Abstract

Scientists working on the wave theory of light in the 19th century took it for granted that there had to be a medium for the propagation of light waves. This medium was called the luminiferous [= “light carrying”] ether. One of the central questions about this medium concerned its state of motion. There were two options: (1) The ether is completely undisturbed by matter moving through it (stationary or immobile ether); (2) Matter drags along the ether in its vicinity and/or in its interior (dragged-along ether). Stellar aberration provided the main argument for the first option (even though a special dragging effect in the case of transparent matter had to be built into the theory to account for refraction). Polarization provided the main argument for the second option. These two options and the arguments pro and con will be explained in more detail below