Books
True or false: Ernest Rutherford split the atom?
by Rebecca Priestley
THE FLY IN THE CATHEDRAL, by Brian Cathcart (Viking, $49.95).
Ask a New Zealander who split the atom and they’ll tell you it was Ernest Rutherford. Ask someone from Ireland and they’ll say it was Ernest Walton. Who?
Brian Cathcart’s The Fly in the Cathedral, subtitled “How a small group of Cambridge scientists won the race to split the atom”, begins 10 years after Rutherford had split it. In 1927, Ernest Walton, a young Irish teetotal Methodist, arrived at Rutherford’s Cavendish Laboratory at Cambridge University. Rutherford had been investigating the atom for more than two decades, and had “weighed it, measured it, prodded it and chipped it but he had never had the means to get inside to see how it worked”, says Cathcart. Years of research trying to determine the structure and composition of the nucleus by bombarding it with alpha particles from radium had yielded limited information; it was like trying to find “a fly in a cathedral”.
A more powerful stream of particles – and a more conclusive result – was believed to be possible using electricity. Rutherford encouraged Walton to work with John Cockcroft to use electrical means to see inside the atom’s nucleus.
By 1930 there were five international research labs in a “race” to develop electrical equipment to accelerate particles to high speeds. In 1932, when Robert Van de Graaf in the United States developed a 1.5 million volt accelerator, an irritated Rutherford told Walton and Cockcroft to “get on with it”. Which they did.
Using their modest 300,000-volt equipment – a handmade array of transformers, rectifiers, glass tubes and vacuum pumps – they bombarded a target of lithium with high-voltage protons and detected alpha particles on a scintillation screen. These alpha particles were evidence that some of the lithium atoms had absorbed a proton and split in half. (“The Atom Split, But World Still Safe”, read the Sunday Express. “Let it be split, so long as it does not explode”, said the Daily Mirror.)
And here’s the snub. Presumably because, like Walton, he’s a Dubliner, and because it would detract from the drama of his story, Cathcart doesn’t mention that Rutherford had split the atom in 1917 by using an alpha particle to knock a proton out of a nitrogen atom. (“Playing with marbles”, Rutherford called it; the newspapers reported that he had “split the atom”.) Though to give the younger scientists credit, Rutherford had knocked a proton out of the atom’s nucleus, but Cockcroft and Walton literally split the atom in two. They went on to win the 1951 Nobel Prize in physics for this achievement.
Despite a bias that will jar with a New Zealand audience, Cathcart has written a lively and accessible book with good use of metaphor to explain the technology to a lay audience. Cathcart boasts of never having had a physics lesson in his life, and perhaps that’s the key. He describes transformers as raising voltage “in something like the way that squeezing the end of a garden hose produces a more powerful jet of water”. He compares physics to baking, where classical laws considered heat, light and energy to be, like milk, continuous, in the sense that any amount may be measured out and added to the mixture. Twentieth-century physics suggested that atoms dealt with energy in discrete and regular amounts – like eggs rather than milk, says Cathcart, and “it’s a perverse cookbook that asks you to separate one-quarter of an egg”.
Alongside the vacuum tubes and rectifiers, Cathcart exposes us to the old-world charm of Cambridge in the 1920s. The physicists wear three-piece suits to the laboratory and observe Rutherford’s civilised home time of six o’clock, when “a technician would progress from workroom to workroom … pulling out all the plugs and throwing all the switches”. Mondays to Saturdays were for working, but on Sundays there was tennis or punting on the Cam, and regular afternoon teas at the Rutherfords’, where Mary Rutherford would chastise her Nobel Prize-winning husband for dribbling into his teacup.
