D O C . 5 0 6 A N N I V E R S A R Y O F N E W T O N ’ S D E AT H 5 0 3 Newton gives us only scant insight into his intellectual workshop. But it may perhaps have happened like this. The movement of the Moon around the Earth was known, and hence also the acceleration which the moon receives from Earth and which must necessarily be directed toward the center of Earth to maintain its orbit. But the acceleration that Earth imparts to falling bodies near its surface is also known. Through comparison, Newton found that these accelerations relate roughly inversely to the square of Earth’s radius and the distance Earth–Moon. The Earth’s force action through gravitation therefore seemed to be inversely proportional to the square of the distance. Shouldn’t any mass act in an analogous way to Earth? This assumption was brilliantly confirmed in that on the basis of this hypothesis— applied to the force action coming from the sun—the laws of planetary motion that Kepler had postulated on the basis of Tycho de Brahe’s observations of the planets could be completely explained. This was easier said than done, because subtle mathematical deductions were required to derive the orbital movements from the law of forces and the law of acceleration. But a brilliant achievement crowned Newton’s law of forces in that, thanks to Kepler’s admirable analysis, the laws of planetary motion were known to a high degree of accuracy. The only remaining cloud in Newton’s sky was that the relation between the Earth’s radius and the Moon’s orbit, mentioned above, fit Newton’s law of forces only approximately but not exactly. But by about six years later, Picard’s determination of the meridian[8] showed that this was explained by an imprecise knowledge of the Earth’s radius at the time, and Newton’s work was confirmed more strongly than any other theory prior to his. Newton’s achievements in the area of light theory were just as path-breaking, but they receive only brief mention here. Even less attention is granted to his per- sonal destiny, that he was a mathematics professor and a master of the mint. But it must be mentioned that the English nation proved worthy of this gift from heaven that Newton represented and still does represent to it and to the world. It must also be said that Newton was steeped in a deep feeling of religiosity, from which he undoubtedly drew a large part of the superhuman energy he needed to fulfill his lifework. Today, Newton’s construct of forces-at-a-distance is replaced by field theories,[9] his law of motion is modified but everything that has been created since is an organic continuation of his ideas and methods. We in Germany remem- ber him today as one of the most important initiators of modern intellectual life. [p. 40]