The coastline paradox, also known as "How long is the English coastline?", is the counterintuitive observation that the coastline of a landmass does not have a well-defined length. This results from the fractal curve-like properties of coastlines.

> The prevailing method of estimating the length of a border (or coastline) was to lay out n equal straight-line segments of length l with dividers on a map or aerial photograph.

> the sum of the segments monotonically increases when the common length of the segments decreases. In effect, the shorter the ruler, the longer the measured border

> The result most astounding to Richardson is that, under certain circumstances, as l approaches zero, the length of the coastline approaches infinity.