To remap the cosmos, Barbour has tapped into both Newton’s and Einstein’s conceptions of nature and then discarded key elements of both. Newton imagined that the universe was spanned by absolute space, which served as a rigid invisible backdrop or grid against which the position of all stars and planets (or farmhouses and the Duck on the Pond pub, for that matter) could be definitively located. Remove all objects from the universe and Newton’s grid would remain while time ticked along at a steady universal rate, as if marked by God’s wristwatch.
Einstein saw time and space as altogether more malleable. During his student days, he had studied the work of James Clerk Maxwell, a Scottish physicist who recognized the speed of light—300,000 kilometers or 186,000 miles per second—as a fundamental property of electromagnetic fields. In Maxwell’s time, most physicists thought that light, like sound, needed some kind of medium for transmission; the mysterious, invisible substance they hypothesized, called the luminiferous ether, would presumably be influenced by the motion of Earth around the sun and the movement of the solar system through the galaxy, a dynamic that stood to alter the speed of light depending on the relative direction from which that light came. But numerous experiments failed to discover any evidence of the ether, and Einstein realized the speed of light must stay constant no matter which direction it came from or how an observer moved.
That understanding contradicted Newton’s view of space. In his physics, you could catch up to anything, even light, if you moved fast enough. But if the speed of light holds steady no matter where you were or how you were moving, it would always seem to zoom away from you at the same constant 186,000 miles per second. Einstein enshrined that principle in his first theory of relativity (special relativity), which states that you can never catch up to a light beam no matter how hard you might try.
Barbour first heard these ideas as a teenage schoolboy in the early 1950s, a time when Einstein was still alive. As a 3-year-old child Barbour had earned the nickname “Why?” from a friend of his mother’s because of his ever-curious nature. Yet upon learning of relativity, he uncharacteristically did not question it. “I was lost in admiration,” he says. “Everyone thought Einstein was the greatest figure after Newton, and so I took it on trust, almost like someone being indoctrinated into a religion.”
It took another decade for Barbour’s questioning nature to overcome his awe. Twenty-four years old and a recent graduate of the University of Cambridge in 1961, he was planning on graduate school in astronomy. But he took a year off the academic conveyor belt to visit Germany and learn two languages: “Russian, because I adored the writer Pushkin, and German, because the first girl I fell for was a German au pair,” he says with a chuckle. So taken was he with the country that he stayed on to complete an astronomy Ph.D. at the University of Cologne, gaining the mathematical and language skills to read Einstein’s texts in their original German and grapple with their meaning.
What struck Barbour most was Einstein’s comment that his intuitive leap about space and time had been inspired by Austrian physicist and philosopher Ernst Mach, whose study of the speed of sound in fluids helped explain the sonic boom heard when objects break the sound barrier. (“Mach numbers” are named in his honor.) Long before Einstein, Mach had advocated a “truly relative” theory, in which objects were positioned only in relation to other tangible objects—Earth relative to sun, pub relative to farmhouse—and not against any abstract background grid. “Mach wanted to obliterate Newton’s absolute space and time, arguing that physics should not be at the mercy of an invisible grid that nobody can verify exists,” Barbour says. “This informed Einstein’s thinking at the time.”
That Machian ideal seized young Barbour, too. “It was something in my psyche,” he says. “The insight resonated very deeply with me.” The more he read, the more Barbour became convinced that Einstein had failed to take Mach’s ideas seriously enough. “I have certain knowledge from my readings in German,” he says, “that Einstein didn’t implement Mach’s ideas in the most direct way because he thought that way was too hard.”
Barbour felt that Einstein had taken a circuitous route to reframing the cosmos. Einstein’s 1905 publication on special relativity seemed to bring him closer to Mach’s camp, dismantling part of Newton’s grid by abolishing the notion that time was absolute. But it did so only by linking time to the three dimensions of space to create a rigid, four-dimensional block of space-time. Then, with the broader, more all-encompassing version of relativity (general relativity) he published in 1916, Einstein reshaped that backdrop into a more malleable four-dimensional space-time. Sure, Einstein’s space could be warped by the presence of massive objects, undulating like the hills of South Newington. But despite the name of his famous concept—the theory of relativity—Einstein’s universe still required a background against which particles and objects could be located in both time and space. Compared to Mach’s ideals, Einstein’s theory was not truly relative.
By 1964 Barbour was almost finished with graduate school and knew he wanted to pick up where Mach had left off. Pursuit of Mach’s concept in defiance of Einstein seemed a path to career suicide. Einstein’s theories were cornerstones of modern physics, whereas Mach’s ideas were largely considered historical curiosities. So Barbour decided to change the rules: Forgoing the security of an academic career, he set out on his own.
That might have seemed reckless to most graduate students, but Barbour’s father had also been an independent scholar, studying Arabic and traveling through the Middle East. “He was a role model to me,” Barbour says. Besides, he had a backup plan. Using his new mastery of Russian, Barbour realized he could work as a translator to pay the bills.
With his newly minted doctorate, young Barbour pressed on where Einstein had feared to tread, coming closer to Mach by dispensing not just with Newton’s rigid grid but with the very concept of space-time. In general relativity, time is a dimension interwoven with the dimensions of space. In Barbour’s universe, on the other hand, time is emergent: It is a measure of how space changes but not a fundamental component of it.
By 1969 Barbour had purchased College Farm, leaving Cologne and moving back to South Newington with Verena Bastian, his German wife. To support his growing family, including son Boris and daughter Jessica, he set up a business as a translator, drawing on his old love of Pushkin and rendering English versions of Russian scientific texts. But all the while, he tinkered away at his Machian model of the universe. “There was the possibility of a big discovery, and I had the scent of something exciting,” Barbour says. The idea was regarded highly enough to make it into the pages of Nature (pdf), banishing any worries he might have had that by shunning academia, he would be dismissed as a crank.
From 1975 on, Barbour joined forces with Bruno Bertotti, a physicist at the University of Pavia in Italy, to take on the juggernaut that is Einstein. They developed a technique known as “best-matching,” in which the motion of an object (for instance, the moon) is tracked solely by its changing distance from other objects (like the sun and the Earth), rather than its changing location against a grid. Similar to playing connect the dots to chart how the moon’s position changes over a fortnight, Barbour imagines a triangle whose corners are formed by the location of the three celestial bodies at one point in time and a second triangle formed by the same bodies a moment later. Using the mismatch in the shapes of the two triangles laid one on top of the other, he can quantify the amount of change that has taken place. He even used his best-matching technique to derive Newton’s laws of motion in a completely new way. He made the effort, he says, just to prove his model worked.