What is the point of a theory of everything?
By MacGregor Campbell (Image: Lorenzo Petrantoni) SUPERGRAVITY. Unified field theory. The ultimate theory. Theory of everything. Physicists give many names to their attempts to unify our understanding of nature under one banner. For some, it is the holy grail of their discipline, and there are few leaps of faith they will not make to reach it: that matter is made of tiny, vibrating strings; that extra dimensions of space exist beyond the three we know about; and that space and time observed closely enough are not smooth and continuous, but grainy and pixellated. For others, the quest for a unified physics is like the hunt for the great white whale: an elusive, perhaps even non-existent, quarry. “Searching for a unification of everything today can be quite unproductive, in my opinion,” says theoretical physicist Carlo Rovelli of the Centre for Theoretical Physics in Marseille, France. Helge Kragh, a historian of physics at Aarhus University in Denmark, identifies a more basic problem: even if we do find a promising candidate and our minds are equipped to fully understand it, who says it is the end of the road? “We cannot possibly know if it is the ultimate theory,” he says. Meanwhile, our existing theories of nature, though far from perfect, are doing a great job in underpinning the technological innovations that improve our lives. Time to ask the question: what is the point of a theory of everything? Unification has been a driving force in physics since at least the days of Newton. To the casual skywatcher of the 1660s,