Peaceful coexistence

For a hundred years, physicists trumpeted the celestial speed limit. Einstein has shown, they said, that nothing travels faster than light. But for a generation now, there has been stunning experimental evidence that hints that some mysterious influences are travelling faster than light.

Contemporary physics rests on two great pillars. Einstein's theories describe the large-scale structure of space and time. Quantum theory describes the small-scale behaviour of matter within space and time: the behaviour of molecules, atoms and other particles. Roughly, one describes the container, and the other the contents. Although research continues, the two traditions are so much at variance that no one has been able to combine them into a single, unified theory or “theory of everything”. Quantum theory emerged piecemeal over many years and its development was driven by experimental results and mathematical guesses. Like most committee efforts, quantum theory was a patchwork of conflicting motivations and strategies. There is one central obstacle to unification: even today no one really understands quantum theory.

For many years, relativity and quantum theory led a peaceful coexistence. The mysteries of quantum theory were dramatized by a series of paradoxes, but the theory worked very well and never threatened to contradict and overthrow its rival. But now things are changing. Recent experiments are revealing that quantum theory is even more strange than expected. Sometimes it appears as a great, conceptual black hole that sucks down into it every attempt to clarify the foundations of physics.