On Friday, February 22, 2019 at 1:34:31 PM UTC-7, Brent wrote: > > > > On 2/21/2019 10:47 PM, agrays...@gmail.com <javascript:> wrote: > > > > On Thursday, February 21, 2019 at 8:38:12 PM UTC-7, Brent wrote: >> >> >> >> On 2/21/2019 4:05 PM, agrays...@gmail.com wrote: >> >> >> >> On Thursday, February 21, 2019 at 1:35:17 PM UTC-7, Brent wrote: >>> >>> >>> >>> On 2/21/2019 5:27 AM, agrays...@gmail.com wrote: >>> >>> >>> >>> On Wednesday, February 20, 2019 at 7:50:51 PM UTC-7, Brent wrote: >>>> >>>> >>>> >>>> On 2/20/2019 1:23 PM, agrays...@gmail.com wrote: >>>> >>>> >>>> >>>> On Wednesday, February 20, 2019 at 12:16:31 PM UTC-7, Brent wrote: >>>>> >>>>> >>>>> >>>>> On 2/20/2019 8:42 AM, agrays...@gmail.com 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 everything-li...@googlegroups.com <javascript:>. > To post to this group, send email to everyth...@googlegroups.com > <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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
