In the late 19th century,
luminiferous aether,
aether or
ether, meaning light-bearing
aether, was the postulated
medium for the propagation of
light. It was invoked to explain the ability of the apparently
wave-based light to propagate through empty space, something that waves should not be able to do. The assumption of a spatial plenum of luminiferous aether, rather than a spatial vacuum, provided the theoretical medium that was required by wave theories of light.