Wednesday, November 06, 2002

Kant's idea that space and time do not exist among things-in-themselves has been curiously affirmed by Relativity and quantum mechanics. In Relativity, time simply ceases to pass at the velocity of light: for photons that have travelled to us as part of the Cosmic Background Radiation, time has stood still for most of the history of the universe. On the other hand, quantum mechanics now posits "non-locality," i.e. physical distances, and so the limitation of the velocity of light in Relativity, don't seem to exist. This means that although time may apply to the wave function, space may not. The full empirical reality of space is only found among discrete particles and objects.

This curious result is the consequence of the Einstein-Podolsky-Rosen (EPR) Paradox, which was intended by Einstein as a reductio ad absurdum of quantum mechanics. If, for instance, a positron and an election are both created from an energetic photon, the conservation of angular momentum requires that one be spinning one way, and the other the other. But the complementary spins are equally probably for each particle. Thus, in quantum mechanical terms, the wave functions of each particle separate without a discrete state being determined. The particles might then separate to even cosmological distances, but as soon as the spin of one particle is observed, the other particle must have the opposite spin, which means that the wave function has collapsed across those cosmological distances and caused the other particle to assume a predictable spin. If this occurs instantaneously, it would violate the limitation of the velocity of light in Special Relativity.

This has now been shown to actually occur on the basis of Bell's Theorem (from John Bell, 1928-1990), meaning that Quantum Mechanics does violate Special Relativity by allowing instantaneous interactions across even cosmological distances. However, once observed, processes must still obey Special Relativity and the limitations of spatial distance, creating the kind of duality described by Kant. Bell himself found this result disturbing, but to Kant it would fit in with his own theory that space is only imposed by the representation of phenomenal objects.

Einstein always objected to quantum mechanics because his metaphysical realism recoiled from the idea that observation would create a different kind of reality than what existed independently. At first Heisenberg's Uncertainty Principle could be interpreted as meaning that the act of observation would physically disturb a system in an ordinary and realistic way, but then it soon became evident that strange things were allowed to happen in the wave function that not only could not be observed but could not even be conceived in ordinary and realistic ways. Reality existed in a different way while under observation than it did in itself.

posted by Shaun Kenney | 11/06/2002 03:45:00 PM | 0 comments

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