Isaac Newton's physics of interparticulate forces and the aether queries.

Contemporaries who only knew Newton's natural philosophy from his published works would have seen him as a thinker who was thoroughly opposed to the concept of an all-pervasive universal aether. There was no need, mathematically or physically, for an aether in the natural philosophy presented in his Principia (1687). Newton insisted that an aether was not only not required, but would actually prevent the smooth running of the world system. This state of affairs changed dramatically, however, when Newton published the second English edition of the Opticks (1717). In a series of eight new 'Queries' interpolated into the sequence of speculative proposals which brought the Opticks to a conclusion, Newton suggested that an aether might be responsible for some optical phenomena and even for gravitational attraction. The aim of this article is to show that this was not a concession on Newton's part to the age-old concept of a mechanical aether, working by material contact action, but was rather a further attempt to promote the speculative physics, presented in earlier queries, which was based on the assumption that many phenomena may be explained by attractive and repulsive forces operating between the invisibly small particles of matter which were held to constitute all bodies.