Newton on elliptical motion. Book page showing text and a diagram concerning elliptical motion as proposed by English physicist and mathematician Isaac Newton (1642-1727). This text (in Latin) is part of proposition 10, problem 5, from book 1 of Newton's 'Philosophiae Naturalis Principia Mathematica' (1686). Book 1 of 'Principia' was titled 'Of the Motion of Bodies' (Latin: De Motu Corporum). Proposition 10 states: 'If a body revolves in an ellipsis; it is proposed to find the law of the centripetal force tending to the centre of the ellipsis'. This was later applied to Newton's laws of motion and his derivation of Kepler's laws of planetary motion.