String theory and the multiverse...the answer to Existence.

[WereKitten]

Soleron said:

WereKitten said:

Soleron said:

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Parallel universes are one valid interpretation of QM, yes. But as we cannot travel to them it's not worth thinking about them.
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In Everett's original work on relative states in QM there's nothing like the "bifurcation of world stories" as often popularized. The so called many worlds interpretation (MWI) in his original proposal is actually "just" a numerically frightening decoherence of the superposed eigenstates when entangled with macroscopic observers.

As such -at least in principle- Everett's interpretation of QM can be testable: if we ever managed to create a small, insulated, simple process of quantum measurement that we can fully reverse, then we should observe "decollapsing" of the wave packets. Or in MWI-speak: we should be able to see the "alternative worlds" originated from that single measurement interfere again in a controlled way. How that would work in practice e.g. how do you keep track of the results is not clear to me :)

To the OP: google for Tegmark's multiverse and look at his type IV multiverse idea if you want an even wilder ride :)

Of course. I just didn't want to go into eigenfunction stuff. Real scientific 'teleportation' and 'time travel' and 'wormholes' also function nothing like the popular science version.

Wouldn't that test give the same answers under Copenhagen?

Under Copenhagen there's no such thing as a reversible quantum measurement process, as the collapse projection is an actual physical phenomenon... no particular explanation, it's just postulated.

According to Everett, the collapse happens only relatively to the component of the observer entangled with the measured quantity, but basically the whole wave function is causally preserved. It's in principle possible to reverse the whole measurement including the observer.

Now the trick is: how much of the macroscopic apparatus do I have to reverse, and how can I keep my notes/memories of the results from being also reversed and thus deleted :) But I guess there could be weird ways the theoreticians have thought to accomplish that, maybe with a mechanism similar to Elitzur-Veidman's.

AFAIK there's no experiment planned to test this.. but there are experiments of nano-optics planned to test the collapse rate of superpositions of macroscopic mirrors, so we might be moving towards the needed finesse.