Hunting the Neutrino
By Frank Close
Ray Davis was the first person to look into the heart of a star. He did so by capturing neutrinos, ghostly particles that are produced in the centre of the Sun and stream out across space. As you read this, billions of them are hurtling through your eyeballs at almost the speed of light, unseen.
Neutrinos are as near to nothing as anything we know, and so elusive that they are almost invisible. When Davis began looking for solar neutrinos in 1960, many thought that he was attempting the impossible. It nearly turned out to be: 40 years would pass before he was proved right, leading to his Nobel Prize for physics in 2002, aged 87.
In June 2006, I was invited by The Guardian newspaper to write his obituary. An obituary necessarily focuses on the one person, but the saga of the solar neutrinos touched the lives of several others, scientists who devoted their entire careers chasing the elusive quarry, only to miss out on the Nobel Prize by virtue of irony, chance, or, tragically, by having already died.
Of them all, the most tragic perhaps is the genius Bruno Pontecorvo.
Pontecorvo was a remarkable scientist and a communist, working at Harwell after the war. When his Harwell colleague Klaus Fuchs was exposed as an atom spy in 1950, Pontecorvo immediately fled to the USSR. This single act probably killed his chances of Nobel Prizes.
In the following years, Pontecorvo developed a number of ideas that could have won him one or more Nobels. But his papers were published in Russian, and were unknown in the West until their English translations appeared up to two years later. By this time others in the USA had come up with the same ideas, later winning the Nobel Prize themselves.
Amongst his ideas, one involved an experiment which Soviet facilities could not perform. But most ironic were Pontecorvo’s insights about neutrinos.
Ray Davis had detected solar neutrinos – but not enough of them. For years, many of us involved in this area of research thought Davis’ experiment must have been at fault. But Pontecorvo had another theory which indicated that like chameleons, neutrinos changed their form en route across space from the Sun to Earth. And he was right. It took many years to prove it, but by 2000 the whole saga was completed. Davis duly won his Nobel Prize, but so many years had elapsed that Pontecorvo by then was dead.
So although my piece for The Guardian began as the life story of Ray Davis, Pontecorvo was there behind the scenes to such an extent that it became his story also. It is also the story of John Bahcall, Davis’ lifelong collaborator, who, to the surprise of many, was not included in the Nobel award.
The lives of these three great scientists were testimony to what science is all about: as Edison put it, genius is 1% inspiration and 99% perspiration.
A final sobering thought to put our human endeavors in context: those neutrinos that passed through you when you started reading this article are by now well on their way to Mars.
Frank Close OBE is Professor of Physics at Oxford Univeristy and a Fellow of Exeter College. He is formerly Head of the Theoretical Physics Division at the Rutherford Appleton Laboratory, and Head of Communications and Public Education at CERN. He has written several books including The Void, Antimatter, Particle Physics: A Very Short Introduction, and his most recent book, Neutrino. Frank Close’s obituary of Ray Davis won the UK Science Writer’s Prize for the ‘Best Science Writing in a Non-Scientific Context’. You can read more on OUPblog by Frank Close here, here, here, and here. This article is cross-posted with permission from the Oxford University Press/BBC Focus Magazine microsite.