Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 276
who spent more than20 years in attempting to findfrom the observations of his master the manner in which theplanets actually move. The results of an enormous amountof calculation on his part are contained in the following threelaws of planetary motions : I. Every planet moves so that the line… … Johann Kepler. 230 AN INTRODUCTION TO ASTRONOMY [ch. viii, 145 III. The squares of the periods of any two planets areproportional to the cubes of their mean distances from thesun. All the complexities of the apparent motions of the planetsare explained by Keplers three simple laws when taken…
Astronomy
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