4 ms·

> First, to clarify (...) It does not mean that signals can be communicated from the future to the past(...) instead, retrocausality means (... it) can influenc

> First, to clarify (...) It does not mean that signals can be communicated from the future to the past(...) instead, retrocausality means (... it) can influence the properties of that particle (or another particle) in the past, even before the experimenter made their choice. In other words, a decision made in the present can influence something in the past. So, hard to explain in layman words: future can't transmit information to the past, but an action that will be taken in the present can influence some properties of a particle in the past. Take two particles, separate them enough, do some "A" thing to one of them and the other instantaneously will have the only possible state that doesn't break the universe. And one viable explanation is that when we've done the "A" thing, this information was transmitted to the particle in the past. We just couldn't measure this before (in the past) because measuring interferes with it, and that property can only be revealed at the same time that we've done the "A" thing. Is that it? Kinda of information is transmitted to the past, just can't be read before some time ?

petters 9y ago
That explanation still seems to allow faster than light communication.
- deleted 9y ago
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emeraldd 9y ago
Based on that description would this sounds like an action in the present is putting constraints on a seemingly unrelated event that has an enforced but currently unobservable relationship in the future. Or something like that. Why do I get the feeling that this starts requiring higher dimensions? Additionally: If any particle in an entangled system get's measured along the full course of it's "enforced relationship into the future" that would be the point where the system collapses. And that's where I'd run into issues .... It would seem a more reasonable explanation that retro-causal relationships would be a fourth physical dimension for the relationship to exist along ... hmmm
mindviews 9y ago
We should be talking about "consistency" being the fundamental idea, not causality. I think "retrocausality" is an especially distracting choice of words. I find the clearest way to think about this is in terms of Feynman Diagrams. Here's a quick intro to some of the rules: http://bolvan.ph.utexas.edu/~vadim/classes/2008f.homeworks/QED.pdf http://bolvan.ph.utexas.edu/~vadim/classes/2008f.homeworks/Q... If you're not familiar, ignore the math and just look at the pictures on the first couple of pages. Take a simple diagram of a photon interacting with an electron (google QED Vertex). Here's a very tiny ASCII version: ~< The squiggly line represents a photon propagating and the straight line segments (which should have arrows pointing a direction) represent an electron propagating. We can rotate this thing around in a bunch of different ways in time so that we have 1 or 2 inputs ("before") an 2 or 1 outputs ("after") in time. For example, with time going left to right, ~< represents a photon decaying into an electron and positron. Flipped around, >~ represents a electron and a positron colliding/annihilating to create a photon. Turned another way you could have a photon and electron as input, and an electron with a changed momentum as the output. For the last case you could say the electron absorbed the photon. But really, these are all the exact same pattern just rotated around in spacetime. So, what is causation? If it's all the same pattern, it's clear that consistency with the pattern is more important than the direction of time's arrow. Speaking very loosely now (there are a bunch of constraints and caveats on what I'm about to say), you can plug these diagrams together to make arbitrarily complicated internal structures. But if they have the same inputs and outputs, they are in a sense consistent. And if you do it just right you can constrain which types of patterns can link up with the one you've set up. So, in the end, only patterns that are consistent with your setup can happen. Which is pretty much what this article is describing.

petters 9y ago

That explanation still seems to allow faster than light communication.

deleted 9y ago
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emeraldd 9y ago

Based on that description would this sounds like an action in the present is putting constraints on a seemingly unrelated event that has an enforced but currently unobservable relationship in the future. Or something like that. Why do I get the feeling that this starts requiring higher dimensions? Additionally: If any particle in an entangled system get's measured along the full course of it's "enforced relationship into the future" that would be the point where the system collapses. And that's where I'd run into issues .... It would seem a more reasonable explanation that retro-causal relationships would be a fourth physical dimension for the relationship to exist along ... hmmm

mindviews 9y ago

We should be talking about "consistency" being the fundamental idea, not causality. I think "retrocausality" is an especially distracting choice of words. I find the clearest way to think about this is in terms of Feynman Diagrams. Here's a quick intro to some of the rules: http://bolvan.ph.utexas.edu/~vadim/classes/2008f.homeworks/QED.pdf http://bolvan.ph.utexas.edu/~vadim/classes/2008f.homeworks/Q... If you're not familiar, ignore the math and just look at the pictures on the first couple of pages. Take a simple diagram of a photon interacting with an electron (google QED Vertex). Here's a very tiny ASCII version: ~< The squiggly line represents a photon propagating and the straight line segments (which should have arrows pointing a direction) represent an electron propagating. We can rotate this thing around in a bunch of different ways in time so that we have 1 or 2 inputs ("before") an 2 or 1 outputs ("after") in time. For example, with time going left to right, ~< represents a photon decaying into an electron and positron. Flipped around, >~ represents a electron and a positron colliding/annihilating to create a photon. Turned another way you could have a photon and electron as input, and an electron with a changed momentum as the output. For the last case you could say the electron absorbed the photon. But really, these are all the exact same pattern just rotated around in spacetime. So, what is causation? If it's all the same pattern, it's clear that consistency with the pattern is more important than the direction of time's arrow. Speaking very loosely now (there are a bunch of constraints and caveats on what I'm about to say), you can plug these diagrams together to make arbitrarily complicated internal structures. But if they have the same inputs and outputs, they are in a sense consistent. And if you do it just right you can constrain which types of patterns can link up with the one you've set up. So, in the end, only patterns that are consistent with your setup can happen. Which is pretty much what this article is describing.