As a postdoc you have the craziest job in the world.
You get your PhD with honors at one of the best universities, and at the same time they kick you out. You apply everywhere in the world, and you have not the faintest clue on which continent or in which time zone you will end up. Then you get a new job at a different university, and you can come and go whenever you want and do whatever you want. You can just think about the most esoteric questions that come to your mind: What is all matter made of? What is happening at the beginning and at the end of the universe? What is time? All that is required is that you write down whatever insights you gain and publish them in scientific journals. Until two years later and irrespective of how good you were—then you get kicked out again, and the whole story repeats itself.
This was the reason I was standing, on this February morning’s dawn, on a beach on the other side of the world. With my Danish friend Ketil I stared, shivering, into Waikiki’s surf, rolling in from the endless Pacific (Fig. 1.1). Finally one of us brought himself to push his board into the water and started to paddle out toward the break, while the sun slowly climbed over the rim of Diamond Head crater.
Figure 1.1. View over Waikiki to Diamond Head crater. (Courtesy Ullstein Bild/Prisma/Steve Vidler)
Surfing in Hawai‘i ranks somewhere between national sport and religion—an active ceremony honoring the Hawaiian god Lono.1 What is most impressive for me about surfing, though, is the suddenness of the experience. In the beginning the water is often totally glassy, but after paddling out for a few hundred meters you reach the reef. Bathed in the first sunlight, a tiny fluctuation created by a storm thousands of miles away grows—as if caused by magic—into a wave. Soon the wave transmutes into an impressive greenish blue wall, a wall that—if after many failed tries, with tired arms and a headache, you manage to catch—accelerates you breathlessly and throws you into an ocean of adrenaline as it breaks into a carpet of snow-colored whitewater.
Physics ideas are like the Hawaiian surf. They seem to come from nowhere, they catch you suddenly without warning, and they draw you into an exhilarating trip. Later, on such days, I would sit in seminars daydreaming of breaking waves, or I would wander restlessly over the Manoa campus of the University of Hawai‘i, gazing at the cliffs overgrown by rain forest, while my brain untangled a clutter of film clips of the surf and thoughts about my present physics project. On one of these afternoons the following thought occurred to me: Assume that our universe, with its three space and one time dimension is embedded in a larger space with many extra dimensions. Our universe, lying there like the carpet in your living room. Could this carpet buckle? Assume further that there are elementary particles that can propagate not only in our common 3 + 1 dimensions but in the whole extra-dimensional space. Could these particles—instead of following the carpet buckles—take a shortcut along the floor? Could they make a “duck dive,” like a surfer diving underneath an incoming wave while paddling out? Could they in this way be faster than everything moving along the bumpy surface? How would it look, then, for an observer on the carpet, or the ocean-surface universe, if these particles traveled even faster than light? Could they actually—according to a well-known paradox in Einstein’s relativity—travel back in time?
At first glance, any single part of this idea seems crazy. Why should the universe have more than three space dimensions? And even if there were reasons, where in the world should these extra dimensions be? What’s the nature of these exotic elementary particles? And why should our universe have even the slightest similarity to a buckled carpet or the surface of the Pacific Ocean on a winter day? Why should something that moves faster than light be able to travel backward in time? How could this be possible at all?
This is all part of a long story, whose beginnings date back more than 3,000 years to ancient Greece. A story that continued in the 1920s at Europe’s universities, and has been augmented by science fiction and recent experiments at the most advanced laboratories for elementary-particle physics—CERN in Geneva, Switzerland, and Fermilab near Chicago. A true story that at times resembles a mystery thriller, with secret cults, dead philosophers, mind-expanding drugs, the mysterious disappearance of brilliant scientists, subterranean research labs, and experiments in Antarctica. It is a story of an elementary particle that, just like the Silver Surfer in the superhero cartoons, surfs to the boundaries of knowledge, of the universe, and of time itself. A story that captivates you as it sucks you into a maelstrom like an oversized wonderland.
Jump on your board and hold tight.