Physics

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

Julian Barbour cuts 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...
Image: Galaxy cluster Abell 1689 seems to be held together by swaths of unseen dark matter; blue shows its theoretically inferred location. But could dark matter be an illusion? Courtesy of NASA