Orbiting the earth 1

Isaac Newton (1642–1727)
De motu corporum in gyrum Liber II
Cambridge, ca 1684

This second example of a manuscript deposited by Newton as Lucasian Professor once more reflects work in composition of the Principia. We see how his ideas on gravity as a centripetal force to give orbital motion occupied him at this period, very shortly after his meeting with Edmond Halley in 1684. Newton’s small sketch on the verso of the first of these folios illustrates it all – ‘the cannon on the mountain top fires off a ball with increasing velocity and it is carried in a curved line … by increasing the velocity … so that it might never fall to the earth…’.

MS Dd.4.18, ff.1v–2r

Extended captions