Re: Einstein's Relativity and Everyday Life -- Clifford M. Will
- From: nospam@xxxxxxxxxxxxxxxx (J. J. Lodder)
- Date: Wed, 7 Jun 2006 00:14:28 +0200
Wolfgang S. Rupprecht
<wolfgang+gnus20060606T071745@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
oldpal <op@xxxxxxxxxxx> writes:
Also, the orbiting clocks are 20,000 km above the Earth, and
experience
gravity that is four times weaker than that on the ground.
How do you figure the gravitational force is four times weaker at
20,000 km above the surface of the earth?
By forgetting about classical physics and the old inverse square law?
Oops.
6378km radius for the earth
26560km radius for the sv's orbit
(/ 26560.0 6378.0) 4.164314832235811 ; ~4x the distance
Since "Force = G * mass1 * mmass2 / (distance ** 2)" we should get
1/16 the gravity at 4x the distance where the gps sv's orbit.
The relativistic clock correction goes with the potential,
not with the force. So with 1/r, so 4 times is OK.
Note that the original text doesn't say 'force',
Jan
.
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- Re: Einstein's Relativity and Everyday Life -- Clifford M. Will
- From: Wolfgang S. Rupprecht
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