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Having a hard time with a simple thought experiment

  1. Jan 13, 2012 #1
    The universe has a uniform electric field E pointed along the x axis. The universe also has a uniform magnetic field B pointed along the y axis.

    Now suppose you have a proton moving along the z axis with velocity v=E/B.

    The electric and magnetic forces will cancel and the proton will move strait along the z axis unaccelerated.

    To find the electromagnetic fields in the reference frame of the proton, you perform a Lorentz transformation and find that the fields are zero.

    So far so good; now transform the fields back into the original reference frame. They are zero now in all reference frames.

    What am I doing wrong?

    Edit. Oops. They're not zero; you end up with a magnetic field only. Ok, I can go to sleep now.
  2. jcsd
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