That the present knowledge of the world of science compels a faith in an all-pervading substance, of marvelous properties, and of intimate relationship to all forms of energy, is shown by the following quotations from Lord Kelvin, who is generally regarded as the world's greatest physicist: "The luminferous ether, that is the only substance we are confident of in dynamics. One thing we are sure of, and that is the reality and substantiality of the luminiferous ether." "What can this luminiferous ether be? It is something that the planets move through with the greatest ease. It permeates our air; it is nearly in the same condition, so far as our means of judging are concerned, in our air and in the interplanetary space." "You may regard the existence of the luminiferous ether as a reality of science." "It is matter prodigiously less dense than air?of such density as not to produce the slightest resistance to any body going through it."