The Earth is very close to a sphere; paper and screens are flat. Turning one into the other always distorts at least one of four things: area, shape, distance and direction. You do not get to keep all four — you choose which to preserve and which to sacrifice, and different projections make different choices.
The Mercator projection
Gerardus Mercator designed his projection in 1569 for one purpose: navigation. On a Mercator map, a line of constant compass bearing is a straight line, which let sailors plot a course with a ruler. That property made it the standard for nautical charts for centuries, and it was later adopted by web maps because it also tiles neatly and keeps local shapes intact at any zoom.
The cost is area, and the distortion grows toward the poles. On Mercator, Greenland (about 2.1 million km²) looks roughly the size of Africa (about 30 million km²) — Africa is about 14 times larger. Alaska looks bigger than Mexico; it is smaller. Russia looks larger than the whole African continent; it is less than half the size. Antarctica becomes an infinitely wide white band along the bottom.
The alternatives
- Gall–Peters: an equal-area projection, so country sizes are honest. The trade-off is shape: land near the equator is stretched vertically and land near the poles is squashed, so everything looks elongated. It became briefly famous in the 1970s and 80s as a political statement about the Global South.
- Robinson: a compromise projection that distorts area, shape, distance and direction each a little and none of them badly. National Geographic used it as its standard world map from 1988 to 1998.
- Winkel Tripel: minimises the combined distortion of area, direction and distance ("tripel" is German for "triple"). It has been National Geographic's standard since 1998 and is widely regarded as the best all-round world map.
- AuthaGraph and Dymaxion (Fuller): fold the globe onto a tetrahedron or icosahedron and unfold it, preserving relative sizes remarkably well at the cost of an unfamiliar shape with no single "up".
- Azimuthal / polar: centres the map on a pole, useful for polar routes and for showing the true relationship of the northern continents.
What to remember
Near the equator, most projections roughly agree. The higher the latitude, the more Mercator exaggerates size. When you want to compare how big two countries actually are, do not eyeball a web map — check the numbers or use a globe. And be aware that a generation raised on the Mercator map tends to overrate Europe, Russia, Canada and Greenland, and underrate Africa, South America, India and Southeast Asia.
The countries-by-area ranking uses actual land area, so it cuts straight through projection distortion.
Compare real sizes →Why there is no perfect map
It is a mathematical fact, proved by Carl Friedrich Gauss (his Theorema Egregium), that a sphere cannot be flattened onto a plane without stretching. So there is no "most accurate" flat map in an absolute sense — only maps that are best for a particular job. Mercator is best for plotting a compass course; an equal-area map is best for comparing sizes; Winkel Tripel is the best general-purpose compromise. The only truly undistorted map of the Earth is a globe.