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Q & A: relativistic time

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Most recent answer: 03/28/2018
Q:
Hello,The famous atomic clock experiment is often quoted as a proof of SR. However, it poses a dilema for me in that it seems to suggest a method for proving a state of uniform motion. On the other hand it is also stated no experiment can determine a state of uniform motion? If the state of motion is relative then either clock can be considered to be in motion and run "slow". So if the clocks start out synchronised and reading the same time, after the uniform motion is completed and the clocks returned to their starting point, would they not read the same time? Hope my question makes sense.
- Brian Bolton (age 71)
Liverpool, UK
A:

How do the clocks get back to a shared location if their motion is uniform? Within a special relativistic framework, there's no way.

Now if you include a general relativistic curved spacetime, it's possible that the overall geometry is closed and that the two clocks, continuing on inertial paths, will ultimately meet up again. That raises interesting questions as to whether in such a geometry there actually would be a globally preferred reference frame, even though local patches have no such preferred frame. (See https://journals.aps.org/prd/abstract/10.1103/PhysRevD.8.1662, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.8.1662)

Mike W.


(published on 03/28/2018)

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