In June 1792, amidst the chaos of the French Revolution, two intrepid astronomers set out in opposite directions on an extraordinary journey. Starting in Paris, Jean-Baptiste-Joseph Delambre would make his way north to Dunkirk, while Pierre-Francois-Andre Mechain voyaged south to Barcelona. Their mission was to measure the world, and their findings would help define the meter as one ten-millionth of the distance between the pole and the equator--a standard that would be used "for all people, for all time."

The Measure of All Things is the astonishing tale of one of history's...