Magueijo is a handsome man of 35 with an easy smile, neatly trimmed black hair, and an athletic build honed by years of karate practice. He was born in Évora, Portugal, a small town southeast of Lisbon that dates to pre-Roman times. His father was a professor of classics, but Magueijo gravitated to science at an early age, mastering Einstein's theory of relativity when he was just 14. By the time he earned his Ph.D., his work in physics was so impressive that Cambridge awarded him a scholarship that had previously been given to Abdus Salam, a Nobel laureate, and the British physicist Paul Dirac, who helped build quantum theory.
Magueijo describes himself as an anarchist—he hates meetings and bureaucracy—yet he quickly adapted to the rigor and eccentricity that characterizes Cambridge. He remembers hearing that one student, citing an obscure, centuries-old university regulation, requested—and received—a beer while taking an examination. Still, there were limits.
"Along the corridors in the physics department I would tell everyone about my big idea," Magueijo says. "The reaction was so negative. People either laughed or looked at me like I was mad. Usually physicists have this natural curiosity. This didn't trigger natural curiosity. The only thing it triggered was laughter." When Magueijo began referring to his theory as VSL, short for varying speed of light, one physicist quipped that it really stood for "very silly."
The disdain threatened more than Magueijo's pride. His research position at Cambridge was near ending, and he needed to find a permanent academic post. Certain that no university would hire him if he openly pursued his theory, Magueijo concentrated instead on cosmic strings—extremely dense threads of matter and energy that may crisscross the universe. "I had to find a job," he says. "This was the main reason I left my theory on the side for a bit."
At the time, many theorists thought cosmic strings might provide a noninflationary explanation for the development of the early universe. Magueijo's research seemed to show otherwise—while cosmic strings may exist, they can't replace inflation. "I wrote a paper that was the death blow to cosmic strings," he jokes. Nonetheless, he might have continued to work on them if not for an unexpected boon. In May 1996 he was awarded a prestigious Royal Society Fellowship. It fully supports a scientist for as long as a decade and allows him to work wherever—and on whatever—he wants. "It meant freedom," he says. "I wasn't going to be under the pressure of applying for a job for a long time, which means I didn't have to solve problems everyone wanted me to solve."
Magueijo soon decided that he'd had enough of cloistered Cambridge and moved to London to join the physics faculty at Imperial College. There he found a sympathetic colleague. "I needed a collaborator," Magueijo says. "These things aren't the product of a single brain. Theoretical physicists don't do experiments—we need someone to talk to, someone who will tell you: This is rubbish."
That collaborator was Andreas Albrecht, then the leading cosmologist at Imperial. Albrecht had made pivotal contributions to the theory of inflation, but he wasn't convinced that it held the final answer. "The way science really produces satisfactory results is when you have competing ideas playing out against each other," Albrecht says. "And then after a lot of work and tension and competition, one clearly wins out." No one had ever devised a significant alternative to inflation.
Albrecht and Magueijo worked in secret at first. If they were going to second-guess Einstein, they had to have something solid before going public. Their idea was revolutionary, but their methods were old school. They worked as Einstein did, on paper or blackboard, betting on the power of pure thought. "For more than a year and a half, I hardly did anything else," Magueijo says. "It was very depressing sometimes because to the outside world suddenly I had stopped being productive. Of course I hadn't, but I didn't tell anyone what I was doing."
The physicists assumed their theory affected only the very early universe. Once the speed of light froze at its current rate, the standard rules of physics would apply. But in that brief initial moment, a variable speed of light would solve two fundamental puzzles of cosmology.
The first is something physicists call the horizon problem: No matter which way astronomers look in the sky, the universe—at the very largest scales—looks the same. Clusters of galaxies spangle the cosmos in a remarkably uniform manner. How is it possible for opposite sides of the universe to be so similar? According to Einstein, the force of gravity, which determines the arrangement of everything in space, travels at the speed of light. How could such widely separated regions affect one another when the effects of gravity and other forces wouldn't have enough time to journey across the universe and back?
The theory of inflation solves the problem by suggesting that the regions of the universe once were
in direct contact—back when the universe was only a few inches around, shortly after the Big Bang. Inflation simply blew them up, preserving the overall uniformity that astronomers still see.
What Magueijo realized was that variable light speed offered an easier solution. If light traveled much faster in the early universe, so would effects like gravity and temperature, which would have connected different regions of the cosmos without the need for inflation. "That was my first thought walking across that field," Magueijo says. "A varying speed of light could actually explain where the cosmic unity of the universe comes from."