• emizeko [they/them]
    ·
    5 days ago

    what really fucks me up is combining this with relativistic effects

    like what if you had a rod 100,000 km long and you started rotating it around one end. does the other end exceed the speed of light? I know the answer has to be no, which means you're going to get all sorts of weird relativistic effects along the rod

    • quarrk [he/him]
      ·
      edit-2
      5 days ago

      I have heard this thought experiment before. I think the answer is that there is no perfectly rigid rod. The nudge at one end travels down the rod as a pressure wave at the speed of sound of the material, which will be much slower than the speed of light. And in reality, centripetal force would tear apart a rod well before its tips rotate at light speed.

    • NewAcctWhoDis [any]
      ·
      5 days ago

      If you put clocks on different parts of the rod, they'd get out of sync. It's weird.

    • m532 [she/her]
      ·
      5 days ago

      The force required to accelerate the outer part above light speed exceeds infinity