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> In addition to potentially rescuing concepts like locality and realism, retrocausal models also open avenues of exploring a “time-symmetric” view of our unive
by kwhitefoot 4y ago
> In addition to potentially rescuing concepts like locality and realism, retrocausal models also open avenues of exploring a “time-symmetric” view of our universe, in which the laws of physics are the same regardless of whether time runs forward or backward.
Usually the fundamental laws are regarded as time symmetric already.
What does this mean:
> Instead, retrocausal models suggest that there is a mechanism that allows circumstances in the future to correlate with past states.
Surely future states inevitably correlate with past states?
Perhaps it all makes sense but that article doesn't make a compelling case.
- QuadmasterXLII 4y agoWe don’t have a time symmetric model of wave function collapse, to my knowledge. If I’m wrong I’d be super curious to read about it
- throwawaymaths 4y agoWe don't have a model of wave function collapse at all, iirc.
- orbifold 4y agoMeasurements are adjoint to state preparation. Depending on what you measured you can prepare a special state at that time to make the system time reversal symmetric.
- bioemerl 4y agoWouldn't many worlds be time symmetric?
- layer8 4y agoYes, but it’s not a model of wave function collapse. Its very premise is that there is no wave function collapse.
- GoblinSlayer 4y agoJust reverse time in the evolution operator.
- derbOac 4y agoNot an expert in this area at all but there have been some experimental findings in the last five or so years that suggest the possibility of retrocausality. This is just one example I found but I think there might be another experiment from a few years ago that was getting some attention at the time (although I might be confusing it with a theory paper): https://www.nature.com/articles/s41598-023-29970-6 https://www.nature.com/articles/s41598-023-29970-6 There are probably better overview articles on retrocausality. https://www.newscientist.com/article/mg23731652-800-quantum-time-machine-how-the-future-can-change-what-happens-now/ https://www.newscientist.com/article/mg23731652-800-quantum-... https://aeon.co/essays/can-retrocausality-solve-the-puzzle-of-action-at-a-distance https://aeon.co/essays/can-retrocausality-solve-the-puzzle-o... https://phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html https://phys.org/news/2017-07-physicists-retrocausal-quantum... I'd have to read through all these more thoroughly but I wonder if there's some "time locality" property in these models?
- coldtea 4y ago>Surely future states inevitably correlate with past states? He means to correlate through effects going the future -> past direction...
- kwhitefoot 4y agoYes, of course. But that is not how correlation is usually expressed. And it also doesn't explain what it means. It just sounds like philosophers doing some hand waving. What can it mean to have an effect propagating into the past? Surely our usual definition of time is simply a series of events. If so then it always points in one direction for the entity sitting at the leading edge, the current event is always succeeded by the next event. All I have to go on is the article, perhaps the source material makes more sense.
- patrakov 4y ago> Usually the fundamental laws are regarded as time symmetric already. Well, in addition to time reversal, you also have to mirror the universe and replace all particles with their anti-particles.