But the brane itself was only one of many parallel sheets floating in the higher-dimensional space that was called the bulk. The sheets were stacked closely together; were even, perhaps, joined at their edges, like the folded musical program of some vast cosmic orchestrion. Some of the sheets had very different properties from others: although the same fundamental rules of nature applied in each, the strengths of the coupling constants—and hence the properties of the macroscopic universe—depended on where a particular brane lay within the bulk.
