Imposing Order on the World

The Frans Hogenberg portrait (1574) shows him pointing at the North magnetic pole.

This leap year with its 366th day on February 29 is a reminder of the ways we (try to) impose order on the world. Some of those ways seem to work pretty well - atomic clocks, GPS, compasses, maps and globes

One person who tried to impose some order on our world who we can learn about in the One-Page Schoolhouse today is Gerardus Mercator. If you need a one-word description of him it would be "mapmaker" but that rather limiting. You could add cartographer, geographer, calligrapher, engraver, a maker of scientific instruments, and a publisher. He was interested in mathematics, astronomy, cosmography, terrestrial magnetism, history, philosophy, and theology.

Gerardus Mercator (5 March 1512 – 2 December 1594) was from the County of Flanders. He is most renowned for creating his 1569 world map based on a new projection. Mercator was one of the pioneers of cartography and in his time was known as a maker of globes and scientific instruments.

Mercator's early maps were in large formats suitable for wall mounting but in the second half of his life, he produced over 100 new regional maps in a smaller format suitable for binding into his Atlas of 1595. This was the first appearance of the word Atlas in reference to a book of maps. However, Mercator used it as a neologism for a treatise (Cosmologia) on the creation, history and description of the universe, not simply a collection of maps. He chose the word as a commemoration of the Titan Atlas, "King of Mauretania", whom he considered to be the first great geographer.

This world map was made by Mercator on two sheets in 1538. Only two copies of the map are extant: this one is from the American Geographical Society Library, another is at the New York Public Library. 

In 1538, he produced his first map of the world, usually referred to as Orbis Imago. But it is his 1569 world map for which he is still remembered. You may have heard of the Mercator Projection, especially if you are a sailor. This cylindrical map projection became the standard map projection for navigation because of its unique property of representing any course of constant bearing as a straight segment.

Such a course is known as a rhumb or, mathematically, a loxodrome. Using it navigators can sail in a constant compass direction to reach its destination, eliminating difficult and error-prone course corrections.

But, as with many manmade ways of imposing order on our world, his constant linear scale in every direction has side effects. The Mercator projection inflates the size of objects away from the equator starting almost imperceptibly but accelerating with latitude to become infinite at the poles. That means that while landmasses near the equator appear accurate,  landmasses at the poles, such as Greenland and Antarctica, appear far larger than their actual size.

The Mercator world map of 1569 is titled Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata . That is Renaissance Latin for "New and more complete representation of the terrestrial globe properly adapted for use in navigation."

While the map's geography has been superseded by modern knowledge, its projection proved to be one of the most significant advances in the history of cartography.

Mercator's 1569 world map showing latitudes 66°S to 80°N.