Dunthorne, Mayer, and Lalande on the Secular Acceleration of the Moon

Abstract

On 19th October 1692 Edmond Halley read a paper to the Royal Society in which he claimed for the first time that the motion of the Moon was subject to a long-term acceleration. The Journal Book of the Royal Society notes the occasion as follows:

October 19, 1692. Halley read a paper, wherein he endeavoured to prove that the opposition of the Medium of the Æther to the Planets passing through it, did in time become sensible. That to reconcile this retardation of the Motions the Ancients and Moderns had been forced to alter the differences of the Meridians preposterously. That Babylon was made more westerly than it ought by near half an hour, both by Ptolomaeus, and those since him. And to reconcile the Observations made by Albategnius at Antioch, and Aracla on the Euphrates, they have been forced to make these places ten degrees more Easterly, than they ought, particularly Mr. Street has made Antioch of Syria in his Table of Longitudes, and Latitudes of places half an hour more Easterly than Babylon, whereas in truth it is about 40 minutes more Westerly. That this difference is found by 4 Eclipses observ’d about the year 900 and that by an Artist not capable of mistaking, that they all 4 agree in the same result and are noe other ways to be reconciled. Hence he argued, that the Motions being retarded must necessarily conclude a finall period and that the eternity of the World was hence to be demonstrated impossible. He was ordered to prosecute this Notion, and to publish a discourse about it. (MacPike 1932, p. 229)