1996 WINNER

Scientists up the anti

Antihydrogen creation opened up a new front in science

Matthew Wesley reports

IN THESE days of "Big Science" (and especially "Big Physics", where the smallest peep into the bowels of the universe seems to need another billion-pound particle accelerator), it is nice to reflect that arguably the hottest topic in modem physics started life, 70 years ago, on a Cambridge academic's desk.

Paul Dirac, a young physicist, was thinking about the electron, which (recalling the dronings of your physics teacher) is a sub-microscopic, negatively charged matter particle. Together with the proton (much heavier, with a positive electric charge) and neutron (no charge at all), it completes a trio of fundamental particles, out of which the atoms and molecules of everyday substances are made.

Many scientists had tried but failed to explain the electron, or indeed any other particle, in terms of Max Planck's quantum theory, that sublime unity of particles, waves and energy. Dirac came to the bizarre conclusion that the electron's very existence required the existence also of an opposing "antielectron" - an opposite number positively charged and apparently made of different stuff: antimatter.

Picturing such a beast is a little like trying to read this page in a mirror: not easy. To Dirac's ordered, logical mind, it was too much like science fiction. And to have "summoned up" such a thing simply by scribbling down equations smacked of witchcraft, which as a scientist he found even worse.

Nevertheless, Dirac overcame his misgivings and published, causing a scientific storm. When Carl Anderson, a University of California doctoral student, later detected such an antielectron (he got his doctorate - and the Nobel Prize), doubts were removed and the new particle - the positron - confirmed.

Doubts then gave way to questions - and some answers - as physicists rushed down this new avenue of research. Extending Dirac's reasoning, protons and neutrons (and, in fact, any particles you care to name) were found to have their own antimatter counterparts. When two such counterparts collide, they annihilate each other and their combined mass vanishes in a thrill of pure energy.

As everything on Earth is made of matter, this explains why the few antiparticles that are created when cosmic rays collide with the Earth's atmosphere (or made in particle accelerators) seldom reach a ripe age - about 0.000000001 second is old! Hence the difficulty involved in studying them, (even with the sophisticated hardware of CERN, the European laboratory for nuclear research), and the atmosphere of triumph following each new advance.

For Walter Oelert's CERN team, last September turned out to be an especially jubilant month. Just as protons and electrons can be fused to form dull, ordinary hydrogen, he and his colleagues were able to go through the looking glass and fuse antiprotons and positrons into just nine atoms of antihydrogen: the first "antielement" to be made.

His atoms, alas, enjoyed but brief lives before hurtling towards the apparatus and consequent annihilation. But, just by showing that it could be done, the CERN team pointed the way to a new era in particle research - and gathered considerable knowledge in the process.

The team is now devoting its new-found expertise to amassing a more plentiful stock of antihydrogen, and keeping this away from matter for long enough to study it. The favoured scheme will use a strong magnetic field to contain antihydrogen within a vacuum more stringent, even, than that of outer space.

Antihydrogen, thus shielded from contact with matter, could be studied at leisure, hopefully answering a few questions. Is it, for example, affected by gravity and electromagnetic fields in the same way as conventional hydrogen?

Then we may know why, of the equal amounts of matter and antimatter thrown up by the Big Bang, matter triumphed and now predominates in the universe; and why mutual antagonism here failed to obliterate all in one cataclysmic energy flash.

'Good heavens,' said Matthew Wesley, 18, when told he had won the Award in the younger category. When he entered, Matthew was working at Ove Arup & Partners, London, doing varied tasks such as electrical and mechanical engineering. This year he will go up to Corpus Christi, Cambridge, to study electrical engineering - `a little more mundane' than the subject of his entry, particle physics