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.

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.

“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

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