Click here to go to the JPU200Y home page. Introduction You may be aware of the fact that Einstein never accepted Quantum Mechanics. He explained his objections by discussing two particular aspects of the theory. One was the fact that the theory is probabilistic, and seems to imply that the future is random. Often this aspect of the theory is characterised as non-locality .
Locality means the reasonable assumption that no signal can travel faster than the speed of light.
This imposes constraints on cause and effect. As we shall see, locality is in some conflict with Quantum Mechanics. To illustrate the conflict we will only need the fact that we can view phenomena such as light as both a wave and as a particle. The following discussion is at the level of an upper year liberal arts course in modern physics without mathematics that is given at the University of Toronto. The legend for the figure is shown to the left.