A person walks on Earth in a straight line, he says he is walking with uniform velocity. But I (from space) see him walking on a curved surface and say that he must be accelerating since he is actually walking on a curved path.

Therefore the person is accelerating in one reference frame and not in other but this contradicts General Relativity which says that acceleration is absolute and not relative.

What does the statement ‘acceleration is absolute’ actually mean? What have I assumed wrong?


By "acceleration is absolute" we mean that in reference frames which move with different accelerations the laws of physics (for instance, Maxwell's equations) will look different. In other words, you can determine your acceleration by conducting experiments locally, without looking at the outside world. If you are in a car, and the car is slowing down, you can tell it without looking outside.

  • $\begingroup$ Correct me if I'm wrong so does this means that the statement ' Accleration is absolute' is not applicable for the above reasoning beacuse the reference frames are not moving with different accleration ? $\endgroup$
    – Curiosity
    May 6 at 16:33
  • $\begingroup$ I am not sure I understand your question. If the person walked at a speed 5 km/s, they would notice that objects fall down at a smaller acceleration if thrown up (because of the centrifugal acceleration of the rotating reference frame). Both reference frames do move with different acceleration. $\endgroup$
    – Pavlo. B.
    May 6 at 16:46
  • $\begingroup$ Ohh got it! I thought about it for a minute and now it makes more sense. Thankyou! $\endgroup$
    – Curiosity
    May 6 at 17:11

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