The periapsis or perihelion advance of Mercury is largely a result of classical perturbation theory in classical mechanics. About 10% of the perihelion advance could not be accounted for by perturbation methods in classical mechanics.
This has to be admired in some ways. Finding the ephemeris of Mercury is tough, for the planet makes brief appearances near the sun in mornings and evenings. Finding an orbital path from its course across the sky is not easy. The second issue is that perturbation methods in classical mechanics are difficult. These were developed arduously in the 19th century and Le Verrier worked on this to find the planet Neptune from the perturbed motion of Uranus in 1848. These methods were worked on through the 19th century. The later work of von Zeipel and Poincare were used to compute the periapsis advance of Mercury, but there was this persistent 43arc-sec/year that resisted these efforts. It was general relativity that predicted this anomaly in ways that are far simpler than the classical perturbation methods. This post-diction of GR was an initial success in the theory, followed up shortly by the Eddington expedition that found the optical effects of GR in a solar eclipse in 1919. LC On Sunday, August 2, 2020 at 3:49:28 AM UTC-5 [email protected] wrote: > > > On Saturday, August 1, 2020 at 10:35:09 PM UTC-6, Alan Grayson wrote: >> >> In flat space, which is tantamount to assuming the absence of gravity, >> and non-zero curvature, a body placed at spatial coordinates x,y,z, will >> move because t increments. But if there is zero curvature, in which >> direction will it move? That is, how is the direction of motion determined? >> TIA, AG >> > > CORRECTION; above, I meant to write, " ... which is tantamount to assuming > the absence of gravity and ZERO curvature, ... " AG > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/a72d6699-91ec-4ebd-9ee3-8d45667a7960n%40googlegroups.com.
