Kindergarten Quantum Mechanics

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The Correspondence Principle in Quantum Mechanics says that in mechanics, the classical theory is the limit of quantum mechanics when Planck's constant goes to zero. Or, in more comprehensible terms, we see quantum effects at the scale of atoms, and classical effects for large objects whose atomic structure is not evident to the senses.

Unfortunately, most people, even physicists, suppose that the Correspondence Principle is universal. They mistakenly conclude that we never see quantum effects in daily life. In fact, we see nothing but quantum effects, because vision itself is a quantum phenomenon. The Correspondence Principle fails to apply at all to optical phenomena. All emission and absorption of photons consists of quantum jumps.

There are many other common quantum phenomena easily observed. Radioactivity, fluorescence, some of the snow on analog TV screens, the randomly varying speckle pattern on a fingernail in sunlight, colors of minerals, and so on. All photosensitive materials, all transistors, all lasers, and all of chemistry are quantum effects. Atoms and molecules, subatomic particles and structures, even the forces of nature (other than gravity) are well understood to be quantum effects.