[time-nuts] Pendulums & Atomic Clocks & Gravity

Bill Beam wbeam at gci.net
Sat May 26 17:06:10 EDT 2007


On Sat, 26 May 2007 13:34:24 -0700, Brooke Clarke wrote:

>Hi Bill:
>
>It's my understanding that a satellite is in free fall, hence zero g.
>

'Free fall' implies that g is not zero!

If g=0 was true, then the satellite would not be falling at all.
It is beacuse g is not zero, that the satellite is in 'orbit' rather
than moving off in a straight line.

Jumping off a cliff also is "free fall" and surely g is not zero.
The only difference between the cliff jumper and a satellite
in orbit is the satellite never reaches the ground.

The rate of a clock does depend on g.

Now a pendulum clock in orbit has infinate period, but not because
g is zero. This is because the pendulum support point is also
in orbit.  This is no different than pushing a pendulum off a cliff.

A pendulum swings back and forth because two forces act on
the bob.  One of the forces is mg and the other is the force of
the pendulum support rod.

Regards,
Bill


>Of course there's a gravitational field at the location of the satellite, the 
>one from Earth being the largest.  Orbital mechanics gives me a headache so 
>let's hear from someone more knowledgeable.
>
>Have Fun,
>


Bill Beam
NL7F





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