The Age of Humans The Age of Humans

Six Weird Ways Humans Are Altering the Planet

From deep holes to flying sheep, some signs of human activity might really perplex geologists in the far future

A Burning Man tribute to the last remnants of humanity, a buried Statue of Liberty, depicted in the 1967 science fiction film, Planet of the Apes. (Courtesy of Flickr user Brian J. Matis)

Space Junk in Low-Earth Orbit


On October 4, 1957, humanity launched its first satellite into space: Russia’s Sputnik 1, which was about the size of a beach ball. More than 50 years later, low Earth orbit is packed with working satellites and loads of space-age debris, such as discarded rocket parts and broken or retired satellites. The U.S. Space Surveillance Network and other organizations track roughly 500,000 pieces of “space junk” as they orbit the Earth, moving as fast as 17,000 miles per hour.  

For space junk, the biggest problem is collisions with other orbital objects. Any fragment of space debris bigger than a centimeter can pierce the wall of a working spacecraft or a satellite. And even small collisions create additional dangerous debris. In 2007, China launched a ballistic missile at its own weather satellite to test defensive technology, while two communications satellites (one American, one Russian) collided in 2009. These two events are responsible for about one-third of existing space debris today.

Orbits decay over time, causing space junk to fall back to Earth, and most pieces burn up when they hit the atmosphere. But higher altitudes make for longer time in orbit. Debris at about 370 miles returns to the ground within a couple years. Anything higher than 620 miles will spend a century or longer in space. Though no one’s been tasked with removing space debris, a few companies and researchers have dreamed up potential trash removal strategies, ranging from orbital tugboats to giant nets to lasers.

About Helen Thompson
Helen Thompson

Helen Thompson writes about science and culture for Smithsonian. She's previously written for NPR, National Geographic News, Nature and others.

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