On Sun, May 22, 2011 at 9:57 AM, James Propp <jpropp@cs.uml.edu> wrote:
Has anyone built a macroscopic object that has spinorial behavior but is not tethered to a frame by strings or ropes? (For an example of what I don't mean, see Ethan Bolker's article "The Spinor Spanner".)
Your body is such an object! Stand facing a wall, arms straight out in front of you, at a distance where you palms just touch the wall. Now rotate one arm in as large circle as possible in a plane perpendicular to the wall; that is, keeping is straight, bring it down, then away from the wall, then up, then towards the wall again. observe that your palm no longer touches the wall. Now repeat the process with a second circle, and observe that your hand now touches the wall. It's not a perfect example, because you don't have the freedom of movement to rotate your arm through 360 degrees in any but that one direction. And it's tethered to the rest of your body (though not by string or ropes, unless you count tendons and ligaments). But it's still cool. Andy andy.latto@pobox.com