In how many ways do we by our theories dodge the crucial problem of how energy is really transmitted, that is, how matter can act on distant matter across seemingly vacant space. Gravity, and indeed all the forms of the attractive forces, come under this head. True, we observe certain regularities in the way in which these phenomena occur, and the phenomenon at one place seems to be somehow dependent on some exercise of force at another place. And so we invent an ingenious theory, and fortify it all around with ponderous algebraic artillery for defense against all attack. And by persistent use of such theories we hypnotize ourselves into the belief that we are truly scientific in method, and are dealing with objective realities, and that these learned theories are something more than pretentious masks to hide our ignorance of real nature; when in reality these theories seem to be only a material screen to shield us from an embarrassing near view of the immediate action of God in all the various phenomena of the world; for not many find it a comfortable thought thus to live continuously beneath the great Taskmaster’s eye.
The theory of the luminiferous ether as the medium of the transmission of light is one of these pretentious bridges of words. Our advancing knowledge of electro-magnetic phenomena may some day drive us back to a modified form of the corpuscular theory of light, and then we can throw this of the ether to the winds. In that case we would at least have a real material cause for the phenomena with which we deal. While the current theory of the ether has so many inconsistencies, and attempts to bridge over so many real chasms in our thinking that it seems truly astonishing to see it taught so long. By the theory of the ether the problems are not solved, they are merely postponed or evaded; for while solving one difficulty it creates a multitude of its own. How then are we better off than before without any such theory?
Being at liberty to invent any sort of qualities for their ether, scientists have tried to imagine such a substance as they think they need. The ether must be a kind of matter; but unlike any matter that we know of it cannot have weight, or else it would gravitate together here and there, thus becoming more abundant in some places than in others; whereas the need is for a material absolutely uniform throughout space, even throughout the interiors of solid bodies, such as the earth and the bodies upon the earth.
Another reason for supposing the ether to be a plenum, filling absolutely all space, is that it must be perfectly frictionless; and for this reason it cannot be composed of particles with spaces between them. It must be frictionless, for otherwise the planets would be retarded in their motions through space. The earth, for instance, is moving along its orbit at the rate of eighteen miles a second; and yet the ether does not pile up in front of it, nor is it made rarer in the wake of the earth. Moreover, during the thousands of years during which astronomers have been making observations absolutely no retardation has been detected in the motions of the earth or of any of the heavenly bodies, even to the smallest fraction of a second.