Both areas of physics above assume that time is solely linear, flowing from past to present to future. If A happens before B and B happens before C, then what happens at A can effect B and C, and what happens at B can effect C. But, what happens at C will never effect what happens at B and A, and what happens at B will never effect what happens at A. This is cause and effect as we normally view things. TSQM mixes things up a bit, but in very subtle ways. Standard quantum mechanics has a wave function (the mathematical object that encodes the above mentioned probabilistic outcomes) that propagates forward in time (from A to B to C). TSQM consists of two wave functions – one propagates forward in time to the present and the other propagates from the future to the present. In other words, the outcome from a measurement obtained in the present (say, at B) depends upon information from the past (what happened at A) and the future (what will happen at C). (I would like to stress this is a very subtle type of retrocausality that in no way violates our everyday notions of cause and effect. I will get a bit more into this below). Modern experiments seem to suggest that what happens at C, can indeed effect measurement at B. See the reference links provided below.
“Aharonov accepted that a particle’s past does not contain enough information to fully predict its fate, but he wondered, if the information is not in its past, where could it be? After all, something must regulate the particle’s behavior. His answer—which seems inspired and insane in equal measure—was that we cannot perceive the information that controls the particle’s present behavior because it does not yet exist.” (*)
“Nature is trying to tell us that there is a difference between two seemingly identical particles with different fates, but that difference can only be found in the future,” he says. If we’re willing to unshackle our minds from our preconceived view that time moves in only one direction, he argues, then it is entirely possible to set up a deterministic theory of quantum mechanics.” (*)
In fact, Aharonov decided to mix things up and instead of making a claim like, “God does not play dice”, he decided to ask a question. What advantage would there be for God to play dice? Is there something we are perhaps missing, that could make us realize there is a deeper reason why nature would at first appear probabilistic. As it turns out, TSQM suggests there is indeed a larger picture we are missing here.
Consider the following three principles:
(1) Genuine Free Will
(2) Cause and Effect
The first two we are well familiar with and, for the most, take for granted. The third is introduced by TSQM. At first glance, all three seem to be mutually exclusive to each other. Free will seems to be prohibited by classical and quantum theory, as discussed above. All your choices are determined, or effected by a preceding physical cause, meaning they can never be truly free (and QM alone didn’t offer much help here). Retrocausality seems to contradict both. How can one have retrocausality without violating our normal notions of cause and effect? And, if there is a “destiny” out there waiting for us (let alone reaching back in time to effect the present), how can we have free will, or choose our own destiny?
It turns out the “rolling of dice”, or the probabilistic nature of Quantum Mechanics, is exactly what one needs to allow those three principles to live together! To set Einstein straight, this is why God plays dice!
When taken in a larger context of a reality which allows a richer structure for spacetime, a seemingly bizarre and perhaps undesirable facet of reality suddenly becomes not only enlightening, but useful beyond our wildest imagination. Not only that, the probabilistic nature of the reality at the quantum scale seems to indirectly imply free will, even if at first glance it appears to be a stumbling block to it. In addition, for the three above-mentioned principles to exist harmoniously it would appear we need a richer view of time than our normal linear time, specifically one that allows for the type of retrocausal influence found within TSQM.
In a subtle fashion, Mother Nature protects free will choice from “destiny”, by making it so one can never be sure if what they observe in the present is really a wave function (i.e. “destiny”) propagating back in time or just error in the measurement process, which is a ramification of the type of measurement used within TSQM – weak measurements. No matter what way they have come at this problem, they cannot get around it. It is only by examining all the measurements (past-present-future) after the fact, that one is able to decipher what really happened. In this way, free choice in the present, as to what measurements one can take, are protected from these subtle retrocausal influences. Further, it has been shown that it is precisely the probabilistic nature of QM that is needed in order for (1) free will, (2) cause and effect, and (3) a subtle retrocausality, to all exist harmoniously.
As you may already know, I also explore parapsychology on this blog, so I can’t help but point out that this is the kind of direction physics needs to head in to accommodate a phenomenon like psi. One type of psi experiment shows that folks seem to react (on an unconscious level) to certain stimuli 1-10 seconds before the stimuli actually happens. This is screaming for a richer view of reality, like the one presented in TSQM, which does allow information from the future to leak into the past. TSQM doesn’t yet provide a mechanism for psi, but it does begin to open up a new window to reality that at least seems conducive to the existence of psi.