Rumold Mercator's double-hemisphere world map, ca. 1637. NYPL, Lionel Pincus and Princess Firyal Map Division.

Today 3/14 is Pi day, a celebration of the irrational number that defines circles and spheres. Why celebrate Pi? Why not.  Circles and spheres have their own magic, from soap bubbles to the globe, as does Pi, a number that never ends and never repeats.

Generally related to spheres, or at least the projection of a sphere onto a chart, the New York Public Library is marking the 500th anniversary the birth of Gerard Mercator (1512-1594), the Flemish geographer, engraver, and maker of scientific instruments, maps, and globes, with Mercator at 500, “an exhibition of extraordinary cartographic works — some of which have not been displayed in decades — that not only illuminate the brilliant mind and skillful hand of the cartographer himself, but also highlight his esteemed position and enduring legacy within the long arc of the history of cartography and geography.”

“Mercator’s contributions have had incredible staying power. His first world map (1538) built upon and improved state-of-the-art mathematical cartography, and was augmented with geographic data from New World discoveries. His pioneering global map projection system (1569) was a boon to mariners and seafarers, while his Ptolemaic atlases helped to revive both the gazetteers (place dictionaries) and map projection systems of the Classical world. His epic, three-volume atlas series made possible a more modern conception of the known world in the 16th century.”

The exhibit is at the Stephen A. Schwarzman Building, Fifth Avenue at 42nd Street, New York, NY 10018-2788 and runs through September 29th, 2012.  Thanks to Wojtek ‘Voytec’ Wacowski for pointing out the exhibit on Facebook.