Feature
Man of mystery
by Marilyn Head
Roy Kerr is feted by the world’s leading scientists.
But few Kiwis have ever heard of him or his extraordinary contribution to the world of physics.
Ask any New Zealander to name the greatest New Zealand scientists and you’re guaranteed to hear the name “Rutherford”, followed by a long pause. If you’re lucky, eventually the names of the Nobel and other prestigious prize-winners may be added, but it’s almost certain that you won’t hear the name Roy Kerr. And yet that name was enough to attract 50 or so top scientists from the world’s premier science institutes to attend a symposium, the “Kerrfest”, in Christchurch recently, to celebrate Kerr’s 70th birthday and to honour this New Zealander who is credited with giving the “most important exact solution to any equation in physics”. It is a mystery how someone described as “one of the top three relativists of the 20th century” could be so little known in his homeland where, at times, an extended transit stopover is enough to qualify for honorary Kiwi status.
The mystery deepens on meeting Kerr. Far from being one of the worthy, but perhaps less appealing, “brown cardy and sandals” types of scientist, he is, in his own words, a “party animal”. Popularly credited with being “good-natured, good-looking and good at everything”, he has a reputation as a “wheeler dealer” businessman, bringing back American sportscars and Rolls-Royces (“terrible cars!”) from sabbaticals, that, coupled with his success as a sportsman and being a national representative and champion bridge player, would seem to invite notoriety rather than the opposite.
Or maybe Kerr’s discovery was in one of those abstruse branches of science dealing with the truly esoteric – string theory or cosmic bubbles – that is beyond the public interest or imagination? On the contrary. Although the Kerr metric is probably not something any of us would care to encounter alone on a dark night, it deals with the one of most exciting branches of science today and one with arguably the highest public profile – the physics of black holes.
Perhaps it is simply part of the Kiwi dilemma that although we love science (and there is some very compelling evidence that we do), we’re less interested in feting our scientists. (We’re certainly less interested in paying them – the New Zealand gold medal, the Rutherford, comes with the princely sum of zero dollars; the Aussie equivalent has a cool $250,000 attached.)
Fulvio Melia, Professor of Physics at the University of Arizona, commenting on the large and appreciative audience that attended the only public lecture held during the symposium, based on his highly acclaimed book The Black Hole at the Centre of Our Galaxy, made the same point. “I do not know of another city of this size in the world where over 400 people would turn up to a public lecture like this, and yet so far I haven’t met a single New Zealander outside the university who has heard of Roy! That is extraordinary when it is his work which basically underpins everything we know about black holes.”
Melia’s lecture, like many others at the Kerrfest, concentrated on examining new observational evidence for these enigmatic objects, which, because of their extreme nature, are proving to be an extreme test bed for the fundamental parameters of general relativity. For example, Einstein’s theory predicts that any rotating body will drag space with it. For slowly rotating bodies like Earth, the effect of this “frame dragging” is very, very small, but we expect that it should be measurable with the recently launched Gravity Probe “B”. But for a rapidly rotating object such as a black hole, the effect would be enormous and is now believed to be a key contributor to the extreme energies produced in the largest supernova explosions and the huge particle jets that stream out from active galactic nuclei.
Yet, before Kerr’s solution in 1963, very few scientists had thought that black holes could actually exist. The 18th-century English mathematician John Michell first postulated the existence of “dark stars”, suggesting that there could be many massive compact stars where the gravitational force within a critical circumference was such that light could not escape. But this was before either the nature of light or gravitation was well understood.
Then Einstein published his gravitational-field equations in 1915, and the remarkable Karl Schwarzschild, while serving in the German army at the Russian front, was able to give the first exact solution, describing the geometry of space around any non-rotating star and predicting the extreme conditions of what we would now call a black hole, but which he called a singularity. Tragically, Schwarzschild died a few months later, though his “elegant and beautiful” calculations of the curvature of spacetime remained a primary tool for physicists for decades. The trouble was that Schwarzschild’s geometry, elegant and crucial as it was, did not describe real stars that did spin, and a failure of imagination among physicists, Einstein included, to anticipate circumstances in which gravity could overwhelm all other forces, for example when a massive star would necessarily implode, led most scientists to conclude that black holes were of theoretical interest only. Indeed, Einstein declared, “Schwarzschild singularities [black holes] do not exist in physical reality!” Whether the singularities existed or not, the world’s leading relativists spent the next 47 years searching for a solution to Einstein’s field equation, which would describe the geometry of space around a rotating star.
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