On 1/8/2014 4:11 PM, LizR wrote:
On 9 January 2014 07:58, John Clark <[email protected] <mailto:[email protected]>>
wrote:
On Tue, Jan 7, 2014 at 2:59 PM, Jesse Mazer <[email protected]
<mailto:[email protected]>> wrote:
> Well, most physicists already agrees physics is time-symmetric
I think you would have enormous difficulty finding one single physicist on
the face
of the earth who says time is symmetrical.... well OK,... maybe a physicist
who just
hag a stroke. You could find many that think Quantum Mechanics states time
is
symmetrical, or almost symmetrical. So much the worse for Quantum
Mechanics.
The equations of Newtonian dynamics are time-symmetric, similarly for relativity (both
SR and GR - even gravitational collapse is reversible according to the equations) - and
quantum mechanics is, too. The only thing in the entirety f physics that isn't based on
time symmetric equations is thermodynamics, which most physicists agree is an emergent
phenomenon, due to a special initial arrangement of the components of the universe
coupled with the likelihood that they will come to occupy more probable states over time..
The second law of thermodynamics is based on the argument that a system in a low entropy
(i.e. improbable) state will head towards a high entropy (i.e. more probable) state
through the statistical result of random movements, because there are by definition far
more probable states than improbable ones. This assumes the dynamical interactions
involved are time-symmetric, since otherwise there would be no need for this argument -
the universe would head that way for some other reason, due to some built-in time
asymmetry. Since there is no such known time asymmetry, thermodynamics relies on a
statistical argument and an improbable initial state. This was all explained by
Boltzmann about 140 years ago.
Look up Schulman's "special state" theory of QM. He uses the time symmetry and a
requirement that there be no "grotesque" states (superposition of macroscopic systems) to
explain the appearance of randomness in QM.
Brent
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