My friend Mary Mowder asked me to post this question after a session we had with the incomparable Tom Allen. We were focusing on Knots and other ropes effects which do not require cutting the rope. One of the things we played with is the "Eskimo Yo-Yo" or "Butterfly." It's the thing where you hold a 3 or 3 1/2 foot length of rope in the center and swings the ends simultaneously in opposite directions. Kind of like the toy called "clackers."
One interesting and somewhat annoying phenomenon that occurs with the Eskimo Yo Yo, is that it has a tendency to slowly change the plane it happens in, forcing you to slowly turn to the right. (At least for us.) It's similar to the phenomenon that physicists call "precession." The dictionary gives, as one definition for Precession: "The movement of the axis of rotation of a spinning body around another axis, outside the body and at an angle to it."
Mary hypothesized that the precession of the rope during the Eskimo Yo Yo effect might be caused by the rotation of the Earth. Frankly, I'm a bit skeptical about that. Still, if it is the cause, then the precession should be in the opposite direction in the Southern Hemisphere. So, on the off chance that this may be read by a magician in South America, Africa, or Australia who also happens to do this bit of rope jugglery, I wonder if you've noticed this precession, and can you tell us in which direction it occurs on your part of the planet? What we characterize as moving to the "right" is actually a Counter clockwise movement to someone viewing the motion from above.
I had suspected that doing the Yo Yo with the opposite hand would change the direction of precession, but this does not seem to be the case in our experiments.
Dennis Loomis
http://www.loomismagic.com