3.4.4.6 The EPR Paradox
Because of its many apparent counter-intuitive aspects, Quantum Mechanics provoked strong public and philosophical debates with many different and even opposing interpretations. According to the standard Copenhagen interpretation, the probabilistic nature of Quantum Mechanics is not a temporary feature which will eventually be replaced by a deterministic theory, but instead must be considered a final renunciation of the classical idea of causality. Einstein, in particular, did not accept this rejection of determinism and causality. In response to this, he is famously quoted as saying: “God does not play with dice”.
Einstein also rejected the concept that the state of a physical system depends on the experimental arrangement for its measurement, stating that a state of nature occurs in its own right, regardless of whether or how it might be observed. Most notably, however, Einstein insisted on the principle of locality, and he believed that there should be a theory that thoroughly and directly expresses the rule against action at a distance. Therefore, he considered that Quantum Mechanics was a currently valid, but not a permanently definitive, theory for quantum phenomena. He thought that its future replacement would require more profound conceptual advances, and would not come quickly or easily.
The Bohr-Einstein debates provided a vibrant critique of the Copenhagen Interpretation, from an epistemological point of view. In arguing for his views, Einstein produced a series of objections, the most famous of which had become known as the Einstein-Podolsky-Rosen, or EPR, paradox.
The EPR paradox is a thought experiment initiated in 1935 by Einstein, Boris Podolsky (1896-1966) and Nathan Rosen (1909-1995) who claimed to demonstrate that the wave-function does not provide a complete description of physical reality, and hence that the Copenhagen interpretation is unsatisfactory.
The purpose of the EPR thought experiment was to expose the profound peculiarities of the quantum description of a physical system, extended over a large region of space. It seemed that, under certain conditions, a quantum system of two entangled particles could in theory exchange information instantaneously or, at least, faster than the speed of light. Einstein called this: “spooky action at a distance”, which clearly contradicts the principle of locality in his Theory of Relativity, that is essentially based on the principle of the constancy and invariance of the speed of light, as the maximum terminal speed in nature, regardless of the frames of reference, as we have described in sections 2 and 3. The phenomena of entanglement, that will also be described further in section 4.4.7, also seems to violate Heisenberg’s sacred uncertainty principle, which declares that not all the classical physical observables, such as position and momentum, of a system can be simultaneously known with unlimited precision, even in principle.
In their famous article titled: “Can Quantum Mechanical Description of Physical Reality be Considered Complete?”, the three scientists concluded that quantum theory was incomplete and should be extended with hidden variables, some thus far unknown properties of the system, that should account for the paradoxical discrepancy. Niels Bohr, on the other hand, favored the view put together in the Copenhagen interpretation of quantum theory, and he utterly refused the idea of hidden variables.
In 1964 John Bell (1928-1990) proposed a mechanism to test for the existence of these alleged hidden variables, and he developed his famous ‘inequality’ as the basis for such a test. This was followed by many experiments to test this inequality; the most successful of which was performed by Alain Aspect (b. 1947) and his colleagues in 1982. Their experiment consisted of light polarization measurements made on entangled pairs of photons, moving in opposite directions, emitted simultaneously in single transitions by Calcium atoms, then measured by sensitive detectors on each side. The results of this experiment clearly violate Bell’s inequality, eliminating the need for the existence of hidden variables and thus supporting the predictions of non-local Quantum Mechanics, which violates Einstein’s locality principle, and even common intuition!
The results showed that apparently the left hand detecting apparatus was sending some kind of message to the right hand photon informing it as to how the left hand apparatus was set up, so that the right hand photon could interact in the appropriate way with the right hand apparatus. But as a matter of fact there is no any communication at all between the left and the right photons, and, if we suppose there is, then the signal would have to travel faster than the speed of light. Some argue, however, that entanglement does not violate causality, since no actual transfer of information happens between the two entangled particles.
Many even more accurate experiments were performed after that, and all show that it is as if time ‘stops’ between the pair of entangled particles and they interact instantaneously, despite the large distance between them. Although this experimental outcome supports the fundamental concepts of the theory of Quantum Mechanics and contradicts Einstein’s locality principle, but there is no adequate theoretical explanation for it, so far.
We have showed before in the Single Monad Model of the Cosmos, and in the introductory chapter I of this book, that the principle of re-creation in the inner levels of time explains such instantaneous interactions, because there is no motion in the common sense that the particle gradually and infinitesimally moves into new positions, but it is re-created in these new positions, that could be at the other end of the Universe, without violating the speed of light limit. We shall explain this further in chapter VI.