About you and about notes on a disturbing error

If you are a person of a certain sensibility you will enjoy reading Professor Richard Montgomery‘s “Notes on a disturbing error found in the book Sub-Riemannian Geometry — general theory and examples by Calin and Chang.

And if you aren’t, you won’t.

Montgomery is enamored also of thinking about the Dzhanibekova effect (which some people prefer to call “the tennis racket effect” or “the tennis racket theorem“), which is on display in this video:

As someone or other described it in words: “a rigid body is rotating around the axis and then SUDDENLY the rotation axis CHANGES ITS POSITION by 180 degrees. And this happens periodically with some time period.”