For hundreds of thousands of years, Earth’s orbit has been a vast and empty space – free from the impact of busy humans below, scurrying around on the surface of the planet.
But in 1957, Soviet Union scientists achieved a historic breakthrough, sending a metal ball with four radio antennae – called Sputnik – so high and speeding so fast that it would reach such a velocity that it would spin in orbit around Earth.
This marked the first steps of the space age, with a handful of objects orbiting the planet by the end of the 1950s.
As the space race between the United States and the Soviets gathered pace, each sent more and more satellites into space. By the end of the 1970s, over 14,000 tracked objects had been launched – with around 7,000 still in orbit, visualised above this globe.
By the end of the 1990s, even more satellites had been launched. Over these decades, other countries joined, and Earth’s back yard became increasingly crowded. Around 20,000 objects were being tracked in orbit at the turn of the millennium.
In the 21st century, private companies began to launch satellites at unprecedented rates. Today, Earth’s orbit is packed with thousands of satellites and fragments – around 32,000 in total – all circling the planet at immense speed. This is even after accounting for the fact that a lot of satellites have fallen out of orbit and been destroyed.
Some reports suggest that by the end of this decade there could be over 60,000 active satellites in space. To begin with, what began with a few scientific and military spaceships has quickly become a constant flow of objects, both public and private, placed in different orbital paths, each serving different purposes.
There is now a diverse collection of satellites orbiting the earth, including communications and weather satellites, navigation satellites and Earth observation technology that captures surface images.
What kinds of objects orbit the Earth?
The images below show how that change has occurred, revealing the rapid growth of circulation and how the area has become quieter with man-made structures.
The United Nations is about to register everything that circulates. However, these new constellations have sparked a heated debate among astronomers about light pollution, and have greatly increased the complexity of managing orbital traffic in an increasingly crowded space.
Increased orbital activity has resulted in a greater risk of collisions. There have been accidents, including a 2009 incident where a US satellite hit a malfunctioning Russian military satellite. Tens of thousands of metal particles are spinning at high speed.
The biggest fear is that future collisions will cause a domino effect where the Earth’s orbit will be filled with small, high-speed metal fragments. That would create near-impenetrable debris that could make the atmosphere dangerous enough to trap humans on Earth.
Jonathan McDowell, who worked at the Harvard-Smithsonian Center for Astrophysics until his retirement this year, spent decades compiling a list of objects that were launched into orbit. He says there is a real threat of a chain reaction from colliding satellites.
“I think the possibility of an explosion is real but it will happen in decades,” said McDowell, who has been tracking satellites since he was a teenager. “The present state of danger is tolerable,” he added with a nervous laugh.
The current system only works because it relies on constant cooperation. Satellite operators manage their operations daily to avoid collisions. If they stop, McDowell warns that it will only take days or weeks for the situation to progress. “This sounds weak,” he says. “All you need is two players to cheat on the same day.”
Removing large inactive satellites could help reduce the risk, he said. Space agencies are actively experimenting with ways to “thick” satellites, including by holding them with nets or a robotic arm attached to another satellite, or by shooting them with high-powered lasers.
Method
The Guardian used data from Space-Track.org, CelesTrak by TS Kelso, and those collected by astronomer Jonathan McDowell, formerly of the Harvard-Smithsonian Institute of Astrophysics, to present as complete a picture as possible of the number of satellites orbiting the Earth.
Space-Track.org provides information obtained from data collected by the US Space Surveillance Network (SSN). It does not represent every man-made object in circulation. This is especially true for satellites that have military or strategic uses.
Data collected by CelesTrack and McDowell have been used to supplement this, helping to fill in some of the gaps in their research.
Across the map at the beginning of this piece, the Guardian shows the satellites that were in orbit at the time. In this image, the Observer has visualized the orbit of the satellites based on the speed of the orbit and the height of the given metrics, and for old satellites these tend to represent when the satellite was in its later life. A satellite can have different speeds and altitudes throughout its life.
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