Evidence, citations, to sort through secondary source material
In situations wherein editors have strong disagreements, assertions and arguments generally are not decisive. In my experience, a good point of evidence frequently can be decisive. A subject as fundamental as this one is often commented on by people who are contenders, who stand as writers of relevant primary materials themselves, etc. I would like to develop a kind of chain of evidence and bring materials out from behind pay walls in the form of legally permissible short quotations whenever possible. P0M (talk) 13:47, 23 April 2025 (UTC)
Arrange by decades P0M (talk) 13:53, 23 April 2025 (UTC)
Video recording of talk by John Archibald Wheeler in which he makes reference to an experiment Carroll Alley made to validate his own work. So the time of recording (not yet known for sure) was later than 1963 when Alley came to the University of Maryland and 2008 when Wheeler died. Transcript follows:
One of the most remarkable features of nature is that a Quantum can pursue two different routes, through two different slits, come together and manifest itself as a single quantum. But nothing prevents one from saying that the quantum might be a photon, to speak of quantum of radiation, or it might be an electron, to speak of a particle. A quantum can go both routes or it can go a single route. And it's possible to choose which. After the particle has already made its travel, you choose - after the particle has decided whether it's going both routes or one route, and after it's got through, you yourself decide which it shall have done. You seem to intervene to change the past. But quantum theory says it can be done. And I had the pleasure to spell out some of the features of such an experimental arrangement. My University of Maryland colleague, Carroll Alley, made changes in the experiment, but without changing the principle, and carried it out. And it checked, so that we now know it is indeed true that one can decide, at the quantum level, whether an object shall go two routes to get to its final point or just one route. You can make the decision after it's already made the trip. That sounds like a contradiction, but it works.
The Quantum Challenge, Greenstein and Zagonc, 2005, p.45
Drawing showing
Earth ⁐ Quasar with a galaxy logo in the middle of the ⁐
Figure 2-10 Hypothetic Extreme Delayed Choice Experiment. Light from a gravitationally lensed quasar is passed through a delayed choice apparatus. In such a situation, we are tempted to say that billions of years of history can be altered by our choice of whether to insert or remove the second beam splitter. P0M (talk) 15:41, 23 April 2025 (UTC)
"A more severe example is depicted in The Quantum Challenge when Greenstein explains a hypothetical delayed-choice experiment using a quasar. Light from the gravitationally lensed quasar (see figure 2)[9] is passed through a delayed-choice experiment on earth. If we then put in a second beam-splitter, according to our previous results, billions of years of history could be altered.[2]
The accompanying illustration shows two paths from a quasar and going around a galaxy to be lensed to earth. P0M (talk) 18:33, 23 April 2025 (UTC)
Was O'Brien reading the first edition of The Quantum Challenge? He does not give page numbers, and the second edition only hints at a possible explanation. Unfortunately, I can't find my first edition. P0M (talk) 18:39, 23 April 2025 (UTC)
January 2010: P0M (talk) 01:19, 24 April 2025 (UTC)
February 2010: P0M (talk) 01:21, 24 April 2025 (UTC)
Demystifying the Delayed Choice Experiment, Bram Gaasbeek. Appendix A:Wheeler's thoughts. Supplies a re-drawing of one found in: [6] J.A. Wheeler, “Mathematical Foundations of Quan- tum Theory”, Academic Press (1978). The diagram provided there is rather sketchy. The one provided by Gaasbeek seems to be correct.
"The Tao of It and Bit," by Cristi Stoica, has an account that is inquiring and worth reading. However, it does not seem to be on a main line from or to Greenstein. I found this looking for sources earlier than Greenstein that might have brought attention to Wheeler's work.
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