Last year, on 5th December, an 89-year-old New Zealander dropped a scientific bombshell. Roy Kerr submitted a paper asserting there is no proof that the catastrophic shrinkage of a massive star to form a black hole results in a point of infinity density. This contradicts the claim that such a “singularity” is inevitable, made by Roger Penrose and Stephen Hawking in the 1960s. “They did not prove what they thought they proved,” Kerr tells me.
Such an assertion, coming from anyone else, might be safely ignored. But Kerr is the theorist who, in 1963 at the age of 29, made the most significant contribution to Albert Einstein’s theory of gravity for 47 years. He found a description of the irresistible tornado of space-time around a rotating black hole. So perfectly does it characterise every last one of these objects in the universe that they are often called Kerr black holes. Kerr presented his result at the first Texas Symposium on Relativistic Astrophysics, held in Dallas just four weeks after the assassination of JFK in the city.
His journey to this point had not been easy. Born in New Zealand’s rural South Island, he was sent to live with family friends when his father went to fight in the Second World War. Forced to earn money counting rubber bands in a Christchurch factory, he showed his talent for out-of-the box thinking by deducing their number from the pattern they made when spread out on a table.
At university in Christchurch, Kerr had to learn a lot of his physics from 19th-century books. But so outstanding was his mathematical prowess that he leapfrogged entire years of study. When he was recommended for a scholarship to Cambridge, he was too young to go. “I spent two years playing snooker and bridge, and I briefly took up boxing until I was dissuaded by a tutor, who was appalled I might sustain brain damage,” he says.
From Cambridge, Kerr went to the US. Despite his meteoric rise in science, however, his life was not charmed. To obtain an American visa, he and his wife Joyce were X-rayed at the US Embassy in London. But Joyce didn’t know that she was pregnant. Their daughter, Susan, was born microcephalic and, though a cheerful child, died at age seven.
Kerr ended up at the Centre for Relativity Theory at the University of Texas in Austin. It was there, in May 1963, that he found an exact description of the shape of the space-time around spinning black hole. It was thought impossible because Einstein’s theory is so complex, describing gravity with 10 formulae rather than Newton’s one.
The first Texas Symposium on Relativistic Astrophysics was convened by a group of scientists who thought Dallas boring, wanted some excitement and realised they might attract researchers by hitching their wagon to the discovery of quasars. These objects, discovered by Maarten Schmidt in March 1963, shocked and baffled astronomers because they typically pumped out 100 times the light of an entire galaxy from a volume smaller than the solar system.
“During my 15-minute presentation, people in the audience chatted and read newspapers and generally ignored me,” Kerr recalls. “Nobody realised I was providing the solution to the quasar mystery.” The extraordinary luminosity of a quasar comes from matter heated to incandescence as it swirls down onto a spinning black hole with a mass of billions or even tens of billions that of the Sun.
Penrose, not Kerr, had been scheduled to present the work because he was deemed a better speaker, and Kerr had gone ballistic when he found out. Penrose would later win the 2020 Nobel Prize in Physics for, among other things, his “singularity theorems”. “It is extremely unlikely singularities exist and goes against known physics,” says Kerr. “Penrose and Hawking made a dodgy assumption.”
On the cusp of his tenth decade, the maverick New Zealander continues to make waves.
