On 6/12/2017 10:13 pm, Bruno Marchal wrote:
On 05 Dec 2017, at 01:48, Bruce Kellett wrote:
On 5/12/2017 3:39 am, Bruno Marchal wrote:
On 04 Dec 2017, at 05:17, Bruce Kellett wrote:
We already know in this case that from the 1p perspective, nothing
change, but the point is that the whole picture remains (described
by) a pure state.
So what? That is purely a theoretical construct, of no practical
importance, as you point out above. When you are considering coin
tosses or molecular chaos, the purely classical description is
completely adequate, whether you want to consider it FAPP or not.
Apparently not, given that in one case shaking the coin long enough
brings the existence of quasi othogonal realities with the coin on
each side, and this despite we cannot detect them in any sensible way.
I see, so it is all a matter of just believing that the other world in
which the coin lands the other way exists -- even though the mathematics
of quantum mechanics and the SWE say that in this case they do not?
So there is no quantum uncertainty involved in standard molecular
chaos, or in the random thermal motion of molecules in liquids or
gasses.
Then you introduce a collapse somewhere.
No collapse anywhere. If you think there is, then point it out!
Well, if the uncertainties of the coin position is amplified by the
quasi-classical chaotic motion due to the shaking, I don't see how the
resulting wave can make the other branches disappearing.
But the uncertainties are not amplified by the shaking. So there is no
other branch that needs to disappear in this case -- the coin toss can
be described purely classically.
My only doubt on this comes from the fact that due to the linearity,
the starting error does not grow up enough for the outcomes to be ever
different, but they don't need to grow up, in fact, if we have still
anything resembling to the "classical" indeterminacy.
What does that mean? Are you conceding the point that the toss is
essentially classical so that there is no splitting?
I am not sure I can make sense of you call "classical", here.
I think that the sense of "classical" is completely clear. It is what
emerges from the quantum when quantum uncertainties and
superpositions are no longer relevant (FAPP or not, the point is that
such things are not relevant).
But then we agree. I was not talking on anything FAPP, here, but on
the existence of inaccessible, but physically real alternate branch.
But there is no such branch, since everything is classical FAPP.
Do you not understand that one of the enduring mysteries of quantum
theory is the emergence of the classical world from the purely
quantum substrate? Decoherence goes a long way towards answering the
underlying problems, but unless something intervenes to exactly zero
the off-diagonal terms in the density matrix, the the understanding
that we have is still only FAPP. But the emphasis here is on
*Practical*, rabbiting on about the multiverse is not in the least
practical, here or anywhere else.
Then we were not discussing the same thing.
We are, in fact, because you appear not to understand the emergence of
the classical world from a quantum substrate. You keep getting them
confused.
Bruce
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