Earth's motion

“ The motion then of the whole Earth is primary, astral, circular, around its own poles, whose verticity arises on both sides from the plane of the æquator, and whose vigour is infused into opposite termini, in order that the Earth may be moved by a sure rotation for its good, the Sun also and the stars helping its motion. ”

“ But, happily, Nature presents no evidence of such a course of events. The earth spins on its axis with quiet and persistent regularity; the unvarying uniformity of its motion of axial rotation has been verified by the observations of generations of philosophers. ”

“ When we remember that the earth is not far from being as heavy as a ball of iron, and that its surface velocity at the equator is about 17 miles per minute, it is easy to form a conception of its uniform motion. ”

“ Having now learned the fact, that the earth moves around the sun, not in a circular but in an elliptical orbit, you will desire to know by what forces it is impelled, to make it describe this figure, with such uniformity and constancy, from age to age. It is commonly said, that gravity causes the earth and the planets to circulate around the sun; and it is true that it is gravity which turns them aside from the straight line in which, by the first law of motion, they tend to move, and thus causes them to revolve around the sun. ”

“ The combined effect of the two motions, the advancing motion of the sun, and the receding motion of the earth, due to its increased orbital velocity, drives the earth towards the aphelion, where its distance from the sun is greatest, and its orbital velocity is the least. ”

“ And these appearances proceed chiefly from the diverse situations which the earth acquires in the course of its motion, after the same manner as it happens to the planets, which appear sometimes retrograde, sometimes more slowly, and sometimes more swiftly, progressive, according as the motion of the earth falls in with that of the planet, or is directed the contrary way. ”

“ It seems perfectly absurd at the present time that anybody should start with a proposition like that to work out a physical theory. Yet it is equally absurd to assume at once that the earth is in motion, and for that reason I have, been anxious to convey to you the evidence by which it is proved generally that the earth is in motion. ”

“ By influences external to this earth the balance of these forces is continually disturbed; and in the effort to restore the equilibrium, we have the production of all the varied forms of matter, and the manifestation of each particular physical principle or power. As motion and attraction, balanced against each other, maintain the earth in her elliptical orbit, so the opposition of forces determines the existence of the amorphous rock, the light-refracting crystal, the fixed and flowering plant, and the locomotive animal.
An eternal round of chemical action is displayed in nature. ”

“ Indeed, the absolute movement of the molecules of a planet ought then to be in the direction of the movement of its centre of gravity; but it does not at all follow that the motion of the rotation of the planets should be in the same direction. Thus the earth should rotate from east to west, but nevertheless the absolute movement of its molecules should be from east to west ”

“ We know that the earth is moving each moment with a velocity of about eighteen miles a second, and the first law of motion assures us that if this globe were submitted to no external force, it would for ever pursue a straight track through the universe, nor would it depart from the precise velocity which it possesses at the present moment. ”

“ But the atmosphere is gravitative, and being gravitative, it is not only held bound to the earth as it revolves on its axis in its onward rush through space, but accepts the revolving motion of the earth, with the result that as the earth revolves on its axis, the atmosphere revolves also. ”

“ The earth also revolves about the sun, having a speed of about 19 miles in a second, or 68,000 miles an hour. This motion of the earth and the other planets about the sun is one of the most stable phenomena we know. ”

“ If, namely, that powerful motion is ascribed to the heavens, it is absolutely necessary to regard it as opposed to the individual motion of all the planets, every one of which indubitably has its own very leisurely and moderate movement from west to east. If, on the other hand, you let the earth move about itself, this opposition of motion disappears. ”

“ If you can reverse the order of this phenomenon, and imagine an irregular retardation of the rapidity of such atomic motion, you can read the story of the formation of the material universe. Follow the chain backward, and with the decrease of velocity, motion becomes tangible matter again, and in accordance with conditions governing the change of motion into matter, from time to time the various elements successively appear. The planets may grow without and within, and ethereal space can generate elemental dirt. ”

“ Yes, I recollect your saying, that if two bodies were fastened together by a wire or bar, their common centre of gravity would be in the middle of the bar, provided the bodies were of equal weight; and if they differed in weight, it would be nearer the larger body. If then, the earth and moon had no projectile force which prevented their mutual attraction from bringing them together, they would meet at their common centre of gravity.
Caroline. The earth then has a great variety of motion, it revolves round the sun, round its own axis, and round the point towards which the moon attracts it. ”

“ Motion. A continued and successive change of place, either of a whole body, or of the particles of [Pg 211] which a body is composed; the earth in revolving upon its axis only, would not change its place as a body, but all the particles of which it is composed, would revolve round a common axis of motion. In revolving in its orbit, its whole mass is constantly occupying a new portion of space. ”

“ The earth being, as it appears by the equality of its diurnal motion and the constancy of the inclination of its axis, composed of homogeneous parts, which attract each other in proportion to their quantity of matter, it would necessarily have taken the figure of a globe perfectly spherical, if the motion of impulsation had been given it in a perpendicular direction to the surface ”

“ It had been urged that, if the earth moved round, its motion would not be imparted to the air, and that therefore the earth would be uninhabitable by the terrific winds which would be the result of our being carried through the air. ”

“ The phenomena of its motion will be somewhat as follows:—As the body recedes from the earth's surface in its upward flight, its velocity suffers a continuous decrease, and an altitude is finally attained where this velocity becomes zero. ”

“ The rotation of the earth on its axis, as we know, causes the familiar daily apparent rising, passing, and setting of all the heavenly bodies. In this apparent motion the planets share as well as the sun, moon, and stars. ”

“ Seeing therefore the variety of Motion which we find in the World is always decreasing, there is a necessity of conserving and recruiting it by active Principles, such as are the cause of Gravity, by which Planets and Comets keep their Motions in their Orbs, and Bodies acquire great Motion in falling; and the cause of Fermentation, by which the Heart and Blood of Animals are kept in perpetual Motion and Heat; the inward Parts of the Earth are constantly warm'd, and in some places grow very hot ”

“ We have a certain rapidly increasing acquaintance with the laws of general atmospheric motion, but of the origin and limits, the beginning and end of that motion, as it manifests itself at any particular time and place, we know nothing. ”

“ If it should happen that the earth came into collision with another body by which its velocity was stopped, 94the principle of the conservation of energy tells us that this energy, which the earth has in consequence of its motion, must forthwith be transformed, and the form which it will assume is that of heat. ”

“ The force of gravity on the earth results in the motion or tendency of all bodies towards its centre, and, similarly, the action of gravitation upon the atoms or particles of a primeval planet resulted in the motion of those particles towards each other. We cannot conceive force otherwise than by its effects, or the motion it produces. ”

“ It ascends from the surface of the earth or ocean laden with a stored energy, the power of which no man can compute, and beside which gravitation is a mere point. In the upper regions of atmosphere this potential force under certain conditions is released and becomes an active factor, not only in the formation of cloud and the precipitation of rain, hail, and snow, but it disturbs the equilibrium of the air and sets that in motion. ”

“ Such currents coming towards the equator, that is, travelling from latitudes where the earth’s eastwardly motion is less to latitudes where that motion is greater, would lag behind, that is, would have a westwardly motion. ”

“ The motion of the earth's axis would reconcile all the facts known, and it must be regarded as a geological desideratum to determine its amount and direction, and to assign the cause of such a movement. ”