On Tuesday, June 10, 2025 at 11:11:26 PM UTC-6 Brent Meeker wrote:
On 6/10/2025 9:47 PM, Alan Grayson wrote: On Tuesday, June 10, 2025 at 9:49:40 PM UTC-6 Brent Meeker wrote: On 6/10/2025 8:41 PM, Alan Grayson wrote: On Saturday, June 7, 2025 at 9:36:55 PM UTC-6 Alan Grayson wrote: https://www.youtube.com/watch?v=DjwQsKMh2v8 *I just watched this video again. It's provocative to say the least, although it doesn't explain the physical mechanism of why space flows into the center of masses, and what happens to "space" at that point. The answer is promised in subsequent videos. I like opinions on this videos, from any expert or quasi expert on GR. Is it really just a coincidence that gravitational * *time dilation in GR can be explained using the same concept of time dilation in SR? AG * *No. GR is just SR in non-flat spacetime. Geodesics replace straight-lines as the longest paths between two events. Brent* *Isn't geodesic motion in non-flat spacetime a postulate of GR? If so, I don't see it as particularly enlightening as an explanation gravity.* *It explains why falling bodies take accelerated paths thru space. It doesn't explain why massive bodies warp spacetime.* *For example, as a test particle moves in free fall, how does it "know" that any departure from geodesic isn't allowed? How does it know to conform to some extremal principle? AG* *Same way as in Newtonian mechanics. Brent* *The Newtonian postulate of inertia is inherently simpler than the GR postulate of geodesic motion on curved spacetime, but your point is well taken. It shows me we've got a lot of work ahead, before we really understand gravity. AG* *As for muon half-life, you and Clark are in agreement that measuring the half-life requires the lab frame to be at rest wrt the muons being measured. But how can this be? A lab atop a mountain sees the muons flying by, same as the lab at rest on the Earth. So perhaps you could elaborate on how this half-life is measured, and where I have made an error. AG* -- 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 view this discussion visit https://groups.google.com/d/msgid/everything-list/4501a5ab-5b14-4db5-95b1-fc3fbb6ba48dn%40googlegroups.com.
