What is nuclear fusion exactly?

[Michael Grove]

IN a world of global warming caused by our addiction to fossil fuel.... If we don't, the future looks decidedly bleak for millions of people on this planet: water and food shortages leading to famine and war.

Nuclear fusion has long been heralded as a potential answer to our prayers. But it's always been "thirty years away", according to the industry joke. Now several start-ups are saying they can make fusion a commercial reality much sooner.