On 9/15/2025 1:16 AM, Alan Grayson wrote:
*You've written that the TP cannot be solved using GR, so why do you
use GR in the turnaround scenario? Please don't ask me to look it up.
If you claim there is no acceleration in GR, I'd like to know how
acceleration is defined, and how it can be calculated to be zero. I
tried using the 2nd derivative of dS, but it doesn't yield zero. AG*
*You have to take the covariant derivative. But it's easy to see even
from a Newtonian perspective. F=ma and F=0 and m>0 hence a=0. If you
measured a with an accelerometer you'd get zero.
See below.
Brent*
I've "solved" the TP a handful of different ways to make clear
what is happening. If it's not acceleration in the Triplet case,
then it's not caused by acceleration. If it's not difference in
acceleration in the equal acceleration case then it's not due to
acceleration difference in any case. If it's not due to stresses
on the clocks in the slingshot case then it's not due to stress on
the clocks in any case. The point is to eliminate every possible
cause of the difference in ages in order to point to the essential
cause.
Brent
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