Talk:Discovery of precession
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[edit] Passages removed from source
I created this article with a cut-and-paste from Hipparchus (astronomer), which has outgrown itself. I rewrote almost everything I took from the source article, but kept most of the information. These two paragraphs contain some things I left out, because it was wrong or misleading (see Hipparchus' talk page for more), or because I wasn't sure what to do with it.
- After him many Greek and Arab astronomers had confirmed this phenomenon. Ptolemy compared his catalogue with those of Aristillus, Timocharis, Hipparchus and the observations of Agrippa and Menelaus of Alexandria from the early 1st century and he finally confirmed Hipparchus' empirical fact that the poles of the celestial equator in one Platonic year (approximately 25,777 sidereal years) encircle the ecliptical pole. The diameter of this circle is equal to the inclination of ecliptic relative to the celestial equator. The equinoctial points in this time traverse the whole ecliptic and they move 1° in a century. This velocity is equal to that calculated by Hipparchus. Because of these accordances, Delambre, P. Tannery and other French historians of astronomy had wrongly jumped to conclusions that Ptolemy recorded his star catalogue from Hipparchus' with an ordinary extrapolation. It was not known until 1898 when Marcel Boll and others had found that Ptolemy's catalogue differs from Hipparchus' not only in the number of stars but in other respects.
- This phenomenon was named by Ptolemy just because the vernal point γ leads the Sun. In Latin praecesse means "to overtake" or "to outpass", and today also means to twist or to turn. Its own name shows this phenomenon was discovered before its theoretical explanation, otherwise it would have been given a better term. Many later astronomers, physicists and mathematicians had occupied themselves with this problem, practically and theoretically. The phenomenon itself had opened many new promising solutions in several branches of celestial mechanics: Thabit ibn Qurra's theory of trepidation and oscillation of equinoctial points, Isaac Newton's general gravitational law (which had explained it in full), Leonhard Euler's kinematic equations and Joseph Lagrange's equations of motion, Jean d'Alembert's dynamical theory of the movement of a rigid body, some algebraic solutions for special cases of precession, John Flamsteed's and James Bradley's difficulties in the making of precise telescopic star catalogues, Friedrich Bessel's and Simon Newcomb's measurements of precession, and finally the precession of perihelion in Albert Einstein's general theory of relativity.
The bits on the French historians and post-Newtonian scientists might be worth reworking if someone had the time and inclination. Maestlin 18:48, 28 March 2006 (UTC)
