The Sun is our lifeline – the source of most energy from our planet. Without the energy that comes from the sun, the Earth would be desolate. Life as we know it would be impossible. Directly or indirectly, the sun furnishes most of the energy which supports life on Earth. This program explains some of the latest theories behind the raging nuclear reactions at the sun's core and how scientists are using instruments both in space and on Earth to study the sun.