Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The Indivisible Universe
Albert Einstein was so unhappy with the uncertainty principle that he accepted Quantum Mechanics only as an incomplete description of the universe. He thought that Quantum Mechanics had neglected some "hidden variables". Once those hidden variables were found, we would have a complete theory without Quantum Theory’s oddities but with all of Quantum Theory’s results.
Quantum Theory is a practical tool to calculate probabilities for sets of particles, but no prescription is provided for calculating quantities of individual particles. Einstein thought that there is an underlying reality where determinism rules and the behavior of the individual particle can be predicted. It is just that Quantum Mechanics is incomplete and has not found out that underlying reality yet.
Einstein was particularly unhappy about the "nonlocality" of Quantum Physics, which he thought constituted a paradox. "Nonlocality" means "action at a distance". In Quantum Physics one can prove that, if they were once part of the same state, two particles will always be connected: once we measure the position of the first one, we instantaneously determine the position of the other one, even if, in the meantime, it has traveled to the other end of the universe. Since no information can travel faster than light, it is impossible for the second particle to react instantaneously to a measurement that occurs so far from it. The only possible explanation for this "paradox" was, to Einstein, that the second particle must have properties which are not described by Quantum Mechanics.
Einstein thought that Quantum Physics provides a fuzzy picture of a sharp reality, whereas for Bohr it provides a complete picture of a fuzzy reality.
Einstein was proven wrong in 1964 by the Irish physicist John Bell (“On the Problem of Hidden Variables in Quantum Mechanics”, published two years later), whose theorem basically ruled out "local hidden variables", precisely the type that Einstein invoked. Bell's conclusion is that, on the contrary, there are objective, non-local connections in the universe. In other words, two particles, once they have interacted, will keep interacting forever (their wave functions get entangled forever). Einstein believed in the law of locality, i.e. that two objects can interact only if they touch each other or if their interaction is mediated by some other object; but Bell proved that the "wave" is enough to provide interaction. Two measurements can be related instantaneously even if they are located in regions too far apart for a light signal to travel between them. Non-locality, or inseparability, is a fact of nature. Objects are not only affected by forces. They are also affected by what happens to other objects.
(More precisely, Bell showed how to test whether a world of properties that are not due to observation and of separated objects is possible. In 1972 John Clauser carried out an actual experiment to perform the test, and its result proved Einstein wrong: either properties are due to observation, or objects are forever connected, or both. Our world cannot possibly have both an observer-independent reality and entanglement-free objects. To be fair to Einstein, Bell assumed that induction is a valid logical method to prove theorems. And, as Nick Herbert has noted, Bell's theorem is metaphysical, not physical, and ultimately relies on the metaphysical assumption that the world behaves in a classical deterministic manner).
This shattered another belief of classical Physics. Newton believed that objects interact through forces that somehow have to travel from one to the other. A cannonball has to travel from the cannon to the walls before the walls explode; and nothing else in the universe is affected. The sun attracts the earth into an orbit, but it doesn't have any effect on the other stars. These are "local" interactions. Einstein added that forces can only travel as fast as light. Therefore, the impact of a force on an object is delayed by the time it takes for the force to reach that object at a speed which cannot exceed the speed of light. "Locality" became a distance: there is only so much in the universe that can exert a force on me, because only so much of the universe can send its force to me during my lifetime. If I live 80 years, an event that occurs more than 80 light-years away from here will never cause any disturbance on my life. Bell proved that this is not the case, because Quantum Theory prescribes the existence of a non-local "force": once two waves have interacted, they are forever entangled.
Note that Heisenberg's "knowledge interpretation" never had a problem with non-locality: obviously, a change in the observer's knowledge does change the observer's knowledge about the entire system, regardless of how "extended" in space the system is. For example, if I observed the two particles at the beginning, when they were in the same place, and noticed that one is black and the other white, and later I observe the white one, I will "know" that the other one is black even if the other one is light-years away from me.
Ensemble InterpretationEinstein didn't give up. Niels Bohr had interpreted the wave function as describing an individual system, e.g. a particle. But Einstein ("Physics and reality", 1936) pointed out that the oddities of quantum mechanics disappear if one interprets the wave fuction as referring to ensembles of systems and not to individual systems. Einstein's "ensemble theory", reprised by the Canadian physicist Leslie Ballentine ("The statistical interpretation of quantum mechanics ", 1970), views the wave function as describing an ensemble of possible states. Lee Smolin then realized that one could interpret Einstein's interpretation upside down: the uncertainty is not about the states of a system (e.g. of an electron), the uncertainty is actually the ensemble of all the systems of that kind in the universe (of all the electrons). Systems of the same kind form an ensemble because the interaction between systems depends not on proximity but on similarity.
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