When discussing any environmental issue in China, it's always a struggle to decide which deserves more emphasis: how dire the situation is, or how hard Chinese authorities are trying to cope with it. China's skies, waters and even sources of food are some of the most poisonously contaminated on Earth. Its efforts to curtail pollution and develop cleaner energy sources are some of the world's most ambitious.

There are lots of way to learn first-hand the principles of flight, but most of them require years of studying or a pilot's license. There is, however, an exception: folding paper airplanes. Da Vinci did it, as did the Wright Brothers and Jack Northrop, and if it's good enough for them, it's good enough for us. So we enlisted two master paper-plane folders, Takuo Toda (current Guinness record holder for the longest timed paper aircraft flight of 27.9 seconds) and Ken Blackburn (a former record holder and engineer at Florida's Eglin Air Force Base), to show us their best cracks at making a long-flying plane out of a sheet of super-light magazine paper.

This morning PopSci's favourite Jetman, Yves Rossy, strapped on his four-engine rigid wing, took a helicopter up into the skies above Rio de Janeiro in Brazil, and once again let it rip. Leaping from the helicopter over Lagoa Rodrigo de Freitas, Rossy zipped around the skies over Rio for more than 11 minutes, taking in some famous Rio landmarks along the way.

If you want a robot to maneuver aggressively, it has to be small. As you scale things down, the "moment of inertia"-the resistance to angular motion-drops dramatically. Our nano-quadrotor robots are made to be as lightweight as possible: less than 90 grams and palm-sized.

A list of current entities permitted by the US Federal Aviation Administration to fly unmanned aerial vehicles in American airspace says one thing very clearly: if you fear the drones, stay the hell out of Texas. The Washington D.C. area as well, for that matter. The list of Certificates of Authorization, obtained by civil liberties group Electronic Frontier Foundation, shows that even as the FAA scrambles to open up US airspace to commercial drones over the next three years, there are already quite a few of them in the sky.

Early in 2008 on the Black Sea coast, a Georgian drone flying over the separatist enclave of Abkhazia transmitted an instantaneous artifact from the age of human flight-the video record of its own destruction by an attacking fighter jet. What happened that day was born of incendiary post-Soviet politics. The Kremlin backed Abkhazia and was furious that Georgia had bought surveillance drones to watch over the disputed ground. Georgia's young government flaunted its new fleet, bullhorning to diplomats and to journalists like me what the drones were documenting of Russia's buildup to war. I remember the Georgian bravado. We have drones. Ha! We have arrived. Tensions led to action. Action came to this: A Russian MiG-29 intercepted one of Georgia's unmanned aircraft, an Israeli-made Hermes 450, which streamed live video of the fighter swinging into position. The jet pilot fired a heat-seeking missile. Viewed on the drone operator's screen down below, the missile grew larger and its exhaust plume grew longer as it rushed near. Then the screen went fuzzy. Georgia's drone was dead.