On Apr 16, 2009, at 7:06 AM, rwg@sdf.lonestar.org wrote:
I've been telling people that the ovoid hole in the Arnold puzzle is a disappointingly nondescript image of an ellipse under a homographic transformation, but on prodding from Veit, found a surprisingly simple form, a/((b*i+c)*(i*sin(t)+d*cos(t)-1/4)+1), where a, b, c, and d are classified under the technology export act. But it occurred to me that my rattleback (a solid plastic lifesize statue of a dead banana slug, with the puzzling ability to spin only counterclockwise on a flat surface)
It rectifies time! I.e., the time-reversal of the rotation is unphysical.
The rectification also takes time -- it is not instantaneous. Have you tried rotating in the unstable sense on a very low friction surface? I expect this will increase the reversal time.
Veit
Spoilsport. Yeah, clearly in the limit of zero friction, it will spin both ways. As usual, friction supplies the time arrow. I have to believe this thing was discovered rather than invented. Reject surfboard? Lopsided kayak? Anyone know? --Bill
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