On 6/20/2019 5:56 PM, Bruce Kellett wrote:
From: *Bruno Marchal* <[email protected] <mailto:[email protected]>>
I don’t think your refutation of step 3 has been understood by anyone.
If someone else want to argue that there is no indeterminacy in the
self duplication experience, he is welcome.
I think that some might challenge your interpretation of this
indeterminacy. This might not be exactly JC's objection to step 3,
but, to my mind, it is a serious difficulty in its own right.
This comes from a recent podcast of a conversation between Sean
Carroll and David Albert:
https://www.youtube.com/watch?v=AglOFx6eySE
This is a long discussion, and the relevant parts of Albert's
objections to MWI and self-locating uncertainty come towards the end.
The essence of Albert's point is that in the duplication case, you ask
"What is the probability that you will find yourself in Moscow (resp.
Washington)?" Putting aside objections to the non-specificity of the
pronoun 'you', I think your answer is that the probabilities are 0.5
for either city. Albert points out that to reach this conclusion, you
use some principle of indifference, or point to some symmetry between
the possible outcomes. Using this symmetry, you claim that the
probabilities must be equal, hence 0.5 for each city. Now, says
Albert, there is another solution that also respects all the
symmetries involved, viz., "I have not idea what the probability is."
You can then easily argue that this is a better solution. Because the
probability 0.5 is not written in the physics of the situation -- it
comes entirely from the classical principle of indifference. So Albert
asks how you are going to verify this probability experimentally --
as a large N limit, or something similar. So you repeat the
duplication N times on your participants. i.e. after the original
duplication you transport the subjects back to Helsinki and repeat the
duplication to Washington and Moscow. You end up with 2^N copies, each
of which has a record of the N cities they found themselves in after
each duplication. You now ask each of them their best estimate of the
probabilities for W or M on each duplication. Of course, you then get
all possible answers, from 1/N for M to 1/N for W. Since,
withprobaility one, the will always be someone who found himself in M
each time, and similarly, someone who found himself in W each time.
Plus all other 2^ possible combinations of results.
But most participants will say they were in Washington approximately N/2
times and Moscow N/2 times, in accordance with a binomial distribution.
Brent
So who has the correct estimate of the probability for W or M on each
duplication? Clearly, the guy who says "I have no idea" has a better
grasp of the situation than the guy who confidently claims, "The
probability for M is 0.5, and similarly for W." These probabilities
are not written in stone, and any attempt at an empirical
determination of the probability will necessarily yield all possible
results.
This is the core problem with understanding the origin of
probabilities in MWI -- self-locating uncertainty is not good enough
when all outcomes occur with probability one.
Bruce
--
You received this message because you are subscribed to the Google
Groups "Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to [email protected]
<mailto:[email protected]>.
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/a8aa900a-cdf2-8a49-c3b6-8dfbd5c36a2b%40optusnet.com.au
<https://groups.google.com/d/msgid/everything-list/a8aa900a-cdf2-8a49-c3b6-8dfbd5c36a2b%40optusnet.com.au?utm_medium=email&utm_source=footer>.
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/everything-list/f9f7a512-c236-1a36-e425-ded472ebd5c6%40verizon.net.
