Speed of gravity: Difference between revisions - Wikipedia

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== Introduction ==

The speed of gravitational waves in the [[general theory of relativity]] is equal to the ''[[speed of light]]'' in a vacuum, {{mvar|c}}.<ref>{{cite book |last=Hartle |first=J.B. |title=Gravity: An introduction to Einstein's General Relativity |publisher=[[Addison-Wesley]] |year=2003 |isbn=978-0-8053-8662-2 |location=San Francisco |pages=332–333}}</ref> Within the theory of [[special relativity]], the constant {{mvar|c}} is not only about light; instead it is the highest possible speed for any interaction in nature. Formally, {{mvar|c}} is a conversion factor for changing the unit of time to the unit of space.<ref>{{cite book |author1-link=Edwin F. Taylor |last1=Taylor |first1=Edwin F. |author2-link=John Archibald Wheeler |last2=Wheeler |first2=John Archibald |title=Spacetime Physics |edition=2nd |year=1991 |page=12}}</ref> This makes it the only speed which does not depend either on the motion of an observer or a source of light and / or gravity. Thus, the speed of "light" is also the speed of gravitational waves, and further the speed of any [[massless particle]]. Such particles include the [[gluon]] (carrier of the [[strong force]]), the [[photon]]s that make up light (hence carrier of [[electromagnetic force]]), and the hypothetical [[graviton]]s (which are the presumptive field particles associated with gravity; however, an understanding of the graviton, if it exists, requires an as-yet unavailable theory of [[quantum gravity]]).

== How gravity works ==

A hypothetical graviton particle is emitted by any atomic particle. It travels through space until it collides with another mass or atomic particle. However, rather than being reflected backwards towards the emitter, the graviton particle 'slides' around the collided particle, and is re-emitted by the collided particle exactly 180 degrees relative to the incident angle. The collided particle is in effect a secondary emitter of the graviton particle. Because of Newton's laws, the collided particle will accelerate towards the original emitter particle. To a macroscopic observer, it appears as if the two atomic particles are exerting some attractive force between them. The mechanism whereby graviton particles slides, or orbits around a collided particle is similar to light reflection and refraction. The graviton's refractive index is such that rather than being reflected back (like a mirror) or refracted by some angle of incidence (like light through water), the graviton is transmitted exactly 180 degrees from the angle of incidence that the graviton hit the attracted mass particle.

This absorption and retransmission of graviton particles by a graviton-collided atomic particle follows the conservation of mass and energy laws, hence a mass can attract surrounding mass infinitely far away, in a spherical region around it.

As predicted by Einstein, these graviton particles travel at the speed of light. Hence, when energy is converted into mass, the gravitational effect of that newly created matter is detectable by dividing spatial radial distance by the speed of light.

== Static fields ==