In 2007, China successfully tested an earth-to-space anti-satellite weapon against an aging orbital weather station. The results of that weapons test, and of an accidental collision between satellites in 2009, now account for most of the hazardous debris in low earth orbit, according to Harvard’s Jonathan McDowell.

Debris is worrying enough at low orbits, where the intentional destruction of an enemy satellite could wreak havoc on existing global communications and navigation systems. Luckily, there are plenty of usable orbits around the earth. There is, however, a single narrow five-to-ten mile band, roughly 23,000 miles above the earth’s surface, where satellites can orbit in lockstep with a fixed point on earth, completing a single revolution around the earth once every 24 hours (rather than once every hour and a half, the speed at which the International Space Station orbits). This thin ribbon is the only point where a satellite can achieve what is known as “geostationary orbit” — where it can function as a “tower 23,000 miles high,” as McDowell puts it. Satellite dishes never have to angle to pick up the signal of a satellite in geostationary orbit. The line of communication is always open — it’s why receivers for satellite television and radio don’t have to constantly be adjusted.

The destruction of geostationary orbit would have worrying consequences for humankind. “Geostationary orbit is vulnerable because it’s a very precise orbit and it’s relatively crowded,” McDowell says. There’s always the possibility that a satellite’s fuel ignites, or that there’s some other mishap in space. “If you add to that the danger of deliberate action then [geostationary orbit] is a resource that we could easily lose if a large explosion were to occur.” And once it’s gone, it’s gone until humankind can invent some kind of orbital garbage-truck.