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Both Brans–Dicke theory and general relativity are examples of a class of relativistic classical field theories of gravitation, called metric theories.In these theories, spacetime is equipped with a metric tensor, , and the gravitational field is represented (in whole or in part) by the Riemann curvature tensor, which is determined by the metric tensor.
The gravity model of migration is a model in urban geography derived from Newton's law of gravity, and used to predict the degree of migration interaction between two places. [1] In 1941, astrophysicist John Q. Stewart [ 2 ] applied Newton's law to the social sciences, establishing a theoretical foundation for the field of social physics.
Gravitation also explains astronomical phenomena on more modest scales, such as planetary orbits, as well as everyday experience: objects fall; heavy objects act as if they were glued to the ground, and animals can only jump so high. Gravitation was the first interaction to be described mathematically.
In addition to Newton's Law of Gravity in the physical sciences, there were other antecedents to Reilly's "law" of retail gravity. In particular, E.C. Young in 1924 described a formula for migration that was based on the physical law of gravity, and H.C. Carey had included a description of the tendency of humans to "gravitate" together in an 1858 summary of social science theory.
In physics, a fifth force refers to a hypothetical fundamental interaction (also known as fundamental force) beyond the four known interactions in nature: gravitational, electromagnetic, strong nuclear, and weak nuclear forces. Some speculative theories have proposed a fifth force to explain various anomalous observations that do not fit ...
Pownall applied the Newtonian concept of gravity to his theory of empire, as evident in his suggestion that the "laws of nature" held the colonies to Great Britain in a manner "analogous in all cases, by which the center of gravity in the solar system" held the planets in their orbits. In making this analogy, Pownall's notion of 'social gravity ...
The gravity g′ at depth d is given by g′ = g(1 − d/R) where g is acceleration due to gravity on the surface of the Earth, d is depth and R is the radius of the Earth. If the density decreased linearly with increasing radius from a density ρ 0 at the center to ρ 1 at the surface, then ρ ( r ) = ρ 0 − ( ρ 0 − ρ 1 ) r / R , and the ...
By cosmic standards, gravity throughout the solar system is weak. Since the differences between the predictions of Einstein's and Newton's theories are most pronounced when gravity is strong, physicists have long been interested in testing various relativistic effects in a setting with comparatively strong gravitational fields.