Initiative - or 'Star Wars' - programme. After more than half a century, all these grand schemes are becoming reality. The control room at JET A view of the machine showing the beam-heating systems The reactor inside the Culham Science Centre, which is managed by the UK's Atomic Energy Authority, recreates the reaction that occurs at the heart of the sun, only more intensely. Here, less than a gram of hydrogen is used, but it's heated to 200 million degrees C by high-energy beams that are among the most powerful and lethal heating devices on Earth. On start-up, when two 50ft white towers aim their barrel-sized particle cannons into the reactor, will it explode into a fireball and swallow our planet like a lump of coke in a blast furnace? Happily, no. When the reactor burns, the hydrogen becomes so hot that no physical container can cool or hold it; so the intense magnetic field holds the swirling vortex of superheated hydrogen in place. The reacting material is completely invisible - it radiates energy at frequencies the human eye can't see - but as the reactor heats, sections of the wall become so hot that the tiles glow red. 'This is save-the-world science. This is the energy holy grail' Meanwhile, the incredibly intense particle beams consist of uncharged atoms flying at more than ten million metres per second. They would instantly vaporise anyone who stood in front of them. Even metal components melt in microseconds if they get in the