|WikiProject Physics||(Rated Stub-class, Mid-importance)|
I am removing the large block of text added on 23 April 2009 by the anonymous editor 22.214.171.124 for many reasons. First, it is a copyright violation because most of the text comes from Einstein's Nemesis#1: DI Herculis apsidal motion puzzle solution by Professor Joe Nahhas and the remainder comes from a dead link also by Nahhas. Second, it is a fringe theory because it states that Einstein's general relativity is wrong. Third, it is much too technical for an article in an encyclopedia. Fourth, it overpowers the rest of the article, which is concerned with Newtonian apsidal precession, that is, that due to the perturbations of other planets. — Joe Kress (talk) 02:12, 31 May 2009 (UTC)
Apsidal precession versus Axial precession
That chart at the bottom of this page about the "effect" of apsidal precession on the seasons can't possibly be right--at least, the reality is too much more complicated to make that chart useful. The chart implies--or requires--that the earth's axis maintains the same orientation as apsidal precession proceeds. Except this isn't true. Both axial and apsidal precession would have the exact same, and indistinguishable, "effect" on the seasons, but it is really incorrect to talk about either without mentioning the other. — Preceding unsigned comment added by 126.96.36.199 (talk) 17:30, 17 July 2012 (UTC)
- I assume you are referring to the directions of the red arrows relative to the equinoctial and solsticial points, which are the four orientations that remain the same through all four figures (they rotate relative to the frame, but not relative to each other). This is what they should do. For example, the vernal equinox is defined such that the red arrow must be tangential to Earth's orbit and its north pole must point (tilt) toward the direction opposite to Earth's direction of revolution around its orbit.
- While Earth's axis precesses −50.3"/Julian year, its elliptical orbit also precesses in the opposite direction +11.6"/Julian year, both relative to the fixed stars or inertial space. Their sum, 61.9"/Julian year, shows that the vernal equinox precesses relative to the perihelion in 1,296,000"/61.9" = 20,900 Julian years. Only one change could be made to the figure, which would be to regard its retangular frame as inertial space. As time progresses clockwise around the frame, the ellipse would then tilt slightly counter-clockwise through the four figures. However, this might be detrimental to understanding the phenomenon because the left figure would no longer be 5,000 years ago, only 15,000 years in the future. As Earth's axis precesses 58% of its 26,000-year axial precession cycle as time progresses through the figure's four ellipses (15,000/26,000=58%), so the red arrow/vermal equinox point (for example) should rotate 58% of 360° or 210° CW from the top figure to the time of the left figure, while the ellipse rotates about 50° CCW (15,000/113,000×360).
- Axial precession and apsidal precession do not have the same affect on the seasons. The graphic shows that their combination has a cycle of 21,000 years, which only indicates a cycle in solar forcing. Another such cycle is the 41,000-year cycle due to Earth's obliquity, the tilt of Earth's axis relative to its orbit. Unfortunately, the ice ages have a 100,000-year period. Read Milankovitch cycles. — Joe Kress (talk) 03:48, 18 July 2012 (UTC)
dependence on gravity field / oblateness
The formulas (and explanations of course) should be added. See for example this paper: precession of orbits about an oblate planet (Greenberg, Astronomical Journal, vol. 86, June 1981, p. 912-914) --Kondephy (talk) 13:11, 19 November 2013 (UTC)