Elements of astronomy ..with explanatory notes, and questions for examination . al bodies, her average distance being about 239,000miles. The measurement of this distance is obtained inthe same way as the distance of the earth from the parallax of the moon is found to be about 57, andthe length of the earths radius being known, the calcu-lation is made as follows. 264. Let M Fig. 51, represent the centre of the moon,E the surface of the earth, 0 its centre, OE a radius ; andMO and ME, lines drawn from the moons centre to the How much hotter is a given surface at the sun than at the ear
Elements of astronomy ..with explanatory notes, and questions for examination . al bodies, her average distance being about 239,000miles. The measurement of this distance is obtained inthe same way as the distance of the earth from the parallax of the moon is found to be about 57, andthe length of the earths radius being known, the calcu-lation is made as follows. 264. Let M Fig. 51, represent the centre of the moon,E the surface of the earth, 0 its centre, OE a radius ; andMO and ME, lines drawn from the moons centre to the How much hotter is a given surface at the sun than at the earth ? What is said re-specting the splendor of the solar light 1 What is the subject of Chapter Second 1 Whatis said respecting the motions of the moon, and her influence upon our globe 1 What issaid in regard to her distance from the earth? How far is she from the earth ? How isher distance in miles ascertained ? What is the amount of her parallax 1 144 SOLAR SYSTEM. earths centre and surface; we thus have a triangle inwhich MEO is a right angle, EMO 57, and MOE 89° FIG MOON S DISTANCE MEASURED. We now select a similar triangle ; suppose M^O1to be such a triangle, and that the side MX)1 is onemile long, then the trignometrical tables show us thatCVE1 must be sixteen thousand five hundred and eightymillionihs of a mile long (016580,) and we establish fromthe sides of the similar triangles the following propor-tion; to wit, .016580 (OE1): 1 (MO1) : : (OE) : 238,613 miles (MO.) The fourth term, found by thecommon rule of three, is the distance of the moon from theearths centre measured in miles. When all the niceties ofcalculation are introduced into the computation theaverage distance is found to be 238,650 miles. 265. Diameter in Miles. In the same manner thediameter of the moon in miles is ascertained, when wehave first learned her distance in miles. For if we repre-sent the moons centre, Fig. 52, by L, and the earths byE, and imagine two lines drawn from the c
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