P.A.M. Dirac has always been mysterious to me. I knew his name, and that he was a theoretical physicist who made contributions to quantum theory, but very little else. What was he like? Where did he live and work? What were his contributions to science? And I really wanted to know what those initials stood for, so I could stop thinking of him as “Pam.” Farmelo’s book answers all these questions.
Dirac was born in Bristol in 1902. He was exceedingly quiet, almost unresponsive, giving one-word responses to those questions he deemed worth answering, and no response at all to small talk. Those who knew him described him as lacking empathy, as being tactless, awkward, and taciturn. He was influenced by the famous verification of Einstein’s relativity theory in 1919, when bending of light by the sun’s gravity was observed during an eclipse. Around the age of 20 he developed a new hobby – taking equations from Newtonian physics and converting them to their relativistic versions.
After earning engineering and mathematics degrees in Bristol, he was accepted into a graduate program at St. John’s College, Cambridge, studying quantum physics and relativity. Here he interacted with some of the most famous scientists of the twentieth century – Eddington, Rutherford, Kapitza, and Oppenheimer. The names of those he worked with or competed against are an indication both of his ability and of the exciting early days of quantum theory during which he worked – names like Bohr, Heisenberg, Born, Pauli, Schrödinger, Ehrenfest, and Fermi.
Among his contributions was a mathematical description of atoms and electrons that didn’t rely on an incorrect visualization, as does the Bohr model of electrons as particles orbiting a nucleus. He completed the first PhD anywhere on the subject of quantum mechanics, found the relationship between Schrodinger’s wave equation and Heisenberg’s quantum theory, and developed a quantum theory of light reconciling its wave and particle nature. He was barely beaten into print by other researchers for several important contributions to quantum theory.
More famously, he developed a quantum theory of the electron, consistent with the electron’s spin and magnetism. The theory was criticized for having negative energy states that seemed to be meaningless, until they turned out to predict antimatter. Later he predicted the existence of magnetic monopoles, which have yet to be discovered.
Dirac’s contributions were recognized when he was offered the Lucasian Professorship of Mathematics at Cambridge (a post formerly held by Isaac Newton and later by Stephen Hawking), and when he shared the 1933 Nobel Prize in Physics with Erwin Schrodinger. But you really know you’ve made it when your textbook is used as a reference by Albert Einstein, as was Dirac’s “The Principles of Quantum Mechanics.” When Einstein had a difficult quantum problem, he’d mutter, “Where’s my Dirac?”
Dirac had an intuition about the structure of reality, a form of visualization using geometrical methods, that he never articulated. He could not, or simply refused – “To draw its picture is like a blind man sensing a snowflake. One touch and it’s gone.”