Image courtesy of the National Snow and Ice Data Center
Daily Arctic sea ice extent for September 23, 2008, was 4.59 million square kilometers (1.77 million square miles). The orange line shows the average extent from 1979 to 2000 for the same date. The black cross indicates the geographic North Pole.
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.