This graphic shows the massive growth of space junk orbiting Earth since 1957

There's a lot of space junk orbiting the Earth these days.
Right now, NASA is tracking about 20,000 pieces of spent rocket parts, defunct satellites and bits of debris larger than a softball that are hurtling around the planet at more than 17,000 mph. There are also about 500,000 objects the size of a marble or larger being tracked as they orbit Earth and millions more that are too small to track, according to NASA.
Those huge numbers can be hard to visualize, but a new video and interactive produced by a scientist and released by the Royal Institution of Great Britain gives viewers a little taste of just how crowded it has become up above the planet since the first satellite made it to orbit.

See also: This cleanup satellite is designed to gobble up space debris like Pac-Man

The scientist — Stuart Grey, a lecturer at University College London — created the visualization to show how the amount of space junk orbiting Earth has changed since Sputnik, the first satellite, launched in 1957. Since then, the number of spent rocket parts and other objects circling Earth has grown by leaps and bounds.

Scientists on the ground track those pieces of space junk to be sure they aren't on a collision course with any satellites still in use.

Space junk is a major problem for space agencies and governments around the world. Even the millions of tiny bits of debris that aren't currently tracked could potentially wreak havoc if they collide with communications satellites and other spacecraft orbiting Earth.
Sometimes even the International Space Station has to move out of the way of some space junk that might pose a danger to the orbiting laboratory and the people living and working within it.
In July, the Space Station needed to change its orbit slightly in order to avoid a piece of debris.
And other times it hasn't been so lucky. Canadian astronaut Chris Hadfield caught sight of a hole in one of the station's huge solar panel arrays in 2013. While that damage wasn't severe, it still shows how crammed things are up there above us.

Bullet hole - a small stone from the universe went through our solar array. Glad it missed the hull. pic.twitter.com/iBHFVfp1p8— Chris Hadfield (@Cmdr_Hadfield) April 29, 2013

So, how did we let it get to this point?
Historically, rocket bodies have been expendable after launch, meaning that after they deliver their payloads, they simply float off into whatever orbit they happen to find themselves, possibly staying above the planet for hundreds of years. Satellites have also collided with one another, creating thousands more pieces of debris.
Also, a Chinese missile test in 2007 produced more than 2,000 pieces of debris alone.
Some researchers are hunting for new ways to clear out debris to make a little more room for satellites to safely circle the planet, and it's possible that companies like SpaceX will eventually make reusable rockets a reality, potentially reducing the number of spent rocket bodies in orbit.

Have something to add to this story? Share it in the comments.