"He has always been fascinated by science and technology," says Jim Gianopulos, co-chairman and chief executive of Fox Filmed Entertainment, the Hollywood studio releasing Avatar . "Whether it's someone at Nasa, or Panasonic or Sony, he's not talking to the chief executive. He's talking to the guys in the lab coats and they are speaking the same language."

His personal life has also shaped his work. When he began developing Terminator - the idea for the cyborg character came to him in a dream - he was in Italy, having been fired from Piranha II . "I was sick, I was broke . . . I had no way to get home and I could barely speak the language," he once told an interviewer. "I felt very alienated and so it was very easy for me to imagine a machine with a gun. At the point of the greatest alienation in my life, it was easy to create the character."

He is an accomplished scuba diver and once held his breath underwater while free diving for three minutes, reaching a depth of more than 100ft. He is not holding his breath for Avatar , though: the director told reporters this week that he had achieved a "zen-like state" since finishing the film. This is a significant departure from his frame of mind on the set. "He has two personalities," says Mr Schwarzenegger. "The first is someone who is casual and relaxed. But as soon as the movie [production] begins he becomes a different person."