Replication Study of Causally Ambiguous Duration Sorting | Winthrop T. Williams

Introduction: The “arrow of time” is so fundamental to our present language and logic that we may think we can logically rule out retrocausation when in fact the lack of retrocausation was built into the axioms underlying that logic. In the absence of these presuppositions, the existence of retrocausation may be no more self-contradictory than the claim that retrocausation does not exist. (Kafatos & Nassikas, 2011).

Empirical results have demonstrated a seconds-to-minutes apparently retrocausal effect manifesting as a correlation between the number of photons measured in an optical system and the future duration of that same photon-detection process (Mossbridge, 2019, 2021). This study is an attempt to replicate this effect.

Methods: Hardware and software were developed independently from those of Mossbridge (2019, 2021), but were operated using the same protocol. Briefly, a light source and photon counter were turned on at the beginning of each run, 33 seconds of photon counts were gathered (in 3 11-second cumulative bins), then a quantum-seeded pseudorandom process was used to select the remaining amount of time photons would be counted. After that duration, the light source and photon counter were turned off. Differences in apparatus include photon detection by a single photon counting module (SPCM), pulse counting using a field programmable gate array, random number generation by discrete logic implementation of an 80-bit shift register pseudorandom number generator clocked by muon detections, a LabVIEW program operating the experiment and appending data to a file, and an RC circuit for ramping the detector voltage up and down which is optically isolated from the computer.

Results: Data have been collected from approximately 34000 trials during 1/2 year of continuous operation from July 27, 2020 to Feb 21, 2021 inclusive. Analysis is in progress.

Discussion: “Post Selection” experiments have demonstrated time symmetry in the evolution of quantum-mechanical systems and are congruent with the standard model of quantum physics (Aharonov et al., 2015). Those experiments support the possibility of apparent retrocausation and show a connection between the direction of causality (arrow of entropic time) and the boundary conditions of the system. Conceivably therefore, such a relationship might be turned around creating what one might call a “time telescope” whereby measurements of retrocausal effects allow us to observe boundary conditions that may be distant in time.


Aharonov, Y., Cohen, E., Waegell, M., & Elitzur, A. C. (2018) The weak reality that makes q1uantum phenomena more natural: Novel insights and experiments. Entropy (Basel, Switzerland), 20(11), 854.

Kafatos, M., & Nassikas A. A. (2011). Retro-causation, minimum contradictions and non-locality. AIP Conference Proceedings, 1408, 291. Published Online: 18 November 2011.

Mossbridge, J. (2019). The influence of future durations on past photon counts in an optical system. 2019 Annual Meeting of the APS Far West Section, 64(17).

Mossbridge, J. (2021). Long time-frame causally ambiguous behavior demonstrated in an optical system [In preparation for publication]. Retrieved from

Published on June 9, 2023