Apart from statics, about which I shall say nothing, there were three chief centres of interest in mechanics in the 1660's: the motions of pendulums; the laws of motion; the free fall of heavy bodies and the motion of projectiles.In the first the influence of Huygens was dominant; I have placed it so because it was of very lively contemporary concern. The second area of interest descended partly from Galileo and partly from Descartes; the third from Galileo alone. Perhaps one (...) should consider adding a fourth area, the investigation of central forces, but this in fact did not attract much attention as yet. (shrink)

Historians of seventeenth-century science have frequently asserted that Kepler's laws of planetary motion were largely ignored between the time of their first publication and the publication of Newton's Principia . In fact, however, they were more widely known and accepted than has been generally recognized.Kepler's ideas were, indeed, rather slow in establishing themselves, and until about 1630 there are few references to them in the literature of the time. But from then onwards, interest in them increased fairly rapidly. In particular, (...) the principle of elliptical orbits had been accepted by most of the leading astronomers in France before 1645 and in England by about 1655. It also received quite strong support in Holland.The second law had a more chequered history. It was enunciated in its exact form by a few writers and was used in practice by some others without being explicitly formulated, but the majority, especially after 1645, preferred one or another of several variant forms which were easier to use but only approximately correct. The third law attracted less interest than the others, chiefly perhaps because it had no satisfactory theoretical basis, but it was correctly stated by at least six writers during the period under review.Between about 1630 and 1650 Kepler's Epitome Astronomiae Copernicanae was probably the most widely read work on theoretical astronomy in northern and western Europe, while his Rudolphine Tables, which were based upon the first two laws, were regarded by the majority of astronomers as the most accurate planetary tables available.Kepler's work certainly did not receive all the recognition it deserved, but the extent to which it was neglected has been much exaggerated. (shrink)

The conventional view of the prehistory of Newton's synthesis in the Principia of his predecessors' work in planetary theory and terrestrial gravitation is still not seriously changed from that which Newton himself chose to impose on his contemporaries at the end of his life. In his own words:‘… the same year ‘1666’ I began to think of gravity extending to ye orb of the Moon & having found out how to estimate the force wth wch [a] globe revolving within a (...) sphere presses the surface of the sphere from Keplers rule of the periodical times of the Planets being in a sesquialterate proportion of their distances from the centers of their Orbs, & having deduced that the forces wch keep the Planets in their orbs must [be] reciprocally as the squares of their distances from the centers about wch they revolve: & thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the earth, & found them answer pretty nearly …’. (shrink)

From the very day in 1686 when Edmond Halley placed Book I of the Principia before the Royal Society, Robert Hooke's claim to prior discovery has been associated with the law of universal gravitation. If the seventeenth century rejected Hooke's claim summarily, historians of science have not forgotten it, and a steady stream of articles continues the discussion. In our own day particularly, when some of the glitter has worn off, not from the scientific achievement, but from the character of (...) Newton, there has been a tendency vicariously to atone for the treatment Hooke received. The judgement Lohne cites with approval from Vavilov appears to summarize the current estimate of the issue—in the seventeenth century only Newton could have written the Principia; nevertheless Hooke first sketched out its programme. What with all the knocks he has received both alive and dead, one feels guilty in assuming the role of “debunker” at this late date. Apologetically draped in sackcloth then, head covered with ashes I venture softly to suggest that Hooke has received more than his due. There is no question here of justifying Newton's behaviour toward Hooke. Wholly lacking in generosity as it appears to me, Newton's behaviour neither deserves nor can receive justification. The question turns rather on Hooke's scientific theories. Granting always his lack of demonstrations, historians have been prone to interpret his words in the light of Newton's demonstrations. A close examination of Hooke's writings does not sustain the interpretation. Contrary to what is generally asserted, he did not hold a conception of universal gravitation. And if he announced the inverse square relation, he derived it from such a medley of confusion as will not allow his claim to priority. (shrink)