DescriptionNewtonian Mechanics is inconsistent with a finite speed of gravity.gif
English: Newtonian mechanics is inconsistent with a finite speed of gravity. The precise consequences depend on the mechanism assumed to underlie gravity. If the speed of gravity equals the speed of light, then, in one model, the Earth would always be pulled toward the optical position of the Sun, which is displaced forward from its geometric position due to aberration. This would cause a pull ahead of the Earth, which would cause the orbit of the Earth to rapidly spiral outward. In another mechanistic explanation for gravity, proposed by Laplace in 1776, the Earth would spiral inwards towards the Sun. Since the Earth's orbit is known to be stable, Laplace concluded that the speed of gravity must be very large, at least 7x106 times the speed of light. In reality, any finite speed of gravity would result in the violation of conservation of energy and conservation of angular momentum.
Gravitational wave astronomers have confirmed that the speed of gravity equals c to a high degree of accuracy. The seeming paradox between the measured finite speed of gravity and the stability of the Earth's orbit is resolved by general relativity.
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