Reviewed geography guide
Mercator Projection and Country Size Distortion
The Mercator projection was designed for navigation: straight lines preserve direction, but areas are grossly distorted near polar regions. It is useful for bearings, not for judging relative country area.
What Mercator is good at
Mercator is conformal, so it preserves local angles and small shapes. A constant compass course appears as a straight line, which made the projection valuable for marine navigation.
That navigation property does not make the map a reliable area comparison. The scale increases away from the equator.
Why northern countries look so large
High-latitude land is stretched in both horizontal and vertical directions. Greenland and Russia therefore occupy much more display area than their territorial measurements justify beside lower-latitude places.
Check the Greenland–Africa comparison or use the interactive comparator to replace projected display area with reviewed measurements and same-scale silhouettes.