By David Roberts and Yves Pomeau
One hundred years ago this month, Albert Einstein unveiled one of mankind’s greatest intellectual accomplishments – his General Theory of Relativity, our current understanding of gravity. Not only did it transform the way we look at space and time, but, unique among modern science theories, it was largely the work of one man’s towering genius.
Before Einstein, heavenly bodies and earthly projectiles alike seemed to move to Isaac Newton’s gravitational laws. Though Newton was not fully satisfied with his theory, which lacked an explanation for how gravity exerts its force, it had withstood centuries of observation. However, in the 19th century, cracks began to appear. Data emerged showing that Mercury’s orbit deviated slightly from Newton’s predictions, which led the French astronomer Le Verrier to predict (incorrectly) a new planet, Vulcan, to explain the discrepancy. A more damning blow came in 1905 when Einstein and others showed that information propagates at a finite speed, refuting Newton’s theory of gravity which required instantaneous influences over unlimited distance.
It took Einstein almost a decade to resolve this apparent paradox. He was able to develop a new theory of gravity and how it works based on a newly developed geometry of curved spaces, as well as Einstein’s own deep insight that feeling the pull of gravity is not fundamentally different from feeling accelerated. (Actually, German mathematician David Hilbert technically might have written down the equations a couple of days earlier, but most – including Hilbert – agreed that this tour de force was Einstein’s.) He argued that gravity arises from warped space and time, as how a tennis ball is drawn towards a bowling ball if both are placed on the surface of a trampoline. Not only did it accurately explain Mercury’s orbit, but it was also able to make a precise prediction of the bending of light by gravity near the Sun – famously observed by Eddington during an eclipse in 1919 that made Einstein a global celebrity. And the pinpoint resolution of modern GPS would not be possible without knowing so exactly how time slows down in a gravitational field. Thus, we have Einstein to thank for Google Maps.
Einstein’s discovery of General Relativity is one of the defining paradigm shifts in the history of science, on par with the Copernican revolution, although of a different nature. Whereas Copernicus built on the work of Islamic scientists and created a (flawed) heliocentric model to match observed data; Einstein derived from basic principles a fundamental physical law that was only later substantiated by observation, a shining example of the Abstract Reasoning approach formalized by Greek thinkers more than 2000 years ago. Interestingly, even though Einstein boldly upended the accepted science of his day, over the course of his career he would prove stubbornly resistant to many new ideas in physics. He even refuted many of the far-reaching predictions of his own theory of gravity, initially opposing the existence of black holes and the expansion of the universe, for example.
But on this centennial, we would like not just to celebrate General Relativity as a glorious leap forward in science, but also as a creative work of art. For the most part, scientists, even brilliant Nobel-prize winning ones, individually are only making refinements to existing theories. And when most major scientific discoveries actually do occur, like calculus, quantum mechanics, the structure of DNA, etc., it is as if they were already in the air– precipitating into the hands of a receptive scientist (if not one, then another) when the moment was ripe. Einstein’s discovery, however, was so far ahead of its time that it could only have been the product of imagination and genius, the like of which has not been seen for a hundred years and may never be again.
David Roberts (@DRobertsNYC), a former academic physicist and diplomat, is currently a Senior Advisor at the Harvard Kennedy School. Yves Pomeau, a corresponding member of the French Academy of Sciences, is Professor Emeritus of physics and math at the Ecole Normale Supérieure and the University of Arizona.