Can the future affect the past? Lent 2023: Day 28

Retrocausality is a theoretical concept in physics positing that something can happen before it's been caused. The future, in other words, can influence the past. This idea, also known as backwards (or retroactive) causation, has been explored in some interpretations of quantum mechanics, such as the delayed choice quantum eraser experiment. 

[The double-slit experiment is well known. A photon passing through can be a wave or a particle until observed. Imagine, as John Archibald Wheeler did, this experiment conducted on a galactic scale, an observer on earth determining whether a photon from a distant star is a wave or a particle. The outcome of that observation would therefore, he said, influence something that happened millions of years ago.]

Retrocausality challenges the relationship between cause and effect that's fundamental to the way in which we understand the natural world. It divides scientists; there's no consensus on whether it's real - and whether it has any real-world applications that we can notice - or whether it's no more than a fanciful theory which stubbornly refuses to be proved or disproved in the lab. Its proponents say that in any case its physical effects would be extremely weak. 

Newtonian physics are based on the assumption that causality operates in one dimension - in a forward direction from cause to effect, just as time runs in one dimension and only forward from past to future. 

While retrocausality is a fascinating concept, its practical implications remain speculative.

So let me speculate for a while. There are many things we can no longer remember. What did you have for breakfast on [random day] in [random year]? Maybe that particular date squares with a memorable medical procedure you underwent, and you clearly remember eating no breakfast that morning. Otherwise, eating a bowl of porridge containing 1,831 flakes of oats as opposed to a bowl with 1,794 flakes has no significance. My breakfast from 10 March 2023 could have retrocausally been changed, and there'd be no effect on past or future. No one, not even I, would notice the change. There's no record, no effect.

Remember the definition of magic - bringing about change in the physical world through supernatural means. Willing outcomes, in other words. Not just seeing into the future, but affecting it. But how about changing the past in a meaningful way? Changing outcomes from ones that happened in the past to ones that didn't happen? Erasing memory of an alternative reality? Or creating (as posited by the many-worlds interpretation of quantum mechanics) a branching-off of a parallel universe at the moment your last spoon dipped into the packet of oats?

If we can (and I believe that in a very limited way) affect the future by willing a positive outcome or forestalling, precluding or mitigating a negative event, could it be possible that we can be currently living in a better reality than one that could have befallen us because of an event in an alternative past?

I write these posts with the future in mind - I return to them to see how my thinking has evolved, and indeed how scientific and philosophical thought has evolved. There are more panpsychists around today than was the case ten years ago - and a lot more scientists open to possibility of the presence of extraterrestrial intelligence on this planet.

Lent 2022: Day 28
Understanding the Infinite and the Eternal

Lent 2021: Day 28
Higher life forms, imagined

Lent 2020: Day 28
The Secret and the Hidden