A cloud Atlas

摘要

How long is Britain's coastline? Ask the same question of a piece of string; it depends on the string. But for an island, the tape measure matters too. As a cartographer zooms in, new inlets and promontories appear. Time and money, if not waves and tides, will eventually call a halt to such diligence. But it is a fact that the shorter the ruler, the longer the coastline. This is the result of "self-similarity": small stretches of coastline look much like bigger ones. Without buildings or trees to fix the scale, a photograph of a one-kilometre bay could easily be confused with that of a aookm one. Such "self-similarity" is every where once you start to look. Focus in on a cloud and wisps resolve themselves into new, smaller wisps that look strangely familiar. Blood vessels branch, and their branches branch in turn.