The day João Magueijo began to doubt Albert Einstein started inauspiciously. It was a rainy winter morning in 1995 at Cambridge University, where Magueijo was a research fellow in theoretical physics. He was tramping across a sodden soccer field, suffering from a hangover and mumbling to himself, when out of the gray a heretical idea brought him to a full stop: What if Einstein was wrong? What if, rather than being forever constant, the speed of light could change? Magueijo stood there in the downpour. What would that mean?
Until this strange notion intruded, Magueijo had been mulling over the most fateful moment in the history of the cosmos, an inconceivably brief instant between 10^-37 and 10^-34 second after the Big Bang. During that tiny interlude, most theorists agree, the universe exploded a second time, doubling in size over and over until a cosmos far smaller than a single proton grew to the size of a grapefruit. It has been expanding ever since, albeit at a more leisurely pace. Inflation, as that primordial growth spurt is called, has dominated cosmological theory for the past 20 years because it explains why the universe looks the way it does today.
But Magueijo never liked inflation theory. The idea that the universe expanded from a subatomic mote in less than a billionth of a trillionth of a trillionth of a second seemed unlikely at best to him, and there are obvious problems with the theory. It relies on a mysterious inflationary field and a weird antigravity particle called an inflaton, neither of which has ever been detected. Magueijo decided there must be a better explanation, and on that wet winter morning eight years ago, it came to him. Cosmologists wouldn't need to invoke inflation if they could bring themselves to give up one of their most sacrosanct laws: The speed of light is, was, and ever shall be 186,282 miles per second.
Magueijo now believes that for a few moments at the beginning of time, the universe's extreme heat made photons—particles of light—zip along much faster than 186,282 miles per second, at almost infinite velocities. Then, as the universe began to expand and cool, its physical properties abruptly changed, just as water suddenly transforms into ice at the freezing point. When the temperature dropped below a critical transition value, light "froze" at the lower speed we now observe.
"It's an act of brutality against the framework of physics," he admits. "You're conflicting with Einstein's theory of relativity—it's very line one. You have to be careful."
