baby_blueThe debate between Einstein and Heisenberg resembles, in many respects, the debate between the realists and the anti-realists that has been unfolding here in the blogosphere. Einstein was deeply troubled by quantum mechanics and what he saw as the skeptical consequences of this theory such that we can never determine whether or not the properties discovered through our measurements of particles belonged to particles themselves. Heisenberg couldn’t see why Einstein & Co. were so bothered by this. Adopting the position of the pragmatist, he thought it enough that the measurements be able to make more or less accurate predictions, and that the question of whether or not the velocity or position measured belonged to the particles themselves was– and I absolutely love this expression! –a “distinction without a difference”.

Along comes John Bell proposing a theorem that would actually allow this debate to be decided. Now, I do not wish to take a position on whether or not we have access to the real properties of particles or whether we are forever limited to our measurements. I think this very much remains an open debate that is unlikely to be decided any time soon. Rather, I would instead like to draw attention to something else that arose as a result of experiments based on Bell’s Theorem.

read on!

I have occasionally been taking to task for refusing to answer questions like “what is the nature of time?”, “what is the nature of space?”, “what are objects?”, “what are primary qualities?”, and for claiming that philosophy cannot provide a priori answers to these questions. The results of experiments based on Bell’s Theorem provide a nice cautionary tale as to why philosophers should practice prudence in answering these sorts of questions. One of the surprising results of these experiments, conducted by Alain Aspect, was the discovery that particles originating from the same source would spin in exactly the same way when subsequently measured despite there being no recognizable connection between the two particles nor any possible causal connection between the two particles. For all intents and purposes, the two particles behave as the same object, despite being vast distances apart from one another. This is what is referred to as “quantum entanglement”.

The experiment has been conducted at a distance of as far apart as 20km, and physicists theorize that exactly the same result would occur were one particle here and the other in another galaxy (how they arrive at this latter conclusion, I do not know). As I observed in my last post, the locality hypothesis lies at the heart of all our science. The thesis here is that objects must directly interact in some way in order to have causal effects on one another. This gave Newtonians quite a headache for a long time because it wasn’t clear how something like action at a distance might be possible. Einstein changed all of this through his theory of General Relativity which showed, in part, how gravitational force is related to the constant speed of light, demonstrating the manner in which there is a local causal interaction. For example, if the sun suddenly blinked out of existence we wouldn’t experience any gravitational effects of this disappearance for eight minutes as this is how long it takes for light to travel here and gravity itself can only exercise its effects within the constraints of the speed of light.

What makes quantum entanglement so surprising is that the mirror actions of the two particles acting in tandem to one another takes place instantaneously, violating this causal constant of interaction. This has led some physicists to argue that the two particles themselves are a part of one and the same object and that there is some deeper underlying unity or oneness to reality of which particles are “aspects”. Here then we have a violation of two of our common sense assumptions about the nature of the world: First, we have what looks like an interaction between two objects that violates the locality hypothesis. Second, we take it for granted– as a sort of “transcendental condition” –that objects are localized in space or that they have a simple location in space, yet here we have an object which is claimed to be one object where its parts can exist on two different sides of the universe. It could be that subsequent inquiry will reveal that the two particles are indeed two objects, not one object, and that the locality hypothesis will somehow be redeemed or salvaged through some sort of discovery as to how these two spatially distributed particles are able to perfectly mirror one another. The point, however, is that this question can’t be answered a priori and were we to set a priori conditions as to what objects must be to be given we would very well be inhibiting this sort of research. Our concepts are not at the outset of research– though there are always provisional ones that guide our inquiry –but rather are the result of research.