Thorium (Th)

This radioactive metal holds the promise of thousands of years of energy for the world. But is it really any cleaner or safer than traditional uranium-based nuclear power? Chemistry Professor Andrea Sella of University College London takes the helm, as he speaks to no less than three nuclear physicists in his quest to discover whether thorium will deliver that godlike bolt of electricity, or just remain a nebulous dream. Prof Bob Cywinski of the University of Sheffield is a fan, whereas Dr Arjun Makhijani of the Institute for Energy and Environmental Research is decidedly not. Meanwhile India presses ahead with its now 60-year-old thorium energy programme, as former nuclear chief Anil Kakodkar explains. (Picture: Human hand holding lightning; Credit: Sergey Nivens/Thinkstock)