"Retrocausality:" the outcome is past

Here's your word for the day. Paul Gilster at Centauri Dreams points out that University of Washington physicist John Cramer has had an experiment in retrocausality funded.

The notion, absurdly reduced, is this: Entangled photons seem to beable to affect each other no matter how widely separated in time or space, the so-called Einstein-Podolsky-Rosen paradox that illuminates the bizarre nature of quantum mechanics. Do a measurement on one and it has an immediate effect on the other. Cramer is testing whether this ’spooky action at a distance’ is the result of communications that move backwards and forwards in time.

Reread the previous sentence. What's being tested is time symmetry, whether the spooky action, the entangled state, is the result of time traveling backward. Think of it this way. Could the entangled outcome (to us) be the past (to entangled photons)?

Paul links to this Seattle Post-Intelligencer story on the research.


Wikipedia: arrow of time