[ExI] Many Worlds

[Rafal Smigrodzki]

On Jan 8, 2008 9:00 PM, Ian Goddard <iamgoddard at yahoo.com> wrote:

>
>
>  How does MWI explain Wheeler's delayed-choice
> experiment? It's importantly unique:
>
>    "Where the classic [ double slit ] experiment
>    demonstrates that physicists' observations
>    determine the behavior of a photon in the
>    present, Wheeler's version shows that our
>    observations in the present can affect how
>    a photon behaved in the past." [*]
>
> It's important to understand that experiment, as that
> difference makes a big difference. The description of
> it starts toward the bottom of page 1 here:
>
> [*] http://discovermagazine.com/2002/jun/featuniverse
>
> In 1984 Wheeler's delayed-choice thought experiment
> was confirmed at the University of Maryland. It was
> confirmed again and published last February, '07:
>
> http://www.sciencemag.org/cgi/content/abstract/315/5814/966
>
### Is this a complex issue? I thought that the MWI answer is pretty
simple - we do not change a particle (or its past or its future) by
looking at it, we merely determine in which branch of the universe we
are with respect to the quantum event that generated the particle and
any other particles entangled with it. Since entanglement assumes
correlations between states of interacting particles (e.g. spins of
electrons), observation of one particle gives us information about the
entangled particles present in our branch, and this information of
valid ever since the event and until the next event, for example our
measurement of states of these particles. It doesn't matter how much
later after the event do we perform out measurement, as long as no
additional quantum events occurred in the meantime (which could erase
the entanglement).

So what is the problem?

Rafal