Already responsible for the IT revolution, could silicon be about to pull off an energy revolution too? We hear from pioneer John Schaeffer about solar power's hippy roots, and Richard Swanson of Sun Power explains why it may be on course to become the world's dominant source of energy. Meanwhile Republican stalwart Barry Goldwater Jr. makes a surprising political bedfellow for solar's traditionally green supporters. (Picture: Californian house covered in solar panels; Credit: Sunrun)