Why Experts Can't Agree on the Lengths of the World's Coastlines

Measuring the distance between two places on a map is pretty straightforward. But if you want to calculate how long a shoreline is, things can get complicated. Just search "U.S. coastline length" and you'll find that results can vary by tens of thousands of miles.

How can cartographers come up with numbers that differ so wildly if they're all measuring the same thing? The answer, according to the video below from RealLifeLore, lies in a phenomenon called the Coastline Paradox.

Measuring the East Coast of the U.S. isn't the same as calculating the miles separating the tip of Florida from the tip of Maine. A coast doesn't follow a straight line. It's made up of divots and curves that start to multiply the closer you zoom in on the map. Accounting for every single detail of the coast is impossible. One, because the shore is always changing shape, and two, because these intricacies go all the way down to the molecular level.

That means cartographers have to pick a unit of measurement with which to estimate the length of the coast. If one team measures in miles and another measures in units of 100 miles, their results will look very different. Smaller measurements produce longer and, technically, more accurate numbers. But at some point, if you keep drilling down to smaller and smaller units, the length of a coastline appears to approach infinity—which doesn't seem entirely right, either. So every measurement of a coastline you see is really just a rough estimate.

The Coastline Paradox isn't the only complication that makes cartography an imperfect science. Even Mount Everest's title as the world's tallest mountain isn't totally uncontested.

Learn more about the Coastline Paradox in the video below.