El Enrrabadore-mor wrote:
It is said that a speeding clock shows less elapsed time than
the stay-at-home clock, because (if already speeding) it is
running at a slower rate. Or else, because it had run at a
slower rate when it was speeding, assuming now it is
stopped near the stay-at-home clock.

While that may be "said", it is wrong in SR. In SR, the motion of a
clock does not affect its rate. But when one compares identical clocks
that have traveled different paths, their elapsed proper times can
differ, due to their different trajectories, not due to any change in
their tick rates.

[... circular motion]

Bailey et al put muons into a storage ring and measured their lifetime
for their circular path. Within experimental resolutions, they have the
same lifetime as muons traveling in a straight line, so their circular
path did NOT affect the internal "clock" that controls their decay. They
were subject to an acceleration of about 10^18 g (1 g = 9.8 m/s^2),
which is FAR greater than claimed in your example. Note this experiment
is a direct implementation of the circular twin scenario, when combined
with measurements of muon decay at rest.


Tom Roberts