After Hours

Geek Trivia: What is the only man-made border consistently visible from space?

What is the only man-made political border consistently visible from space? Our Trivia Geek provides the answer.
The Great Wall of China made news earlier this month when scholars announced that, first, the Great Wall is actually Great Walls and, second, that the Great Walls are twice as long as originally thought.

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.


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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 a...

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I would have to quibble with the description of the India-Pakistan border as being the only one consistently visible from space. What about North Korea's borders with South Korea and China? Its neighbors are both awash with light at night with NK being an almost oceanic dark void between them. And how about the border between Haiti and the Dominican Republic, visible by day from orbit because Haiti forests have been pretty much decimated for firewood and its neighbor's forests are mostly intact. And the India-Pakistan border is not visible by day, so, so much for consistency, there. There's three more.


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The part of China that borders North Korea is very rural and lighting in that region is very sparse, and what is there is fairly far from the border itself. You can't make out that border at all. And Haiti might be clearing their forests out, but it's not noticeable from space. Trees and grass look an awful lot alike from that high up. I can't even tell for sure what is forest and what isn't, in this photo taken from the ISS: Also, consistency doesn't mean the same thing as "always". It is consistent, in that it's always visible on the same schedule. You are absolutely right about the border of North and South Korea, though. The DMZ is lit up almost as brightly as the Indo-Pakistan border, and is certainly visible every night from the ISS and other satellites:

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