Albert Einstein’s theory of general relativity describes the effect of gravitation on the shape of space and the flow of time. But for more than four decades after its publication, the theory remained largely a curiosity for scientists; however accurate it seemed, Einstein’s mathematical code—represented by six interlocking equations—was one of the most difficult to crack in all of science. That is, until a twenty-nine-year-old Cambridge graduate solved the great riddle in 1963. Roy Kerr’s solution emerged coincidentally with the discovery of black holes that same year and provided fertile testing ground—at long last—for general relativity. Today, scientists routinely cite the Kerr solution, but even among specialists, few know the story of how Kerr cracked Einstein’s code.

Fulvio Melia here offers an eyewitness account of the events leading up to Kerr’s great discovery. *Cracking the Einstein Code* vividly describes how luminaries such as Karl Schwarzschild, David Hilbert, and Emmy Noether set the stage for the Kerr solution; how Kerr came to make his breakthrough; and how scientists such as Roger Penrose, Kip Thorne, and Stephen Hawking used the accomplishment to refine and expand modern astronomy and physics. Today more than 300 million supermassive black holes are suspected of anchoring their host galaxies across the cosmos, and the Kerr solution is what astronomers and astrophysicists use to describe much of their behavior.

By unmasking the history behind the search for a real world solution to Einstein’s field equations, Melia offers a first-hand account of an important but untold story. Sometimes dramatic, often exhilarating, but always attuned to the human element, *Cracking the Einstein Code* is ultimately a showcase of how important science gets done.

“*Cracking the Einstein Code* is at once an explanation of what black holes are, a description of their place in the universe, as well as a scientific biography of Kerr. The uniqueness of Melia’s book lies with Kerr’s biography, a story that deserved to be told but wasn’t until now. Elegant with expert pacing.”

"Einstein’s theory of general relativity was around for decades before it was possible for astrophysicists to study it. And when they finally cracked the code, they simultaneously discovered black holes. In this gripping intellectual history of the Golden Age of General Relativity, Melia, an astrophysicist, introduces a cast of driven, thoughtful young scientists who dedicated their careers to divining the physical manifestations of Einstein’s theories. The book, studded with candid photographs of everyone from Roger Penrose to Vitaly Ginzburg, follows mathematician Roy Kerr as he strives to develop the first exact solution to the Einstein equations, forever altering physics."

"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's field equations for general relativity does not immediately tell you what the gravitational field surrounding a real object is actually like....Melia knows his physics and has found a compelling story."

"Today, experiments are slowly shedding light on Einstein's theory, and theoreticians are still trying to find a rigorous way to quantise it. Much of this research uses the results so brilliantly obtained by Roy Kerr, whose work is honoured by this modest but agreeable book."

"A wonderful, touching book about the life and work of one of the great unsung heros of physics, Roy Kerr, the New Zealander who, in 1963, extracted from Einstein's scarily complex equations of gravity an exact description for a real-life, 'spinning' black hole."—Marcus Chow,
*New Scientist,* "The Best Books of 2009"

— Marcus Chow, New Scientist
"A delight to read. Highly recommended."

— Choice