Retroactive phenomena seem impossible in the physical world. But within theoretical physics there is the Wheeler’s delayed choice experiment, a thought experiment in quantum physics proposed by John Archibald Wheeler in 1978. The results Wheeler predicted have since been confirmed by actual experiment.
Wheeler’s experiment is a variation on the famous double-slit experiment. In Wheeler’s version, the method of detection used in the experiment can be changed after a photon passes the double slit, so as to delay the choice of whether to detect the path of the particle, or detect its interference with itself. Since the measurement itself seems to determine how the particle passes through the double slits – and thus its state as a wave or particle – Wheeler’s experiment has been useful in trying to understand certain strange properties of quantum particles. Several implementations of the experiment from 1984-2007 showed that the act of observation ultimately determines whether the photon will behave as a particle or wave, verifying the unintuitive results of the thought experiment.
Introduction
Wheeler’s experiment consisted of a standard double-slit experiment, except that the detector screen could be removed at the last moment, thereby directing light into two more remote telescopes, each one focused on one of the slits. This allowed a “delayed choice” of the observer, i.e. a choice made after the presumed photon would have cleared the midstream barrier containing two parallel slits. The two telescopes, behind the (removed) screen could presumably “see” a flash of light from one of the slits, and would detect which path the photon travelled.
Wheeler’s astronomical experiment
In a response to the argument that at short distances interactions at the screen with slits in it might be compromised by “knowledge” of events that occur at the location of the detector screen, Wheeler is reported to have come up with a more elaborate thought experiment. Wheeler suggests that one may imagine a more extraordinary scenario wherein the scale of the experiment is magnified to astronomical dimensions: a photon has originated from a star or even a distant galaxy, and its path is bent by an intervening galaxy, black hole, or other massive object, so that it could arrive at a detector on earth by either of two different paths.
First experiment
The first experimental realization of a delayed-choice experiment was carried out by Carroll Alley, Oleg Jakubowicz, and William Wickes in 1984 at the University of Maryland, cited by John Wheeler in his autobiography. Wheeler gave a seminar on the delayed-choice idea at the U of M in 1979 that inspired Alley and Wickes, who knew Wheeler well from their days as students and faculty at Princeton University, to work with Jacubowicz to translate the gedanken-experiment (thought experiment) into a laboratory test. The experiment confirmed the quantum mechanical predictions for a photon’s behavior in an interferometer that is randomly reconfigured or not after the photon passes through the initial beam-splitter.
Most recent experiment
In 2007, the first “clean” experimental test of Wheeler’s ideas was performed in France by the team of Alain Aspect, Philippe Grangier, Jean-François Roch et al.
Additional experiments
In 2000, Yoon-Ho Kim, et al., reported success in their delayed choice quantum eraser experiment, a variation that combines Wheeler’s delayed choice experiment with a quantum eraser experiment, so that the choice to observe the photon or not is done after it hits the detector.
Future experiments
Researchers with access to radio telescopes originally designed for SETI research have pointed to the possibility, and have explicated the practical difficulties, of conducting the Wheeler experiment with actual stellar objects. (Wikipedia)
References:
- Wheeler, J.A. and Zurek, W.H. ;
- Wheeler’s “delayed choice”, in Quantum Theory and Measurement, edited by J.A. Wheeler and W.H. Zurek, Princeton Univ. Press (1983).
- E.g., V. Jacques, et al., “Experimental realization of Wheeler’s gedankenexperiment,” Science 315 966 (2007), e-print at https://www.arxiv.org/abs/quant-ph/0610241 ; A.G. Zajonc et al., Nature, 353, 507 (1991); P.G. Kwiat et al., Phys. Rev. A 49, 61 (1994); T.J. Herzog et al., Phys. Rev. Lett., 75, 3034 (1995); T.B. Pittman et al., Phys. Rev. Lett., 77, 1917 (1996). The Jacques experiment is described in Physics World, “Photons denied a glimpse at their observer” (Feb. 15, 2007),
PK Effect on Pre-Recorded Targets by physicist Helmut Schmidt
From: https://www.mind-energy.net/archives/218-A-Brief-Introduction-to-Retro-PK.html
A Brief Introduction to Retro-PK
An interesting study was published in the latest issue of the Journal of Parapsychology that reports a possible lunar modulation effect on retroactive psychokinesis effects. Before I attempt to describe the results of that study in a post, I thought I would provide a little background on retroactive psychokinesis for those in this group unfamiliar with the concept so that it a bit more clear as to what I am talking about in the post:
Precognition is often considered to be most perplexing form of ESP because it appears to be retrocausal; that is, it seems to involve a “backwards acting in time” process in which an effect appears to precede it cause, counter to our usual assumptions that cause leads to effect. It turns out that psychokinesis (PK, or “mind over matter”) occurring on the microscopic (i.e., subatomic) scale also appears to be capable of producing a “backwards acting in time” effect of its own, and this effect is called retroactive psychokinesis, or “retro-PK,” for short.
One of the first to report statistical evidence for retro-PK effects was physicist Helmut Schmidt (1976), then of the Mind Science Foundation in Texas, who was also the one to introduce the random number generator (RNG) to parapsychology as a useful apparatus for testing microscopic PK. In a regular PK test conducted in real-time, a subject attempts to mentally influence the electronic “coin-flips” of a binary RNG as the RNG is producing them. What Dr. Schmidt did differently in his study is that he had the RNG produce the “coin-flips” before the subject even attempts to influence them (how much time before ranged from hours to even days), recording the results on magnetic tape without anyone looking at what they were. Later on, during the actual test, Dr. Schmidt would play back the tape with the recorded RNG data to the subject, at which time the subject would try to influence them. But wait a minute…if the RNG data are already recorded on tape, and are thus already assumed to be “set in stone,” how can the subject possibly influence them by PK? This is where the “backwards acting in time” assumption comes in. Since the RNG data are already recorded, it would seem that in order to influence the data by PK, the subject would have to direct his or her PK influence backwards in time to the moment that the data were being recorded.
