Speed dating oxford

Putting the Sun immobile at the origin, when the Earth is moving in an orbit of radius R with velocity v presuming that the gravitational influence moves with velocity c, moves the Sun's true position ahead of its optical position, by an amount equal to v R/c, which is the travel time of gravity from the sun to the Earth times the relative velocity of the sun and the Earth.

The pull of gravity (if it behaved like a wave, such as light) would then be always displaced in the direction of the Earth's velocity, so that the Earth would always be pulled toward the optical position of the Sun, rather than its actual position.

In classical theories of gravitation, the changes in a gravitational field propagate.

A change in the distribution of energy and momentum of matter results in subsequent alteration, at a distance, of the gravitational field which it produces.

Changes in the motion of the attracting body are transmitted by some sort of waves.

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Thus, the speed of "light" is also the speed of gravitational waves and any massless particle.The first attempt to combine a finite gravitational speed with Newton's theory was made by Laplace in 1805.Based on Newton's force law he considered a model in which the gravitational field is defined as a radiation field or fluid.Such particles include the gluon (carrier of the strong force), the photons that make up light (hence carrier of electromagnetic force), and the hypothetical gravitons which make up the associated field particles of gravity (however a theory of the graviton requires a theory of quantum gravity).The speed of physical changes in a gravitational or electromagnetic field should not be confused with "changes" in the behavior of static fields that are due to pure observer-effects.The consequence of this is that static fields (either electric or gravitational) always point directly to the actual position of the bodies that they are connected to, without any delay that is due to any "signal" traveling (or propagating) from the charge, over a distance to an observer.This remains true if the charged bodies and their observers are made to "move" (or not), by simply changing reference frames.As is now known, it may be considered to be infinite in the limit of straight-line motion, since as a static influence, it is instantaneous at distance, when seen by observers at constant transverse velocity.For orbits in which velocity (direction of speed) changes slowly, it is almost infinite.These changes in direction of a static field, because of relativistic considerations, are the same for an observer when a distant charge is moving, as when an observer (instead) decides to move with respect to a distant charge.Thus, constant motion of an observer with regard to a static charge and its extended static field (either a gravitational or electric field) does not change the field.

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