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

[Dr Bruce Griffiths]

Bill
Bill Beam wrote:
> 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.
>
>   
Only, if you insist on sticking to Newtonian physics with all its 
attendant problems.

>> 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.
>
>   
A finite gradient doesn't imply that the field itself is nonzero, except 
of course towards the extremeities of the satellite.
>
> Regards,
> Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics)
>
>
> Bill Beam
> NL7F
>
>
>   
Bruce