larry harson <
larryharson66@gmail.com> wrote:
On Monday, January 1, 2024 at 10:33:15?PM UTC, J. J. Lodder wrote:
larry harson <larryh...@gmail.com> wrote:
On Monday, January 1, 2024 at 3:12:45?PM UTC, J. J. Lodder wrote:
larry harson <larryh...@gmail.com> wrote:
If two identical clocks are held rigidly at different heights
within the Earth's gravitational field, the bottom clock will
display a smaller elapsed time compared to the higher clock as a consequence of the former's greater acceleration.
Are there other examples of the effects of rigidness within a gravitational that have been experimentally observed?
Do you really think that the effect will go away
if the higher clock is floating up in a balloon?
No, I don't think the effect will go away because their distance
distance apart is still being rigidly maintained, however it's done.
It will go away if the clocks are allowed to free fall; but then the clocks can no longer be compared in a common proper frame AFAIK.
You are wrong about that too.
For example, the Galileo sat clocks go faster
than those in the GPS sats.
(because they are in higher orbits)
Both kinds, being sats, are of course in free fall,
Jan
Are you sure about this?
Yes, very.
I find it difficult to believe that identical clocks orbiting the Earth,
and hence in free fall, at different heights tick at different rates to
one another in their respective proper frames.
('to one another in their proper frames' is a contradiction in terms.
You are confused)
Each clock ticks at the same rate, according to itself.
(so in its proper frame)
By postulate, and in principle unobservable, except indirectly.
However, when you compare the sat clock
with an identical clock on the ground
you find that it ticks at a different rate.
This is the famous GPS relativity correction.
The correction depends on the orbit the sat is in,
and even on where it is in its orbit. (when the orbit is excentric) [1]
The correction is small for low sats, such as the ISS, greater for GPS,
still greater for Galileo sats, and greatest for GAIA,
which is at L2, so practically 'at infinity',
as far as the Earth is concerned.
Now navigation sats don't listen to each other directly,
but it is obvious that they would need to apply corrections
to each other's clock signals, if they did.
In particular GPS sats would see Galileo clocks as ticking faster.
There are other sats however that do listen to the navigation sats
to know where they are. (the GRACE missions for example)
They must apply appropriate corrections.
What seems more likely IMO
is that the proper rates of the clocks are adjusted, because of their different orbital velocities wrt one another, so that their rates are the same as that of the inertial clock at the center of the Earth; hence maintaining a common global time rate.
BTW, the standard common reference is TCG, which is the time of a clock
that co-moves with the barycentre of the Earth-Moon system,
but is out 'at infinity' as far as the potential of the Earth
is concerned.
If you're correct, then I'm also wrong in the reply I gave to Tom Roberts above.
Indeed,
(but I haven't read it)
Jan
[1] Excercise: where is the clock fastest, at apogee or at perigee?
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