Elements of astronomy ..with explanatory notes, and questions for examination . on is nearer to the surface of the earthwhen in the zenith than when upon the horizon, by about When will no eclipse occur? Upon what does the extent of terrestrial surface coveredby the shadow depend ? Give the two illustrations? What is the greatest extent ofsurface obscured by the shadow 1 State wliut is said respecting the penumbra and itsbreadth 1 Illustrate from Fig. 62. ALTITUDE OF THE MOON. 183 4,000 miles, it may happen that a solar eclipse #takesplace in one part of the world, and not in another. Twoplace
Elements of astronomy ..with explanatory notes, and questions for examination . on is nearer to the surface of the earthwhen in the zenith than when upon the horizon, by about When will no eclipse occur? Upon what does the extent of terrestrial surface coveredby the shadow depend ? Give the two illustrations? What is the greatest extent ofsurface obscured by the shadow 1 State wliut is said respecting the penumbra and itsbreadth 1 Illustrate from Fig. 62. ALTITUDE OF THE MOON. 183 4,000 miles, it may happen that a solar eclipse #takesplace in one part of the world, and not in another. Twoplaces may be so situated that the moon is on the horizonat one station and in the zenith at the other, when a solareclipse is about to happen. Now it is possible that thelunar shadow may fall just short of the place where themoon appears upon the horizon, but as the other stationis nearer to the moon by about 4,000 miles, the shadowmay reach the latter place, and the sun will consequentlyfor a short time be there eclipsed. 368. This phenomenon is illustrated by Fig. 63. FIG. AIiTITUDE OF THE MOON ITS EFFECT ON ECLIPSES. Here ZBHE represents the earth, OR the moons orbit,M and M1 two positions of the moon, and S, S1 hershadow. To a spectator at H, the moon M is on thehorizon, and there is no eclipse, since the shadow doesnot reach him, but when the moon in her orbitual mo-tion is at M1 she is in the zenith to a spectator at Z, andthe shadow reaches the earth causing an eclipse,l though 1. The distance between the centres of the moon in the two positionsM and M1 is equal to the distance between the extremities of S, S1,, to the radius of the earth, or about 4,000 miles. By dividing thelength of the moons orbit by the time of her revolution, we obtain hervelocity, which is more than 2,000 miles per hour. The moon thereforemoves from M to M1 in less than two hours, and the shadow is likewisecarried from S to S1 in the same time. Explain how the altitude of the moon modifies ec
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Keywords: ., bookcentury1800, bookdecade1850, bookidelem, booksubjectastronomy
