[time-nuts] FW: Pendulums & Atomic Clocks & Gravity

Bill Beam wbeam at gci.net
Tue May 29 09:51:50 UTC 2007


On Tue, 29 May 2007 16:31:40 +1200, Dr Bruce Griffiths wrote:

>Ulrich, Didier
>
>Talking about forces, gravitational fields etc makes no physical sense 
>if the observer's reference frame isn't specified.
>For an observer in/on a satellite orbiting about the Earth with their 
>reference frame fixed with respect to the satellite.
>There is no gravitational field, whatever methods chosen to measure a 
>gravitational field (within the satellite) will always produce a null 
>result.

Not true.
Very simple experiments will show occupants of the satellite that they
are in a non-inertial reference frame.  (Release a few test masses
about the cabin and you will observe that they move/accelerate for no
apparent reason, unless the satellite is in free fall which you'll know soon
enough,)  The experimenter must conclude that the satellite is undergoing
acceleration due to the influence of an attractive (gravitational) field.

Just because NASA calls it 'microgravity' doesn't make it true.  It means
NASA is wrong.  Weightlessness is not the same as zero-g.

>Pendulum clocks fail to work, given an initial push they will just 
>rotate around the pivot, provided the pivot suitably constrains the 
>motion of the pendulum (ie a shaft running in a set of ball or roller 
>bearings or similar and not a knife edge pivot).
>
>If, however the satellite acts as a rigid body and has a large enough 
>diameter then it would be possible for an observer on the satellite to 
>detect a gravitational field gradient.

Therefore, you must conclude that somewhere inside the satellite g is not zero.

>If the satellite is large enough and orbits close enough to the Earth, 
>this gravitational field gradient would tear the satellite apart.
>
>For an observer located on the Earth however the motion of the satellite 
>can be accurately described by Newtonian mechanics where the centripetal 
>pull of gravity acts on the satellite causing it to have a centripetal 
>(radial) acceleration as it orbits the Earth.
>
>
>Bruce
>

Regards,
Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics)


Bill Beam
NL7F





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