3 ms·

I always figured this was because of acceleration. If an object is rotating it will experience a constant acceleration because it's path through spacetime is cu

I always figured this was because of acceleration. If an object is rotating it will experience a constant acceleration because it's path through spacetime is curved (equivalence principle). So being at rest you experience no forces in your local reference frame, rotating = acceleration in your local reference frame. I'm not sure why the rest of the universe rotating around the bucket would impart acceleration upon it because the rest of the universe is outside the buckets local reference frame. What sort of mechanism can transfer acceleration through rotation from one reference frame to another? (genuine question) After all, it's acceleration within the local reference frame that lets the object 'feel' the acceleration rotation - it lets the object 'feel' it's curved path through spacetime, so it knows it is rotating and not the universe around it.

smallnamespace 9y ago
This is begging the question though -- relativity presupposes the existence of a 4D spacetime upon which you can do your calculations, so at that moment when you state that the local reference frame is not accelerating, is the moment that you declared that the object is not rotating but the universe is. However relativity also admits the description of spacetime where the entire universe rotates and the object's edges are experiencing constant acceleration. One way to look at relativity is note that local observers can disagree about apparent distances, times, velocities, and accelerations, they are all able to use Lorentz transforms to answer the question of 'what would another observer see'. So in any relativistic description of this universe, all observers need to agree on whether the object in the middle is rotating or not -- but this appears to be a free parameter. In other words, General Relativity fails to fully follow Mach's principle on a global scale.

smallnamespace 9y ago

This is begging the question though -- relativity presupposes the existence of a 4D spacetime upon which you can do your calculations, so at that moment when you state that the local reference frame is not accelerating, is the moment that you declared that the object is not rotating but the universe is. However relativity also admits the description of spacetime where the entire universe rotates and the object's edges are experiencing constant acceleration. One way to look at relativity is note that local observers can disagree about apparent distances, times, velocities, and accelerations, they are all able to use Lorentz transforms to answer the question of 'what would another observer see'. So in any relativistic description of this universe, all observers need to agree on whether the object in the middle is rotating or not -- but this appears to be a free parameter. In other words, General Relativity fails to fully follow Mach's principle on a global scale.