An Attempt to Prove the Motion of the Earth from Observations

Hooke's 1674 Cutlerian Lecture — anticipating the inverse-square law and stellar parallax

Tradition: Royal-Society experimental philosophy / Newtonian-prehistory celestial mechanics

Hooke's 1674 lecture — earliest published statement of the inverse-square hypothesis for celestial motion

Published in 1674, 'An Attempt to Prove the Motion of the Earth from Observations' is a short Cutlerian Lecture by Hooke at Gresham College that contains one of the most consequential anticipations of Newtonian celestial mechanics. The pamphlet describes Hooke's astronomical-observational work attempting to detect stellar parallax (the apparent annual displacement of nearby stars against more distant ones that would be observable if the Earth orbits the sun); Hooke believed he had detected such parallax (his observations were in fact too imprecise — actual stellar parallax was first measured by Friedrich Bessel in 1838), but the philosophical-physical conclusion he draws is the consequential one. The pamphlet ends with what Hooke calls 'A System of the World differing in many particulars from any yet known' — three principles that anticipate Newtonian gravitational mechanics by 13 years (before the 1687 Principia): (1) 'all caelestial Bodies whatsoever, have an attraction or gravitating power towards their own Centers, whereby they attract not only their own parts, and keep them from flying from them, as we may observe the Earth to do, but that they do also attract all the other caelestial Bodies that are within the sphere of their activity'; (2) 'all bodies whatsoever that are put into a direct and simple motion, will so continue to move forward in a streight line, till they are by some other effectual powers deflected and bent'; (3) 'these attractive powers are so much the more powerful in operating, by how much the nearer the body wrought upon is to their own Centers' (universal gravitation decreasing with distance — Hooke would later, in his 1679-80 correspondence with Newton, propose specifically inverse-square gravitation). The pamphlet is the principal evidence for Hooke's claim to priority in the development of universal gravitation; the Hooke-Newton priority dispute over universal gravitation (which broke out in 1686-87 with the Principia's publication) centred on whether Hooke's 1674 statement and his 1679-80 correspondence with Newton entitled him to priority.