Text: The Newtonian law is thus stated by Herchel: "Every particle of matter in the universe attracts every other particles of matter with a force directly proportioned to the mass and inversely to the square of the distance between them. Under the influence of such an attractive for mutually urging two spherical gravitation bodies toward each other, they will each, when moving in each other's neighborhood, be deflected into an orbit concave toward each other, and describe one about the other regarded as fixed, or both around their common center of gravity curves, whose forms are limited to those figures known in geometry by the general name of conic sections. It will depend, in any assigned case, upon the particular circumstances or velocity, distance and direction, which of these curves shall be described, whether an ellipse, a circle, a parabola, or an hyperbola; but one or the other it must be, and any one of any degree of eccentricity it may be; and that in every case, the angular velocity with which the line joining their centers moves, must be inversely proportional to the square of their mutual distance, and that equal areas of the curves described will be swept over by their line of junction in equal times." This statement includes the first and second law of Kepler. His third law is, that "the squares of the periodic times of any two planets are to each other in the same proportion as the cubes of their mean distances from the sun."

See Also: LEVITATION, VACUUM

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