Feb 16, 2024 06:49 PM
(This post was last modified: Feb 16, 2024 07:27 PM by C C.)
https://iai.tv/articles/in-the-quantum-w..._auid=2020
INTRO: Two particles affecting one another [seemingly] faster than light seemed unimaginable but there is no denying the facts. This mystery has inspired much skepticism from lay folk and Nobel prize winners alike. But how do we solve this? Emily Adlam argues, that retrocausality, the idea the future can affect the past, is the key to solving this quantum enigma.
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EXCERPTS: . . . it’s important to note that there are two importantly different conceptions of retrocausality that one might adopt here. The first is the ‘two arrows’ approach, which is perhaps what most people think of first when they hear the term ‘retrocausality’ - it suggests there are literally two distinct arrows of causation pointing in opposite directions, so we have evolution both forwards in time and backwards in time. The alternative is the ‘all-at-once’ approach, in which there is no process of evolution at all, and instead the laws of nature work in an atemporal way to pick out the whole course of history at once, in much the same way as the rules of sudoku constrain the whole grid at once rather than starting at one side and moving to the other side.
[...] Which of these conceptions of retrocausality should we choose? Well, there is an obvious problem with the ‘two arrows’ conception: it seems liable to produce logical paradoxes...
[...] The all-at-once picture, meanwhile, can’t possibly produce logical contradictions, because the whole point of this approach is that the entire course of history is selected all together, in a logically consistent way. But there’s a catch - it’s not entirely clear that an ‘all-at-once’ model is really local in the ordinary sense...
[...] Ultimately, it seems the contradiction with relativity in the Bell correlations arises because we are trying to fit these correlations into a model based on time evolution, which forces us to pick a reference frame on which the correlations take effect. If we stop trying to do that, much of the tension with relativity goes away, so we end up with a model which is non-local but still entirely in line with the underlying principles of special relativity. Thus introducing retrocausality in the all-at-once sense offers a very interesting route to reconciling the Bell experiments with relativity, and we are just beginning to explore the implications of this possibility for our ideas about time, causation and gravity... (MORE - missing details)
INTRO: Two particles affecting one another [seemingly] faster than light seemed unimaginable but there is no denying the facts. This mystery has inspired much skepticism from lay folk and Nobel prize winners alike. But how do we solve this? Emily Adlam argues, that retrocausality, the idea the future can affect the past, is the key to solving this quantum enigma.
- - - - - - - - -
EXCERPTS: . . . it’s important to note that there are two importantly different conceptions of retrocausality that one might adopt here. The first is the ‘two arrows’ approach, which is perhaps what most people think of first when they hear the term ‘retrocausality’ - it suggests there are literally two distinct arrows of causation pointing in opposite directions, so we have evolution both forwards in time and backwards in time. The alternative is the ‘all-at-once’ approach, in which there is no process of evolution at all, and instead the laws of nature work in an atemporal way to pick out the whole course of history at once, in much the same way as the rules of sudoku constrain the whole grid at once rather than starting at one side and moving to the other side.
[...] Which of these conceptions of retrocausality should we choose? Well, there is an obvious problem with the ‘two arrows’ conception: it seems liable to produce logical paradoxes...
[...] The all-at-once picture, meanwhile, can’t possibly produce logical contradictions, because the whole point of this approach is that the entire course of history is selected all together, in a logically consistent way. But there’s a catch - it’s not entirely clear that an ‘all-at-once’ model is really local in the ordinary sense...
[...] Ultimately, it seems the contradiction with relativity in the Bell correlations arises because we are trying to fit these correlations into a model based on time evolution, which forces us to pick a reference frame on which the correlations take effect. If we stop trying to do that, much of the tension with relativity goes away, so we end up with a model which is non-local but still entirely in line with the underlying principles of special relativity. Thus introducing retrocausality in the all-at-once sense offers a very interesting route to reconciling the Bell experiments with relativity, and we are just beginning to explore the implications of this possibility for our ideas about time, causation and gravity... (MORE - missing details)
