You may have heard that the Great Wall of China or the Pyramids of Egypt are structures that can be seen with the naked eye from space. But is this true, and which man-made structures can actually be seen from above the Earth’s atmosphere?
To answer this question, we need to define the boundary of Earth’s atmosphere and outer space, which is known as the Kármán line, named after physicist Theodore von Kármán. It is generally defined as 100 kilometers above the Earth’s surface. This is considered the observation point from which one looks down at Earth from beyond the Kármán line. Assuming we are observing under clear skies, the following structures have been determined to be visible and not visible from this altitude:
The Bingham Canyon Mine (also known as the Kennecott Copper Mine) is the largest and deepest open-pit mine created by humans. It is located 32 kilometers southeast of Salt Lake City, Utah, USA. This copper mine is so large that it is not only clearly visible to the naked eye from beyond the Kármán line but was also seen by astronauts aboard NASA’s shuttles flying at altitudes of 305 to 531 kilometers above sea level.
The Three Gorges Dam, a massive dam across the Yangtze River in China, is also visible from space according to NASA. The dam stands 185 meters tall and is over 2 kilometers long, making it the largest and most expensive hydroelectric dam ever constructed.
The Palm Jumeirah Islands in Dubai can also be seen with the naked eye from space. Using an 800mm lens, you can observe these islands from the International Space Station (ISS), which orbits at a height of 400 kilometers above sea level.
Additionally, former ISS commander Chris Hadfield noted that he could also observe some highways, particularly those cutting through barren areas like deserts, depending on weather conditions and lighting. In the image taken by Chris Hadfield, one can see a road that appears as if someone has drawn it on the ground.
So, can the Pyramids of Giza or the Great Wall of China be seen from space?
In the case of the Pyramids of Giza, opinions vary. For example, astronaut Tim Peake believes that the Pyramids cannot be seen with the naked eye and can only be visible through an 800mm lens. However, former ISS commander Leroy Chiao insists that he spotted the pyramids while in orbit. Chiao stated: “There are many things visible from the ISS even with the naked eye. I have looked for the large pyramids with a telephoto lens, and I could identify the two largest pyramids with the naked eye as long as the lighting and weather conditions were good; they appeared as two small dots.”
The image at the top shows the pyramids Menkaure, Khafre, and Khufu at Giza. This photo was taken on July 25, 2012, using a Nikon D3X camera with a 1200mm lens from the International Space Station. The image was also cropped and contrast-enhanced to make the pyramids more visible.
As for the Great Wall of China – the most famous example of a man-made structure that can supposedly be seen from space, the reality is that it is not visible. Astronaut Chris Hadfield confirmed in a tweet that: “It is too narrow and it follows the contours and colors of the natural terrain.” Leroy Chiao, who also took the first photo of the Great Wall from space, admitted that it was not visible in that image.
However, many cities around the world can be seen from space. Astronaut Clayton Anderson, who spent 152 days on the ISS in 2007, stated: “We can see cities as gray spots when looking through the windows of the ISS. One of my favorite cities – Omaha, Nebraska, appears before me as a large gray spot, while its sister city, Lincoln, is a much smaller gray spot.” He also shared that the Sahara Desert is a favorite viewing location: “Every time I fly over this desert, it seems different, especially when viewed through the camera lens.”
