Dear Fellow Time Travelers,
In a recent essay, I riffed a bit on Master Dogen's sense of time(s) and timeless, that future is just the past tomorrow, while the present is future today, that future flows into present and past as the present and past flow into the future ... and more ...
Well, recent experimental results and theorizing by physicists makes that look tame! Here's a taste ...
Reality is stranger than any dream. Perhaps because reality is a dream? Hmmm.
Gassho, J
stlah
In a recent essay, I riffed a bit on Master Dogen's sense of time(s) and timeless, that future is just the past tomorrow, while the present is future today, that future flows into present and past as the present and past flow into the future ... and more ...
Time Flies Free ...
https://www.treeleaf.org/forums/show...ime-Flies-Free
https://www.treeleaf.org/forums/show...ime-Flies-Free
Well, recent experimental results and theorizing by physicists makes that look tame! Here's a taste ...
Time Twisted in Quantum Physics: How the Future Might Influence the Past
The 2022 physics Nobel prize was awarded for experimental work demonstrating fundamental breaks in our understanding of the quantum world, leading to discussions around “local realism” and how it could be refuted. Many theorists believe these experiments challenge either “locality” (the notion that distant objects require a physical mediator to interact) or “realism” (the idea that there’s an objective state of reality). However, a growing number of experts suggest an alternative approach, “retrocausality,” which posits that present actions can affect past events, thus preserving both locality and realism.
... This concept offers a novel approach to understanding causation and correlations in quantum mechanics, and despite some critics and confusion with “superdeterminism,” it is increasingly seen as a viable explanation for recent groundbreaking experiments, potentially safeguarding the core principles of special relativity.
... In 2022, the physics Nobel prize was awarded for experimental work showing that the quantum world [in so-called "entanglement," also known as "spooky action at a distance"] must break some of our fundamental intuitions about how the universe works. [ ** "entanglement" is a phenomenon by which one particle can effectively "know" something about another particle instantaneously, even if those two particles are separated by a great distance, with no obvious present connection or causal relationship between them.]
Many look at those experiments and conclude that they challenge “locality” — the intuition that distant objects need a physical mediator to interact. And indeed, a mysterious connection between distant particles would be one way to explain these experimental results.
Others instead think the experiments challenge “realism” — the intuition that there’s an objective state of affairs underlying our experience. After all, the experiments are only difficult to explain if our measurements are thought to correspond to something real. Either way, many physicists agree about what’s been called “the death by experiment” of local realism.
But what if both of these intuitions can be saved, at the expense of a third? A growing group of experts think that we should abandon instead the assumption that present actions can’t affect past events. Called “retrocausality,” this option claims to rescue both locality and realism.
... The quantum threat to locality (that distant objects need a physical mediator to interact) stems from an argument by the Northern Ireland physicist John Bell in the 1960s. Bell considered experiments in which two hypothetical physicists, Alice and Bob, each receive particles from a common source. Each chooses one of several measurement settings, and then records a measurement outcome. ... Bell realized that quantum mechanics predicts that there will be strange correlations (now confirmed) in this data. They seemed to imply that Alice’s choice of setting has a subtle “nonlocal” influence on Bob’s outcome, and vice versa – even though Alice and Bob might be light years apart. ...
... Retrocausal models propose that Alice’s and Bob’s measurement choices affect the particles back at the source. ...
[Another possible explanation for this spookey-action-at-a-distance is] called “superdeterminism.” Superdeterminism agrees with retrocausality that measurement choices and the underlying properties of the particles are somehow correlated.
But superdeterminism treats it like the correlation between the weather and [a] barometer needle. It assumes there’s some mysterious third thing – a “superdeterminer” – that controls and correlates both our choices and the particles, the way atmospheric pressure controls both the weather and the barometer.
So superdeterminism denies that measurement choices are things we are free to wiggle at will [i.e., change by our choices], they are predetermined. Free wiggles would break the correlation ... Critics object that superdeterminism thus undercuts core assumptions necessary to undertake scientific experiments. They also say that it means denying free will, because something is controlling both the measurement choices and particles.
These objections don’t apply to retrocausality. Retrocausalists do scientific causal discovery in the usual free, wiggly way. We say it is folk who dismiss retrocausality who are forgetting the scientific method, if they refuse to follow the evidence where it leads.
... What is the evidence for retrocausality? Critics ask for experimental evidence, but that’s the easy bit: the relevant experiments just won a Nobel Prize. The tricky part is showing that retrocausality gives the best explanation of these results. ...
... [W]e and others have argued that retrocausality makes better sense of the fact that the microworld of particles doesn’t care about the difference between past and future.
We don’t mean that it is all plain sailing. The biggest worry about retrocausation is the possibility of sending signals to the past, opening the door to the paradoxes of time travel. But to make a paradox, the effect in the past has to be measured. If our young grandmother can’t read our advice to avoid marrying grandpa, meaning we wouldn’t come to exist, there’s no paradox. And in the quantum case, it’s well known that we can never measure everything at once.
