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<DIV>Hi Doug,</DIV>
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<DIV>Sorry, I don’t understand what you mean.</DIV>
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<DIV>Sagnac effect is dt = 4 Pi w R^2 / c^2</DIV>
<DIV>It is explained by the fact the two photons do not travel the same
distance</DIV>
<DIV>In this case, there is no composition law for velocity</DIV>
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<DIV>Could you precise what you mean by “<FONT face="Courier New">Fresnel drag
does occurin the Fiber optic gyroscope</FONT>” ?</DIV>
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<DIV>Thank you</DIV></DIV></DIV></BODY></HTML>