This paper discusses experimental findings from the Princeton Engineering Anomalies Research project supporting the existence of retrocausal information flow. Possible alternative explanations to retrocausation are examined for each experiment. In each case it can be shown that retrocausal information flow is either a parsimonious explanation, or the only currently available explanation, for the observational data. Gedankenexperiments are then examined to demonstrate that regardless of observational effect size, empirical phenomena of the type seen in these experiments cannot produce time paradoxes.The theoretical discussion pursuant to the experimental data covers some of the basic problems in the physical representation of time. Human perception of time incorporates a dichotomy: the past is known but cannot be changed, the future is presumed to be indeterminate and hence controllable but unknowable in advance. Physical formalisms have difficulty in representing this dichotomy, arriving in the most extreme case at the completely deterministic Einsteinian block universe view of spacetime. Strict physical determinism, however, currently seems implausible due to apparently essential indeterminism at the quantum scale.Retrocausal phenomena attack the dichotomy on empirical rather than theoretical grounds, since if past events can be causally influenced by future events either the past is malleable or the future is knowable. This approach allows a resolution of the past/future dichotomy by additional approaches other than strict determinism: the past may be indeterminate, or both past and future can contain a mixture of deterministic and indeterminate events.
This paper discusses experimental findings from the Princeton Engineering Anomalies Research project supporting the existence of retrocausal information flow. Possible alternative explanations to retrocausation are examined for each experiment. In each case it can be shown that retrocausal information flow is either a parsimonious explanation, or the only currently available explanation, for the observational data. Gedankenexperiments are then examined to demonstrate that regardless of observational effect size, empirical phenomena of the type seen in these experiments cannot produce time paradoxes.The theoretical discussion pursuant to the experimental data covers some of the basic problems in the physical representation of time. Human perception of time incorporates a dichotomy: the past is known but cannot be changed, the future is presumed to be indeterminate and hence controllable but unknowable in advance. Physical formalisms have difficulty in representing this dichotomy, arriving in the most extreme case at the completely deterministic Einsteinian block universe view of spacetime. Strict physical determinism, however, currently seems implausible due to apparently essential indeterminism at the quantum scale.Retrocausal phenomena attack the dichotomy on empirical rather than theoretical grounds, since if past events can be causally influenced by future events either the past is malleable or the future is knowable. This approach allows a resolution of the past/future dichotomy by additional approaches other than strict determinism: the past may be indeterminate, or both past and future can contain a mixture of deterministic and indeterminate events.
Retrocausal models of quantum mechanics add further weight to the conflict between causality and the possible existence of free will. We analyze a simple closed causal loop ensuing from the interaction between two systems with opposing thermodynamic time arrows, such that each system can forecast future events for the other. The loop is avoided by the fact that the choice to abort an event thus forecasted leads to the destruction of the forecaster's past. Physical law therefore enables prophecy of future events only as long as this prophecy is not revealed to a free agent who can otherwise render it false. This resolution is demonstrated on an earlier finding derived from the two-state vector formalism, where a weak measurement's outcome anticipates a future choice, yet this anticipation becomes apparent only after the choice has been actually made. To quantify this assertion, weak information is described in terms of Fisher information. We conclude that an already existing future does not exclude free will nor invoke causal paradoxes. On the quantum level, particles can be thought of as weakly interacting according to their past and future states, but causality remains intact as long as the future is masked by quantum indeterminism. Quanta 2016; 5: 53–60.
This paper presents a conceptual and analytical investigation into the limits of temporal access through the combined perspectives of causality, relativity, quantum mechanics, thermodynamics, and information theory. The work introduces the concept of the “Temporal Causality Barrier,” a selective and logically grounded framework that distinguishes between passive temporal observation and active temporal intervention. The paper argues that passive observation of the past is both physically permissible and continuously occurring through ordinary causal processes such as light propagation, memory, historical records, and astronomical observation. In contrast, active intervention into the past including backward information transfer, causal alteration of previous events, and closed causal loops is shown to generate logical contradictions and violations of causal consistency. The analysis critically examines major theoretical approaches related to time travel and retrocausality, including closed timelike curves, Novikov’s self-consistency principle, Deutsch’s quantum closed timelike curve model, and the two-state vector formalism in quantum mechanics. The paper argues that while some interpretations may mathematically describe retrocausal correlations, none currently provide an operational mechanism for backward information transmission without encountering paradoxes or information-theoretic inconsistencies. The framework further connects the causal structure of spacetime with the thermodynamic arrow of time, emphasizing the role of entropy, light cone geometry, and information propagation in preserving temporal coherence. The work also explores broader philosophical implications concerning the nature of time, consciousness, causality, and agency within a causally structured universe. Rather than proposing a new physical force or replacing existing theories, this paper provides a logically structured analysis of why temporal observation is compatible with known physics while active temporal intervention remains fundamentally constrained by both physical law and logical consistency.
