The aether drag hypothesis proposed that the luminiferous aether is dragged by or entrained within moving matter. According to one version of this hypothesis, no relative motion exists between Earth and aether. According to another version, the Earth does move relative to the aether, and the measured speed of light should depend on the speed of this motion ("aether wind"), which should be measurable by instruments at rest on Earth's surface. In 1818, Augustin-Jean Fresnel proposed that the aether is partially entrained by matter. In 1845, George Stokes proposed that the aether is completely entrained within or in the vicinity of matter.
