On 11/22/2023 4:23 AM, John Clark wrote:
On Tue, Nov 21, 2023 at 7:45 PM Brent Meeker <meekerbr...@gmail.com>
wrote:
>> There is plenty of direct evidence that quantum weirdness
exists, even the father of the Copenhagen Interpretation Niels
Bohr admitted that "/*Anyone who is not shocked by Quantum
theory does not understand it*/". Something must be behind all
that strangeness and whatever it is it must be odd, very very
odd. Yes, many world's idea is ridiculous, but is it
ridiculous enough to be true? If it's not then something even
more ridiculous is. As for the Copenhagen interpretation, I
don't think it's ridiculous, I think it's incoherent, and if
you ask 10 adherents what it's saying you'll get 12 completely
different answers, but they all boil down to "/just give up,
don't even try to figure out what's going on/". But I think
one must try.
/> I think that's very unfair to Bohr. His basic observation was
that we do science in a classical world *of necessity*./
Bohr was a great scientist but I think he was a lousy philosopher.
Bohr thought there was a mystical interface between quantum events and
conscious awareness, some call it the "Heisenberg Cut", but neither
Bohr nor Heisenberg could explain the mechanism behind this mysterious
phenomenon nor could they say exactly, or even approximately, where
the hell the dividing line between the classical world and the quantum
world is. By contrast Many Worlds has no problem whatsoever explaining
the mechanism behind the Heisenberg cut or where the dividing line is
because the Heisenberg cut does not exist and there is no dividing
line, everything is quantum mechanical including the entire universe.
I think this is the reason the Many Worlds interpretation is more
popular among cosmologists than among scientists in general.
>///Only in a classical world can we make measurements and keep
records that we can agree on. /
But the Copenhagen adherents can't agreeeven among themselveswhat a
"measurement" is or what a "record" means, but Many Worlds people are
in agreement, all measurements are a change in a quantum state but a
quantum change is not necessarily a measurement.
> /when we study the microscopic world we must use quantum
mechanics, but our instruments must be classical. /
We can pretend our instruments are classical, in our everyday life we
can pretend that everything is classical, but we've known for nearly a
century that is just a useful lie we tell ourselves because reality is
not classical, it is quantum mechanical.
/> You can treat a baseball as a quantum system composed of
elementary particles; but your measurements on it must still give
classical values. /
As I said before, you can live your entire life by pretending that
classical physics is all there is and in fact billions of people have
had successful lives doing so, but that doesn't make it true. In
theory classical measurements can be exact,but quantum measurements
cannot be even in theory. If we wish to study the fundamental nature
of reality we're going to need to perform experiments with things when
they are in very exotic conditions that we will never encounter in
everyday life, and when we perform these difficult experiments we find
the things get weird, very very weird, and that demands an
explanation. And waving your hands and saying there is a Heisenberg
cut is not an explanation.
/> Since the development of decoherence theory this boundary can
be quantified in terms vanishing of cross-terms in a reduced
density matrix. /
Forget theory, every time the precision of ourquantum***EXPERIMENTS*
improves the lower limit of this mythical boundary between the
classical world and the quantum world gets larger, I think it's as
large as the entire universe.
>///What is left unexplained,*in MWI* as well as Copenhagen, is the
instantiation of a random result with probability proportional to
the diagonal elements of the reduced density matrix./
If the concept of "probability" is to make any sense and not be
paradoxical it must be a real number between 0 and 1, and all the
probabilities in a given situation must add up to exactly 1. Gleason's
theorem proved that given those restraints, probability can always be
expressed by the density matrix, that is to say the Born Rule. So the
real question is; Schrodinger's equation is completely deterministic
so why do we need probability at all? The Copenhagen people have a
range of answers to that question, some say Schrodinger's equation
needs to be modified by adding a random element, but they can't agree
on exactly what it should be, others say it is improper to even ask
that question, but they can't agree among themselves exactly why it is
improper. The Many Worlds people have a clear and simple explanation,
until you open the box and look you have insufficient information to
know for certain if you are in the branch of the Multiverse where
Schrodinger's cat is alive or the branch in which the poor cat is
dead. Before you open the box all you can do is play the odds, and
the Born Rule tells you the way to make the best guess possible.
You pretty much ignored everything I wrote and were exercised to refute
the idea of Heisenberg's cut, which neither Bohr or I endorsed. Do you
deny that science relies on definite recorded results and simply
postulating an evolving wave function does nothing without a theory of
how we see definite events? Many world has no clear explanation of how
many worlds there are and how they get weighted or divided or multiplied
to satisfy Gleason's theorem. I think they are no better than "the wave
function collapses". Decoherence theory at least gives us an idea of why
a measurement in the general sense produces an apparently classical world.
Brent
John K Clark See what's on my new list at Extropolis
<https://groups.google.com/g/extropolis>
bqp
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