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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).
A gravity map is a map that depicts gravity measurements across an area of space, which are typically obtained via gravimetry. Gravity maps are an extension of the field of geodynamics. Readings are typically taken at regular intervals for surface analysis on Earth. [1] Other methods include analysis of artificial satellite orbital mechanics ...
where ρ 2 = ρ(x, y, z) is the mass density at the volume element and of the direction from the volume element to point mass 1. is the gravitational potential energy per unit mass. Earth's gravity field can be derived from a gravity potential (geopotential) field as follows:
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression.
The mass of the oceans is approximately 1.35 × 10 18 metric tons or about 1/4400 of Earth's total mass. The oceans cover an area of 361.8 million km 2 (139.7 million sq mi) with a mean depth of 3,682 m (12,080 ft), resulting in an estimated volume of 1.332 billion km 3 (320 million cu mi). [193]
If Earth's shape were perfectly known together with the exact mass density ρ = ρ(x, y, z), it could be integrated numerically (when combined with a reciprocal distance kernel) to find an accurate model for Earth's gravitational field. However, the situation is in fact the opposite: by observing the orbits of spacecraft and the Moon, Earth's ...
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.
On Earth the effect on gravity of elevation is 0.3086 mGal m −1 decrease when going up, minus the gravity of the Bouguer plate, giving the Bouguer gradient of 0.1967 mGal m −1. More generally, for a mass distribution with the density depending on one Cartesian coordinate z only, gravity for any z is 2π G times the difference in mass per ...