James asks what's going on inside (unexpectedly) our eyeballs/brains to produce the apparent rotation. Here's my half-baked possible explanation. Consider the images on the retina of concentric circles moving relative to the eye. Unless their centre happens to lie directly on the line of motion, these are not circles: they are slightly elliptical, with axes which are rotating. Successive frames then interfere to produce fringing, which rotates in sync. Although individually each change is tiny, Fourier analysis by the visual system reinforces the effect to perceptible level --- as happens with other similar effects invovling motion past regular railings, etc. Fred Lunnon On 4/10/15, Simon Plouffe <simon.plouffe@gmail.com> wrote:
hello,
Me too, I thought first it was caused by the square grid of my screen, this is why I printed it : the same effect.
Simon Plouffe _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun