Since the early 20th century, nature’s fundamental constituents have been modeled as indivisible particles-the most familiar being electrons, quarks and neutrinos-that can be pictured as infinitesimal dots devoid of internal machinery. The idea underlying string unification is as simple as it is seductive. Such was the case until December 1984, when John Schwarz, of the California Institute of Technology, and Michael Green, then at Queen Mary College, published a once-in-a-generation paper showing that string theory could overcome the mathematical antagonism between general relativity and quantum mechanics, clearing a path that seemed destined to reach the unified theory. This set the stage for more than a half-century of despair as physicists valiantly struggled, but repeatedly failed, to meld general relativity and quantum mechanics, the laws of the large and small, into a single all-encompassing description. While spectacularly successful at predicting the behavior of atoms and subatomic particles, the quantum laws looked askance at Einstein’s formulation of gravity. Niels Bohr and a generation of intrepid explorers ventured deep into the microrealm, where they encountered quantum mechanics, an enigmatic theory formulated with radically new physical concepts and mathematical rules. Will the Large Hadron Collider’s ATLAS proton-smasher detect signs of strings?īut by 1930, the landscape of physics had thoroughly shifted. With these achievements, Einstein envisioned that a grand synthesis of all of nature’s forces was within reach. Ten years later, Einstein extended these insights with his general theory of relativity, providing the most refined description of gravity, the force governing the likes of stars and galaxies. In 1905, Einstein linked space and time, showing that motion through one affects passage through the other, the hallmark of his special theory of relativity. The next two steps, big ones at that, were indeed vintage Einstein. About 200 years later, James Clerk Maxwell took the unification baton for the next leg, showing that electricity and magnetism are two aspects of a single force described by a single mathematical formalism. Isaac Newton united the heavens and Earth, revealing that the same laws governing the motion of the planets and the Moon described the trajectory of a spinning wheel and a rolling rock. Unification has become synonymous with Einstein, but the enterprise has been at the heart of modern physics for centuries. That was 30 years ago this month, making the moment ripe for taking stock: Is string theory revealing reality’s deep laws? Or, as some detractors have claimed, is it a mathematical mirage that has sidetracked a generation of physicists? What followed proved to be the most exciting intellectual odyssey of my life. The only thing I needed to drop was a neophyte’s inhibition to run with the world’s leading physicists. The field was young, the terrain fertile and the atmosphere electric. Then, just a couple of months later, the prestigious (if tamely titled) journal Physics Letters B published an article that ignited the first superstring revolution, a sweeping movement that inspired thousands of physicists worldwide to drop their research in progress and chase Einstein’s long-sought dream of a unified theory. There’s nothing happening in fundamental physics. Change fields now while you still can, many said. But within a couple of weeks, the more advanced students had sucked the wind from my sails. I had a freshly minted bachelor’s degree in physics from Harvard, and I was raring to launch into graduate study. In October 1984 I arrived at Oxford University, trailing a large steamer trunk containing a couple of changes of clothing and about five dozen textbooks.
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