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.
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.
Saibal
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