MadSci Network: Physics |
Dear Martin, The gravity force is not the same throughout the Earth because Earth is not a homogeneous body, and is not exactly spherical. Topography, mass distribution, distance to the center of the Earth and centrifugal force are some kind of things that affect gravity. For example, the equatorial theoretical gravity is equal to 9.780318 ms-2, in pole region it is equal to 9.832177 ms-2 due to a) closer to center of earth (positive signal), b) centrifugal force diminished with latitude (positive signal), c) excess mass due to bulge of earth at equator (negative signal). I said "theoretical gravity" because this value is calculated on a ellipsoidal surface that aproximate to the Earth surface. In other words, there are a exact mathemathic expression to calculate it. See more about gravity in: http: //rubble.phys.ualberta.ca/~doug/G221/SecII/L3erthdim.html Regards, Emilson P. Leite IAG/USP - Brazil.
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