| Physics + Dirac = Poetry Essay, Research Paper
Physics + Dirac = poetryWho was the 20th century’s greatest English-speaking poet? TS Eliot, WB Yeats, Sylvia Plath? Not for me; my nomination is the theoretician Paul Dirac, honorary poet laureate of modern physics. It is a status he richly deserves because of his amazing ability to write down fundamental equations – the poems of science. Whereas poetry uses highly-charged combinations of words, equations are the most succinct descriptions of the aspect of reality they describe. Dirac’s most famous poem enabled him successfully to predict the existence of antimatter, a triumph that his colleague, the quantum pioneer Werner Heisenberg, judged to be the supreme achievement of 20th-century physics. Dirac, born in 1902, believed that the fundamental theories of physics have mathematical beauty. Something different from the subjective concept of beauty in art. It is not a matter of opinion. And something that is mathematically beautiful remains so everywhere and for all time. Dirac had an “almost religious” faith that nature’s fundamental laws have this beauty. This working philosophy, together with its spectacularly successful results, have made him the godfather of fundamental physics, even though he has been dead for 17 years. With what might be described as a characteristically English pragmatism, Dirac made aestheticism into a practical tool (quite fitting for someone who trained as an engineer). Rather than setting out to solve problems, his work was one long search for the “pretty mathematics” that underlies the workings of the universe. He once said that a good deal of his work consisted of “simply examining mathematical quantities that physicists use and trying to fit them together in an interesting way, regardless of any application the work may have”. This is a bit like a trying to write a poem by assembling the words in an attractive order and then seeing if it reads as poetry. Dirac commended this aesthetic approach to theoretical physics in a lecture he gave in 1974, advising a group of Har vard graduate students to be concerned only with the beauty of their equations, not with what the equations mean. Their supervisors were nonplussed. Dirac’s aestheticism is a dubious research philosophy unless you’re blessed with superhuman intuition, something he had in abundance. Like poetic facility, it cannot be taught. Dirac discovered his beautiful equation in 1927, when he was a 25-year-old fellow at St John’s college, Cambridge. By combining quantum theory with the special theory of relativity, it sensationally explained the electron’s spin (observed experimentally two years before), as well as its magnetism. But the equation had another trick up its sleeve. After three years of studying puzzling properties of the equation, he concluded in 1931 that it predicted a new particle that had exactly the same mass as the electron but the opposite electric charge. A year later in California, the experimenter Carl Anderson discovered a particle with precisely these properties among cosmic ray showers raining down from outer space. Dirac and Anderson initially knew nothing of each other’s work, but when the results were published it was clear that Anderson had unwittingly detected the first example of what became known as “antimatter”. Modern cosmology tells us that at the beginning of the Big Bang there was almost as much of this antimatter as common-or-garden matter. So Dirac had, courtesy of his equation, been the first to glimpse what was once nearly half the material universe, about which the rest of humanity had no inkling until he let them in on the secret. His aesthetic strategy yielded another intriguing prediction in 1931 when, after persevering with some mathematically beautiful equations, he predicted another new type of particle, the magnetic monopole. We usually think of north and south poles as coming in pairs, but Dirac pro duced equations suggesting there exists a particle with a single pole. No one has yet observed such a particle, but this idea has long been part of state-of-the-art thinking about fundamental theories. Its detection would be a posthumous Diracian coup. His work and his style of doing theoretical physics remains powerfully influential in modern string theory. According to this theory, everything fundamentally consists of tiny pieces of string, each about a millionth of a billionth of a billionth of a billionth of a centimetre long. In this picture, the fundamental particles, such as electrons and quarks, are actually vibrating pieces of strings, much too small to see. Although not a single experiment has come out in support of this theory, its mathematical structure has a compelling beauty for string theorists. It is this beauty that leads so many theorists to believe that the theory is too beautiful to be wrong. Dirac would have been proud of them. Dirac’s aesthetic sensibilities did not extend to poetry of the literary kind. On hearing that the Manhattan project supremo Robert Oppenheimer was writing poems, a puzzled Dirac remarked in a rare outburst of cross-cultural criticism: “I do not see how a man can work at the frontiers of physics and write poetry at the same time. They are in opposition. In science you want to say something nobody knew before, in words which everyone can understand. In poetry you are bound to say something that everybody knows already in words that nobody can understand.” Even allowing for a bit of uncharacteristic hyperbole, I would beg to differ. Like Eliot’s The Waste Land, Dirac’s work is not immediately accessible to everyone. But both reward our perseverance with a fresh appreciation of reality. · Graham Farmelo is contributing editor to It Must be Beautiful: Great Equations of Modern Science, published this month by Granta
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