MANY biographies of Albert Einstein document the hurdles he faced as he struggled to develop his theory of gravity, known as general relativity, which Einstein finally published in 1916. What is often overlooked is that this was only the beginning. Just as knowing the rules of chess does not, by itself, allow you to win tournaments, having Einstein鈥檚 field equations for general relativity does not immediately tell you what the gravitational field surrounding a real object is actually like.
Of particular concern was the gravitational field of a massive, rotating body 鈥� after all, nearly everything in the universe seems to rotate. It sounds deceptively simple, but as explains, it was actually a fiendishly complex problem, one that defied an answer for decades. New Zealand-born physicist finally 鈥渃racked the Einstein code鈥� in the early 1960s. Melia, himself a physicist, clearly interviewed Kerr extensively for this book, which is part history, part scientific biography.
The most intriguing application of Kerr鈥檚 solution is in describing objects that are so massive and so dense that their gravitational field prevents even light from escaping. Einstein himself was sceptical that such 鈥渂lack holes鈥� could exist in nature. Just as Kerr was developing his solution, however, the first compelling evidence for black holes was found. Today, black holes are thought to be commonplace, including the 鈥渟upermassive鈥� variety that lurk at the centre of most galaxies, and Kerr鈥檚 solution has become a vital tool in astrophysics and cosmology.
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Melia knows his physics and has found a compelling story. My only complaint is that he relays an urban myth at the start of his preface: that Galileo, shortly before his death, was offered a professorship at Harvard University. Historians insist that there is no evidence to support that notion.
University of Chicago Press
