<P> 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 . In a more physically correct sense, the "speed of gravity" refers to the speed of a gravitational wave, which is the same speed as the speed of light (c) as predicted by General Relativity and confirmed by observation of the GW170817 neutron star merger . </P> <P> The speed of gravitational waves in the general theory of relativity is equal to the speed of light in a vacuum, c . Within the theory of special relativity, the constant c is not exclusively about light; instead it is the highest possible speed for any interaction in nature . Formally, c is a conversion factor for changing the unit of time to the unit of space . 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 any massless particle . Such particles include the gluon (carrier of the strong force), the photons that make up light, 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). </P>

Why is the speed of gravity the speed of light
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