"Gunner" wrote in message
...
On Fri, 26 Dec 2003 05:57:11 GMT, Mark
wrote:



Ian Stirling wrote:

Given a homogenous spherical earth.


Which does not exist. Which is your point.


At the equator there is centrifugal force which isn't a factor at the
poles, and there is a land mass under the south pole the north pole
doesn't have. Then there's the thing about the earth actually being an
oval.

And then there's the thing about densities of the earths crust. And the
thickness. And the turbulent nature of what lies 40 miles down. What
about 2 miles? 3,4,5,6 miles? It all adds up and just how many decimals
does someone want to carry it out to in order to prove their answer?

?

You choose your point on the earths surface, mayhaps I'll find another.

It's a black hole argument. That is, it can suck up any answer without
resolution. Unless we involve a geologist who will tell what spot on
earth has the highest gravimetric verses centrifugal force.



These types of threads are masturbatory.

When I was exploring for oil and gas, we had Gravity Detectors, which
measured the local gravity pull in a given area. Significant
differences in some areas. No idea how they worked.

Gunner

Gravity is quite easy to measure, you just weigh a known mass. You use a
spring
scale and not a balance beam. The gravitometers
used in the old days were simply a scale with a microscope to read the
result.
I saw an old one at a museum. The mechanism used a quartz thread coiled
into a spring.
Quartz was needed because of it's low hysteresis. The entire unit
was built into a can about 5 inches in diameter and 12 inches tall. It was
ruggedly built
so that it could be hauled out in the field for oil exploration. It
probably dated from
the 1950's.

Gravitometers are also used in submarine navigation. You can detect the
presence of underwater mountain ranges.

Pete.