## Dreams of a Final Theory

At the most basic level of nature, maintain many physicists, lies a bedrock of reality. After decades in which one level of subatomic particles has been shown to rest on an even more elementary (if more elusive) level, we seem tantalizingly close to reaching that bedrock.

DREAMS OF A FINAL THEORY is a report from the field, written by someone who has led the way in the search. In 1979, Weinberg received a Nobel Prize for his work in unifying two basic natural forces—the weak nuclear force and electromagnetism—in a theoretical framework. The “final theory” of his title will combine these forces plus the remaining two—gravity and the strong nuclear force—in some ultimate grand design.

What might this design look like? Weinberg admits that its discovery may lie centuries away, but like any adventurous scientist he hazards a guess, backing some yet-to-be-formulated version of the new theory of strings. And what are strings? Weinberg likens them to “tiny one-dimensional rips in the smooth fabric of space.” Their existence would account for such particles as gravitons—the building blocks of gravity—and many other particles as well.

Any book on modern physics is liable to present some difficulty to the ordinary reader. After all, the concept of “rips” in the “fabric” of space is a challenging one, and Weinberg acknowledges that the enormous difficulties inherent in string theory have created hostility even among fellow scientists. Fortunately Weinberg is a graceful and lucid writer, even when his subject is opaque. He expects to find great beauty in the final theory, whatever its oddity or complexity, and manages to convey an exhilarating sense of that beauty to his readers.