Astronomy for the use of schools and academies (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908, Rolfe, W. J. (William James), 1827-1910 · New York : Potter, Ainsworth, & Co. · leaf 64
move from P\o Pl in the same time that it would movefrom P2 to P\ or from P* toPs; then the dark spaces, whichwould be swept over by a linejoining the sun and the planet,in these equal times, would allbe equal. A line drawn from the sun to a planet is called theradius vector of the planet. The… … Fig. 56. 4<S ASTRONOMY. follows that a planet must move fastest when at perihelion,and slowest at aphelion. Keplers See and Law of planetary motion is usuallystated as follows : The radius vector of a planet describesequal areas in equal times in every part of the planetsorbit. 46. Keplers Third…
Astronomy
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