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Issue 9 of the wonderful online magazine Nautilus is now available to read, and offers a fantastic collection of articles on the theme of ‘Time’. One of the pieces I recommend checking out is George Musser’s article “The Quantum Mechanics of Fate“, which delves into the (possible) mystery of retrocausality in modern physics:

Physicists as renowned as John Wheeler, Richard Feynman, Dennis Sciama, and Yakir Aharonov have speculated that causality is a two-headed arrow and the future might influence the past. Today, the leading advocate of this position is Huw Price, a University of Cambridge philosopher who specializes in the physics of time. “The answer to the question, ‘Could the world be such that we do have a limited amount of control over the past,’ ” Price says, “is yes.” What’s more, Price and others argue that the evidence for such control has been staring at us for more than half a century.

That evidence, they say, is something called entanglement, a signature feature of quantum mechanics…

…The standard interpretation of entanglement is that there is some kind of instant communication happening between the two particles. Any communication between them would have to travel the intervening distance instantaneously—that is, infinitely fast. That is plainly faster than light, a speed of communication prohibited by the theory of relativity.

…Price asks us to consider the impossible: that doing something to either of the entangled particles causes effects which travel backward in time to the point in the past when the two particles were close together and interacting strongly. At that point, information from the future is exchanged, each particle alters the behavior of its partner, and these effects then carry forward into the future again. There is no need for instantaneous communication, and no violation of relativity.

Before we get too carried away with the possibilities afforded by retrocausality, it should be noted that even those investigating it clearly say it’s all a bit speculative right now. Furthermore, Musser points out that, even assuming retrocausality is real, “our control of the past is very limited — as it must be, if the universe is to avoid imploding in a big logical paradox. Quantum mechanics is set up to deny you that influence. It creates an eddy in the river of time, but only a little one” (sidenote for anyone else that thought it: yes I did hear Arthur Dent saying “Ah, is he?” when I read that sentence).

Nevertheless, I couldn’t help thinking of Professor Daryl Bem’s controversial findings that suggest humans may have the ability to ‘feel the future’. I wonder what those physicists investigating retrocausality might say about what it allows in terms of presentiment in humans – still inconceivable, or is it a mechanism for such an effect?

Make sure you check out all the stories in Issue 9 of Nautilus, there is some truly fascinating and beautiful writing to enjoy (for instance, see this wonderful piece on the life and work of acclaimed physicist John Archibald Wheeler).

Link:The Quantum Mechanics of Fate

Link: Issue 9 of Nautilus: “Time”