On 2/7/2014 2:45 PM, [email protected] wrote:
On Friday, February 7, 2014 10:30:06 PM UTC, Brent wrote:
On 2/7/2014 1:37 PM, [email protected] <javascript:> 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
--
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 post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/groups/opt_out.
