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Modified Newtonian dynamics (MOND) is a theory that proposes a modification of Newton's laws to account for observed properties of galaxies. Modifying Newton's law of gravity results in modified gravity, while modifying Newton's second law results in modified inertia. The latter has received little attention compared to the modified gravity ...
The theory was inspired by the Wheeler–Feynman absorber theory for electrodynamics. [3] When Richard Feynman, as a graduate student, lectured on the Wheeler–Feynman absorber theory in the weekly physics seminar at Princeton, Albert Einstein was in the audience and stated at question time that he was trying to achieve the same thing for ...
Entropic gravity provides an underlying framework to explain Modified Newtonian Dynamics, or MOND, which holds that at a gravitational acceleration threshold of approximately 1.2 × 10 −10 m/s 2, gravitational strength begins to vary inversely linearly with distance from a mass rather than the normal inverse-square law of the distance.
It is a generalisation of the vector form, which becomes particularly useful if more than two objects are involved (such as a rocket between the Earth and the Moon). For two objects (e.g. object 2 is a rocket, object 1 the Earth), we simply write r instead of r 12 and m instead of m 2 and define the gravitational field g(r) as:
This suggests the definition of a new class of inertial motion, namely that of objects in free fall under the influence of gravity. This new class of preferred motions, too, defines a geometry of space and time—in mathematical terms, it is the geodesic motion associated with a specific connection which depends on the gradient of the ...
In physics, f(R) is a type of modified gravity theory which generalizes Einstein's general relativity. f(R) gravity is actually a family of theories, each one defined by a different function, f, of the Ricci scalar, R. The simplest case is just the function being equal to the scalar; this is general relativity.
The 12th-century scholar Al-Khazini suggested that the gravity an object contains varies depending on its distance from the centre of the universe (referring to the centre of the Earth). Al-Biruni and Al-Khazini studied the theory of the centre of gravity, and generalized and applied it to three-dimensional bodies.
Newton–Cartan theory (or geometrized Newtonian gravitation) is a geometrical re-formulation, as well as a generalization, of Newtonian gravity first introduced by Élie Cartan in 1923 [1] [2] and Kurt Friedrichs [3] and later developed by G. Dautcourt, [4] W. G. Dixon, [5] P. Havas, [6] H. Künzle, [7] Andrzej Trautman, [8] and others. [9]