As impossible as it may sound, all three of Dr. Schmidt’s (1976) initial experiments did indeed produce results supportive of an ostensibly backwards-acting PK effect, with the results having statistical odds ranging from twenty to one, to nearly a thousand to one, against chance occurrence. When he then compared these retro-PK results with regular PK results, he found little difference between them, suggesting that both worked nearly the same. Nearly two decades later, Dr. Schmidt (1993) had repeated these experiments under the close, watchful eyes of five outside witnesses (who were psychologists, physicists, or other parapsychologists), producing a combined retro-PK effect that had odds of about 8,000 to 1 of not being due to chance alone.
Since Dr. Schmidt reported his first retro-PK study in 1976, many other parapsychologists have attempted to reproduce his work by conducting retro-PK studies of their own, and by the time that Dr. Schmidt had reported the second study in 1993, 16 other studies by eight different researchers had also been reported. Dr. Dick Bierman (1998) of the University of Amsterdam carried out a meta-analysis of all of the retro-PK studies conducted by Schmidt and others between 1975 and 1993 to see how robust the effect really was, finding that together they produced evidence for a positive retro-PK effect that had statistical odds of around 18 million to 1 against chance.
Stimulated by these retro-PK results, Matthew Watkins and John Walker founded the Retro Psycho Kinesis Project, a long-term, Internet-based retro-PK experiment that is hosted on Walker’s Fourmilab website (https://www.fourmilab.ch/rpkp/). Since 1996, the project has been running individual retro-PK experiments using data recorded and saved beforehand from an RNG that uses radioactive decay as its source of randomness, and the results are updated in a daily summary. The project is ongoing, so it is possible for anyone on the Internet to participate in the retro-PK experiments (if you want to learn more or even participate in the experiments, go to the Web address above). It is the data collected as part of the Fourmilab Retro Psycho Kinesis Project since 1997 that was used in the study of a possible lunar modulation effect on retro-PK, which I will discuss in a post to follow.
References (in order of text citation):
- Schmidt, H. (1976). PK effect on pre-recorded targets. Journal of the American Society for Psychical Research 70(3), July. pp. 267 – 271.
- Schmidt, H. (1993). Observation of a psychokinetic effect under highly controlled conditions. Journal of Parapsychology 57(4), December. pp. 351 – 372.
- Bierman, D. J. (1998). Do psi phenomena suggest radical dualism? In S. R. Hameroff, A. W. Kazniak, & A. C. Scott (Eds.) Toward a Science of Consciousness II: The Second TUSCON Discussions and Debates (pp. 709 – 713). Cambridge, MA: MIT Press/Bradford.
Dick Bierman in Mind and Matter1-1 (nov. 2003)
DOES CONSCIOUSNESS COLLAPSE THE WAVEFUNCTION, by Dick J. Bierman University of Amsterdam
A conceptual replication of the Hall-experiment to test the ‘subjective reduction’ interpretation of the measurement problem in Quantum Physics is reported. Two improvements are introduced. First the delay between pre-observation and final observation of the same quantum event is increased from a few microseconds in the original experiment to 1 second in this replication. Second, rather than using the observers conscious response as the dependent variable, we use the early brain responses as measured by EEG. These early responses cover a period where the observer is not yet conscious of the quantum event. Results support the ‘subjectivereduction’ hypothesis because significant difference between the brain responses of the final observer are found dependent upon the pre-observer looking or not looking at the quantum event(exact binomial p <0.02). Alternative ‘normal’ explanations are discussed and rejected. It is concluded that the present results do justify further research along these lines.
The Problem
In 1977 Hallet al (Hallet al, 1977) reported an experiment that, according to their description, tested the most radical solution to the ‘measurement problem ’in quantum physics, namely the proposition that:…. The reduction of the wave packet is a physical event which occurs only when there is an interaction between the physical measuring apparatus and the psyche of some observer…..They defended their experiment writing:…although we concur that there is a genuine problem of the reduction of the wave packet, we do not intend in our paper to defend this opinion against those who maintain that it is a pseudo problem…..In spite of many attempts, like the relative state solution (Everett, 1957) and the introduction of non-linear terms in the Schrödinger equation (Ghiradi, 1986), the measurement problem seems still not be solved. This failure to clearly resolve the problem has left the physics community polarized with some contending the problem remains a fundamental shortcoming in the quantum formalism and others holding that there is no reduction of the wave packet at all(Bohm and Hiley, 1997; Griffith, 2002; Dieksand Vermaas, 1998). Costa de Beauregard (1976), Walker (1971, 1988, 2000) and later Stapp (1993) have argued, using arguments provided by a.o. von Neumann (1955) and Wigner (1967), that none of these solutions are acceptable and that subjective reduction is still a possible and even preferred alternative. We, like Halletal, do not wish to fight this or any other position with regard to the proper interpretation of the quantum formalism and the role of the measurement therein, but like Halland his collaborators, we would like to investigate this problem experimentally…… https://arxiv.org/ftp/physics/papers/0312/0312115.pdf
So there is the relevance of a parapsychological experiment for one of the most central problems in quantum physics.
According to the Whitehead, an English mathematician, theoretical physicist and philosopher, consciousness can work backwards in time.
According to John Wheeler a positron was perhaps an electron that moved backwards in time. (Richard Feynman in his Nobel Lecture).
