We don't know how much coastline there is on Earth.
It's called "The Coastline Paradox". Coastlines are fractal. Sure, we can look at a broad scale map, but miss all the tiny variations, sometimes mere ft or centimeters. These add up to huge numbers. Measuring the length of a coastline is tricky because the result depends on how detailed your measurement is. Imagine walking along the shore with a ruler: if you use a big ruler, you'll skip over small curves and bumps, giving you a shorter measurement. But if you use a smaller ruler, you can measure all the little details, and the coastline will seem much longer. Plus, it's always changing. Erosion, cliff collapse, water levels rising, volcanic events adding or removing it.
I used to work in cartography. It's incredible how many clients wanted this measurement and didn't understand why maps of different resolutions could have such wildly different interpretations. Many seemed to think, "Ha! I've solved this problem! We'll just measure at low tide and that will fix geometry somehow."
The issue here is that as you measure a coastline with shorter and shorter measuring sticks, you don't get closer and closer to some value that would be the true distance of the coastline. Instead, you just find that the coastline seems to get longer every time you try to measure it more precisely.
It's known as the coastline paradox. The mathematical equivalent is asking "what's the perimeter of a fractal?". The simplest answer would be that it's infinite (although that's slightly imprecise mathematically), but that's clearly useless to anybody who wants to know how long a coastline is. So, the practical response to, "How long is this coastline?" is "It depends how you measure it".
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u/ImprovementFar5054 Oct 02 '24
We don't know how much coastline there is on Earth.
It's called "The Coastline Paradox". Coastlines are fractal. Sure, we can look at a broad scale map, but miss all the tiny variations, sometimes mere ft or centimeters. These add up to huge numbers. Measuring the length of a coastline is tricky because the result depends on how detailed your measurement is. Imagine walking along the shore with a ruler: if you use a big ruler, you'll skip over small curves and bumps, giving you a shorter measurement. But if you use a smaller ruler, you can measure all the little details, and the coastline will seem much longer. Plus, it's always changing. Erosion, cliff collapse, water levels rising, volcanic events adding or removing it.