On Tue, Nov 26, 2019 at 11:04 PM Bruno Marchal <[email protected]> wrote:
> On 20 Nov 2019, at 14:51, John Clark <[email protected]> wrote: > > > "*R**ealism is "counterfactual definiteness", the idea that it is > possible to meaningfully describe as definite the result of a measurement > which, in fact, has not been performed (i.e. the ability to assume the > existence of objects, and assign values to their properties, even when they > have not been measured)*. > > > Yes, that is Einstein’s physical realism. It is implied by Mechanism. It > should not be confused with physicalism, which assumes that the only > explanation of physical realism is that there is a primary (irreducible) > physical reality. With mechanism, the physical realism is entailed by the > fact that nobody can change the relative measure on all computations in > arithmetic, no more than changing the value of 666. > The arithmetical reality makes the physical and statistical > “counterfactual definiteness” as solid as 2+2=4, or Ex(x+2=4), without any > need of an ontological commitment on some “universe” or “matter”. > Quantum mechanics itself is not counterfactually definite. Einstein was wrong about this. A free electron is described by a wave packet which is a superposition of states of definite momentum and position. There is no actual "position" for the electron until it interacts with a screen or some similar device. This is demonstrated by simple two-slit interference. There is no pre-existing position, unless you want to embrace Bohm's pilot wave theory, in which the electron does have a definite, though unknown, position at all times. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQQ2rw2tKKnVfrmObYa8F5SMcREaHUwU%3D2UFsSMuKx4LQ%40mail.gmail.com.