Still, there’s work to do in devising concrete retrocausal models that enforce this restriction that you can’t measure everything at once. So we’ll close with a cautious conclusion. At this stage, it’s retrocausality that has the wind in its sails, so hull down towards the biggest prize of all: saving locality and realism from “death by experiment.”
Written by:
Huw Price, Emeritus Fellow, Trinity College, University of Cambridge
Ken Wharton, Professor of Physics and Astronomy, San José State University
The 2022 physics Nobel prize was awarded for experimental work demonstrating fundamental breaks in our understanding of the quantum world, leading to discussions around “local realism” and how it could be refuted. Many theorists believe these experiments challenge either “locality” (the notion that distant objects require a physical mediator to interact) or “realism” (the idea that there’s an objective state of reality). However, a growing number of experts suggest an alternative approach, “retrocausality,” which posits that present actions can affect past events, thus preserving both locality and realism.
... This concept offers a novel approach to understanding causation and correlations in quantum mechanics, and despite some critics and confusion with “superdeterminism,” it is increasingly seen as a viable explanation for recent groundbreaking experiments, potentially safeguarding the core principles of special relativity.
... In 2022, the physics Nobel prize was awarded for experimental work showing that the quantum world [in so-called "entanglement," also known as "spooky action at a distance"] must break some of our fundamental intuitions about how the universe works. [ ** "entanglement" is a phenomenon by which one particle can effectively "know" something about another particle instantaneously, even if those two particles are separated by a great distance, with no obvious present connection or causal relationship between them.]
Many look at those experiments and conclude that they challenge “locality” — the intuition that distant objects need a physical mediator to interact. And indeed, a mysterious connection between distant particles would be one way to explain these experimental results.
Others instead think the experiments challenge “realism” — the intuition that there’s an objective state of affairs underlying our experience. After all, the experiments are only difficult to explain if our measurements are thought to correspond to something real. Either way, many physicists agree about what’s been called “the death by experiment” of local realism.
But what if both of these intuitions can be saved, at the expense of a third? A growing group of experts think that we should abandon instead the assumption that present actions can’t affect past events. Called “retrocausality,” this option claims to rescue both locality and realism.
... The quantum threat to locality (that distant objects need a physical mediator to interact) stems from an argument by the Northern Ireland physicist John Bell in the 1960s. Bell considered experiments in which two hypothetical physicists, Alice and Bob, each receive particles from a common source. Each chooses one of several measurement settings, and then records a measurement outcome. ... Bell realized that quantum mechanics predicts that there will be strange correlations (now confirmed) in this data. They seemed to imply that Alice’s choice of setting has a subtle “nonlocal” influence on Bob’s outcome, and vice versa – even though Alice and Bob might be light years apart. ...
... Retrocausal models propose that Alice’s and Bob’s measurement choices affect the particles back at the source. ...
[Another possible explanation for this spookey-action-at-a-distance is] called “superdeterminism.” Superdeterminism agrees with retrocausality that measurement choices and the underlying properties of the particles are somehow correlated.
But superdeterminism treats it like the correlation between the weather and [a] barometer needle. It assumes there’s some mysterious third thing – a “superdeterminer” – that controls and correlates both our choices and the particles, the way atmospheric pressure controls both the weather and the barometer.
So superdeterminism denies that measurement choices are things we are free to wiggle at will [i.e., change by our choices], they are predetermined. Free wiggles would break the correlation ... Critics object that superdeterminism thus undercuts core assumptions necessary to undertake scientific experiments. They also say that it means denying free will, because something is controlling both the measurement choices and particles.
These objections don’t apply to retrocausality. Retrocausalists do scientific causal discovery in the usual free, wiggly way. We say it is folk who dismiss retrocausality who are forgetting the scientific method, if they refuse to follow the evidence where it leads.
... What is the evidence for retrocausality? Critics ask for experimental evidence, but that’s the easy bit: the relevant experiments just won a Nobel Prize. The tricky part is showing that retrocausality gives the best explanation of these results. ...
... [W]e and others have argued that retrocausality makes better sense of the fact that the microworld of particles doesn’t care about the difference between past and future.
We don’t mean that it is all plain sailing. The biggest worry about retrocausation is the possibility of sending signals to the past, opening the door to the paradoxes of time travel. But to make a paradox, the effect in the past has to be measured. If our young grandmother can’t read our advice to avoid marrying grandpa, meaning we wouldn’t come to exist, there’s no paradox. And in the quantum case, it’s well known that we can never measure everything at once.
Still, there’s work to do in devising concrete retrocausal models that enforce this restriction that you can’t measure everything at once. So we’ll close with a cautious conclusion. At this stage, it’s retrocausality that has the wind in its sails, so hull down towards the biggest prize of all: saving locality and realism from “death by experiment.”
Written by:
Huw Price, Emeritus Fellow, Trinity College, University of Cambridge
Ken Wharton, Professor of Physics and Astronomy, San José State University
Reality is stranger than any dream. Perhaps because reality is a dream? Hmmm.
Gassho, J
stlah
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