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Physics

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    $\begingroup$ The seed field might be the magnetic field of the sun but what we have today is that the magnetic field of earth cancels that of the sun in a way to protect the us from the solar wind. So I do not know how the induced field cancels the originating seed field and still sustain itself. $\endgroup$
    – M.Sameer
    Commented Aug 24, 2011 at 20:17
  • $\begingroup$ The seed field could be just random variation? Or does the magnetic field of the Sun/galaxy seed the fields of other planets? $\endgroup$
    – endolith
    Commented Aug 24, 2011 at 21:30
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    $\begingroup$ This may be a stupid question, but why does the induced current generate a magnetic field that reinforces the original magnetic field? I though that Lenz's rule states that the induced current will always counteract its cause? $\endgroup$
    – jdm
    Commented Aug 24, 2011 at 21:57
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    $\begingroup$ Aaah, right, that makes sense. The energy for the field comes from the rotation. This reminds me of a perpetuum-mobile-attempt I came up with as a kid. Placed on a magnetic pole of the earth, it would rotate (thru the earth's rotation) in the magnetic field, and generate electricity. My physics teacher couldn't tell me why it wouldn't work, or where the energy would come from. Months later I realizes it would slow down the earth's rotation, albeit by a tiny amount. $\endgroup$
    – jdm
    Commented Aug 24, 2011 at 23:49
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    $\begingroup$ How does this not violate Lenz's law? $\endgroup$
    – Ron Maimon
    Commented Oct 8, 2011 at 21:56