Greetings--I think I've confused myself about rotational motion in special relativity. Suppose you had a cog-shaped object in space that you caused to rotate by shining a focused beam of light onto its side.(adsbygoogle = window.adsbygoogle || []).push({});

Classically, if we treated the light as discrete photons carrying some momentum, the cog would spin faster and faster to some arbitrarily fast angular velocity. (Also, the cog would be pushed back.)

However, we know that the velocity of any part of the cog cannot increase past c, so this imposes a maximum angular velocity. Hence there is a contradiction. How would we treat this system in special relativity?

Thanks,

Flip

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# Rotations in Special Relativity

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