The Great Wall was originally commissioned by the first historical emperor of China, Qin Shi Huang, at the dawn of the Zhao Dynasty between 220 and 206 BC. However, the contemporary Great Wall is actually a series of fortifications built, rebuilt, connected, and extended over the course of 13 dynasties, and when all those walls are taken together, they stretch over 13,000 miles -- more than twice the length most list for the Great Wall of China today.
This sheer scale has led to the urban myth that the Great Wall of China is the only man-made structure visible from space. "Visible" and "space" are pretty fluid terms but, suffice it to say, almost no human being could spot the wall with the naked eye from even the lowest of low Earth orbits. That isn't because the Great Wall is too small, but because it's composed of the same clay as the ground it sits on, meaning there isn't enough contrast for the human eye to discern the Wall.
Much shorter airport runways and roads are visible from space, particularly those that run through deserts, simply because of the contrasting hue of grey-black concrete against yellow sand.
Great Wall enthusiasts insist that, in very low orbits in perfect weather conditions at dusk or dawn when shadows are longest, the Wall is visible from space -- making it the only man-made political border visible from space (as it was designed to demarcate and defend the border of historical China). That's stretching the definition of "visible" and violating the definition of "only," as another man-made border is consistently visible from space.
WHAT IS THE ONLY MAN-MADE POLITICAL BORDER CONSISTENTLY VISIBLE FROM SPACE?Get the answer.
Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger -- amusing and abusing IT pros. Read his full profile. You can also follow him on his personal blog.