![]() ![]() Reva Kay Williams, University of Florida, developed a rigorous proof that validated Penrose's mechanism. Roger Penrose had proposed a mechanism that relies on frame-dragging-related effects for extracting energy and momentum from rotating black holes. Indirect validations of gravitomagnetic effects have been derived from analyses of relativistic jets. More subtle predictions, such as induced rotation of a falling object and precession of a spinning object are among the last basic predictions of general relativity to be directly tested. The main consequence of the gravitomagnetic field, or velocity-dependent acceleration, is that a moving object near a massive, non-axisymmetric, rotating object will experience acceleration not predicted by a purely Newtonian (gravitoelectric) gravity field. This apparent field may be described by two components that act respectively like the electric and magnetic fields of electromagnetism, and by analogy these are called the gravitoelectric and gravitomagnetic fields, since these arise in the same way around a mass that a moving electric charge is the source of electric and magnetic fields. This approximate reformulation of gravitation as described by general relativity in the weak field limit makes an apparent field appear in a frame of reference different from that of a freely moving inertial body. The analogy and equations differing only by some small factors were first published in 1893, before general relativity, by Oliver Heaviside as a separate theory expanding Newton's law. ![]() The most common version of GEM is valid only far from isolated sources, and for slowly moving test particles. Gravitomagnetism is a widely used term referring specifically to the kinetic effects of gravity, in analogy to the magnetic effects of moving electric charge. Gravitoelectromagnetism, abbreviated GEM, refers to a set of formal analogies between the equations for electromagnetism and relativistic gravitation specifically: between Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein field equations for general relativity. For the specific gravitational analog of magnetism, see frame-dragging.ĭiagram regarding the confirmation of gravitomagnetism by Gravity Probe B This article is about the gravitational analog of electromagnetism as a whole. ![]()
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