have needed to go near a telescope to do so. But >>>> unfortunately they didn't, it's one of the great failures of nerve or >>>> imagination in the history of science. >>>> >>> >>> > Boltzmann indeed predicted a low entropy state sometime in the past. >> >> >> Yes but Boltzmann thought that you could ignore boundary conditions and >> the second law of thermodynamics alone was enough to logically deduce that >> in the distant past the universe must have been in a very low entropy >> state, but in 1876 Loschmidt pointed out that Boltzman was wrong about >> that, he said you can't deduce a irreversible process, like the increase of >> entropy, from classical dynamics alone because if you just reverse the >> velocity of the particles in high entropy state B it will evolve back into >> the low entropy state A that produced it. And knowing that there are >> VASTLY more high entropy states than low entropy states and asked what >> state produced the stat we're in now you'd have to answer that it was >> almost certainly one of those enormously numerous high entropy states >> UNLESS you made a further assumption, the past hypothesis, the idea that >> the universe must have started out in a very very low entropy state. >> >> John K Clark >> >> >> >> >> >> -- >> 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 post to this group, send email to [email protected]. >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/d/optout. >> > > > -- > 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 post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > http://iridia.ulb.ac.be/~marchal/ > > > > -- > 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 post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > -- 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 post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
