We’ve all heard the stories about stuff on Earth you can see from space. What does that mean anyway? From where in space? Earth, after all, is located in space. Is it where the atmosphere ends? And from that point, what can you see on the surface?
There are a variety of altitudes we use in orbit about the planet. It depends on what you want to do. But we’re talking about being able to see things like the Great Wall of China from space, and now we’re seeing that space is not an exact location. Astronauts have said the Great Wall of China is visible from low Earth orbit (99-1,200 miles from Earth), or at least the lower end of that range. But you won’t be able to see it unless conditions are “very favorable.”
If you look at the chart, you’ll see the Karman line, 62 miles (100 km) in altitude. This is an altitude regarded in the aerospace industry as the boundary between Earth’s atmosphere and the vacuum of space. You’ll also see that the International Space Station is 200-250 miles (322-402 km) away from Earth, and that the space shuttle orbited at 115-400 miles (185-644 km). These are at the lower end of low Earth orbit, but, according to NASA, it would take a far higher degree of visual acuity than a normal human eye to see the Great Wall of China. It does not stand out any more than other man-made objects.
But from low Earth orbit, one can make out a great deal of what’s going on upon the planet’s surface. Cities can be seen pretty clearly with the naked eye. Astronauts have been able to use binoculars to see landmarks like dams, airports and bridges. Two individual landmarks on Earth, the Greenhouses of Almeria and the Kennecott Copper Mine, are visible from space; the former covers an area of around 50, 000 acres (200 km2) while the latter is around 2.5 miles (4 km) across. But if you happen to be in space and you want to see the pyramids or Stonehenge, you’re out of luck.