Quote:
Originally Posted by HarryT
No, that's not entirely corrrect. You are absolutely right that a large mass does cause the path of light to "bend", but this is actually the result of the presence of the mass "bending space" - the photons travel in a "straight line through space", but space itself is "curved". This was one of the earliest experimental tests of the General Theory of Relativity. During a total eclipse of the Sun is 1919, Sir Arthur Eddington performed an experiment involving photographing the positions of stars close the the eclipsed Sun, and showed that their apparent position in the sky was slightly altered, to just the extent predicted by General Relativity, as a result of the light from the star passing close to the Sun.
Although, however, the path of the light is changed, its speed is not. The speed of light is constant for all observers - that is the central tenet of relativity.
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Considering that light can enter a black hole but not exit, isn't the terminal speed of light that enters a black hole zero? Is this not caused by the gravitational force exerted the black hole?