On Saturday, February 8, 2014 12:44:30 AM UTC, Brent wrote: > > On 2/7/2014 2:45 PM, [email protected] <javascript:> wrote: > > > On Friday, February 7, 2014 10:30:06 PM UTC, Brent wrote: >> >> On 2/7/2014 1:37 PM, [email protected] wrote: >> >> >> On Monday, February 3, 2014 6:27:14 AM UTC, Brent wrote: >>> >>> On 2/2/2014 10:12 PM, [email protected] wrote: >>> >>> Namely that however you jig it, there's still going to be huge spacetime >>> distortion representing the sun and a tiny one representing the earth, >>> which - I thought - had to bias the objectively true relation between the >>> sun and the earth for the earth being gravitationally dominated by the sun >>> not the other way around. >>> >>> >>> So the question was whether one could just consider the Sun, calculate >>> the spacetime metric due to its mass, and then calculate the orbit of the >>> Earth as an inertial path in that metric? In that case of course the >>> answer is no. The metric has to take into account the mass of the Earth as >>> well as the Sun. Just as in Newtonian theory, the Sun and the Earth, and >>> Jupiter and the other planets all move around their mutual center-of-mass. >>> The center-of-mass is roughly near the surface of the Sun on the side >>> nearest Jupiter. >>> >>> Brent >>> >> >> Hi Brent - Sure, but is it ok to look at the sun and the earth together, >> purely as their geometry's in spacetime, and say "that one goes around that >> one" to the same sort of accuracy we can say the earth goes around the sun >> without invoking relativity. Or is doing that running foul of the basic >> principles in play of relativity ? >> >> >> I'm not sure what you're asking. The corrections to a simple "stationary >> Sun, orbiting Earth" due to Jupiter are much bigger than any GR effect. >> >> Brent >> > > if you're willing to keep trying I would also like to...but please be > assured I will understand anytime you no longer want to. So trying again > here, I would first recap one sense of what this has been about.... > > - I related an experience I had a few years back, when some people much > more knowledgeable than I in relativity...at least factually > speaking...argued that relativity was a fundamentally different way of > explaining the universe (with no dispute from me so far)....such that, you > literally could not sensibly talk about frame-free visualizations. I > responded that I thought that was only true up to a point, because for > example, the spacetime geometry of a much larger and much smaller object, > could be visualized as a single landscape for the purpose of saying > something very general, like "that one goes around that one". > > Which they explicitly then ruled out. > > Of course, this statement was always untrue strictly speaking because both > go round a common centre of mass. But the question here, is: > > - was that more knowledgeable source correct > > - was I correct > > - was one but not the other exclusively correct, if so which one > > - was there a good chance neither were correct, and you'd have to see what > was actually said to be sure > > - Is what I am saying to you now, which I think is a fairly good capture > of what I said then, correct .....so far as it goes > > > My friend Bill Jefferys who used to teach astronomy at Univ of Texas says > it doesn't matter what reference frame you choose as far as the physical > events go, it just makes the math harder or easier. So sometimes you use a > geocentric frame and sometimes a heliocentric frame and so forth... > > Brent > but can you throw the relative character out of the window, and speak of an 'absolute landscape' implied by relativity theory that is made up of all the gravity wells, that definitely suggests a 'reality' that goes beyond the principle of equivalence. In that, the landscape shows what's big and what's small, so the relation between them, in one big picture. I ask this in context that acknowledges it wouldn't be any good for resolving much useable knowledge about the world. In fact none at all, save that reality does imply such a reality is really there.
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