Retrocausality: Physicists Ponder Whether the Future Can Influence the Past

Poster for Time-Travel Movie 'Primer'

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"

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Gwedd's picture
Member since:
8 April 2006
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22 hours 29 min

I believe that time travel is not only possible, but has happened and will continue to do so.

It all is a part of the multi-verse. An infinite number of parallel universes, each identical in it's beginning, but changed via time travel. To my mind, it's a sublime creation of Diety, who ensures that when you or I or someone else travels backward in time, that we go to some different universe, where whatever we do to alter history continues only in THAT particular thread, and not in the one you left.

When you enter your time machine and set the date you wish to travel to, the machine automatically randomly selects a parallel universe and drops you off there to experience life, interact with the locals, and generally muddle things up. Then, when it's time to come home, you are brought back to your own time, just a second after you originally left, and thus unable to change your own universe.

Of course, the other universe is messed up, the one you left, that is. However, whatever changes you effected while there might not be readily apparent to those who live within that portion of the multi-verse. To them, life has gone on splendidly (hopefully) since the great catastrophe of XXXX. It's a fascinating subject to consider.

But if one accepts, as I do, that there are an infinite number of parallel universes, then time travel would have a nill effect upon your own ans you leave and arrive at your original universe, having visited a similar but likely different universe which you likely messed up.

There's a novella in there if I can get it fleshed out and written. :)

Respects,
Gwedd

emlong's picture
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18 September 2007
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6 hours 6 min

In a sense, all of existence "is" time travel. The most obvious instance of time travel is the phenomena of ghosts who appear to have one foot in the past and one in the present.

nicoleallenB's picture
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3 February 2014
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32 weeks 4 days

I thought, the past influence the future. We learn to make decisions to prevent the mistakes of the past. With this article, it opened up my mind to think more.

qraal's picture
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21 February 2006
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Daryl Bem's work would surely be a manifestation of the quantumness of our brains and their operation. But exactly what it lets us do - how far we can "feel the future" is fuzzily indefinable. A few seconds forward would help. But like anything in biology it'd be subject to natural selection (even helping meaningful mutations appear, maybe?) However there'd be a down-side. A few days forward... a bit too debilitating to be constantly some other when, I'd say. Yet the occasional mutation might allow some people to feel further forward than most.

The Universe is not only stranger than we imagine, it's stranger than we CAN imagine.

emlong's picture
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18 September 2007
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If Time is fundamentally an illusion then there is no past or future in the usual sense of those terms which can be another way of saying they are the same thing.

VecordaeEternum's picture
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15 March 2006
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Retrocausality is a tough nut to test for and isn't necessarily the best explanation for spooky action at a distance.

One could take the position that time itself is illusory, in which case it is also assumed to be arbitrary and pretty much anything can happen. In this case retrocausality is also illusory and arbitrary.

One could also take the position that the flow of time is an emergent phenomenon, which would imply that it is dependent upon the interactions of more fundamental forces. In this case it would be appear to be consistent when taken in aggregate, but prone to all sorts of weird things when you look at it too closely. In this case retrocausality may not occur at all or only occur rarely, mostly as a sort of faltering in the overtone that is time.

One could take the position that the flow of time is a fundamental force itself, operating with absolute predictability and consistency on a set continuum. In this case, retrocausality is absolutely possible and operates predictably.

Just my two pence.

emlong's picture
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18 September 2007
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For those of us who have seen a lot of ghost busting under reasonably controlled conditions the "test" is right there and has proven the reality of time travel and maybe even retrocausality.

VecordaeEternum's picture
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Your interpretation of what, exactly, is happening in those cases far from universal, I think. My own experiences haven't hinted at the possibility of time travel, but I fully admit that they are very, very subjective.

Out of curiosity, even if one were to take "ghosts as proof of time travel" at face value, how is that evidence for retrocausality? One assumes that one would need to encounter the spirit of someone who hasn't been born or died yet or somehow influence the past in some discernible way by interacting with an entity in the present.

emlong's picture
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18 September 2007
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That is why I said "maybe" even retrocausality. It is a fair but not proven supposition that if a civil war veteran can appear in full period dress with swishing saber marching down the veranda of my father's ranch house as I and many of my family witnessed several times then his encounter with us may have ramifications for the "time" in which his self at least partially exists. If this were a "residual" haunting - purely a matter of some past event having been somehow recorded in the local material fabric with playback then maybe not, but a ghost that intelligently interacts with beings in the present may bring something of that interaction back to his historical time. In other words, the ghost can be said to have "glimpsed the future," and may have then taken some sort of actions (or just reactions) that modify his present (our past or prehistory) because of that glimpse. I am simply pondering implications

tobadzistsini's picture
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4 February 2014
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Why not dismiss the entire concept of temporal paradoxes? It appears our paradigm isn't causative, but associative.

For example, I go back in time, kill my grandfather, yet I still exist, and when I return to my future my grandfather still died in 2008. My return to that timeline is (for lack of a better term for this agency) causality shifted me into a different branch where that event happened.

This opens up bitter, philosophical arguments about what guides that agency.

My understanding of George Musser's article is he's making an argument for our universe being deterministic but infinitely flexible so all paths between A and B are available for travel, but there's no chance of ending up at Q, bypassing the intervening letters.

Once Huw Price can finagle someone to prove this mathematically or experimentally, it'll make contemporary science look quaint like candles and cuckoo clocks.

red pill junkie's picture
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12 April 2007
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After I read Jacques Vallee's Messengers of Deception, I started to lean more & more into that viewpoint.

It's not the depth of the rabbit hole that bugs me...
It's all the rabbit SH*T you stumble over on your way down!!!

Red Pill Junkie
_______________
@red_pill_junkie

emlong's picture
Member since:
18 September 2007
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6 hours 6 min

If there is no sequential time, can there be temporal paradoxes?