# Brans-Dicke theory

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## Brans–Dicke theory

(branz dik) A relativistic theory of gravitation put forward in the 1960s by Carl Brans and Robert Dicke as a variant of Einstein's general theory of relativity. It is considered by many astronomers to be the most serious alternative to general relativity. It is a scalar-tensor theory, i.e. a theory in which the gravitational force on an object is due partly to the interaction with a scalar field and partly to a tensor interaction. Newton's gravitational constant is replaced by a slowly varying scalar field. The effect is to allow the strength of gravity to decrease with time. In the limit that this variation is zero, the various Brans–Dicke theories of gravitation that now exist reduce to Einstein's general relativity. Current observations limit the variation of Newton's gravitational constant to be less than one part in 10^{10}per year. This means that for local applications of a noncosmological nature Brans–Dicke theory is indistinguishable from general relativity.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## Brans-Dicke theory

[¦bränz ¦dik ‚thē·ə·rē] (relativity)

A theory of gravitation in which the gravitational field is described by the tensor field of general relativity and by a new scalar field, which is determined by the distribution of mass-energy in the universe and replaces the gravitational constant.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

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