Alfred Wegener: Difference between revisions

The creation of a mondernizedmodernized edition of these tables had applications to a problem in astronomy in which both Bauschinger and Forster were keenly interested. About thirty years before, in 1870, the American astronomer Simon Newcomb had discovered that the set of tables he was using to predict the position of the Moon showed increasing deviations from the Moon's actual position. This was disturbing to Newcomb because the tables in question had been prepared by the German astronomer Peter Hansen, probably one of the greatest master of celestial mechanics since Laplace. To figure out what had gone wrong, Newcomb traveled to Europe to study even older tables of the Moon's motion. He found that the farther he worked back before 1750, the greater the discrepancy became. He conceived the notion, based on his confidence in Hansen, that the reason for the discrepancy had to be a variation in Earth's rate of rotation. Newcomb worked steadily on this problem until the end of his life, assembling astronomical records back to preclassical antiquity to try to determine the pattern of rotational variation.

Alfred provided a correction for the difference between Toledo, Spain -- the 0° of longitude in the tables -- and Greenwich, England -- the 0° of longitude for modern astronomy. He uncovered a systematic sixteen-minute offset in the tables resulting from a discrepancy between the Alfonsine way of calculating the mean time of a transit and the modern method of doing so. Finally, he devised a formal to eliminate a correction in the tables meant to account for the precession of the equinoxes which empoloyedemployed a (nonexistent) celestial motion called a "trepidation", which the modern user must discount. He also drew up a concise glossary of Latin technical terms for which there were no German counterparts, since the concepts in question had vanished from astronomy before German had become a scientific language.

He had to provide extensive notes to give astronomical calculators the means to use them. The calculators in question were not machines, but observatory staff whose job it was to perform actual calculations. It required several explanations. The tables for the Sun are used differently thatnthan the tables for the Moon. Meanwhile, there are separate sets of tables for each of the planets. Latitudes are calculated in a way quite different from the calculation of longitude and distance. These require separate tables and figures showing the geometry of the relationships.