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Objects visible from space

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Man-made structures visible from earth orbit without mechanical aids (such as a camera or binoculars) include highways, dams, and cities. The most commonly cited example, the Great Wall of China is not the easiest one to see.

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Man-made structures visible from earth orbit without mechanical aids (such as a camera or binoculars) include highways, dams, and cities. The most commonly cited example, the Great Wall of China is not the easiest one to see. Part of the problem of discerning fact from urban legend is defining how far up is "space", which could be anywhere from 60 miles up (the edge of space), or 180 miles up (from Apollo 12's obital), to the moon, which orbits about 237,000 miles away. A best estimated definition would be in the hundreds of miles into space. Another definition is the [[K%C3%A1rm%C3%A1n line]], which is at the altitude of 100 km (just over 60 miles) above the Earth's sea level. That line is accepted by the Fédération Aéronautique Internationale (FAI), which is an international standard setting and record-keeping body for aeronautics and astronautics, as the boundary between the Earth's atmosphere and outer space. Cities are easily distinguishable from surrounding countryside by both shuttle astronauts in an Earth orbit 135 miles (217 kilometers) high. They are just as visible on the Space station, which is in a higher orbit, circling the planet at 250 miles (400 kilometers). Using binoculars, the astronauts can see roads, airports, dams, harbors, and even large vehicles and ships. At an orbit of 160 to 350 miles, many such objects are visible from the Space Station. The concept has entered popular culture as a meme ("Many are familiar with the claim...") trivia questions, metaphor, urban legend, and proverb, that certain constructed objects or effects are so large as to be visible from outer space. For example, a giant beaver dam in Canada was described as "so large it is visible from outer space." Field and Stream asked and answered, "How big? Big enough to be visible ... from outer space."