The motion is determined by initial conditions. It is not something determined by some other physics.
LC On Monday, August 3, 2020 at 2:18:07 PM UTC-5 [email protected] wrote: > > > 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/daeddeef-f682-4f47-a791-52adc6e8452en%40googlegroups.com.
