Stathis Papaioannou writes:
> Here is another way of explaining this situation. When there are multiple 
> parallel copies of you, you have no way of knowing which copy you are, 
> although you definitely are one of the copies during any given moment, with 
> no telepathic links with the others or anything like that. If a proportion 
> of the copies are painlessly killed, you notice nothing, because your 
> successor OM will be provided by one of the copies still going (after all, 
> this is what happens in the case of teleportation). Similarly, if the number 
> of copies increases, you notice nothing, because during any given moment you 
> are definitely only one of the copies, even if you don't know which one. 

> However, if your quantum coin flip causes 90% of the copies to have bad 
> experiences, you *will* notice something: given that it is impossible to 
> know which particular copy you are at any moment, or which you will be the 
> next moment, then there is a 90% chance that you will be one of those who 
> has the bad experience. Similarly, if you multiply the number of copies 
> tenfold, and give all the "new" copies bad experiences, then even though the 
> "old" copies are left alone, you will still have a 90% chance of a bad 
> experience, because it is impossible to know which copy will provide your 
> next OM.

I'm not sure I fully understand what you are saying, but it sounds like
you agree at least to some extent that "copies count".  The number of
copies, even running in perfect synchrony, will affect the measure of
what that observer experiences, or as you would say, his subjective
probability.

So let me go back to Bruno's thought experiment and see if I understand
you.  You will walk into a Star Trek transporter and be vaporized and
beamed to two places, Washington and Moscow, where you will have two
(independent) copies wake up.  Actually they are uploads and running on
computers, but that doesn't matter (we'll assume).  Bruno suggests that
you would have a 50-50 expectation of waking up in Washington or Moscow,
and I think you agree.

But suppose it turns out that the Moscow computer is a parallel
processor which, for safety, runs two copies of your program in perfect
synchrony, in case one crashes.  Two synchronized copies in Moscow,
one in Washington.

Would you say in this case that you have a 2/3 expectation of waking up
in Moscow?

And to put it more sharply, suppose instead that in Washington you will
have 10 copies waking up, all independent and going on and living their
lives (to the extent that uploads can do so), sharing only the memory
of the moment you walked into the transporter.  And in Moscow you will
have only one instance, but it will be run on a super-parallel computer
with 100 computing elements, all running that one copy in parallel and
synchronized.

So you have 10 independent copies in Washingon, and 100 copies that
are all kept in synchrony in Moscow.  What do you expect then?  A 90%
chance of waking up in Washington, because 9/10 of the versions of you
will be there?  Or a 90% chance of waking up in Moscow, because 9/10 of
the copies of you will be there?

I think, based on what you wrote above, you will expect Moscow, and that
"copies count" in this case.

If you agree that copies count when it comes to spatial location, I
wonder if you might reconsider whether they could count when it comes
to temporal location.  I still don't have a good understanding of this
situation either, it is counter-intuitive, but if you accept that the
number of copies, or as I would say, measure, does make a difference,
then it seems like it should apply to changes in time as well as space.

Hal Finney

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