[time-nuts] FW: Pendulums & Atomic Clocks & Gravity
Neville Michie
namichie at gmail.com
Mon May 28 23:33:37 UTC 2007
> Hi All,
I am still having difficulty getting my head around the gravity point.
Now I accept, in principle, that due to relativity an intense
gravity field will slow a clock.
My problem is visualising where you will find this field.
At the centre of this planet gravity (from the planet) is zero. This
comes about by an elegant piece of
calculus that shows that everywhere inside a hollow sphere the
gravity is zero. So a clock in the centre of Earth
runs at the same rate as one on the surface? or does it run faster
because the one on the surface has the planetary gravity acting on it?
I think that the one inside the Earth runs faster.
But when you are between the Earth and Moon at a point where gravity
forces are neutral we should have the same rate as centre of planet?
Now the way to measure gravity is to measure the force on a test
mass. If there is zero force there is zero gravity, except when you
are in orbit.
This can be tested with 3 crossed gyroscopes that show your angular
velocity. If your angular velocity is negligible then the magnitude
of the gravity field is proportional to the force on a test mass.
Unless you are in free fall accelerating towards a mass.
I guess my question really is" can you know that you are in a zero
gravity field so your clock is running at the fastest rate?"
Or is relativity relative. Does relativity only show up when there
are two frames of reference being compared, so there is no ultimate
reference frame with the fastest clock? Or can any clock have a
single relativity correction applied to it? How do you measure the
gravitational potential at any site? (ie the scalar quantity that
would be used to correct your clock).
Has anyone got a clear answer?
cheers, neville Michie
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