The Insider News

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So ultimately everything boils down to the choice of whether to keep time symmetry or no-retrocausality, as Leifer and Pusey's argument shows that you can't have both. Since time symmetry appears to be a fundamental physical symmetry, they argue that it makes more sense to allow for retrocausality. Doing so would eliminate the need for action-at-a-distance in Bell tests, and it would still be possible to explain why using retrocausality to send information is forbidden.

"The case for embracing retrocausality seems stronger to me for the following reasons," Leifer said. "First, having retrocausality potentially allows us to resolve the issues raised by other no-go theorems, i.e., it enables us to have Bell correlations without action-at-a-distance. So, although we still have to explain why there is no signaling into the past, it seems that we can collapse several puzzles into just one. That would not be the case if we abandon time symmetry instead.

"Second, we know that the existence of an arrow of time already has to be accounted for by thermodynamic arguments, i.e., it is a feature of the special boundary conditions of the universe and not itself a law of physics. Since the ability to send signals only into the future and not into the past is part of the definition of the arrow of time, it seems likely to me that the inability to signal into the past in a retrocausal universe could also come about from special boundary conditions, and does not need to be a law of physics.

Read more at: https://phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html#jCp

Kent Sharkey wrote:

That 'splodey sound you hear is my head

Instead, retrocausality means that, when an experimenter chooses the measurement setting with which to measure a particle, that decision 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.

Kent Sharkey wrote:

We’re gradually learning that smart home devices can be quite valuable for police.

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Stack Overflow is an American social network of specialists who are trying to fill the knowledge gap. The site follows a question and answer format, with the best answers being voted to the top by members. Moderator Josh Heyer told BBC Trending that users had been lobbying the company for years to try and get it to take a position in favour of net neutrality.