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 more than 60,000 active satellites in space. Launch by launch, what began with a handful of scientific and military spacecraft has accelerated into a constant flow of objects, publicly and privately owned, placed into different orbital lanes, each serving a variety of purposes.
There is now a diverse collection of satellites spinning around the globe, including communication and weather satellites, navigation satellites and Earth observation technology that takes images of the surface.
What kind of objects are orbiting Earth?
The visuals below show how that change happened, revealing the rapid growth of objects in orbit and how space has quietly become crowded with human-made infrastructure.
The United Nations is close to registering all objects in orbit. Still, these new mega-constellations have sparked intense debate among astronomers regarding light pollution, and have significantly added to the complexity of managing orbital traffic in an increasingly crowded space.
The surge in orbital activity has created a significant collision risk. There have already been crashes, including a 2009 event where a US satellite hit a defunct Russia military satellite. Tens of thousands of tiny fragments of metal are now spinning at high velocities.
The big fear is that future collisions will cause a domino effect where Earth’s orbit becomes cluttered with tiny, high-speed bits of metal. That could create a near-impenetrable layer of debris that would make space launches so dangerous it would essentially trap humans on Earth.
Jonathan McDowell, who worked at the Harvard-Smithsonian Center for Astrophysics until he retired this year, has spent decades compiling a list of objects launched into orbit. He says there is a genuine threat of a chain reaction from satellites smashing into each other.
“I think the cascade potential is real but it would happen over decades,” said McDowell, who has been tracking satellites since he was a teenager. “The current danger level is sort of tolerable,” he added with a nervous laugh.
The current system only works as it relies on constant cooperation. Satellite operators move their craft daily to avoid collisions. If they stopped, McDowell warns it would take only days or weeks for the situation to spiral. “This feels fragile,” he says. “All you need is for two players to screw up on the same day.”
Getting rid of large defunct satellites would help reduce the risk, he said. Space agencies are actively testing ways to “deorbit” satellites, including by capturing them with nets or a robotic arm attached to another satellite, or by shooting them off course with high-powered lasers.
Methodology
The Guardian has used data from Space-Track.org, TS Kelso’s CelesTrak, and that collected by the astrophysicist Jonathan McDowell, formerly of the Harvard-Smithsonian Center for Astrophysics, to present as full a picture as possible of the number of satellites orbiting Earth.
Space-Track.org provides data sourced from information gathered by the US Space Surveillance Network (SSN). It does not represent every human-made object in orbit. This is especially the case for satellites with a military application or those that are classified.
The data collected by CelesTrack and McDowell has been used to add to this, to help fill in some gaps based on their research.
Throughout the map at the start of this piece, the Guardian is showing the satellites that were in orbit at that time. In this graphic, the Guardian has visualised the orbit of satellites based on the orbit speed and height metrics provided, and for older satellites these tend to be representative of when the satellite was in its later life. A satellite can have different speeds and heights throughout its lifetime.