The Large Hadron Collider will begin operation next year and will test some intriguing suggestions for what might lie beyond the standard model of particle physics. One of the most surprising ideas centers on the possible existence of extra dimensions of space.
Physicists speculate about such a possibility for several reasons. One is that we don’t know any reason such dimensions cannot exist, whereas we do know how they might be hidden. No theory, not even Albert Einstein’s general theory of relativity, stipulates a particular number of dimensions. People have often made the mistake of believing only in what they could see. We don’t perceive extra dimensions, but that doesn’t mean those dimensions aren’t there.
String theory provides another reason to consider extra dimensions. The theory might consistently incorporate physicists’ current conceptions of the very small and the very big in the universe—quantum mechanics and general relativity—a feat no earlier...
