Category:Light

This category collects work on the nature and propagation of light: its speed and whether that speed is constant, its emission and absorption, the photon, and the experiments that bear on all three.

The questions gathered here are foundational to much of this wiki. Whether the velocity of light is independent of the motion of its source is the point on which special relativity and emission theory divide; whether light requires a medium is the question of the aether; and whether light is a wave, a particle, or a structure in a field bears directly on the models of matter collected under Category:Toroidal Ring.

Entries include analyses of the Michelson–Morley, Sagnac, Fizeau, Ives–Stilwell and Michelson–Gale experiments, one-way versus two-way light speed measurements, GPS timing evidence, stellar aberration, the optical Doppler effect, and theories of the photon.