. The Boston school compendium of natural and experimental philosophy .. . eir axes cause; 461. What is said with regardto the motion of the heavenly bodies ? When do they move with the greatest ve-locity ? When is their motion the slowest ? What is Keplers law ? ASTRONOMY. 197 Fig. 136. Illustration. In fig. 136, let S represent the Sun, and E theEarth and the ellipse or oval be the earths orbit or path around theSun Bv lines drawn from the Sun at S to the outer edge of the figure, the orbit is divid-ed into twelve areas (orparts) of different shapes,but each containing thesame quantity of sp
. The Boston school compendium of natural and experimental philosophy .. . eir axes cause; 461. What is said with regardto the motion of the heavenly bodies ? When do they move with the greatest ve-locity ? When is their motion the slowest ? What is Keplers law ? ASTRONOMY. 197 Fig. 136. Illustration. In fig. 136, let S represent the Sun, and E theEarth and the ellipse or oval be the earths orbit or path around theSun Bv lines drawn from the Sun at S to the outer edge of the figure, the orbit is divid-ed into twelve areas (orparts) of different shapes,but each containing thesame quantity of , the spaces E S A,A S B, D S F, &c. are allsupposed to be equal. Nowifthe earth, in the space ofone month will move in itsorbit from E to A, it willin another month movefrom A to B, and in thethird month from B to C,&c; and thus will describe(or rather more properly-speaking, pass by) equalareas in equal times. The reason why theearth (or any other heav-enly body) moves with agreater degree of velocityin its perihelion, than inits aphelion, may likewise. be explained by the same Earth in its progress from Thus:FtoL being constantly actuated by the suns attraction, must, (as is the case with a stone when fallingto the earth,) (See No. 110,) move with an accelerated L, the suns attraction becomes stronger, on account of the near-ness of the earth ; and consequently in its motion from L to E, theearth will move with greater rapidity. At E, which is the perihe-lion of the earth, it acquires its greatest velocity. Let lis now de-tain it at E, merely to consider the direction of the forces by whichit is actuated. If the suns attraction could be destroyed, the forcewhich has carried it from L to E, would carry it off in the dottedline from E to G, which is a tangent to its orbit. But while the Earthhas this tendency to move towards G, the suns attraction is contin-ually operating, with a tendency to carry it to S. Now when abody is actuated by two forces,
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Keywords: ., bookcentury1800, bookdecade1830, booksubjectphysics, bookyear1837
