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On the Connexion of the Physical Sciences von Somerville, Mary (eBook)

  • Erscheinungsdatum: 27.09.2016
  • Verlag: anboco
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On the Connexion of the Physical Sciences

Science, regarded as the pursuit of truth, must ever afford occupation of consummate interest, and subject of elevated meditation. The contemplation of the works of creation elevates the mind to the admiration of whatever is great and noble; accomplishing the object of all study, which, in the eloquent language of Sir James Mackintosh, 'is to inspire the love of truth, of wisdom, of beauty-especially of goodness, the highest beauty-and of that supreme and eternal Mind, which contains all truth and wisdom, all beauty and goodness. By the love or delightful contemplation and pursuit of these transcendent aims, for their own sake only, the mind of man is raised from low and perishable objects, and prepared for those high destinies which are appointed for all those who are capable of them.' Astronomy affords the most extensive example of the connection of the physical sciences. In it are combined the sciences of number and quantity, of rest and motion. In it we perceive the operation of a force which is mixed up with everything that exists in the heavens or on earth; which pervades every atom, rules the motions of animate and inanimate beings, and is as sensible in the descent of a rain-drop as in the falls of Niagara; in the weight of the air, as in the periods of the moon. Gravitation not only binds satellites to their planet, and planets to the sun, but it connects sun with sun throughout the wide extent of creation, and is the cause of the disturbances, as well as of the order of nature; since every tremor it excites in any one planet 2is immediately transmitted to the farthest limits of the system, in oscillations which correspond in their periods with the cause producing them, like sympathetic notes in music, or vibrations from the deep tones of an organ. The heavens afford the most sublime subject of study which can be derived from science.


    Format: ePUB
    Kopierschutz: watermark
    Seitenzahl: 1330
    Erscheinungsdatum: 27.09.2016
    Sprache: Englisch
    ISBN: 9783736416154
    Verlag: anboco
    Größe: 2558 kBytes
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On the Connexion of the Physical Sciences


Attraction of a Sphere-Form of Celestial Bodies-Terrestrial Gravitation retains the Moon in her Orbit-The Heavenly Bodies move in Conic Sections-Gravitation Proportional to Mass-Gravitation of the Particles of Matter-Figure of the Planets-How it affects the Motions of their Satellites-Rotation and Translation impressed by the same Impulse-Motion of the Sun and Solar System.

It has been proved by Newton, that a particle of matter ( N. 6 ) placed without the surface of a hollow sphere ( N. 7 ) is attracted by it in the same manner as if the mass of the hollow sphere, or the whole matter it contains, were collected into one dense particle in its centre. The same is therefore true of a solid sphere, which may be supposed to consist of an infinite number of concentric hollow spheres ( N. 8 ). This, however, is not the case with a spheroid ( N. 9 ); but the celestial bodies are so nearly spherical, and at such remote distances from one another, that they attract and are attracted as if each were condensed into a single particle situate in its centre of gravity ( N. 10 )-a circumstance which greatly facilitates the investigation of their motions.

Newton has shown that the force which retains the moon in her orbit is the same with that which causes heavy substances to fall at the surface of the earth. If the earth were a sphere, and at rest, a body would be equally attracted, that is, it would have the same weight at every point of its surface, because the surface of a sphere is everywhere equally distant from its centre. But, as our planet is flattened at the poles ( N. 11 ), and bulges at the equator, the weight of the same body gradually decreases from the poles, where it is greatest, to the equator, where it is least. There is, however, a certain mean ( N. 12 ) latitude ( N. 13 ), or part of the earth intermediate between the pole and the equator, where the attraction of the earth on bodies at its surface is the same as if it were a sphere; and experience shows that bodies there fall through 16·0697 feet in a second. The mean distance ( N. 14 ) of the moon from the earth is about sixty times the mean radius ( N. 15 ) of the earth. When the number 16·0697 is diminished in the ratio ( N. 16 ) of 1 to 3600, which is the square of the moon's distance ( N. 17 ) from the earth's centre, estimated in terrestrial radii, it is found to be exactly the space the moon would fall through in the first second of her descent to the earth, were she not prevented by the centrifugal force ( N. 18 ) arising from the velocity with which she moves in her orbit. The moon is thus retained in her orbit by a force having the same origin, and regulated by the same law, with that which causes a stone to fall at the earth's surface. The earth may, therefore, be regarded as the centre of a force which extends to the moon; and, as experience shows that the action and reaction of matter are equal and contrary ( N. 19 ), the moon must attract the earth with an equal and contrary force.

Newton also ascertained that a body projected ( N. 20 ) in space ( N. 21 ) will move in a conic section ( N. 22 ), if attracted by a force proceeding from a fixed point, with an intensity inversely as the square of the distance ( N. 23 ); but that any deviation from that law will cause it to move in a curve of a different nature. Kepler found, by direct observation, that the planets describe ellipses ( N. 24 ), or oval paths, roun

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