by Scott Teresi
www.teresi.us/writing



        A person often thinks of chance as something which occurs randomly according to some probability, although within some constraints of a system. Probability is simply the extrapolation to infinity of the outcome of an event, given our knowledge of its past behavior, and saying nothing about its cause. However, these events do not occur genuinely randomly, without cause. In classical physics, most things are entirely deterministic, which by definition means they have causes. A set of dice will come up snake eyes as a result of the minute, nearly instantaneous physical processes which occur as part of the interaction between the dice and the flat surface they tumbled over. In other words, systems which appear to behave randomly in classical physics are actually governed by a variety of "hidden" variables. Whether these interactions are accurately measurable or not does not matter.

        By contrast, events within the quantum physical world are often governed by different principles. Chance takes on a different meaning. For instance, if a particle emits two electrons, they must travel away from the particle in opposite directions in order to obey conservation of energy. Until their position is actually measured, however, the electrons head away from the particle according to the formula for a wave. One electron’s position could be anywhere; it is up to this different type of chance to "decide." Yet, when one electron’s position is measured, its companion electron will always be measured in the opposite direction. Both electrons’ paths seem to have been predestined. What events could have led up to this arbitrary yet coordinated decision? Quantum chance decided where they would end up, and yet they were still opposite each other. No theory can yet provide a definitive reason for this. Might there be hidden variables? This extra complication seems very unlikely. This manner must be the result of the nature of particles in the quantum world. The properties of quantum particles–obeying the wave equation–result in this bizarre behavior, a different kind of chance.

References

Rohlich, Fritz. From Paradox to Reality. Cambridge: Cambridge University Press, 1987.

Sklar, Lawrence. Philosophy of Physics. San Francisco: Westview Press, Inc., 1992.