"Are space and time fundamental concepts or are they approximations to other, more subtle, ideas that still await our discovery?"

It is hard to conceive of a universe that does not exist in space and persist through time: space and time seem to be the basic framework of the cosmos. Yet what is space and what is time? Are they "things" or are they merely the language we use for organizing events we witness in the world? Moreover, are they even fundamental? Could it be that space and time conveniently summarize more basic ideas somewhat as temperature summarizes the motion of atomic constituents? Will we one day discover "atoms" of space and time---true, fundamental elements which space and time as we now know them are simply coarse approximations?

Brian Greene is a professor of physics and of mathematics at Columbia University and author of The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for an Ultimate Theory.