Re: Simple Sagnac

sal:
>Here's a (relatively) simple view of the Sagnac effect:
>
>http://www.physicsinsights.org/sagnac_1.html
>
>I tried to cut through the fog of algebra that often obscures web pages
>that talk about the Sagnac effect: The math on the page includes nothing
>harder than a Lorentz transform, and no messy integrals. In fact, the
>Sagnac effect is pretty simple if one avoids getting bogged down in the
>details of the rotation.
>
>Unlike Eugene and Wittke I don't claim this page contains earth-shattering
>new physics, nor that it displays such blinding brilliance on my part that
>you should wear sunglasses while reading it, but none the less some might
>find it worthwhile. If you don't understand the Sagnac effect, take a
>look at it; maybe my point of view will help.
>
>And the effect certainly seems to put paid to ballistic theory, as Paul
>Andersen has been saying for ages and ages (though I never quite
>understood what he meant until I worked it out for myself).
>
>Comments welcome, of course!


The easiest way to see what's happening in the sagnac effect is to use
the 4 mirror apparatus to analyze it and take a circle as a limiting
case:

rotation
direction
->->-
__
/ \
| |

\ / __
A A


The light ray that traverses in the direction of rotation obviously
has to travel further to go from point A to point A than the light ray
that travels opposite the rotation direction.


.