On 9/12/2017 11:49 am, smitra wrote:
On 09-12-2017 00:03, Bruce Kellett wrote:
On 9/12/2017 4:21 am, Bruno Marchal wrote:
On 08 Dec 2017, at 00:22, Bruce Kellett wrote:
On 8/12/2017 3:31 am, Bruno Marchal wrote:
On 06 Dec 2017, at 12:19, Bruce Kellett wrote:
But as I pointed out, thermal motion gives momenta of magnitudes
such that the quantum uncertainties are negligible compared to
the thermal randomness. And thermal motions are not coherent.
You seem to work in Bohr QM, with some dualism between the quantum
reality and the classical reality.
Not at all. The (semi-)classical world emerges from the quantum
substrate; if you cannot give an account of this, then you have
failed to explain our everyday experience. And explaining that
experience is the purpose of physics.
No problem with this, except for your usual skepticism of Everett's
program (say).
Skepticism is the scientific stance.....
You are right that this does not change anything FAPP, but our
discussion is not about practical applications, but metaphysics.
No, we were talking about tossing a coin, we were not talking about
metaphysics. Your metaphysics has served merely to confuse you to
the extent that you do not understand even the simplest physics.
That is ad hominem remark which I take as absence of argument.
You don't take kindly to criticism, do you Bruno?
All I said is that without collapse, shaking a box with some coin
long enough would lead to the superposition of the two coin state.
You seem to be the one confusing the local decoherence with some
collapse. The Heisenberg uncertainties are great enough to amplify
slight change of the move of the coin when bouncing on the wall.
That is simply assertion on your part, without a shred of argument or
justification. When one looks at the arguments, such as that put
forward by Albrecht and David (referred to by smitra), one finds that
the emperor has no clothes!
Similarly, a shroedinger car, once alive + dead, will never become a
pure alive, or dead cat. It will only seems so for anyone looking at
the cat, in the {alive, dead} base/apparatus. Superposition never
disappear, and a coin moree or less with a precise position, is
always a superposition of a coin with more or less precise momenta.
The relation is given by the Fourier transforms, which gives the
relative accessible states/worlds.
I pointed out that for a macroscopic object such as a coin, the
uncertainty relations give uncertainties in positions and/or momentum
far below any level of possible detection. And I gave an argument with
an actual calculation -- not just an assertion. Uncertainties in the
constituents of the object are uncorrelated, random, and cancel out.
So although the superposition originating from the big bang is intact
from the bird's point of view, it is so completely irrelevant for
everyday purposes that it is an insult to even refer to the
classicality of the world as FAPP -- it is complete. Relying on the
charge of "FAPP" as a justification for your assertions is nonsense.
It's not irrelevant if you don't have the information that locates you
in a sector where the uncertainties are indeed small enough. You have
to start with the complete state in the bird's view, and then consider
the sector where you have some definite information and then project
onto that subspace. If you do that, then your coins are not at all in
a precisely enough classical state but rather in superpositions
(entangled with the environment) that lead to wildly different
outcomes of coin tosses.
E.g. in the bird's view there exists exact copies of me that live on
planets that are not the same, some will have a radius of a few
millimeter larger than others. Here exact copy means exactly the same
conscious experience, which is then due to exactly the same
computational state of the brain described by some bitstring that's
exactly the same.
So, from totally different decoherent branches of the wavefunction one
can factor out some bitstring describing a conscious experience, the
reduced state of the rest of the universe in that sector is then a
superposition of a many different effectively classical states.
If this were not true then each single conscious experience would
contain in it information about such things as the exact number of
atoms in the Earth, Sun etc. etc.
I prefer to live in the real world, so I would rather not indulge your
fantasies.
Bruce
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