ScienceDraw up a list of the most influential Irish men and women in the tide of human affairs, and you would be hard pressed to put anyone ahead of Ernest Walton.
This scientist from Dungarvan, the son of a Methodist minister, was one of the founders of particle physics and the man who in 1932 split the atom.
Walton was a modest, fairly ordinary kind of man except that he transformed the world as it was then known. The photograph of him with his boss, Sir Ernest Rutherford, and his co-researcher, John Cockcroft, taken when their success was announced, shows a chubby, bespectacled figure in a suit a size too small with bulging pockets. On his face is an expression that mingles bashfulness with an almost childlike glee at being the cleverest boy in the class.
That delight was the result of Walton and Cockcroft winning the feverish race between scientists around the world to smash open the nucleus of an atom. Even finding that nucleus, said Rutherford, was like searching for "a gnat in the Albert Hall" or, as the newspapers put it, a fly in a cathedral.
Walton's "red letter day" came in Cambridge on April 14th, 1932. Working alone in the lab, he set up the equipment developed with Cockcroft, much of it bizarrely held together with plasticine. To avoid electrocution, Walton crawled on all fours across the wooden floor to a little hut at the bottom of his accelerator to check on progress. There he saw what initially could hardly be comprehended. First Cockcroft and then Rutherford confirmed it: they had not only penetrated but also shattered the nucleus of lithium.
Irish journalist and historian Brian Cathcart tells this story of "science's greatest discovery" with tremendous panache. The drama of the race to split the atom is genuinely nerve-wracking. Even though we know the outcome, the sense of relief and exhilaration as Walton and Cockcroft finally get there is irresistible. Rutherford always told young physicists that if their research could not be explained in terms comprehensible to barmaids it was not worth doing. In our more politically correct times it is enough to say that Cathcart explains the technical aspects of the narrative both elegantly and simply; the only equation to grapple with is Einstein's famous E=MC2.
There is an appealingly old-fashioned quality to the story. Walton, in a scene reminiscent of Brief Encounter, noticed his future wife by chance whilst waiting for a train. Everyone at his Cavendish laboratory stopped promptly at 4 p.m. for tea. Porters closed the building at 6 p.m. sharp every night, irrespective of delicate work in progress. The labs remained shut on Sundays and for much of the long holiday.
Yet beneath this "scones, jam and lashings of ginger beer" exterior lay Rutherford's hard-nosed approach to research. Work at the Cavendish was ruthlessly directed towards the study of the interior of the atom. When results were slow, staff were berated in Rutherford's office. Just the day before Walton's and Cockcroft's breakthrough, the prickly professor, in a familiar haze of pipe-smoke and having just electrocuted himself, barked at them to get on with it and "stop messing about".
The sense of innocence surrounding their discovery did not last long. In 1945, a similar process was used to explode the first nuclear bomb. Cathcart argues that "just as it would be an exercise in anachronism to suggest that they should have foreseen this sequence so it would be wrong-headed to say that, knowing the nucleus might be dangerous, they should have made the decision to leave it alone".
If Walton and Cockcroft had not done it, others would. Nevertheless, in our nuclear age, it is impossible not to feel a certain unease at Rutherford's cheerful rationalisation that scientists "are rather like children, who must take a watch to pieces to see how it works".
As it happened, this particular watch was not so much a timepiece as a ticking time-bomb.
Richard Aldous teaches history at UCD. His biography of Malcolm Sargent is published by Pimlico
The Fly in the Cathedral: How a Small Group of Cambridge Scientists Won the Race to Split the Atom By Brian Cathcart Viking Penguin, 308pp. £14.99