On 04 Feb 2014, at 01:55, LizR wrote:
On 4 February 2014 13:32, Jesse Mazer <laserma...@gmail.com> wrote:
On Mon, Feb 3, 2014 at 6:29 PM, LizR <lizj...@gmail.com> wrote:
SR directly demonstrates block time via the relativity of
simultaneity. This can be tested experimentally.
The relativity of simultaneity is a claim about physics, not
metaphysics. Specifically, it's a claim that the laws of physics
work exactly the same in all inertial frames, which have different
definitions of simultaneity. If someone agrees that no frame's
definition of simultaneity is "preferred" in any physical sense, but
that one is "metaphysically preferred" in a way that is wholly
invisible to all possible experiments, this would not contradict SR
or the relativity of simultaneity as a physical principle.
OK, maybe what I should have said is that no one has come up with an
explanation for the ROS that doesn't include the concept of space-
time being a 4D manifold.
I'm not sure if that leaves us with a physical or metaphysical
problem (or maybe no problem at all!)
That said, if you subscribe to any form of Occam's razor or even a
criteria of "elegance" when it comes to choosing between different
metaphysical hypotheses, it seems a lot simpler to assume that there
is no metaphysically preferred definition of simultaneity, just as I
think many would agree the MWI is the simplest way of interpreting
the physical theory of QM. Adding extra "purely metaphysical"
entities to a theory, which don't correspond to anything that
appears in the mathematical formalism of the theory itself (which
would apply to things like a "true present" or to hidden variables
in QM), seems a bit like postulating that there are invisible
intangible elves sitting on each person's head which have no causal
effects on anything we can measure; sure it's logically possible,
but it seems like a very inelegant and arbitrary way for reality to
work.
The MWI is deterministic, however, and hence has hidden variables.
No. The Schroedinger equation which calculates wavefunction
evolution in QM is already fully deterministic, the MWI just
dispenses with the extra postulate of "wavefunction collapse" on
measurement, which is the only random element in QM. Determinism
only implies hidden variables if you assume each experiment has a
*unique* outcome, and that this outcome is generated in a
deterministic way by the initial conditions. If you assume that the
physical state at the end of an experiment is a quantum state that's
a superposition of many possible classical results, then this can be
calculated from a prior quantum state using just the standard
Schroedinger equation.
Well, yes, of course. The MWI is defined as QM with no collapse, and
the SWE is deterministic, therefore we have realism....don't we?
Careful: in this context realism often means "collapse" or "unicity of
outcome", like in Bell's paper. or even in EPR, where realism is
thought only with the implicit assumption of unique universe.
In other context, physical realism means that physics is independent
of us, like in "arithmetic realism" (arithmetic is independent of us).
Bruno
OK, I may have used the wrong terminology here. Maybe "hidden
variables" means something different from what I thought. I assumed
the MWI, being completely deterministic (a "block multiverse") had a
definite state at all times, and that therefore there is stuff that
we can't measure but is there, even so - which I thought meant
hidden variables. But I may have messed up.
(That said, time symmetry could also be termed hidden variables, I
think?)
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