Here again Newton appears as a pioneer. Newton’s corpuscular theory, however, proved wholly untenable when Foucault showed that the velocity of light in water is less than in air, which is the very reverse of what the corpuscular theory demands, but which does agree with Huyghens’ wave theory.
But Huyghens’ wave theory postulated some medium in which the waves can act. To this medium the name “ether” was given. However, all attempts to show the presence of such an ether failed. Naturally enough, some began to doubt the existence of an ether altogether.
Huyghens’ wave theory received a new lease of life with Maxwell’s discovery that light is an electromagnetic phenomenon; that the waves set up by a source of light were comparable to waves set up by an electrical disturbance.
Zeeman next showed that magnetism was also, closely related to light.
A study of Zeeman’s experiments led Lorentz to the conclusion that electrical phenomena are due to the motion of charged particles called “electrons,” and that the vibrations of these electrons give rise to light.
The conception of the electron as the very fundamental of matter was arrived at in an entirely different way: from studies dealing with the discharge of electricity through gases and the breaking up of the atoms of radium.
If matter and light have the same origin, and if matter is subject to gravitation, why not light also?
References
For the general subject of light the reader must be referred to a rather technical work, but one of the best in the English language: Edwin Edser, Light for Students (Macmillan, 1907).