On 04/01/2010 02:20 PM, Jed Rothwell wrote:
> Steven V Johnson wrote:
>
>> Can someone refresh my memory about the precise time measurements
>> conducted with atomic clocks positioned at different elevations on the
>> surface of Earth.
>
> Gravity or acceleration slow down time.
*WRONG*
A momentarily comoving inertial observer who is colocated with an
accelerating observer will find that their clocks are ticking AT THE
SAME RATE.
In short, acceleration does not slow down clocks. This is predicted
theoretically and has, IIRC, been confirmed experimentally.
I think you, also, may be confused about gravitational time dilation.
It's *NOT* caused by the field strength; it's caused by the potential
difference.
In other words, neither a strong gravitational field NOR acceleration
affect clocks. Time is affected by how far down in a gravity well you
are, and in an "acceleration field", time measurements are affected by
your position in the field -- but not directly by the acceleration, nor
directly by the strength of gravity.
In all cases, if space is flat (no gravity), an accelerated clock will
be found to be ticking at the same rate as a non-accelerated
("inertial") clock which just happens, at a brief instant in time, to be
moving at the same rate as the accelerated clock.
A clock being whirled around and around on a string will run slow *only*
as a result of the expected time dilation due to its velocity. The fact
that it's being accelerated by the string does not result in any
additional effect on its rate. Similarly, unstable particles in
accelerators have their half lives extended by time dilation due to
their velocity, but *not* by any effect of the accelerating fields
acting on them.
