Wagon wheels

[P3D Paul S. Boyer <boyer@xxxxxxxxxxxxx>]

Wolfie wrote: "I have heard people say that they have seen the "wagon
wheels phenomenon"
[ refering to how they appear to go backwards in movies ] while
looking
at hubcaps spinning around while out in normal sunlight, I have seen
this
myself and only realised that it's probably happening because that
persons
eyes are still in "sync" with a computer monitor."

I don't think so.  The wagon wheels phenomenon predates computer
monitors.  It is a beat phenomenon between the frequency of the
cine-camera and the spoked wheel's rotation.  It is a stroboscopic
effect, similar to the stroboscopes used to adjust the speed of
old-fashioned turntables for those vinyl records they used to have.
In the latter case the beat is betweem the black marks on the
stroboscope platter and the flicker frequency of the light used to
observe it.  By adjusting the speed of the turntable, one can make
the stroboscope seem to rotate either forward or backward, and the
same is true of the wagon wheels in old movies of stagecoaches.

Now, in order to have this wagon-wheel phenomenon work in ordinary
sunlight, there must be some frequency beating with the wheel's, and
it would have to be either in the light source, or in the visual
system.  The sun doesn't flicker in a way that would do this, so
there would have to be a physiological effect.  That could be tested
by running a stroboscope in the sunlight, and looking for a beat, and
using the strobe to determine the causitive frequency.  If the
computer monitor has really imposed some such frequency on your
visual system, the frequency you come up with should match something
in the monitor.

Much luck!

--Paul S. Boyer   <boyer@xxxxxxxxxxxxx>


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