On Fri, Oct 18, 2019 at 6:31 PM Bruce Kellett <[email protected]> wrote:
*> I see, Deutsch was testing the idea that it was consciousness that >>> collapsed the wave function. But, apart from a few flirtations with the >>> idea, none has ever taken that seriously. It is certainly not part of the >>> Copenhagen Interpretation.* [...] *given SR, there can be no signal >>> informing one observer of the other's results.* >>> >> >> I see.... no I take that back I don't see. You used a very odd word in >> the above that I don't understand at all, the word is "observer". >> > > *> And you dishonestly deleted all the intervening explanatory text.* > I must have inadvertently deleted that "intervening explanatory text" so well that now even I can no longer find it, and that's a pity as it could solve the greatest mystery of the age. Please repeat your explanation of exactly what a "observer" is, a explanation that is different from the one provided by Many Worlds as you don't like that one for some reason. > *> if you erase or not the welcher weg information 'before' the signal >>> photon hits the screen, then presumably some, presently unknown physics, >>> could send this information to the screen and influence the result there.* >>> >> >> So you admit it. If you continue to insist Many Worlds do not exist then >> to explain an experiment that has been performed many times you must >> postulate new physics and mess with Schrodinger's Equation. >> > > > Not at all. The results of the experiment are easily explained within > the structures of conventional quantum mechanics, whatever interpretation > one wishes to adopt. There is nothing mysterious here. > There is a lot of mystery here! In 2007 entangled photons were sent 89 miles between La Palma and Tenerife, the decision to erase or not to erase was made in less time than it took for light to travel those 89 miles and hit the detector: Quantum Spookiness Spans the Canary Islands <https://www.scientificamerican.com/article/entangled-photons-quantum-spookiness/> The last potential loophole, the freedom of choice loophole, was pretty much closed in April 2018. That loophole says that maybe your measurement settings that chose between erase and don't erase are not really random after all, there might be a deterministic process that makes the choice and misleads us: Quantum entanglement loophole quashed by quasar light <http://www.astronomy.com/news/2018/08/distant-quasars-confirm-quantum-entanglement> They state that: *"Arguably the most interesting assumption is that the choice of measurement settings is “free and random,” and independent of any physical process that could affect the measurement outcomes. As Bell himself noted, his inequality was derived under the assumption “that the settings of instruments are in some sense free variables, say at the whim of experimenters, or in any case not determined in the overlap of the backward light cones.”* So to close this loophole they didn't use a standard random number generator to make the choice to erase or not erase the information in the short amount of time it takes light to travel those 89 miles before (yes BEFORE) the photon hit their detector; instead they used the light from a distant quasar to make the decision, so if its a conspiracy to mislead us (as Superdeterminism says) it's a grand conspiracy indeed. They conclude: *"This experiment pushes back to at least 7.8 billion years the most recent time by which any local-realist influences could have exploited the “freedom-of-choice” loophole to engineer the observed Bell violation"* >> If you decide to erase or not to erase after the photon passes the slits >> but before it hits the photographic plate then to explain the results >> you've either got to embrace Superdeterminism, backward causality or Many >> Worlds. >> > > *> No, you have got it wrong here. No need for any of this. * That's it? That's all you've got to say? If you have a explanation for all the odd stuff coming from the 2 slit experiment that has been bedeviling scientists for a century, a explanation not involving Superdeterminism, backward causality or Many Worlds then please enlighten a poor mortal such as myself. > >> why the big delay between thought experiment and real experiment? >> Because although it's simple in concept it's very difficult to actually >> perform, you need super fast electronics and a very good random number >> generator to make the split second decision to erase or not to erase in the >> ultra short amount time between the photon passing the slit and it hitting >> the photographic plate. If you could take your time and wait until after it >> hit the plate Lewis could have not just talked about it but actually done >> the exparament in 1926 and he wouldn't have needed advanced electronics; >> steam powered, or even horse powered, machinery would have been good >> enough. >> > > *>The decision to erase or not to erase is made at a space-like separation > from the screen in the experiment * > Exactly! I guess you're conceding my point. If you take your time and wait until after the photon hits the screen there will be insufficient spacetime separation for the experiment to produce new meaningful results, so you've got to make the distance between the slit and the screen to be very large, or make the decision to erase or not erase very quickly, or both. *The decision to erase or not to erase must be made in less time than it takes for light to move between the slits and the photographic plate* to preclude the possibility that a unknown signal of some sort is moving between the slit and the plate influencing things. > > *> Delaying the choice until after the photons hit the screen achieves the > same end.* > I guess you're not conceding my point after all and would prefer to embrace logical inconsistency. > *> Why do you think it is called "delayed choice" after all?* > Because the choice to erase or not to erase is delayed until long after the photon has passed the slit, it could be made a billion years after it passed the slit, and the decision could be made one nanosecond before the photon hit the photographic plate, but it must be *before* or you will see nothing new or interesting. One might naively think that the photon either passed through one slit or two and whatever you do after it passed the slits can't change that fact, but it can! As long as the photon is still in transit if you erase the which way information you see a interference pattern and if you don't erase that information there is no interference pattern. And that is seriously weird and seriously interesting. If you wait to make the decision until after the picture is made the results are not weird at all and is in fact dull as dishwater because you'll learn nothing new that Thomas Young didn't discover in 1801 when he performed the 2 slit exparament for the very first time; when Young looked at his screen he also did not have any which way information and that's why he saw a interference pattern. >>you can't expect to learn anything if you look at the developed >> photograph and then decide whether to erase the which way information or >> not. If you decide to erase the information do you imagine you will see the >> photograph change before your eyes?? >> > > *> Yes, of course you do: you just select the subsets of photons that were > quantum-erased by passing the left polarizer (respectively, the right > polarizer) to see the interference patterns emerge from the apparent > no-interference blob.* > Ah Bruce.....in that case you are very obviously erasing the which way information BEFORE it hits the screen or photograph that you're looking at! >> If that's the way the exparament turns out and a interference pattern >> exists but Many Worlds does not exist then how do you explain the existence >> of a signed document testifying that somebody observed the photon going >> through one and only one slit and the he knew which one? Inquiring minds >> want to know. >> > > > *The signed document is irrelevant because it does not contain the > welcher weg information.* > The signed document doesn't say which slit but it doesn't need to because it DOES say the photon went through one and only one slit. So if Many Worlds, Superdeterminism and Backward Causality are all wrong and the photons only went through one slit then why on earth is there a interference pattern on that photographic plate? Inquiring minds want to know. > *> I really do think that you have to do a bit more work in order to > understand what is going on here.* > I'm not a expert on this so I may be shaky on some subtle point in this experiment, but some things are not subtle and at least I understand the big stuff; and there is nothing bigger than the FACT that the which way information is erased AFTER the photon passed the slits but BEFORE it hits the photographic plate and actually makes a picture. That's Delayed Choice 101, it's the very first thing you've got to understand to make any sense whatsoever about what's going on in this experiment! 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv0J%2BffkLetYD9duHXdDmBx-1iBUS3fdNEnvHtC2AUFJ6A%40mail.gmail.com.
