This is a goodun! It got me, I had to watch the answer video and say OOOHHHHH! But then, I'm not so bright any more. Bon apetit! [Spinning Tube Trick] Spoiler alert -- it's explained below. BTW, this has all the makings of a good bar trick. Might be worth a free beer.

The spinning tube trick.

liuzengqiang March 29, 2013, 3:34pm 11

A paper discussing this:

Seems dense.