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In my lecture notes on General Relativity, I have the following statements that are said to be wrong in Special Relativity:

  • Every physical observer measures a speed of light equal to $c$.
  • Every physical observer measures the same speed of light.
  • For every physical observer the speed of light is constant.

In a previous course I took, where some Special Relativity was covered, these three statements were assumed to be correct. I'm actually confused right now. Can someone please clarify what's going on?

Qmechanic
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sequence
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1 Answers1

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1 SR assumes no gravity

2 SR assumes all observers are moving inertially.

If there is a gravitational field (eg light passing close to the sun so spacetime is distorted), or if observers are accelerating or rotating (an observer on rotating Earth will measure the "apparent" speed of distant galaxies to be much greater than c) then SR does not apply (unless modified in simple cases) and GR applies.

John
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