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22 Januari 2018

Is Einstein's Greatest Work All Wrong—Because He Didn't Go Far Enough?

Is Einstein's Greatest Work All Wrong—Because He Didn't Go Far Enough?

From a farmhouse in the English countryside, gentleman scientist Julian Barbour plots to take relativity to its logical extreme and redefine the very nature of gravity, space, and time.

Fields  Theoretical physics, history of scienceAlma mater  University of Cambridge, University of CologneKnown for  timeless physics (the thesis that time is an illusion)Residence  Oxfordshire, United Kingdom


Julian  Barbourcuts an unlikely figure for a radical. We sip afternoon tea at his farmhouse in the sleepy English village of South Newington, and he playfully quotes Faust: That I may understand whatever binds the world’s innermost core together, see all its workings, and its seeds. His love of Goethe’s classic poem, about a scholar who sells his soul to the devil in exchange for unlimited knowledge, is apropos. Forty years ago, Barbour’s desire to uncover the innermost workings of the universe led him to make a seemingly reckless gamble. He sacrificed a secure and potentially prestigious career as an academic to strike out on independent research of his own. His starry-eyed quest: upending Albert Einstein’s theory of relativity, and with it our understanding of gravity, space, and time.

It was less than a century ago that Einstein was the most radical physics thinker around. With his general theory of relativity, he discarded the traditional notion of space and time as fixed and redefined them as flexible dimensions woven together to create a four-dimensional fabric that pervades the universe. In Einstein’s vision, this stretchy version of space-time is the source of gravity. The fabric bends and warps severely around massive objects such as the sun, drawing smaller objects such as planets toward them. The force that we perceive as gravity is the result.

Yet Einstein’s fabric left a few loose threads that cosmologists have struggled to tie up ever since. For one, general relativity alone cannot explain the observed motions of galaxies or the way the universe seems to expand. If Einstein’s model of gravity is correct, around 96 percent of the cosmos appears to be missing. To make up the difference, cosmologists have posited two mysterious, invisible, and as yet unidentified ingredients: dark matter and dark energy, a double budget deficit that makes many scientists uncomfortable. Einstein also failed to deliver an all-encompassing theory of “quantum gravity”—one that reconciled the laws of gravity observed on the scale of stars and galaxies with the laws of quantum mechanics, the branch of physics that explains the behavior of particles in the subatomic realm.

While other scientists tread softly around the edges of Einstein’s theory, hoping to tweak it into compliance, Barbour and a growing cadre of collaborators see a need for a bold march forward. They aim to demolish the space-time fabric that stands as Einstein’s legacy and remap the universe without it. This new cosmic code could eliminate the need to invoke dark matter and dark energy. Even more exciting, it could also open the door to the theory of quantum gravity that Einstein was never able to derive. If Barbour is right, some of the most fundamental things cosmologists think they know about the origin and evolution of the universe would have to be revised.

“We have radically reformulated Einstein in a different light that might be valuable for understanding cosmology and quantum gravity,” Barbour says. “It is a very ambitious hope that it could play such a role.”

Barbour’s penchant for mapping space and time is apparent even before we meet. His home, College Farm, is hidden away some 20 miles from the nearest city of note, Oxford. Knowing that visitors often struggle to find the 17th-century farmhouse, he has sent two sets of directions. The first includes detailed instructions for navigating through the village’s rolling hills along sunken roads, passing thatched cottages, the local Duck on the Pond pub, and the ancient church near his home. Those directions might have served equally well for locating Barbour’s house at the time it was built in 1659, a few decades before another English physicist, Isaac Newton, wrote his Principia, setting down the ideas about motion and gravity that dominated physics for almost three centuries.

In one respect Barbour has spent 40 years faithfully preserving Newton’s universe, meticulously restoring the farmhouse’s period features. He proudly shows me that each window frame is adorned with a small metal animal figure—a lion, a stag, a cockerel, and the flying horse Pegasus. The lion is Barbour’s favorite because it is original; the rest he had specially made based on designs seen in other buildings of the same era in the village. He taps the sturdy stone wall surrounding the window. “These were here 350 years before us and our modern conceptions of physics,” he tells me, “and chances are they’ll still be standing 350 years after we’ve gone.”

By contrast, the second set of directions for finding Barbour’s farmhouse—GPS coordinates—work only in the modern, post-Einstein reality. The satellite navigation system pinpoints positions on Earth to within 10 meters (30 feet) in a matter of seconds by comparing the timing of signals received from a number of satellites at known locations above the globe.

The system works with such stunning accuracy because it compensates for the fact that clocks on fast-orbiting satellites run at different rates from those on the ground. The fact that gravity and motion affect the flow of time was discovered by Einstein as a core element of his theory of relativity.

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 

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