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So I encountered a physics faculty who asked (during a quantum mechanics class) what the difference between special and general relativity is. When I answered that spacetime in SR is flat while in GR it can be curved, he avoided confirming whether or not my answer was right. Instead he emphasized that SR is inertial while GR is non-inertial. This bugs me as what I've commonly known is that curvature is the difference between SR and GR.

One thing that confuses me about the statement that "SR is inertial while GR is non-inertial" is what exactly it means. Isn't the principle of equivalence (physics laws are the same in inertial frames) consistent in both SR and GR?

Also another thing that I find trouble with is when people say that relativity is the physics of fast moving objects. I've always been under the impression that in relativity, we study physics in a way where time and space are in equal footing.

jboy
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  • Special relativity applies only in inertial frames, some 'special' frames. On the other hand, general relativity applies to all frames. – ParadigmShift Aug 29 '19 at 14:46
  • Re: "fast moving bodies". What people mean is just that if you take v<<c in special relativity you recover Newtonian physics. So the physics of slow-moving bodies (in inertial frames) is Newtonian physics. – Anyon Aug 29 '19 at 14:56
  • @Sciencisco, SR handles non-inertial frames just fine. See, for example, Can Special Relativity Handle Acceleration?: "It's a common misconception that special relativity cannot handle accelerating objects or accelerating reference frames. Sometimes it's claimed that general relativity is required for these situations, the reason being given that special relativity only applies to inertial frames. This is not true." – Alfred Centauri Aug 29 '19 at 15:21
  • I consider your answer to be correct. – G. Smith Aug 29 '19 at 16:15

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