Why do countries look bigger on 2D maps than they actually are? Why do they work this way instead of them being their actual size in comparison to others?
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There are 2d maps that don’t change the size of objects. The Mercator projection just isn’t one of them.
The Earth is a sphere, and spheres have fundamentally different geometric properties to flat surfaces. So you cannot map a sphere onto a flat plane without distorting *something*. You can change sizes, angles, or other things, but you can’t preserve everything at once. In particular, a map must either distort angles or areas; it cannot preserve both.
The Mercator projection was designed for navigation, because it has the property that lines of constant bearing (that is, you’re always going the same direction on a compass) correspond to straight lines on a Mercator map. Since those are the measurements you usually have on a ship (or had at the time the projection was created), it makes plotting courses easy.
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As for why it distorts sizes: think about how the globe is shaped. There’s a lot more land between 10 N and 20 N than there is between 80 N and 90 N, because the band 10 N to 20 N has to go around the “fat” part of the globe, while the 80-90 N goes around the thin bit near the poles. But the Mercator projection has to make both the same horizontal length to work, which means the 80-90 band gets stretched to be the same size as the 10-20 band.
Mercator is just one of dozens and dozens of projection styles. The Earth is a 3D globe, a sphere like a ball. You see everything as its real sizes and with real angles and distances and areas. But when you put that onto a 2D image, something must be distorted because a 2D image is flat, not curved. If the Earth were a cylinder where you could just unroll the map then you’d probably be fine. But it’s not, things get narrower so to speak as you go farther north or south from the equator.
Long story short, with Mercator they were trying to preserve angles between points which is more useful for navigation. But when you preserve angles you have to sacrifice things like the size of shapes to account for the fact that they are spaced differently at higher latitudes.
Different projections are meant for different things. Some are better for looking at polar areas, some are better for looking at countries or states that go north-south, some are better for east-west-lying countries and states. And it all depends on your goal in making the map and what information you’re trying to show.
When we make a map, we typically make it on flat paper. We’re mapping a ball, though. The surface of a ball has some different properties than the surface of a flat sheet. For instance, a triangle may have three 90-degree corners on a sphere, but not on paper.
To fit this triangle onto paper, we have to tweak it to fit. So we can be consistent, we need to have a rule for how we tweak things to fit, and that rule will cause some kind of stretching or twisting.
The mercator projection minimizes the stretching near the equator and preserves local angles at the cost of stretching near the poles. The triangle I mentioned earlier would appear as a square on the mercator.
In any map projection, you will get distortion because a sphere won’t perfectly map onto a 2D surface.
The Mercator Projection is very bad at preserving size but very good at preserving shape.
It’s bad at preserving size because at the poles (remember each pole is a single point), everything gets stretched out to be the entire width of the map, where as at the equator (the entire circumference of Earth) is the exact same width on that projection.
If you have the beam of a projector hit a flat surface at the regular angle the sizes are the same. If you angle that surface, the image is stretched. This can also be seen with street markings that look very elongated from above but when you see them from inside the road they look more normal.
https://www.explainxkcd.com/wiki/index.php/977:_Map_Projections
Different map projections are used because they prioritize different things. Mercator preserves angles. If you needed something that preserved areas, you’d sacrifice the angles.
Primary school teacher here… work with 5 year olds every day 🙂
Draw a map on an orange.
Cut it into eight pieces vertically.
Eat the orange so just the skin remains.
Now lay those eight segments down flat on a table
See how the middle of the segments meet up? That’s countries near the equator.
See how as you move to the top or bottom there are ever increasing gaps that need to be filled in to join the edges together?
That’s why countries are bigger in the Mercator projection.
(By the way, check out https://www.thetruesize.com for some Mercator projection fun)
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