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1927
The Copenhagen Interpretation

Schrödinger's equation describes the subatomic world, but the world that we know seems to follow the rules of classical—not quantum—mechanics. How can this be? Danish physicist Niels Bohr (shown here in polka-dotted tie, years later) provides a possible answer in a 1927 lecture on his theory of "complimentarity," which forms the basis for what will later be known as the Copenhagen Interpretation. By this time, researchers are aware of another surprising result of the double-slit experiment (when conducted with electrons). If, in the course of the experiment, the researchers try to track the electron as it passes through the slits, the electron starts acting like a particle, not a wave—the interference pattern on the screen disappears. The Copenhagen Interpretation holds that the very act of measuring (or observing) the electron's position causes something called "waveform collapse." In other words, observed matter acts like a particle.


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