Re: Macroscopic Emergence in MWI worlds

On 19 August 2013 21:57, Gary Oberbrunner <[email protected]> wrote:
> On Mon, Aug 19, 2013 at 3:53 PM, hibbsa <hibbsa-/[email protected]> wrote:
>>
>>
>> --- In [email protected], David Deutsch <david.deutsch@...>
>> wrote:
>> > On 19 Aug 2013, at 16:55, hibbsa <hibbsa@...> wrote:
>> >
>> > > So the problem is, MWI has basically has no macroscopic influence.
>> >
>> > Compared with what?
>>
>> compared to most all major scientific theories I should think. Even QM
>> minus mwi is hugely influential since it is probably behind a large amount
>> of the emergence that creates macroscopic reality.
>>
>
> Isn't "QM minus MWI" = Copenhagen?  In other words by "subtracting" MWI,
> you're really adding in the collapse postulate, since MWI is just QM
> without collapse.
>
> Are you really just saying that MWI is untestable?  I.e. that it doesn't
> make an refutable predictions?  That's a valid criticism.  I think IF we
> can build a large-scale quantum computer, such that it can do more than a
> theoretical perfectly efficient computer occupying the same spacetime, that
> would be a refutation of Copenhagen, since all that computation has to be
> done somewhere.

The CI makes no predictions. The CI makes ad hoc modifications of QM
and the precise details of what predictions QM will make depend on the
precise details of the modifications. But there is no explanation of
those precise details because if such an explanation existed the
theory wouldn't be ad hoc. So the CI makes no predictions.

For example, if the wave function collapses the precise of details of
where and how that happens will affect the results of experiments. But
the problem of why we can't see other versions of objects around us
has been solved by decoherence, so there is no need for the collapse
and no explanation of where and how it happens.

As a result, the CI can't be used to explain anything about emergence.
The other "interpretations" of QM have similar problems.

You are laying the blame for the untestability of other
interpretations on the MWI. This is analogous to saying that modern
cosmology is untestable when compared to creationism and this is a
fault in evolution. The truth is that creationism makes no
predictions: God could have made the universe 6000 years ago (or five
minutes ago, or two seconds ago, or he could make and destroy the
universe every time the number of seconds since the Big Bang is a
prime number, or...) and made it look like it is billions of years
old. That's not a fault in modern cosmology.

Alan