The Principia and comets. (English) Zbl 0641.01006

According to Newton’s law of gravitation any conic section is a possible orbit for any celestial body, comets included. The author surveys the sections of the ‘Principia’ – in its first as well as its third edition – which deal with comets, e.g. their orbital parameters, their planetary origins, their luminosity variation, tail formation, periodicity, and mass – supposed to be of the same order of magnitude as the masses of planets. He also traces, in letters exchanged with John Flamsteed and Edmond Halley, the key role played by the Great Comet of 1680 for the discovery of the law of gravitation.
Reviewer: Kr. P. Moesgaard

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