The white whale of energy, scientists have been hyping the potential of nuclear fusion since, oh, the first hydrogen bomb was dropped over the Marshall Islands in 1952. It's easy to see why: nuclear fusion powers the sun, and it holds out the possibility of near-limitless electricity, without pollution. But decades of research have gone by and scientists remain incapable of creating a sustainable fusion reaction that could be used to create reliable power. That could be changing, however. Construction has begun on the International Thermonuclear Experimental Reactor (ITER), a $15 billion project that will rely on magnetic fields that are 100,000 times stronger than the Earth's to create the conditions necessary for viable fusion. The plant is scheduled to be switched on in 2018 assuming everything goes right. Nuclear fusion remains a long shot, but if the world is going to avert climate change, we'll need some luck, too.