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Waves, particles and events

Wave particle duality is another reason to suspect a discrete model might account for the seemingly paradoxical behavior at the quantum level, Quantum mechanics is a theory of waves not unlike the waves that appear on a still lake as a rock is dropped in. Detecting a particle has an effect like dropping the rock. The future expectation of where the particle can be found spreads out as a wave. The higher or lower the water level is relative to the still lake the more likely one will observe the particle at that location. The area where the particle might be found spreads out over time just as the ripples in the lake do.

Missing in contemporary physics is the connection between the wave and the particle. In quantum mechanics probabilities continually change but nothing ever happens. The connection between events (like seeing a particle) and probabilities is made through metaphysical interpretations. The first and most widely known of these is the called the Copenhagen Interpretation. This claims a conscious observation `collapses' the wave function. We make one observation (drop a rock in the water) wait for a time and make a second observation. This second observation instantly causes the waves from the first observation to disappear making the lake perfectly still again. Then another rock is dropped in and a new wave spreads out from the new location where we observed the particle.

The waves that move out from an observation were not invented with quantum mechanics. Something similar happens in classical probability theory. The difference is that in the classical theory there is a fully deterministic model of how events proceed. However we have imperfect knowledge of the initial conditions. Thus, after making an observation of say the location of the ball on a roulette wheel, we can only make approximate predictions about where the ball will land. With more accurate information we can make better predictions and it is possible with enough computing power to beat the odds in Las Vegas until they kick you out of the casino.

In classical probability theory the collapse of a probability `wave' function has no physical significance. It is only a matter of getting more accurate information. What collapses is our degree of ignorance about what is happening physically. The external world is unaffected. The quantum wave function is different. We can observe this function physically through interference effects. We can change its structure by, for example, having it pass through a polarizing filter as described in Section 8.3. Thus to think that a conscious observation collapses a physical wave function is to go beyond what most people think of as science. The Copenhagen Interpretation avoids this by asserting there are two domains of reality the quantum and the macroscopic. Consciousness observation connects the two domains. The process of quantum collapse becomes a metaphysical link between these domains rather than being a physical event.