Gravity models are used in various
social sciences
Social science is one of the branches of science, devoted to the study of societies and the relationships among individuals within those societies. The term was formerly used to refer to the field of sociology, the original "science of so ...
to predict and describe certain behaviors that mimic gravitational interaction as described in
Isaac Newton
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the grea ...
's laws of
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
. Generally, the social science models contain some elements of
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...
and distance, which lends them to the metaphor of physical gravity. A gravity model provides an estimate of the volume of flows of, for example, goods, services, or people between two or more locations. This could be the movement of people between cities
or the volume of trade between countries.
A gravity model cannot accurately predict flows, but is instead a measure against which actual observed values can be compared, highlighting where those flows are unexpectedly high or low.
Social science gravity models:
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Gravity model of trade
The gravity model of international trade in international economics is a model that, in its traditional form, predicts bilateral trade flows based on the economic sizes and distance between two units. Research shows that there is "overwhelming ev ...
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Trip distribution
Trip distribution (or destination choice or zonal interchange analysis) is the second component (after trip generation, but before mode choice and route assignment) in the traditional four-step transportation forecasting model. This step matches ...
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Gravity model of migration 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. Newton's law states that: "Any two bodies attract one another with a forc ...
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Two-step floating catchment area (2SFCA) method The two-step floating catchment area (2SFCA) method is a method for combining a number of related types of information into a single, immediately meaningful, index that allows comparisons to be made across different locations. Its importance lies in ...
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Reilly's law of retail gravitation
References
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