Page:Aether and Matter, 1900.djvu/221



. As an assistance to the formation of a judgment on these questions, it will be convenient to insert here a free translation of the considerations by which Lorentz supported the possibility of an explanation, of the kind above developed, of the negative result of Michelson's experiments on the influence of material convection on phenomena of optical interference.

"However extraordinary this hypothesis may appear at first sight, it must be admitted that it is by no means gratuitous, if we assume that the intermolecular forces act through the mediation of the aether in a manner similar to that which we know to be the case in regard to electric and magnetic forces. If that is so, the translation of the matter will most likely alter the action between two molecules or atoms in a manner similar to that in which it alters the attraction or repulsion between electrically charged particles. As then the form and the dimensions of a solid body are determined in the last resort by the intensity of the molecular forces, an alteration of the dimensions cannot well be left out of consideration.

"In its theoretical aspect there is thus nothing to be urged against the hypothesis. As regards its experimental aspect we at once notice that the elongation or contraction which it implies is extraordinarily minute. It would involve a shortening in the diameter of the Earth of about $6 1⁄2$ centimetres. The only experimental arrangements in which it could come into evidence would be just of the type of this one of Michelson's which first suggested it.

"It is worthy of remark, that we are led precisely to this law of alteration of dimensions when we assume first that, without taking account of molecular motions, in a solid body left to itself the forces of attraction and repulsion acting on each molecule maintain themselves in equilibrium, and secondly—for which there is admittedly no evidence—that the same law applies to these molecular forces, as regards their alteration