[extropy-chat] Is Many Worlds testable?

[scerir]

>> But I do not understand why the document cannot
>> tell the 'welcher weg'.

John writes:
> If the document says which slit the electrons went through there is no
> point
> to the experiment because everyone agrees what will happen, no
> interference
> bands. If you don't include that information and the conventional
> interpretation is correct then a conscious mind has collapsed the wave
> function and it will remain collapsed even if the mind has forgotten about
> it, so you will still see no interference bands.  But if MWI is right then
> the information on which electron went through which slot no longer
> exists,
> so the universe where it went through slot A is identical to the one where
> it went through slot b and so will merge. So now we have a universe with
> indications it went through both slots hence interference bands on that
> precious all important photographic plate.

Ok. I think I understand more now. So the document is relevant
here _only_ because it reminds us that the quantum mind did know
the 'which way' of every single particle. Since this information
has been erased from the quantum mind (before the particle hits
the plate) the orthodox and the MW interpretations give different
outcomes.

One could say that the erasure does not delete
the information, and that this information is now in the
environment, and that another quantum mind could get it,
but this is another topic.

One could even ask, according to the orthodox interpretation,
if the quantum mind really collapsed itself the wave function.
Since its memory has been erased immediately before the particle
reached the plate, and the document is silent, one could even
think (Wigner's friend) that the eventual collapse or the
eventual interference is only due to the final observer of the
plate, depending on _his_ knowledge of the 'which way'.

>> I've got the impression that Deutsch thinks that
>> consciousness causes the collapse.

> Not true, according to Many Worlds consciousness
> has nothing to do with it.

Yes yes. I was only saying that Deutsch thinks that, according
to the orthodox interpretation, the collapse is due to the
consciousness of the observer.

> In fact in Many Worlds the wave function never collapses at all, it never
> falls into just one thing, instead all possibilities are realized. The
> Many
> World people take the mathematics seriously and the mathematics say
> nothing about a function collapsing, that was just thrown in by the
> Copenhagen people because they just assumed it did. Many Worlds is
> cheap on assumptions but expensive in universes. Another advantage is
> that unlike Copenhagen it doesn't have to explain exactly what an
> observation is because observation has nothing to do with it either.

Yes, but there is a huge difference. According to MWI
the wavefunction is something real. According to
the orthodox interpretation it is not real/physical,
and the collapse isn't real/physical either, it is just
a reduction of a probability packet.