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.
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
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