What “equal-area” preserves
A flat map cannot keep every property of a round Earth intact. The Gall-Peters projection chooses to preserve area: if one region covers twice as much ground as another, it also takes up twice as much space on the map. That makes comparisons of countries’ and continents’ relative sizes more faithful than on projections that enlarge some regions more than others.
The projection does this by dividing the globe into latitude bands. Near the equator, those bands are stretched vertically on the map. Farther north and south, they are compressed vertically while distances across them are stretched horizontally. The adjustments balance so each patch keeps its area, even as its outline changes.
Why the outlines distort
On a globe, lines of longitude converge toward the poles. A rectangular map instead places them parallel, so it gives high-latitude regions too much east–west room unless another dimension is altered. Gall-Peters compensates by squeezing those regions north–south. Near the equator, the reverse adjustment is most noticeable: places look taller than their outlines on a globe would suggest.
The result is a map useful for comparing area, but not for judging familiar shapes or local distances. It is one answer to the flat-map problem, not a way around it: the projection decides which distortion matters least for its purpose. On Gall-Peters, a continent keeps its share of the map’s area, while its silhouette pays the price.
