Rattleback: Difference between revisions

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A '''rattleback''' is a semi-ellipsoidal [[top]] which will rotate on its axis in a preferred direction. If spun in the opposite direction, it becomes unstable, "rattles" to a stop and reverses its spin to the preferred direction.

This spin-reversal appears to violate the law of the [[angular momentum#Conservation of angular momentum|conservation of angular momentum]].[{{citation needed]}} Moreover, for most rattlebacks the motion will happen when the rattleback is spun in one direction, but not when spun in the other. Some exceptional rattlebacks will reverse when spun in either direction.<ref name="motivate">{{cite web|title=Introduction to Hugh's Talk |work=Millennium Mathematics Project |url=http://motivate.maths.org/conferences/conf14/c14_talk1.shtml |archive-url=https://web.archive.org/web/20040306062339/http://www.motivate.maths.org/conferences/conf14/c14_talk1.shtml |url-status=dead |archive-date=2004-03-06 |publisher=[[University of Cambridge]] |access-date=2013-10-19 }}</ref>

This makes the rattleback a physical curiosity that has excited human imagination since prehistoric times.<ref>"celt, n.2". OED Online. September 2012. Oxford University Press. 1 October 2012 <http://www.oed.com/view/Entry/29533?isAdvanced=false&result=2&rskey=EPfrjA&></ref>