The third, viz. that the squares of the periodic times are proportional to the cubes of the mean distances... History of Astronomy - Page 53 by George Forbes - 1909 - 200 pages Full view - About this book
...times. And he had found, near the end of his life, a third law connecting the different orbits. (3) The squares of the periodic times are proportional to the cubes of the semi-axes major (or of the mean distances). 81. Attempts had even been made to explain the planetary...