Thomas precession is a consequence of the fact that infinitesimal lorentz transformations don't commute.

coordinate systems:

Now, tex2html_wrap132 . It is actually, tex2html_wrap133 where tex2html_wrap134 and tex2html_wrap135 . The rate of change of tex2html_wrap136 is tex2html_wrap137 using tex2html_wrap138 . The normal precession is: tex2html_wrap139 By adding these up, you get the total angular momentum. Since g=2 for spin, the zeeman effect is explained.

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