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lets say that we have a cube made of say 1kg, and using some means, managed to impart enough angular momentum to make it rotate at the speed of light or at least 99% of light speed. ignoring the fact that it would take infinite energy to do so, what would happen?

you can take some theoretical liberties when it comes to the answer.

im a high schooler who rather recently learnt about the fundamental theories of relativistic mechanics on my own, i dont know much about the maths and equations in this field but i will try my best to understand.

thanks for helping me out!

Qmechanic
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Shanmukha Evani
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  • As I said in https://physics.stackexchange.com/a/686011/123208 it's not possible for normal materials to spin anywhere near the speed of light. Spinning bodies are limited by the speed of sound. – PM 2Ring Mar 01 '24 at 11:52
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    Does this answer your question? What happens if a super fast rotating ball accelerates near speed of light? – Agnius Vasiliauskas Mar 01 '24 at 11:52
  • While true, I think the fact that a material disc well break well below such speeds is a cop out. Now suppose you are considering certain material effects in a rotating frame. Like if you are at the center of a merry go round and a light in the lap bounces up and down. How long does it take the light to go up in down in the lab frame, vs. the rotating frame? Alpha Centauri in a sense goes around the earth once every 24 hours. It's 4 light years away. If V=Rw, you get a V faster than light. So what's going on? I don't know. – R. Romero Mar 01 '24 at 16:52
  • @R.Romero That's a reasonable objection. We want to know what happens during the formation of magnetars, which have fairly high rotation, and the speed of sound in neutron star material can approach a significant fraction of c. But in that scenario, we need GR to handle the spacetime curvature. As a bonus, it's easier to handle rotating frames in GR than in SR. – PM 2Ring Mar 01 '24 at 17:36
  • could you explain why it cant exeed the speed of sound? im a bit new to this field of mechanics – Shanmukha Evani Mar 01 '24 at 17:56
  • BTW, in the frame co-rotating with the Earth, we reach c at a radius of ~27.4816 au, which is within the orbit of Neptune. – PM 2Ring Mar 01 '24 at 17:57
  • @Shanmukha It's related to this issue: Is it possible for information to be transmitted faster than light by using a rigid pole? – PM 2Ring Mar 01 '24 at 18:01
  • Basically, the molecules in the rotating ball are pushing each other around, and those pushes are mechanical vibrations, so they travel at the speed of sound. – PM 2Ring Mar 01 '24 at 18:05

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