On Sunday, August 2, 2020 at 5:00:22 PM UTC-6, Alan Grayson wrote: > > > > On Sunday, August 2, 2020 at 1:55:15 PM UTC-6, Lawrence Crowell wrote: >> >> I looked at the precession question, wrote it in WORD and then posted it >> in the wrong thread. A big line of anti-virus defense is working off-line. >> I do a lot of work locally and pop on and off the internet. I try to never >> leave my machines on-line with an open port for anyone or any bot to enter >> to cause mischief. >> >> With this the question is odd. How something moves in free and flat space >> and spacetime is just determined by its initial conditions. >> >> LC >> > > If one starts with SR and zero curvature of spacetime, and places a test > particle in that spacetime spatially at rest, how will spacetime tell > matter how to move if spacetime isn't curved? AG >
I think in this situation the direction of motion is ambiguous. AG > >> >> >> >> On Sunday, August 2, 2020 at 9:05:57 AM UTC-5 [email protected] wrote: >> >>> >>> >>> On Sunday, August 2, 2020 at 5:30:36 AM UTC-6, Lawrence Crowell wrote: >>>> >>>> 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 >>>> >>> >>> I appreciate your grasp of the history, but you haven't answered my >>> question and don't seem aware of what it is (plus you posted your reply on >>> the wrong thread). AG >>> >>>> >>>> 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/dddfe57e-d619-446b-949a-90d2b23e4576o%40googlegroups.com.
