Good guess, Mr. Tordoff, but no cookies. The Frank Garcia Tally-Ho Circle Backs bit is not like the optical illusion "shimmer". (But I can understand the confusion!) This, BTW, is called the Moire Effect. For the Moire Effect definition click here. For a excellent Moire Effect click here. And how to make a Moire Effect click here.
You're more on the money, Mr. McCabe, with the Wagon Wheel solution but, I believe, just a little off the mark. For a explaination of the Wagon Wheel Effect click here. For a scientific explaination (in PDF format) click here.
I believe Mr. Garcia's fine effect is similar to a strobe effect but without the strobe! i.e. it imitates the strobe effect. Anything can appear to BE under the influence of a strobe to the human eye if it is small enough and moving very fast in a short distance. e.g. the Tally-Ho card is moving a slight fraction in a nano-seconds' time (as opposed to the much bigger movement of wagon wheels matching slower shutter speeds, wagon wheels on wagon wheels- Pete's aforementioned sun effect, and drops of water falling UPWARD). Does this make sense?... Mr. Powers?
It's rare when science is solely used and incorporated into close-up magic. Kudos to Frank Garcia for bringing us and Richard Kaufman for reminding us about "The Magic Tally-Ho Playing Card"!
[ March 27, 2002: Message edited by: Steve Spicer ]