# s-phys: more about retrocausality

<<  In a new paper (..) [AA] have lent new theoretical support for the argument that, if certain reasonable-sounding assumptions are made, then quantum theory must be retrocausal >>

<< 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 >>

<< "Speculatively, if there is retrocausality in the universe, then it might be the case that there are certain eras, perhaps near the big bang, in which there is not a definite arrow of causality. You might imagine that a signature of such an era might show up in cosmological data, such as the cosmic microwave background. However, this is very speculative, and I have no idea what signatures we might expect yet." >> Matthew S. Leifer.

<< The physicists don't have any experiments lined up to test retrocausality—but as the idea is more an interpretation of observations rather than making new observations, what's needed most may not be a test but more theoretical support >>

Lisa Zyga. Pysicists provide support for retrocausal quantum theory, in which the future influences the past. July 5,  2017.

https://m.phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html

Matthew S. Leifer,  Matthew F. Pusey. Is a time symmetric interpretation of quantum theory possible without retrocausality?   Proc. Royal Soc. A. June  2017 Volume 473,  issue 2202 doi: 10.1098/rspa.2016.0607 Publ. Jun. 21, 2017.

http://rspa.royalsocietypublishing.org/content/473/2202/20160607

https://arxiv.org/abs/1607.07871