On Monday, August 3, 2020 at 12:15:23 PM UTC-6, Alan Grayson wrote: > > > > On Monday, August 3, 2020 at 8:55:17 AM UTC-6, Alan Grayson wrote: >> >> >> >> 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 >> > > No. It doesn't spatially move, but it moves in space-time since the > observer's clock continues to advance. AG >
What bothers me about this is that the spatial coordinates generally depend on each other, and time. In this situation will the geodesic equations yield a solution where the spatial coordinates remain fixed? 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/1eb6b644-3bcc-444e-a61d-2bf7aabdd10fo%40googlegroups.com.
