The question "What is motion?" is so often asked, and just as often unsatisfactorily answered, that we will endeavor to throw some light on the subject. When a body occupies successively different positions in space, we say it is in motion. A log which rolls along the ground, a horse that walks along a road, a boat descending a river with the current, are instances of bodies in motion. Each of these changes its position in regard to objects which we call fixed, although really there is no stand-still in nature ; but as we relatively take part in the same motion as the trees, the hills and other land-marks, to us they appear as fixed. To return to our question " What is motion ?" we reply, motion is the result of the action of the elemental forces of nature ; and as they are always at work, and ever have been, motion is eternal, illimitable, and all-present. We call these forces electricity, magnetism, gravity, attraction, chemical action, and life, together with heat and light. To these forces may be traced all the wondrous changes of nature that are daily going on around us; and to the application of these forces to our own wants and requirements, we ascribe all that man has done to render easy the high roads of civilization, and make ways for truth through the trackless ocean. Nature is the prime action, and art the combined and controlled action of them ; or, in other words, in nature they act governed only by their own laws, and in art their laws are made subservient to the wants of man. The planets in their movements around the sun, the sun carrying, by the force of his attraction, the planetary system through space, the motions of all the heavenly bodies, are the result of combined at mobility and gravity. The trees growing in the field, animals increasing on the earth, and man standing as a presiding genius over the whole, owe their existence to life and chemical action. The rock crumbling under the action of the weather, the steamer crossing the mighty deep, the locomotive pursuing its undeviating path, are the results of heat. Light shines everywhere, and influences all created things. These are the motors of creation out of the power of man to create, but in his power to control. Venturing cautiously a little deeper into the subject, we find that all the above mentioned forces are related intimately the one to the other, and that in many instances, one can develop the rest. Thus, electricity can develop heat, light, magnetism, attraction, and chemical action, but not gravity or life, for life, we know, is the direct gift of a Higher Power ; and it would really seem that all these which we now call separate and distinct are but the developments of one great force which yet remains to be discovered. Much has been said and written on this subject, but without contributing any great amount of knowledge to that already in our possession, as each author has taken more trouble to prove some theory of his own than to investigate the simple truth. This much, however, we know, that the above are the fountains of motion, and there are no effects that cannot be traced to them.
This article was originally published with the title "Motion and Motors" in Scientific American 13, 12, 93 (November 1857)