In Newtonian mechanics, the inertial forces depend on the reference frame and the other forces are invariant. Are they still invariant when special or general relativistic effect are involved?

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    $\begingroup$ Why do you think the non-inertial forces are invariant? $\endgroup$ – G. Smith May 7 at 5:33
  • $\begingroup$ @G.Smith, because mechanical forces depend on relative velocities and accelerations only and those don't change under Galilean transformations? $\endgroup$ – Jan Hudec May 8 at 8:23
  • $\begingroup$ Consider, for example, the Newtonian gravitational force between two particles. It doesn’t depend on their relative velocity or relative acceleration but rather on their relative position. Now consider a rotation, which is one kind of Galilean transformation. The relative position of the particles, and thus the force on each one, is not invariant under a rotation. $\endgroup$ – G. Smith May 8 at 15:48
  • $\begingroup$ @G.Smith, oh, right, the direction relative to the coordinate system of the reference frame will somewhat obviously differ. However the magnitudes, and the relative angles, shouldn't, no? $\endgroup$ – Jan Hudec May 8 at 20:18
  • $\begingroup$ I think that's right, but that's not what "invariance" means in physics. $\endgroup$ – G. Smith May 8 at 22:05

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