On Wednesday, February 20, 2019 at 12:30:01 AM UTC-7, Philip Thrift wrote: > > > > On Wednesday, February 20, 2019 at 1:06:25 AM UTC-6, agrays...@gmail.com > wrote: >> >> >> >> On Tuesday, February 19, 2019 at 8:16:51 PM UTC-7, Brent wrote: >>> >>> >>> >>> On 2/19/2019 5:10 PM, agrays...@gmail.com wrote: >>> >>> >>> *What you wrote makes no sense. It fails to explain why motion occurs in >>> the absence of force. AG * >>> >>> >>> So did Newton: "A body in motion will remain in motion." >>> >> >> *Right, but Newton "explained" why a body at "rest" can start moving, via >> the application of "force". What does "rest" mean in GR and what causes >> "motion" from that pov? Incidentally, when I posed the question of why >> space and time must be fused in relativity. I didn't know the answer. I >> came to a partial explanation by posing the question. AG* >> >>> >>> > > Physics doesn't really explain anything. It only creates expressions in > different mathematical dialects that we interpret. >
*Right. That's why I put the quotes around *explained*. AG * > > > https://www.newyorker.com/science/elements/a-different-kind-of-theory-of-everything > > > > In 1964, during a lecture at Cornell University, the physicist Richard > Feynman articulated a profound mystery about the physical world. He told > his listeners to imagine two objects, each gravitationally attracted to the > other. How, he asked, should we predict their movements? Feynman identified > three approaches, each invoking a different belief about the world. The > first approach used Newton’s law of gravity, according to which the objects > exert a pull on each other. The second imagined a gravitational field > extending through space, which the objects distort. The third applied the > principle of least action, which holds that each object moves by following > the path that takes the least energy in the least time. All three > approaches produced the same, correct prediction. They were three equally > useful descriptions of how gravity works. > *Except that it's wrong to put Newton's gravity theory on the same level as Einstein's. Also, I think we can dispense with the Principle of Least Action and just use the geodesic hypothesis as a postulate of GR. We could say that God preferred a unique path, the extremal, rather than having to choose among an uncountable set of paths for each path between distinct events in the manifold. AG* > > “One of the amazing characteristics of nature is this variety of > interpretational schemes,” Feynman said. ... “If you modify the laws much, > you find you can only write them in fewer ways,” Feynman said. “I always > found that mysterious, and I do not know the reason why it is that the > correct laws of physics are expressible in such a tremendous variety of > ways. They seem to be able to get through several wickets at the same time.” > > ... > > - pt > -- 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.
