Text: To detect the momentum of a photon, one actually detects the momentum of an interacting particle of mass. Photons as such are not directly detectable. Indeed, the photon is not just a "massless particle" and no one really understands just what it is. See Richard Kidd, James Ardini, and Anatol Anton, Evolution of the Modern Photon, American Journal of Physics, 57(1), Jan. 1989, p. 27-35.

See Also: ATOMOLE; ATOMOLINI; PHONON; LIGHT; QUANTUM; MASS

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