Warped Passages Read Free

Unseen Dimensions?
    Even if physics with extra spatial dimensions permit these intriguing scenarios, you might still wonder why physicists concerned with making predictions about observable phenomena would bother to take them seriously. The answer is as dramatic as the idea of extra dimensions itself. Recent advances suggest that extra dimensions, not yet experienced and not yet entirely understood, might nonetheless resolve some of the most basic mysteries of our universe. Extra dimensions could have implications for the world we see, and ideas about them might ultimately reveal connections that we miss in three-dimensional space.
    We wouldn’t understand why Inuit and Chinese people share physical features, either, if we failed to include the dimension of time that lets us recognize their common ancestry. Similarly, the connections that can occur with additional dimensions of space might illuminate perplexing aspects of particle physics, shedding light on decades-old mysteries. Relationships between particle properties and forces that seemed inexplicable when space was shackled to three dimensions seem to fit together elegantly in a world with more dimensions of space.
    Do I believe in extra dimensions? I confess I do. In the past, I’ve mostly viewed speculations about physics beyond what’s been measured—including my own ideas—with fascination, but also with some degree of skepticism. I like to think this keeps me interested, but honest. Sometimes, however, an idea seems like it must contain a germ of truth. One day on my way to work about five years ago, as I was crossing the Charles River into Cambridge, I suddenly realized that I really believed that some form of extra dimensions must exist. I looked around and contemplated the many dimensions I couldn’t see. I had the same shock of surprise at my altered worldview that I experienced when I realized that I, a native New Yorker, was rooting for the Red Sox during a playoff game against the Yankees—something else I never anticipated I’d do.
    Greater familiarity with extra dimensions has only increased my confidence in their existence. Arguments against them have too many holes to be reliable, and physical theories without them leave toomany questions unanswered. Furthermore, as we’ve explored extra dimensions in the last few years, we’ve expanded the range of possible extra-dimensional universes that can mimic our own, suggesting that we’ve identified only the tip of the iceberg. Even if extra dimensions don’t conform precisely to the pictures I will present, I think they are very likely to be there, in one form or another, and their implications are bound to be surprising and remarkable.
    You might be intrigued to know that there could be a vestige of extra dimensions hidden in your kitchen cabinet—on a nonstick frying pan coated with quasicrystals . Quasicrystals are fascinating structures whose underlying order is revealed only with extra dimensions. A crystal is a highly symmetric latticework of atoms and molecules with one basic element repeated many times. In three dimensions we know what structures crystals can form, and which patterns are possible. However, the arrangement of atoms and molecules in quasicrystals does not conform to any of these patterns.
    An example of a quasicrystalline pattern is shown in Figure 2. It lacks the precise regularity you would see in a true crystal, which would look more like the kind of grid you would see on a piece of graph paper. The most elegant way of explaining the pattern of molecules in these strangematerials is with a projection—a sort of three-dimensional shadow—of a higher-dimensional crystalline pattern, which reveals the symmetry of the pattern in a higher-dimensional space. What looked like a completely inexplicable pattern in three dimensions reflects an ordered structure in a higher-dimensional world. The nonstick frying pans that are coated with quasicrystals exploit the structural