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## Main Question or Discussion Point

what's the difference between special relativity and general relativity?

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what's the difference between special relativity and general relativity?

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bapowell

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Nabeshin

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Special relativity does NOT deal with a) accelerated reference frames or b) gravity. General relativity deals with both (at the same time, actually. The two situations are equivalent).

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jtbell

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For gravitation, you need the curved spacetime of GR.

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Fredrik

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SR describes a spacetime called Minkowski spacetime, which is completely unaffected by the matter it contains. It's still different from the Newtonian/Galilean spacetime, which has all the properties that we intuitively associate with space and time. There's a natural way to associate a coordinate system with each inertial observer in both of those spacetimes. The main difference is that in Minkowski spacetime, there's a finite speed c that's the same in all of those coordinate systems, while in Galilei spacetime, the only invariant speed is infinite. This has a number of weird consequences, including time dilation, length contraction and relativity of simultaneity.

Minkowski spacetime is one of the solutions of GR. It's actually a solution that describes a universe that's completely empty, with no matter at all. SR is a theory of matter (that doesn't affect the properties of spacetime) and motion in that particular spacetime.

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Nabeshin

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I stand corrected!candeal with accelerated reference frames (in the absence of gravity) in SR, with the help of some calculus. In these situations, spacetime is still "flat."

For gravitation, you need the curved spacetime of GR.

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