On a typical classroom wall map Greenland looks about as big as Africa, which is actually 14 times larger. That distortion comes from Gerardus Mercator’s 1569 world map, printed on 18 sheets and explicitly corrected for the use of sailors. Portolan charts worked in the Mediterranean, but on the open Atlantic a straight line on flat parchment drifted off course. Mercator’s math turned rhumb lines, paths of constant compass bearing, into straight lines, so a navigator could draw a line with a ruler and hold one heading. The price was stretching the map both east to west and north to south by the same growing ratio toward the poles, which makes the poles impossible to show.

The tragedy was that sailors could not use it until the marine chronometer let them find longitude more than a century later. Once in classrooms, the map was blamed for shrinking equatorial nations. Arno Peters promoted the Gall-Peters projection in 1972, seven North American cartography groups urged an end to rectangular maps in 1989, and in 2025 the African Union, led by Togo, campaigned for the Equal Earth projection. Yet Mercator lives on in phones as Web Mercator, because a conformal map keeps street corners at true right angles.

• Brazil is almost five times the size of Alaska, and Madagascar more than twice Great Britain.
• The light bulb inside a globe explanation describes a different, more distorted projection.
• Studies in the 1990s and 2000s found weak evidence for a measurable Mercator bias effect.
• A UN resolution promoting equal area maps passed 164 to 1, with the United States the lone vote against.
• Web maps cut off at 85.05113 degrees latitude to make the world a square for 256 pixel tiles, and UTM splits Earth into 60 zones.