Page 199 - 89 history of astronomy_opt

It took him nine years more[3] to dis-
cover his third law, that the squares of the
periodic times are proportional to the cubes
of the mean distances from the sun.
These three laws contain implicitly the
law of universal gravitation. They are sim-
ply an alternative way of expressing that
law in dealing with planets, not particles.
Only, the power of the greatest human in-
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