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What are our limitations on being able to spin a disc or rod to create a relativistically fast tip/edge speed?

My thoughts are you should be able to increase the radius of the spinning object to offset the growing tensile strain as you increase RPMs, would this increase be so massive that it would not feasible to build?

I was surprised that I couldn't find experiments doing something like this for the purpose of testing special relativity, the highest speed I could find for a massive spinning object was for a fly-wheel with and edge speed going a few Mach (still impressive, I just must be missing something as to why we haven't done faster).

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  • $\begingroup$ see en.wikipedia.org/wiki/Ehrenfest_paradox it explains that a rigid disc can not spin at relativistic speeds $\endgroup$
    – Adrian Howard
    Commented Aug 6, 2019 at 2:46
  • $\begingroup$ interesting, so a disc wouldn't be able to spin faster than the speed the sound travels through it? $\endgroup$
    – Joe
    Commented Aug 7, 2019 at 0:40

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there simply are no materials strong enough to withstand the tensile stresses caused by spinning at relativistic speeds. if you were to do the calculation, you would see that no experiment is necessary to establish that fact. If you were to try the experiment anyway, be warned that a spinning flywheel contains an immense amount of stored energy which gets released in an instant when the flywheel explodes under stress. the flywheel is converted into a bomb and its broken pieces become shrapnel.

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  • $\begingroup$ Yep pretty sure this would have to be done in space just for the safety reasons $\endgroup$
    – Joe
    Commented Aug 5, 2019 at 17:17
  • $\begingroup$ @Joe - actually space is a pretty bad place to send high velocity chunks of shrapnel off into. I would suggest a nice deep mine with lots of concrete/void spaces to absorb energy. $\endgroup$
    – Jon Custer
    Commented Aug 5, 2019 at 18:24

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