On 12/10/2017 4:06 AM, smitra wrote:
On 09-12-2017 21:12, Brent Meeker wrote:
On 12/9/2017 2:36 AM, smitra wrote:
Yes, it's a different argument but it's also generically correct.
But I do think for the discussions in this list it doesn't matter
all that much whether an initial single branch will diverge into
multiple branches due to effectively classical dynamics.
Branching due to effectively classical dynamics is a contradiction in
terms. If it's effectively classical it can't branch.
Counterexample: A perfectly balanced pencil on its one atom wide tip.
Air turbulence will dominate which way it falls.
A variant of this involving longer time scales is a rectangular block
that's standing on the floor. Due to quantum tunneling it will
eventually tip over. The time scale depends on the width and height.
Suppose that we keep the height at 10 cm, but make the width very
small but still much larger than the size of an atom, such that the
block will fall on time scales of the order of 10^18 years.
If we cover the surface of a Mars-sized planet with such blocks
placed one centimeter apart, then we need about 1.4 10^18 blocks. If
one block falls, then it will trigger the next block to fall and
eventually all the blocks will fall. So, the blocks will start to fall
within a time scale of just a year, and we can observe this from a
satellite orbiting Mars.
So, even though everything looks like in the classical domain FAPP,
the time scale of 10^18 years on which quantum tunneling occurs looks
like infinity FAPP, you'll still have a splitting in the MWI view of
how the blocks will fall within just a year.
Objections like that thermal fluctuations dominate quantum
fluctuations can be easily address by imagining cooling down the
entire planet to sufficiently low temperatures. Compared to the
falling pencil, this example is a more robust against such
objections, e.g. a single photon colliding with the pencil would
already cause it to tip over, but it won't cause a block to tip over.
But your wrote "effectively classical dynamics". Your examples are
applying quantum dynamics.
Brent
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