Luminiferous Ether

Wave Theory of Light— If we stand beside a pond of still water and throw a stone into it we shall see a series of waves passing out in concentric circles from the center of the disturbance. If there be a chip or a leaf floating on the surface it will be apparent, on watching this object, that there is no forward motion of the water itself (unless the stone be so large relatively to the pond as to cause a marked displacement of the water) but that the individual molecules simply rise and fall in the vertical direction, each communicating its motion to the next, so that the wave travels forward. The accepted theory regards the propagation of light as being due to a similar wave motion in the luminiferous ether, an invisible, imponderable substance pervading all matter, the wave motion originating in any self-luminous body.*

*One theory regards the propagation of light as consisting of a series of irregular pulses which are transformed into a simple harmonic motion on encountering any material obstacle, but since we are dealing with light only after it has encountered such obstacles the above statement may be taken as correct.

Paul L. Anderson, Pictorial Photography, 1917.

This provides an interesting contrast to the theory advanced by Oliver Wendell Holmes in 1859. Rather than particles that stick, Anderson promotes the idea of harmonic waves. It’s interesting, in retrospect, that both theories can be taken as correct. Except for the luminiferous ether part, of course. Unless you’re talking to a poet.