Gravitational Field Intensity Factors
I know that the density of the materials on Earth affect
the gravitational field intensity. What are some other factors that
affect the local intensity of gravity? Latitude? Altitude? others?
Altitude does affect the local gravitational acceleration. When two
objects move away from each other, the gravitational force they exert on
each other weakens. As a result, each experiences a smaller
acceleration due to gravity. A high altitude location is further away
from Earth than is a low altitude location. I am told that
gravitational acceleration at the top of a tall mountain can be as
0.2m/s^2 less that at the bottom of the mountain. I am sure there are
other effects, but this one is the easiest to actually measure.
In the simplest terms, the distance between two bodies of masses is
exponentially, inversely proportional to the gravitational field intensity.
In other, words, the further the distance between two bodies of masses, in
this case by altitude from the earth's center of mass, the weaker the
gravitational force or intensity between the two bodies.
My MS work included a gravity survey in Utah and I assure you that elevation,
latitude, time of day, positions of the sun and moon, nearby topography such
as hills and valleys, the type of rock you are standing on, and even the time
of year all affect the value of gravity you measure. That is if you are sitting
still on land. If you are measuring gravity on the ocean from a moving ship here
are several other effects that come into play.
Space and time are limited so before I get too heavily into the subject, let me
recommend that you look up "gravity surveying" and/or "gravity surveying
corrections" on Google. You will get more information than you probably
want. Also if you can find a book entitled "Geophysical Prospecting" by Milton
Dobrin, there is a good treatment of gravity in there, too.
R. W. "Bob" Avakian
Oklahoma State Univ. Inst. of Technology
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Update: June 2012