Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 56
s along a meridian. If the statement is true for this case, it will be true for all others, because a sphere has the same curvature in every direction. Suppose the observer starts from Oi, Fig. 5, and travels northward to O2. The length of the arc O1O2 is proportional to the angle a which it… … Fig. 5. — The change in the di-rection ■ of the plumb line isproportional to the distancetraveled along the surface ofthe earth. 28 AN INTRODUCTION TO ASTRONOMY [ch. ii, 10 These lines are respectively perpendicular to COi and CO2.Therefore the angle between them equals the angle a. Thatis, the…
Astronomy
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