Impossible?

In Nonplussed!, popular-math writer Julian Havil delighted readers with a mind-boggling array of implausible yet true mathematical paradoxes. Now Havil is back with Impossible?, another marvelous medley of the utterly confusing, profound, and unbelievable—and all of it mathematically irrefutable.

Whenever Forty-second Street in New York is temporarily closed, traffic doesn''t gridlock but flows mor...