22 April 2009

What about antimatter bombs?

Even if physicists could make enough antimatter to build a viable bomb, the cost would be astronomical compared to existing weapons, like this

Read more: The five greatest mysteries of antimatter

Antimatter was a lethal weapon. Potent, and unstoppable. Once removed from its recharging platform at CERN… A blinding light. The roar of thunder. Spontaneous incineration.

The idea that humanity might one day harness the annihilative power of antimatter for destructive purposes has a ghastly fascination – and it’s a central part of the Angels and Demons plot, in which a bomb containing just a quarter of a gram of antimatter threatens to obliterate the Vatican.

Relax, says Rolf Landua, a physicist at CERN. There’s a very good reason why nothing like that is going to happen any time soon. “If you add up all the antimatter we have made in more than 30 years of antimatter physics here at CERN, and if you were very generous, you might get 10 billionths of a gram,” he says. “Even if that exploded on your fingertip it would be no more dangerous than lighting a match.” Patients undergoing PET scans have natural radioactive atoms in their bloodstreams emitting tens of millions, if not more, positrons to no ill effect.

Even if physicists could make enough antimatter to build a viable bomb, the cost would be astronomical. “A gram might cost a million billion dollars,” says Landua. “That’s probably more than Barack Obama wants to invest right now.” Frank Close, a particle physicist at the University of Oxford, points out the time problem, too. “It would take us 10 billion years to assemble enough anti-stuff to make the bomb Dan Brown talks about,” he says.

If that seems reassuring, unfortunately the same kind of reasoning does for antimatter as a clean, green energy source. “Maybe it would work if there were lumps of antimatter that nature had spent 15 billion years making for us,” says Close. As it is, we would have to make them one anti-atom at a time, which costs far more energy to make it than we would get out of it – about a billion times more, says Landua.

That’s not to say we can’t harness antimatter in new ways. In 2007, physicists David Cassidy and Allen Mills of the University of California, Riverside, made the first molecules comprised of more than one positronium atom. Positronium atoms quickly annihilate into high-energy gamma rays, so pack lots of them together, and it should be possibly to get them annihilating and emitting light in synchrony – creating an enormously high-powered “gamma-ray annihilation laser” that could be used to image objects as small as atomic nuclei, or to set off nuclear fusion in reactors.

Read more: The five greatest mysteries of antimatter