ABSTRACT
Halley had made his first acquaintance with Isaac Newton two years earlier, in 1682. The Lucasian Professor of Mathematics, known outside Cambridge as the author of a few remarkable papers on light and color and as a secretive mathematical prodigy, might perhaps be of help in disentangling the riddle, so Halley now looked him up to ask him “what he thought the Curve would be that would be described by the Planets supposing the force of attraction towards the Sun to be reciprocal to the square of their distance from it.” 349 To which query Newton answered right away that it would be an ellipse. Halley, “struck with joy & amazement”, asked in return how his host knew that. To which query Newton answered that he had calculated it; which answer both men perfectly understood to mean that, rather than just the lucky guess it had so far seemed at best, this was a property amenable indeed, as Hooke had vainly boasted and as Wren and Halley still hoped, to rigorous proof.
