This Thursday marks twenty years since China's military ended the 1989 Tiananmen Square pro-democratic demonstrations by killing off hundreds of students, workers, and ordinary civilians. It's fitting, then, that in celebration of the anniversary, the government is once again curbing free speech. Censors have been at it for weeks, but now they've even begun cutting citizens off from Twitter, Flickr, Hotmail, and Microsoft's live.com.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.