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The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution within Earth) and the centrifugal force (from the Earth's rotation).
These changes can be the result of mass displacements inside the Earth, or of vertical movements of the Earth's crust on which measurements are being made. [c] The first gravimeters were vertical accelerometers, specialized for measuring the constant downward acceleration of gravity on the Earth's surface. The Earth's vertical gravity varies ...
At a fixed point on the surface, the magnitude of Earth's gravity results from combined effect of gravitation and the centrifugal force from Earth's rotation. [2] [3] At different points on Earth's surface, the free fall acceleration ranges from 9.764 to 9.834 m/s 2 (32.03 to 32.26 ft/s 2), [4] depending on altitude, latitude, and longitude.
The Kármán line, defined as 100 km (62 mi) above Earth's surface, is a working definition for the boundary between the atmosphere and outer space. [238] Thermal energy causes some of the molecules at the outer edge of the atmosphere to increase their velocity to the point where they can escape from Earth's gravity.
As P 0 n (x) = −P 0 n (−x) non-zero coefficients J n for odd n correspond to a lack of symmetry "north–south" relative the equatorial plane for the mass distribution of Earth. Non-zero coefficients C n m, S n m correspond to a lack of rotational symmetry around the polar axis for the mass distribution of Earth, i.e. to a "tri-axiality" of ...
where R is the ideal gas constant, T is temperature, M is average molecular weight, and g 0 is the gravitational acceleration at the planet's surface. Using the values T=273 K and M=29 g/mol as characteristic of the Earth's atmosphere, H = RT/Mg = (8.315*273)/(29*9.8) = 7.99, or about 8 km, which coincidentally is approximate height of Mt. Everest.
The publication of the law has become known as the "first great unification", as it marked the unification of the previously described phenomena of gravity on Earth with known astronomical behaviors. [1] [2] [3] This is a general physical law derived from empirical observations by what Isaac Newton called inductive reasoning. [4]
The precise strength of Earth's gravity varies with location. The agreed-upon value for standard gravity is 9.80665 m/s 2 (32.1740 ft/s 2 ) by definition. [ 4 ] This quantity is denoted variously as g n , g e (though this sometimes means the normal gravity at the equator, 9.7803267715 m/s 2 (32.087686258 ft/s 2 )), [ 5 ] g 0 , or simply g ...