>> 1) That accelerometers do NOT measure gravity, but rather 
>> all the
>>    forces other than gravity which are applied to an 
>> object.

> Huh? The accelerometers I have here measure gravity just 
> fine!

> Perhaps you meant to say that they measure the net sum all 
> of the
> accelerations of an object, including gravity.

Both people mean the same thing, probably.

Explanation by thought experiment:

1. Toss your unit in the air so that it is not contacting 
the ground. What acceleration forces does it measure.

2.    Place unit on a table in a vibration free environment. 
What acceleration forces are reported?

In the case of the table the force contributed to react 
against gravity is key to the accelerometer being able to 
detect gravity.

If you had the standard hypothetical "totally evacuated 
tunnel through the centre of the perfectly uniform and 
spherical earth" and dropped your assembly into it, it would 
happily oscillate to and fro forever, JUST reaching the 
surface on the far side and then returning to you and so on. 
At the extremes it would be at zero V and 1g. In the middle 
it would be at high V and zero g.

At all stages in the above situation the on board 
accelerometer would measure zero acceleration in all 
directions.

A zero thickness object doing a close pass slingshot past a 
neutron star (assuming no 'atmosphere') such that it is 
accelerated to say 10,000g at closest approach, will 
experience zero gravity "on board" throughout the pass. The 
various stories on neutron star disasters during 
slingshotting occur due to gravity differentials across the 
objects (ships people etc). Any POINT sees zero net g.



        Russell 

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