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Gravitational field
In physics, a gravitational field is a model used to explain the influence that a massive body has.^{[1]} The influence extends into the space around itself, producing a force on another massive body. Thus, a gravitational field is used to explain gravitational phenomena (effects). It is measured in newtons per kilogram (N/kg).
In the original Newtonian concept, gravity was a force between point masses. Following Newton, Laplace attempted to model gravity as some kind of radiation field or fluid. Since the 19th century explanations for gravity have in terms of a field model, rather than a point attraction. This revolution was brought about by Einstein's general theory of relativity. Most scientists believe that the gravitational field and its gravitational waves are the physical interpretations of Einstein's equations of general relativity.
In a field model, rather than two particles attracting each other, the mass of objects distort spacetime. This distortion is what is perceived and measured as a "force". In such a model matter moves in certain ways in response to the curvature of spacetime.^{[2]} One can say either there is no gravitational force,^{[3]} or that gravity is a fictitious force.^{[4]}
References
 ↑ Massive body = body with mass, not just a large body, but all bodies with mass.
 ↑ Geroch, Robert 1981. General relativity from A to B. University of Chicago Press. . http://books.google.com/books?id=UkxPpqHs0RkC&pg=PA181. Chapter 7, page 181
 ↑ Grøn, Øyvind & Hervik, Sigbjørn 2007.. Einstein's general theory of relativity: with modern applications in cosmology. Springer. . http://books.google.com/books?id=IyJhCHAryuUC. Chapter 10, page 256
 ↑ Foster J. & Nightingale J.D. 2006. A short course in general relativity. 3rd ed, Springer. . http://books.google.com/books?id=wtoKZODmoVsC. Chapter 2, page 55

