On 2/21/2019 5:27 AM, [email protected] wrote:
On Wednesday, February 20, 2019 at 7:50:51 PM UTC-7, Brent wrote:
On 2/20/2019 1:23 PM, [email protected] <javascript:> wrote:
On Wednesday, February 20, 2019 at 12:16:31 PM UTC-7, Brent wrote:
On 2/20/2019 8:42 AM, [email protected] wrote:
On Wednesday, February 20, 2019 at 7:09:10 AM UTC-7, John
Clark wrote:
>/Newton "explained" /
Why did you put explained in quotation marks? If you can
predict what something is going to do then you've
explained it, the better the prediction the better the
explanation. I don't know what else the word could
possibly mean. And in science no explanation is perfect,
but some are less wrong than others.
*QM better illustrates the justification for quotes. Many
interpretations that make the same predictions. AG *
/> why a body at "rest" can start moving, via the
application of "force"/
And Einstein explained that a body moving in a geodesic
through 4D spacetime will take a path that is not a
geodesic if a force is applied. The Earth is moving in a
straight line (aka a geodesic) through curved spacetime;
the reason Earth's orbit looks elliptical to us is due
to map distortion, the same reason that in a flat map of
the curved surface of the Earth Greenland looks larger
than South America and is almost as large as Africa.
Except that it's even worse, in one we're projecting the
2 D curved surface of the Earth into the flat 2D surface
of the map, but with Einstein we're projecting a curved
4D volume into a flat 3D volume.
/> What does "rest" mean in GR /
In General Relativity moving in a geodesic is as close
as you can get to the traditional idea of rest, but as
long as time passes you're going to be moving through 4D
spacetime.
*If you're at spatial rest in spacetime in the presence of a
gravitational source, how does GR explain the subsequent
spatial motion? AG
*
When you were at "spatial rest" you had a force applied to
you. Removing it allowed you to follow a geodesics path
through spacetime....also known as "falling".
Brent
*So it seems that GR doesn't explain motion; rather, it assumes
motion is a natural state of things. AG
*
So called "standing still" is just motion in the time direction
only...in Newtonian and special relativity as well. Just as there
is no absolute motion, there's no absolution motionless
either...it's called "relativity" for a reason.
Brent
*Other than gravity, the remaining known forces are moderated, or
shall we say "caused by" particles. Doesn't GR remain an exception;
that is, wouldn't it preclude the existence of a graviton? TIA, AG
*
Gravitons, the weak-field limit quanta of the gravitational field,
aren't precluded. They are implicit in string-theory; which is why
string theory is a candidate for the quantum theory of gravity. The
problem is there's no mathematically consistent way to extend the
graviton, weak field, picture to the strong field limit and predict what
happens in a black hole where GR predicts a singularity.
Brent
/> what causes "motion" from that pov?/
Force, same as with Newton.
John K Clark
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