These films aren’t quite silent, but they’re about as close as you can get for videos of snowmobiles. They star the competitors from the 2006 Clean Snowmobile Challenge, sponsored by the Society of Automotive Engineers in the snowy plains of Michigan. Teams from 15 colleges tricked out stock snowmobiles to cut back on noise and emissions. The resulting sleds got the green light from the National Science Foundation, which will drive the winner on a research trip to the sensitive ecosystem of Greenland’s polar ice cap. But speaking as someone who recently got snowed in at the Detroit airport, I’d rather keep one of these on hand in Michigan. —Lauren Aaronson
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.