Dicing with death rays

The appeal of the death ray as portrayed in pop culture is simple: it lets you get things done with minimal fuss.

The classic sci-fi death ray is seductively clinical. Rather than hurting people it just takes them out of the picture with a laser-like magic beam of light. How it does so is never fully explained.

The wonder weapon dates back further than Star Trek - all the way to Archimedes. The ancient Greek inventor apparently designed and deployed a 'burning mirror' that had an adjustable focal length. This proto-death ray may have ignited ships in the Roman fleet as it invaded the city of Syracuse.

The dream fizzled out only to be reborn during the 1920s. The death ray was a theoretical particle beam, or electromagnetic weapon, that interested Serbian scientist Nikola Tesla. The electronics wizard of his day, Tesla possessed the uncanny ability to dream up, design, build and test inventions in his mind. The death ray, he said, could wipe out 10,000 enemy aircraft at a distance of 320 kilometres with 'a tremendous electrical repelling force'. No defence against it could be devised, he added, arguing that the beam would penetrate anything. Not for the first time, people thought Tesla was crazy.

The critics may have had a point because the beam he talked about failed to materialise. Even so, the idea of a dazzling supergun fired the imagination of sci-fi writers, blossoming into the ray gun brandished by warriors such as Flash Gordon. The superhero deployed it during his regular stints at saving civilisation from evil.

A death ray the size of a smartphone is unlikely to become a reality any time soon, thanks to some acute technical hurdles. For a start, one would require compact, lightweight but extremely potent batteries that packed as much power as a truck-sized electrical generator - 100 kilowatts. A typical laptop battery only kicks out 50 watts and a car battery only one or two kilowatts, briefly. And a car battery would be far too heavy for a soldier to heft.