The amount of space garbage in Earth's orbit is getting out of control, warns the U.S. Defense Department, noting that the build-up of burnt-out satellites, rocket debris, and missile fragments has reached a "tipping point" and threatens to destroy one of our functioning suborbital satellites. Here, a quick guide to our space junk problem, and the unusual solution proposed by Japan:

How much junk, exactly, is orbiting the Earth?
About 370,000 pieces, says the Stockholm International Peace Research Institute. The garbage ranges from defunct satellites and abandoned spacecraft to nuts and bolts (quite literally).

What danger does it pose?
If two large pieces of this "space junk" crash into each other, the debris could destroy a functioning commercial satellite. "Just one little collision might knock out not only your cell phone conversations," says Chris Matyszczyk at CNET, "but also, perhaps, even your reality-TV pleasure or your closest family dependent — yes, your GPS."

Really? How serious are these crashes?
Pretty serious. A U.S. communications satellite collided with a defunct Russian military probe back in 2009, at a combined speed of around 15,000 mph. The resulting crash left 1,500 pieces of space junk directly in the path of the International Space Station, which had to perform a complicated maneuver to avoid being struck.

What can be done about it?
The Japanese Aerospace Exploration Agency has a solution. It has teamed up with Nitto Seimo, a fishing net manufacturer, to design a giant, metallic net to be launched into space. The net would rotate around the planet, and collect the orbital trash. Once the net is full, gravity would pull it toward Earth — and it would burn up as it re-entered the atmosphere. Japan wants to launch the net within the next two years.

Why Japan?
Well somebody had to do it, says Paul Wallis at Digital Journal. "The space around Earth is like a pigsty." The fact that the Japanese have a solution, and not the U.S. or Russia, "speaks volumes." Our space industry is "more obsessed with bean counting than practicalities." If NASA had any sense, says Wallis, it would establish an international agency to deal with this problem.
Sources: Daily Telegraph, Daily Mail, Crunchgear, CNET, Digital Journal