From Glossary of Meteorology
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(Also called gravity, force of gravitation.) The mutual attraction between bodies possessing mass.

Within Newtonian mechanics the gravitational force between two point masses (bodies small in extent compared with r, the distance between them) m1 and m2 is
where the Newtonian constant of gravitation G is 6.672 x 10-11 m3 kg s-2. This force is directed along the line between the two point masses. Forces between extended bodies can be determined by conceptually dividing them into sufficiently small parts, calculating the gravitational forces between them according to the previous equation, and adding these forces vectorially. The gravitational field intensity (or simply gravitational field) of a system of masses at any point is the gravitational force the system would exert on a unit mass at that point. Thus gravitational, electric, and magnetic fields are defined in a similar way. A gravitational field is an acceleration field, the acceleration due to (not of) gravity.
See apparent gravity.