Letter: Messages coming back from several futures (1)

From Andy Howe, Sheffield, UK

So, letting the future affect the past might explain quantum weirdness (17 February, p 28). That’s a mind-bending postulate for the desired effect.

Take your example of a measurement on one photon instantaneously affecting the measurement of its entangled partner, regardless of the distance between them and of the speed of light. Adam Becker reports proposals that the measurement sends a message back in time to when the photon pair was created, giving the partner particle information about what state it should be in when the first one is measured.

But this can’t be changing the past. It means that the message always was there when the photon pair was created. So the future is predetermined: at least when and where the measurement will occur, and by implication the future in general.

We might avoid this by considering “the message” as a probability cloud encompassing all possible messages about when and where either photon could be measured in the future. Or maybe the messages back in time create alternative universes where all the alternative futures happen. Hang on: these ideas sound rather like the quantum weirdness this hypothesis seeks to avoid…