Since the first satellite was launched in 1957, humans have sent thousands of objects into orbit. We don't always bring them back. The result is that Earth is now surrounded by a cloud of rubbish — broken satellites, discarded rocket stages, fragments from collisions, even a spatula that a spacewalking astronaut accidentally let go of. All of it orbiting at tremendous speed. All of it a hazard.
How much is up there?
The European Space Agency estimates there are around 36,500 objects larger than 10 centimetres in orbit, about 1 million between 1 and 10 centimetres, and over 130 million pieces smaller than that. Most of this is space debris — sometimes called "space junk" — objects with no purpose, on no controlled flight path, just endlessly circling the Earth.
Imagine a busy motorway where cars don't have steering or brakes and travel at 28,000 kilometres per hour. Every smash creates more broken pieces, which become new hazards that cause more smashes. That's the situation building in orbit — and unlike a motorway, you can't clear up the wreckage easily.
Why it's dangerous
In orbit, even a tiny object becomes a serious threat. A 1-centimetre fragment travels at around 28,000 km/h — roughly eight times the speed of a bullet. At that speed, a small piece of paint can crack a spacecraft window. A larger fragment could destroy a satellite entirely or, in the worst case, endanger astronauts on the International Space Station.
The ISS regularly performs debris avoidance manoeuvres — firing its engines to dodge tracked fragments. It's happened dozens of times.
The Kessler syndrome
The nightmare scenario is called Kessler syndrome, named after a NASA scientist who described it in 1978. If debris density gets high enough, collisions start creating more fragments, which cause more collisions, which create more fragments, in a runaway chain reaction. Eventually, certain orbital altitudes could become so full of shrapnel that they're unusable — not just for new satellites, but potentially trapping us on Earth for centuries.
What's being done about it?
Several companies and space agencies are developing ways to clean up debris — using nets, harpoons, magnets, or robotic arms to capture and de-orbit large fragments. The UK-built RemoveDEBRIS satellite tested some of these methods. Progress is slow, partly because international law makes it legally complicated to touch another country's satellite — even a broken one.
Since 1957, humans have been sending objects into space. We don't always bring them back. Now Earth is surrounded by a cloud of rubbish in space. This rubbish includes broken satellites and old rocket parts. It even includes a spatula that an astronaut dropped during a spacewalk. All of it flies around Earth at enormous speed. All of it is dangerous.
How much is up there?
The European Space Agency has counted the space rubbish. There are around 36,500 pieces bigger than 10 centimetres. That is about the length of a pencil. There are about 1 million pieces between 1 and 10 centimetres. There are over 130 million pieces even smaller than that. Most of this is called space debris, or "space junk." These objects have no purpose. Nobody is controlling them. They just keep circling Earth.
Imagine a busy road full of toy cars with no steering wheels and no brakes. Now imagine those cars moving faster than anything you have ever seen. Every crash creates more broken pieces. Those broken pieces cause more crashes. That is exactly what is happening in space. And unlike a road, nobody can easily sweep up the mess.
Why it's dangerous
In space, even a tiny piece of rubbish is very dangerous. A 1-centimetre fragment travels at around 28,000 kilometres per hour. That is about eight times faster than a bullet from a gun. At that speed, even a tiny flake of paint can crack a spacecraft window. A bigger piece could completely destroy a satellite. In the worst cases, it could put astronauts in serious danger.
The International Space Station is where astronauts live and work in space. It often has to fire its engines to move out of the way of tracked debris. This has happened dozens of times.
The Kessler syndrome
Scientists worry about something called Kessler syndrome. It is named after a NASA scientist who wrote about it in 1978. Imagine knocking over one domino in a very long line. It hits the next one, which hits the next, and so on. Kessler syndrome works the same way. One crash creates more fragments. Those fragments cause more crashes. Those crashes create even more fragments. If this gets bad enough, some parts of space could fill up with so much flying rubbish that they become impossible to use. This could last for hundreds of years.
What's being done about it?
Some companies and space agencies are trying to clean up space. They are testing tools like nets, harpoons, magnets, and robot arms. The idea is to grab large pieces of debris and pull them back towards Earth to burn up safely. A satellite built in the UK, called RemoveDEBRIS, helped test some of these ideas. However, progress is slow. This is partly because of international law. Even if a satellite is broken and useless, it is still legally owned by the country that launched it. That makes it complicated to touch or move it.