Perhaps you, like me, followed the recent saga of Tiangong-1, the malfunctioning Chinese space station that came hurtling back to earth from orbit last week — thankfully — without incident. Well, the whole thing got me wondering just how big a problem man-made objects falling from the sky really is. So, I headed over to the Harvard-Smithsonian Center for Astrophysics in Cambridge to get the skinny from astrophysicist Jonathan McDowell.  

"I’ve been interested in how we’re using space since I was in college," said McDowell. "I think most people don’t know how much more stuff there is in space now than there was when I was a kid."

Not much of that stuff will go the way of Tiangong-1. And while that might be good news for Chicken Little, McDowell says the real concern is not those few objects that fall back to earth. It’s the fact that the vast majority of them won't.  

"There are over 18,000 tracked pieces of stuff in space," said McDowell. "And most of that is junk."

Long gone are the Cold War days when it was just the U.S. and Russia playing in space. Today some 60 countries operate satellites in orbit. Add to that the hundreds more small satellites conducting university research and all those large commercial satellites powering everything from your broadband internet to your cellphone.

"But that’s a small part of what’s up there," said McDowell. 

There are decades worth of dead, broken and inoperative satellites and the thousands of satellite pieces — everything from discarded lens caps to broken antennas — that fall off of them. And then, there are the rockets on which they all rode into space.

"Every time you launch a satellite, the rocket stage that put the satellite in orbit also ends up in orbit," explained McDowell. 

Some of those, especially the older ones, degrade over time with fuel still in them and have a tendency to explode.

"And suddenly you don’t have one piece of space junk," said McDowell. "You have several hundred pieces of space junk after a large boom." 

But space is space after all. So how much clutter are these 18,000 objects really creating up there?

"Space is ... mostly empty," said McDowell. "Even with all that junk, the average distance between two pieces of junk is maybe a couple hundred miles."

 Which might not sound so bad, but they're traveling so fast that even a couple hundred miles isn't a safe distance apart. "This stuff is whizzing around the earth in different directions at 17,000 miles an hour," said McDowell.

That can lead to collisions, like in 2009, when two communications satellites slammed into each other — creating more than 300 new pieces of trackable space junk. And the law of averages suggests that won’t be the last crash we see on the orbital highway.

"We fear that that’s the beginning of a chain reaction that could reduce our wonderful, expensive, intricately built constellations of aerospace technology into metal confetti making a Saturn’s ring around the Earth," said McDowell.

Yikes. So just how close are we to a doomsday scenario?  

"Just like with the oceans, humanity’s approach to environmental cleanup is we only start doing it when it’s almost totally too late," said McDowell. "So I think the answer is we’re in the doomsday scenario. But we can still get out of it because we have time."

The hope is to show that a piece of space junk trapped in a net will begin falling from orbit, eventually descending back to Earth where it will burn up, harmlessly, in the atmosphere.

And, McDowell says, we are starting to make strides. Last week — to much less fanfare than the falling space station — was the arrival of a new experiment at the International Space Station, set to be deployed in the coming months, called RemoveDEBRIS. It will test a few methods of capturing larger pieces of space junk, including harpooning it, and — no joke — tossing a net over it.

"And the idea, operationally, is that you’d have a tether on that net and you’d reel it in so it’s sort of like fishing for satellites," explained McDowell. 

And McDowell says there’s other good news. The urgency of the issue is, today, squarely on the radar of scientists and space agencies. Both NASA and the European Space Agency have groups dedicated solely to the problem. And in addition to RemoveDEBRIS, there are several more promising experiments coming down the pike.

"People are — I think — being a lot more innovative in the last couple years in their ideas about how to tackle this," said McDowell. "The era of active debris removal is coming. The era of the space garbage truck I think is gonna be on us in just a few years."

And if McDowell is right, and we are finally on the cusp of working out how to begin the wholesale cleanup of Earth’s orbit, that leaves just one tiny wrinkle left to iron out: Figuring out how to fund it.  

Whether its up there in the sky or back here on Earth, I wanna know what’s piquing your curiosity these days. Email me at and let me know. Who knows, I might just look into it for you.