>> Philosophical claims
>> are of such fundamentality that they cannot come in conflict with
>> genuine empirical fact and genuine scientific theory (this is one of
>> the reasons why the indeterminism of the "Copenhagen
>> Interpretation" of Quantum Mechanics is not scientific; it is *not*
>> resolvable, even in principle, by empirical observation *except* by
>> being empirically *falsified*).
>DNAunion: The part about the Copenhagen Interpretation of quantum
>mechanics seems wrong or incomplete to me.
Chris
Though I recommend that readers read the rest of DNAunion's post for
context, I'm
putting my response here to get to the chase quickly.
As *always* in scientific experiments, there are assumptions involved in
this experiment.
Two alternate assumptions *seem* to be the only relevant ones in this case:
Einstein's
view that the relevant spins were determined at creation time, and Bohr's
that they were
determined at detection time.
But: What if neither is true? I can think of at least two alternate
assumptions. Or, what if
one of the other many assumptions involved was wrong in some (possibly
subtle) way?
Further, note that, even if we accept the results of the experiment, it
does not affect the
determinism of the result. If the spin of one particle is determined at
detection time, but
*not* indeterministically, and if there *is* "spooky (instantaneous) action
at a distance,"
all of the math and all of the results would *still* be the same.
The results of the experiment are fantastic, wonderful, exciting. But they
don't invalidate
determinism. My initial claim stands. It's not even logically possible for
empirical
evidence to invalidate indeterminism as such. It is only possible for it to
invalidate
*specific* claims of determinism (such as Einstein's, in this case), claims
in which a
specific causal relation is asserted. If that specific relationship does
not hold, we may be
able to show it empirically. For example, if I claimed that the way dice
landed was
determined completely by the positions of the planets (and gave a formula
or other
means of specifying the outcome of a throw of dice based on the positions
of the
planets), it would be easy to test whether this was true or not.
But, if we determined that it was not true, we would not be justified in
saying that the dice
behaved in a truly indeterministic way; there might be *other* causal
factors at work that
determine the way the dice land.
The Bell experiments show, maximally, that the determination of spin in one
particle
forces the spin state of the other, but it does not show us *how* that
initial determination
of spin occurs, other than that it (seems) to occur at the time of
detection, and (probably)
not at creation time. What if the spin of both particles is determined
*before* they are
"created"? What if, at detection time, there is a strictly deterministic
process by which
the spin of the particle is "set" at that time?
--Chris
>Einstein and 2 others devised a thought experiment aimed at
>showing the Copenhagen School's interpretation to be false/illogical
>(the experiment is known as ERP, for Einstein and the other 2, whose
>names I can't remember off the top of my head).
>In a pair creation event, spin is conserved. That is, if a pair of
>particles is created, with one of them having a "down spin", the other
>must have an "up spin" (think of it as conservation of electricl
>charge: if an electron is created, with a negative 1 charge, and
>positron is also created, with a positive charge, so both cancell each
>other out: that is, you can't create charge or spin). The determination
>of which particle would have which spin is not predictable - just the
>net result of the two, 0 spin, is.
>Einstein and the others said that the spins were determined AT THE
>TIME OF PARTICLE CREATION: one was CREATED with an up spin
>and one was CREATED with a down spin. The Copenhagen School
>held that the spins were in superposition: neither up nor down, and
>both up and down, UNTIL THE TIME OF DETECTION, at which point
>the wave function collapses and a definite value is actualized.
>The EPR thought experiment involved sending the two particles off
>in different directions immediately after the pair creation event, and
>passing one of them through a detector. At that instance, that
>particle's spin (up or down) would be known (determined/created,
>according to Copenhagen, but merely found out according to
>Einstein). To maintain conservation of spin, at the same, exact,
>instant the one detector found the spin of the one particle, the other
>particle's spin would have to be the opposite (either merely found to
>be the opposite, according to Einstein, or to actually be MADE to be
>the opposite, according to Copenhagen School).
>If the spin was created/determined only once the detection was
>made (i.e., was in a superposition before that time), then the
>influence on the other particle's spin would be INSTANTANEOUS
>regardless of the separating distance - that is, faster than the speed
>of light. Einstein ridiculed such a notion as "spooky action at a
>distance", thus "disproving" the Copenhagen interpretation.
>However, experiments known as Bell experiments have since been
>devised that can settle the matter EMPIRICALLY. Mathematical
>proofs were generated showing that there is a measurable
>difference between the two possibilities (that the spin is determined
>at the time of pair creation, or only later at the time of first
>detection).
>Subsequent runnings of the experiments, including refinements,
>have shown that Einstein and his colleagues were wrong, AND THAT
>THE COPENHAGEN SCHOOL'S INTERPRETATION WAS CORRECT - the
>two particles' spins are actually indeterminate (in superpositions)
>until the first one is actually detected, and then, instantaneously,
>regardless of distance, the other particle's spin is determined/set
>(having to be the opposite spin of the first).
>
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