We'd be lost without maps. They show us how to get where we want to go and teach us how we got to where we are. We use new maps to find our way around in today’s world, and we study and appreciate old maps for a better understanding of where we’ve been. March 5 is the birthday of Gerard Mercator, born in 1512 and one of history's most famous map makers, as well as a notable geographer and maker of globes and scientific instruments. In 1595 he published a book of his maps, with the first appearance of the word "Atlas" in a geographical context. Mercator's legacy lives on today in the familiar map projection bearing his name, representing sailing courses of constant bearing as straight lines — an innovation that is still employed in nautical charts.