On Thursday, August 13, 2015 at 3:24:08 AM UTC+10, John Clark wrote: > > On Mon, Aug 10, 2015 Pierz <[email protected] <javascript:>> wrote: > >> > >> Consider a set-up in which a photon is polarized in the z direction, so >> that we know that the particle will, with probability 1, pass through >> another polarizer also oriented in the z direction. However what of the >> situation where the second polarizer is oriented at 45 degrees to the first >> one? In that case, the probability is 0.5 that the photon will pass >> through. If it does, then obviously the probability is 1 that it will also >> pass through a third polarizer also oriented at the same angle. >> >> There is an interesting variant to that experiment that's easy to > perform. Set one polarizer at Z degrees and a second one at Z + 90 degrees > and there is a 0% chance that a photon will make it past both, but place a > third polarizer between them set at an intermediate angle of Z+45 degrees > and there is a 25% chance a photon will make it through all three > polarizers. Try it at home, it's really quite counterintuitive, adding a > third sheet of dark plastic actually makes things get brighter. > Yes, which reflects the fact that photons that pass through the intermediate polarizer have their wave functions collapsed, if you think in those terms. Their quantum state is reset in the 45 degree orientation.
> > >> So what is going on in the multiverse in this scenario? >> >> When a photon hits a polarizer sometimes the universe splits and > sometimes it does not, > Well, if you're going to talk about 'splitting' (Deutsch would say it differentiates), it always splits - into a branch in which the photon passes through and a branch in which it doesn't. > it depends on the angle of the polarizer and perhaps on something else > too. We know from experiment that Bell's inequality is violated so we know > for sure that in the Many Worlds Interpretation, just like every other > quantum interpretation, at least one of the following must be wrong: > > 1) Realism (things exist in a definite state even if they are not measured) > 2) Determinism > 3) Locality > > The Many Worlds Interpretation is realistic so if it's true then nothing > determines if the universe splits or not (it's random) > It's not random! The whole point of MWI is that it all happens, and the randomness arises from which branch "you" end up in (ah, the pronouns again!). I'm sure you understand that, so this statement confuses me. > and all we can do is assign probabilities based on the angle of the > polarizer (cos(Z)^2) . Or it is deterministic after all, something did > indeed cause it to split but the cause can not be local, your decision on > what angle to place the second polarizer somehow went back in time and > changed the photon before it even reached the first polarizer because the > future can effect the past. One thing is certain, whatever turns out to be > true it's weird. > >> > >> What is going on at the point of the photon's interaction with the >> polarizer in an MWI account? >> >> The universe may or may not split depending on angle Z of the polarizer > + X. X could be a random factor, and that's OK, there is no law of logic > that says every effect must have a cause. Or X could be a non-local cause. > But one thing X can not be is a local cause, we know that from experiment. > > And it's true, you can't determine probabilities by counting branches. > > Not by counting the number of eigenvalues, but by treating the probability amplitude associated with each eigenvalue as a measure of underlying worlds - well that was my understanding. > John K Clark > > > > > > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
