Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Rotation at close to the speed of light

  1. Sep 24, 2012 #1
    Let's say I had an object in space, a ring in this particular case, who was using light energy to spin itself up. The ring was built with a reactor inside of it along with a passenger/observer (we'll call the inside observer Bob for now). Bob, the ring, and the reactor are pretty much indestructible for arguments sake. The reactor produces 1000Mw of electrical energy. But the cool part about the rings reactor is that it is supposed to be able to emit the energy out past the ring. What happens to energy being sent from the ring out towards the Energy reciever? Bob looks at the readings of the reactor which should function normally due to his frame of reference, or is that wrong? What does the outside world recieve?

    What happens to electrons spinning around atoms at close to the speed of light? Are they slowing down the closer you get to the speed of light? Lets say you had an atom who had electrons rotating around it at 5% the speed of light and you reached 99% the speed of light in your rotating ring. What happens during that last 5% of your moving up to speed?

    If mass increases the closer you get to the speed of light shouldn't the energy produced by a reactor also increase? It's protons and electrons now have more mass, what does that mean for atomic mass now? Not that I would but if I split an atom in this state wouldn't it's effects be greater?

    With electrical energy does that mean it'll take more energy to offset the balance between protons and electrons? Or would the effects of the offset be greater?

    I've got more weird follow up questions but we'll just stick with this for now.
  2. jcsd
  3. Sep 24, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The ring: I don't think you have given us enough information about the problem. What does the reactor actually do, and how is its energy transmitted to the outside?

    Electrons bound to atoms: Classical theories of point particles aren't very useful when you're dealing with subatomic particles. We need a quantum theory, and in a quantum theory, electrons aren't tiny balls in orbit. So what are they? The funny thing is that quantum theories don't really tell us that, at least not unambiguously. This makes it pretty hard to come up with a meaningful answer to your question.
  4. Sep 24, 2012 #3


    User Avatar
    2017 Award

    Staff: Mentor

    In a non-accelerating frame, in the rest frame of the atoms, electron orbitals are unchanged - you can go to other systems with a Lorentz transformation, and see that the orbitals are flattened a bit in the direction of movement.
    Keep in mind that relativistic velocity addition does not work like the classic one - 99% c "plus" 5% c is just ~0.991%c.

    In your ring, the acceleration will change the orbitals, and you'll have problems to find materials where the atoms keep in their position.

    Energy cannot be produced. If you mean the electric power, it depends on the frame you are in.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook