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According to one of Einstein's postulates related to special relativity, > "the laws of physics remain invariant in their form and nature in all inertial frames".

But global inertial frames don't exist in this universe, so how is Einstein's postulate justified?

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marked as duplicate by Jon Custer, stafusa, AccidentalFourierTransform, Sebastian Riese, Kyle Kanos Jul 16 '18 at 10:05

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    $\begingroup$ Related: physics.stackexchange.com/q/17459 $\endgroup$ – user191954 Jul 14 '18 at 4:25
  • $\begingroup$ what do you mean there are no inertial frames? $\endgroup$ – JEB Jul 14 '18 at 4:30
  • $\begingroup$ Clearly inertial frames exist, as they are defined to be frames whose accelerometers would read zero relative to another inertial frame. You must mean, “no absolute inertial frame exists”. But, like, that’s the whole point of relativity.. $\endgroup$ – InertialObserver Jul 14 '18 at 4:33
  • $\begingroup$ This postulate holds in any frame, not just inertial frame. $\endgroup$ – safesphere Jul 14 '18 at 4:55
  • $\begingroup$ @safesphere dis you forgot the word locally? $\endgroup$ – Rumplestillskin Jul 14 '18 at 8:27
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For locality. The general relativity extends the special postulates with the equivalence principle which postulates that there exists an accelerated frame that "cancels" the external gravitional field locally. And in fact, there exists inertial frames "locally at least", you have for example an orbiting space station. At the end the astronaut inside it seems to be floating, doesn't he?

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