On 28 May 2017, at 14:23, Pierz wrote:
On Sunday, May 28, 2017 at 10:28:52 AM UTC+10, Russell Standish wrote:
On Thu, May 25, 2017 at 06:30:07PM -0700, Pierz wrote:
> Recently I've been studying a lot of history, and I've often
thought about
> how, according to special relativity, you can translate time into
space and
> vice versa, and therefore how from a different perspective we can
think of
> the past as distant in space rather than time: my childhood being
40 light
> years away, rather than 40 years for instance. I can visualise my
own body
> as a sort of long, four dimensional tendril through spacetime, of
which I
> only ever see a three-dimensional cross-section. This is the block
universe
> idea of course. What occurred to me recently was that the past, in
any
> physical theory I know of, is "locked down". There is only a
single history
> consistent with the present (ignoring the microscopic ambiguities of
> quantum interference effects), but the present is consistent with
multiple
> futures.
This assumption is wrong. There are many histories (pasts) consistent
with our present. If we don't know some fact about the past (eg
T. Rex's colour), then pasts with different colours of T.Rexes are all
compatible with our present. Only when we make a measurement that
distinguishes between different facts about the past, do we eliminate
some of those pasts from the compatibility list.
I think there's a confusion there between human ignorance and
physical ambiguity - the same confusion expressed in the
Schrödinger's Cat thought experiment. The resolution of that paradox
lies in decoherence. The fact of the cat's death or survival spreads
into the environment in a myriad of ways, whether or not we are
measuring them: the cat's cooling after death, the shift of its
weight as it falls and so on. At that point it is not in a
superposition any more.
With respect to us (in our local branches). Decoherence jworks fine
with the the many-worlds, but becomes a "magical explanation" without.
OK?
We are merely ignorant of its state. I would argue the same applies
to the colour of T. Rex. The past is not in a superposition of
possible values, but we are ignorant of those values.
For all practical purpose. But there are temporal form of Bell's
inequality violation which suggest that in principle (tacking track of
all the particles the T-Rex interacted with (!)) we could make
measurement showing interference of "different T-rex".
Now I think it is interesting to contemplate the possibility that
more than one macroscopic history (one with green and one with red
T. Rexes) might lead to the same present,
Of course, we need that, indeed.
but I think it extremely unlikely - that would constitute a
macroscopic quantum interference effect.
But without collapse, the "unlikely" is only practical, making
different past capable to interfere, or not. They don't need to
interfere for existing. It is only to detect them. If you arise enough
of your memory, you can "bactrack" up to T-rex, in principle (add the
grain of salt).
I suspect only one possible colour is consistent with the present,
even though it looks superficially like any colour is possible.
OK.
Bruno
There are, however, arrows of time - past and future are asymmetric,
the future is more uncertain than the past. But I don't see how you
can leverage that into support for the MWI.
--
----------------------------------------------------------------------------
Dr Russell Standish Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Senior Research Fellow hpc...@hpcoders.com.au
Economics, Kingston University http://www.hpcoders.com.au
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