On Fri, Mar 9, 2018 at 6:22 PM, Russell Standish <[email protected]> wrote:
Hi Russell *> Alan was claiming that motion of a free particle along a geodesic was an > unjustified assumption in relativity.* But its not unjustified or an assumption if that's the way we observe things move, and it is. > *> If he were asking why is momentum conserved, then one could answer it > along the lines of Vic Stenger's symmetries, utilising Noether's theorem.* Yes but Noether's theorem couldn't be invoked and the conservation of momentum produced from it unless there was a symmetry, in this case the fact that the laws of physics are the same at all points in space. Someone could then ask why that is, and at this time the best answer we could give is that’s just what we observe. As far as I can see it is not a logical necessity, physics could have been different from one place to another but we see that is not the case. And Einstein said mass/energy tells spacetime how to curve and spacetime tells mass/energy how to move, but if this were not true it would contradict observations but not produce any logical self contradictions that I know about. In physics if you keep asking recursive "why is that?” questions eventually you'll come to a brute fact. Put it another way, I don't think the laws of physics could be derived from pure logic alone regardless of how intelligent you are, that's why we need observation. John K Clark -- 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.
