Look out the window of your pressurized house into the deadly vacuum of space, and this is the last thing you want to see.

But that's exactly what astronaut Tim Peake saw earlier this year, a chip in the window of the International Space Station.

[gasp] Thanks science for quadruple layered space glass.

Whatever made that mark was only half the width of a human hair.

VOICEOVER: It was an attack from near Earth orbital cosmic debris-- also known as space junk.

[music playing] In the early days of the space race the number one priority was just getting stuff up there, preferably before everyone else.

In the 60 years after Sputnik there's been about 5,000 successful satellite launches, and more than 1,300 are in operation today.

But we put a few hundred million pieces of trash up there while we were at it.

Space debris comes in all sizes.

We currently track about 17,000 man-made objects larger than 10 centimeters.

But for every one of those there's 10,000 too small to see on radar.

Many of those invisible millions are things like flecks of paint, rocket exhaust, or metal shavings.

But those are all big enough to do damage.

You can't argue with kinetic energy.

When v is really, really big, a really, really small m can do bad things.

Only one in 10 tracked objects is an actual working spacecraft.

If satellites were old cars Earth's doorstep would look a lot like Steven Avery's front yard.

2/3 of space junk is close to Earth.

Reminder that's where the space people live.

Among that we find the odd spatula, lost glove.

But more than 10,000 bits of large debris are leftover from collisions or explosions.

In 2009 a US communications sat collided with a dead Russian military satellite creating more than 1,000 new pieces of large debris.

Luckily Sandra Bullock made it out OK.

If there's any known object with more than a 1 in 10,000 chance of collision, NASA maneuvers the ISS to safety.

And one satellite or another is moved out of harm's way on almost a monthly basis.

Unfortunately most objects in orbit can't be maneuvered.

Exploding satellites are rare, but old rocket stages with unburned fuel have gone boom lots of times.

Explosions can also happen if you, say, fire a missile at a satellite.

But surely, no one would do that, right?

Of course we would do that.

In 2007 China destroyed one of their weather satellites to test a kind of space battering ram weapon.

That single collision made more than 2,300 pieces of debris larger than a golf ball, and millions too small to track.

Now everybody got pretty mad at China for that.

But the US did the same thing in 1985 when it shot down a satellite with an aircraft launched missile.

[music playing] But when it comes to the worst idea in the history of space pollution, perhaps nothing compares to the summer of 1963 when we put a ring around Earth.

Before the first satellites fast long distance communication meant bouncing radio waves off the high atmosphere, but the quality was not great.

We tried big shiny balloons, permanent radio reflectors, but that didn't really work either.

So the Air Force devised a plan to make the largest radio antenna ever.

On May 9th, 1963, the project West Ford Satellite released 20 kilograms of copper wire above the earth.

And it slowly formed a ring of metal between the North and South poles too small to see with the naked eye, but dense enough to bounce radio signals off of.

Those copper needles were very light.

So most have probably fallen back to Earth.

But thanks to the extreme cold of space many of the Project West Ford needles were welded into clumps and are still orbiting Earth to this day.

But the chance of any two pieces of debris running into each other are astronomically small.

But even one accident could be enough to spell disaster.

In 1978 NASA scientist Donald Kessler described a domino effect scenario where debris from one collision would lead to other collisions, each creating more debris and more destruction until nothing was left in orbit, The Kessler Effect.

We don't know exactly what it would take to set off that chain reaction, but we may have already put the pieces in place.

And even if we stopped space launches today we still have to clean up what's already there.

We've proposed some pretty wild ideas for dealing with all that space junk orbital harpoons, lasers, space tugboats, even a real life Pac-Man.

But all of these remain ideas.

None of them have gotten off the ground yet.

Only six or so people actually live up there.

But space junk is a problem for all of us.

Imagine life without what's up there no satellites keeping trains, planes, and automobiles running, not to mention the power grid, communications, the global financial system, and definitely no YouTube.

For a long time we've treated space like we used to treat the ocean.

It's really big.

So who cares what we dump there.

Maybe it's time for a little space environmentalism.

We'll never set sail to distant lands if it's too dangerous to step off shore.

Stay curious.