Discussions on indeterminism in physics focus on the possibility of an open future, i.e. the possibility of having potential alternative future events, the realisation of one of which is not fully determined by the present state of affairs. Yet, can indeterminism affect also the past, making it open as well? We show that by upholding principles of finiteness of information one can entail such a possibility. We provide a toy model that shows how the past could be fundamentally indeterminate, while also explaining the intuitive (and observed) asymmetry between the past-which can be remembered, at least partially-and the future-which is impossible to fully predict.
The possibility of retrocausation has been considered to explain the occurrence of anomalous phenomena in which the ostensible effects are preceded by their causes. A scrutiny of both experimental methodology and the experimental data is called for. A review of experimental data reveals the existence of such effects to be a serious possibility. The experimental methodology entails some conceptual difficulties, these depending on the underlying assumptions about the effects. A major point is an ambiguity between anomalous acquisition of information and retrocausation in exerted influences.A unifying theory has been proposed, based upon the fundamental randomness of quantum mechanics. Quantum mechanical randomness may be regarded as a tenacious phenomenon, that apparently is only resolved by the human observer of the random variable in question. This has led to the “observational theory” of anomalous phenomena, which is based upon the assumption that the preference of a motivated observer is able to interact with the extant indefinite random variable that is being observed. This observational theory has led to a novel prediction, which has been corroborated in experiments. Moreover, different classes of anomalous phenomena can be explained by the same basic mechanism. This foregoes retroactive causation, but, instead, requires that macroscopic physical variables remain in a state of indefinite reality and thus remain influenceable by mental efforts until these are observed. More work is needed to discover the relevant psychological and neurophysiological variables involved in effective motivated observation. Besides these practicalities, the fundamentals still have some interesting loose ends.
In 2011, Daryl Bem published a report of nine parapsychological experiments showing evidence of retrocausal information transfer. Earlier in 2016, the team of Bem, Tressoldi, Rabeyron, and Duggan published the results of a meta-analysis containing 81 independent replications of the original Bem experiments (total of 90 with the originals).[1] This much larger database continues to show positive results of generally comparable effect size, thus demonstrating that the effects claimed by Bem can be replicated by independent researchers and greatly strengthening the case for empirically observed retrocausation. Earlier (2011) work by this author showed how a modification of one of Bem’s original experiments could be used to test the mechanism implicitly proposed by Echeverria, Klinkhammer, and Thorne to explain how retrocausal phenomena can exist without any risk of self-contradictory event sequences (time paradoxes). In light of the new publication and new evidence, the current work generalizes the previous analysis which was restricted to only one of Bem’s experimental genres (precognitive approach and avoidance). The current analysis shows how minor modifications can be made in Bem’s other experimental genres of retroactive priming, retroactive habituation, and retroactive facilitation of recall to test the EKT anti-paradox mechanism. If the EKT hypothesis is correct, the modified experiments, while continuing to show replicable retrocausal phenomena, will also show a characteristic pattern of distortion in the statistics of the random selections used to drive the experiments.
Certain quantum phenomena, including delayed-choice experiments, entanglement swapping,and post-selection effects, exhibit correlations that appear to imply retrocausality or backwardinfluence from future measurement to past events. This paper proposes a resolution that doesnot invoke backward time travel, modification of unitary dynamics, or exotic spacetime struc-tures. Instead, apparent retrocausal effects are shown to arise from a forward-only processtermed Probability Observation Shift, in which irreversible constraint formation selects amongpre-existing coherent histories. The observer’s effective history may change, but no physicalprocess propagates backward in time. This mechanism preserves causality, avoids paradox, andprovides a unified interpretation of several quantum “time-reversal” paradoxes.