The Results…

So you were probably surprised to learn that Bell’s Theorem does prove that there is a theoretical difference between realism, in which quantum mechanics is determined by some unknown factor, and the orthodox view, in which quantum mechanics is ill-defined until a measurement is made. Worse yet, realism actually CONTRADICTS quantum mechanics- a realist’s only hope, then, is that experiment will favor their answer, and show that somewhere there is an error in quantum mechanics.

But alas, even though many, many experiments were run, all of them favored quantum mechanics. They tried everything they could think of to explain this- including setting the orientations of the detectors after the photons were in flight (most of the experiments were done with photons), but nothing resolved the problem. In the end, experiments showed that in this world we live in, “pure” quantum mechanics is right, and the realism and agnostic positions must be abandoned, leaving us only with the orthodox position.

Now, this hasn’t resolved the EPR Paradox, except to say that locality must break down on the quantum level- or we must redefine it. Initially, the idea of “influence” was rather ambiguous. However, physicists now look at locality as something with “causal” power. This isn’t much clearer, but the argument is that the observation of the electron does not, in some strict sense, “cause” the positron’s spin to collapse. This is because the person measuring the electron’s spin cannot force it to be something- he/she can merely measure it. Thus, in some sense, he/she cannot actually CONTROL the positron’s spin, merely discover what it must be by observing the electron’s spin, which will be collaborated by observation. Thus, causality is taken to mean to create a CHANGE in some physical property, and not just to cause that property to be known. The other type of influence is called “ethereal”- it does not transmit energy or information, and the only evidence for it is a correlation that must come from comparing two sets of data.

BUT WAIT!!! If you were following the last section closely, you noticed that Bell’s Theorem only applies to local hidden variables, because we assumed that the electron measurement was independent of the positron measurement. But, what if somehow λ sensed the direction the electron was being measured, and then traveled faster than the speed of light to ensure that the spin of the positron was right? We don’t know of anything that acts like this- all forces, etc are all inherently local, and it would be necessary that λ doesn’t transfer energy to not contradict relativity. Additionally, this is hugely conceptually difficult- because traveling faster than the speed of light implies going backwards in time. When you measured that electron, the λ traveled backwards in time to affect what was measured- so you were influencing the PAST on this theory. It’s unclear if this destroys the causal locality mentioned above, but if so then we would have all sorts of causality problems with murdering grandfathers, etc. In general, physicists reject this theory because then we can never know how any measurements in the future are influencing what we are doing now, although perhaps they should be less adamant about the position.

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