“When we finally find the theory we’re all looking for, a theory that unifies quantum mechanics and relativity, it will involve retrocausality.”
– Avshalom Elitzur
One of the most ubiquitous occurrences in our universe, entanglement describes how measurements performed on one system influence other systems entangled with it, no matter how far apart they are. In fact, these instantaneous correlations can occur over such great distances that it is very difficult, if not impossible, to reconcile the phenomenon of entanglement with our common understanding of cause and effect. While time-forward causality may seem a valid notion at the level of human experience, it does not adequately describe quantum physical reality.
In 2004, Caslav Brukner, Samuel Taylor, Sancho Cheung and Vlatko Vedral conducted a gedankenexperiment showing that moments of time can become entangled as particles do — the inference being that a moment in time may be an observable in the same way that a location in space is an observable. A year earlier, physicists Thomas Rosenbaum, Sayantani Ghosh and colleagues proved that the power of entanglement — once thought to be confined to subatomic particles — can produce measurable effects on macroscopic objects. In the area of psi research, there are over three decades’ worth of data likewise suggesting that entanglement can be observed on a larger, “life-size” scale and may involve moments of time. Perhaps the most thought-provoking experiments in this area have involved retropsychokinesis (RPK), a so-called “paranormal” phenomenon wherein random events which occurred in the past are apparently influenced in the present by the directed consciousness (intention) of a human observer.
35 years ago, Helmut Schmidt pioneered studies on the effects of human intention on random event generators (REGs) — machines which generate a string of qubits that can be imagined as a stream of coins flipping in the air. Using REG data which were prerecorded and unobserved, Schmidt showed that his subjects were able to influence selected “heads or tails” events which had occurred up to six days earlier. More recently, Brenda Dunne and Robert Jahn (PEAR) conducted close to 87,000 similar (and statistically significant) REG/RPK experiments. Elmar Gruber’s retrocausation experiments (“PK Effects on Pre-Recorded Group Behaviour of Living Systems” European Journal of Parapsychology, 3, 1980, 167-75) showed that conscious intention can seemingly influence the past activity of both animals and humans. In one of the human trials, the effect size was 0.74, which is over twenty-three times greater than the effect size of most prescription drugs (0.032). These studies — and numerous others involving everything from steel marbles to human skin conductance and heart rate — have shown the apparent effect that conscious intent has on altering events which have already occurred… Or, at least, events which have “already occurred” from our commonly held perspective.
So how valid is that perspective? In consideration of the evidence, it would seem that our concept of cause and effect and our understanding of time are at odds with physical reality. The laws of quantum physics are largely time symmetric and invariant under time reversal, yet the temporal order established by scientific method is one of causality. Can we seriously and thoroughly investigate retrocausality — let alone advanced causality, super causality, mutual influence, simultaneity, etceteras — while working under the assumption of cause and effect?