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The gravitational effects of the Moon and the Sun (also the cause of the tides) have a very small effect on the apparent strength of Earth's gravity, depending on their relative positions; typical variations are 2 μm/s 2 (0.2 mGal) over the course of a day.
Vector field (blue) and its associated scalar potential field (red). Point P between earth and moon is the point of equilibrium. In physics, a gravitational field or gravitational acceleration field is a vector field used to explain the influences that a body extends into the space around itself. [1]
Gravitational field strength within the Earth Gravity field near the surface of the Earth – an object is shown accelerating toward the surface If the bodies in question have spatial extent (as opposed to being point masses), then the gravitational force between them is calculated by summing the contributions of the notional point masses that ...
The strength of the gravitational field is numerically equal to the acceleration of objects under its influence. [78] The rate of acceleration of falling objects near the Earth's surface varies very slightly depending on latitude, surface features such as mountains and ridges, and perhaps unusually high or low sub-surface densities. [79]
The current standard for sensitive gravimeters are the superconducting gravimeters, which operate by suspending a superconducting niobium sphere in an extremely stable magnetic field; the current required to generate the magnetic field that suspends the niobium sphere is proportional to the strength of the Earth's gravitational acceleration. [7]
However, a spherical harmonics series expansion captures the actual field with increasing fidelity. 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 ...
Goddard Mars Model (GMM) 3 is a gravity map of the gravitational field on the planet Mars. [2] Three orbital craft over Mars, the Mars Global Surveyor (MGS), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO) assisted in the creation of the GMM 3 by the study of their orbital flight paths. [2]
For such problems, the rotation of the Earth would be immaterial unless variations with longitude are modeled. Also, the variation in gravity with altitude becomes important, especially for highly elliptical orbits. The Earth Gravitational Model 1996 contains 130,676 coefficients that refine the model of the Earth's gravitational field.