Nuclear fission (the process by which nuclear power plants produce energy) is much easier to control than nuclear fusion (the process by which the sun burns, and nuclear weapons work). Small nuclear fusion reactors have been built, but a large-scale, sustainable fusion reactor has yet to be attempted—until now. A consortium of seven member bodies (the US, EU, Russia, China, Japan, South Korea, and India) has chosen a location in France to build the world’s first. And while even its champions concede it could be decades before it’s dispensing energy, nuclear fusion is cleaner and yields three to four times more power than fission.

The project is called ITER, for International Thermonuclear Experimental Reactor, and it is the second-largest cooperative international scientific endeavor (ranking behind only the Space Station). It will use a donut-shaped magnetic field to contain gases that will reach temperatures comparable to those at the core of the sun, in excess of 150 million degrees C (270 million F), and will produce 10 times more power than it consumes
.