The coastline paradox refers to the counterintuitive observation that the length of a coastline is not well-defined due to its fractal-like properties. The measurement of coastline length depends on the units used and the level of detail considered. The paradox was first discovered by Lewis Fry Richardson and further researched by Benoit Mandelbrot. The coastline paradox is often criticized for its theoretical nature and its comparison to fractals, as coastlines are finite and not self-repeating. Various solutions have been proposed to address the paradox, but it remains a mathematical concept within models.
https://en.wikipedia.org/wiki/Coastline_paradox