On Friday, February 22, 2019 at 1:34:31 PM UTC-7, Brent wrote: > > > > On 2/21/2019 10:47 PM, [email protected] <javascript:> wrote: > > > > On Thursday, February 21, 2019 at 8:38:12 PM UTC-7, Brent wrote: >> >> >> >> On 2/21/2019 4:05 PM, [email protected] wrote: >> >> >> >> On Thursday, February 21, 2019 at 1:35:17 PM UTC-7, Brent wrote: >>> >>> >>> >>> 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] 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 >>> >> >> *ISTM that gravitons would be inconsistent with GR, which derives >> gravitating motion from geometry, not mediating particles. AG* >> >> >> It is conceptually inconsistent, just as GR is conceptually inconsistent >> with Newtonian gravity. But that doesn't mean the theories make detectably >> different predictions in the domain where we can test them. Notice how >> difficult it was to test GR vs Newton. >> >> Brent >> > > *Even if gravitons are detected, and they account for "force" consistent > with the other three forces, wouldn't there remain the task of changing the > form of gravity to make it covariant? AG* > > > Gravitons, as quanta of the metric field, are already relativistic > particles and covariant. >
*I thought it's the equations of motion for the particular force, not the mediating particles, that must be covariant. On a related topic for this thread, where does GR depart from Mach's principle? That is, what did Einstein implicitly (or explicitly) deny about Mach's principle? TIA, AG * > > *Would that require tensors? AG* > > > Dunno. But it would have to reduce to GR in the weak field statmech > limit, so it would have something that reduced to tensors in that limit. > > 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] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > > > -- 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 https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
