Spin Length Contraction

Discussion in 'Physics & Math' started by Dedocta, Feb 20, 2023.

  1. Dedocta Registered Member

    Messages:
    10
    I see, hmm then if pi isn’t a conserved quantity, how could it possibly show up in Einsteins field equations?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Neddy Bate Valued Senior Member

    Messages:
    2,548
    Well length is "frame-dependent" in SR, and yet the Lorentz equations still contain variables for x, y and z. Even if the circumference of a rotating disk were to be equal to pi*diameter*gamma in the disk perimeter's 'frame', then the equation still contains pi.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Neddy Bate Valued Senior Member

    Messages:
    2,548
    By the by, you can quote someone's text by hitting the "reply" button on the lower right hand side...
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. James R Just this guy, you know? Staff Member

    Messages:
    39,421
    You can also enclose any text in [quote][/quote] tags. It makes it much easy to tell when you're quoting and when you're responding.
     
  8. Dedocta Registered Member

    Messages:
    10
    Ahhh I see - haven’t used forums since the 2000s, did I answer your questions?
     
  9. phyti Registered Senior Member

    Messages:
    732
    Maybe the circumference expands instead of contracts.

    Please Register or Log in to view the hidden image!

     
  10. phyti Registered Senior Member

    Messages:
    732
    spin;

    If heat is applied to a nut bound to a bolt via rust, the nut expands radially allowing it to be removed.
    If energy is applied to a disk causing it to rotate at high angular velocities, it would expand radially.
    I see similarities.
     
  11. phyti Registered Senior Member

    Messages:
    732
    Ehrenfest paradox, Wikipedia

    Grøn states that the resolution of the paradox stems from the impossibility of synchronizing clocks in a rotating reference frame.[15]If observers on the rotating circumference try to synchronise their clocks around the circumference to establish disc time, there is a time difference between the two end points where they meet.

    The modern resolution can be briefly summarized as follows:

    1. Small distances measured by disk-riding observers are described by theLangevin-Landau-Lifschitz metric, which is indeed well approximated (for small angular velocity) by the geometry of the hyperbolic plane, just as Kaluza had claimed.
    2. For physically reasonable materials, during the spin-up phase a real disk expands radially due to centrifugal forces; relativistic corrections partially counteract (but do not cancel) this Newtonian effect. After a steady-state rotation is achieved and the disk has been allowed to relax, the geometry "in the small" is approximately given by the Langevin–Landau–Lifschitz metric.
     
  12. Dedocta Registered Member

    Messages:
    10
  13. phyti Registered Senior Member

    Messages:
    732

Share This Page