There is an ill-concealed skeleton in the closet of physics: "As they are currently formulated, general relativity and quantum mechanics cannot both be right." Each is exceedingly accurate in its field: general relativity explains the behavior of the universe at large scales, while quantum mechanics describes the behavior of subatomic particles. Yet the theories collide horribly under extreme conditions such as black holes or times close to the big bang. Brian Greene, a specialist in quantum field theory, believes that the two pillars of physics can be reconciled in superstring theory, a theory of everything.

Superstring theory has been called "a part of 21st-century physics that fell by chance into the 20th century." In other words, it isn't all worked out yet. Despite the uncertainties--"string theorists work to find approximate solutions to approximate equations"--Greene gives a tour of string theory solid enough to satisfy the scientifically literate.

Alternative view of a physicist not in the Superstring Camp

I've read popular books on superstrings/M-theory (Greene's being the prime example), and I've watched TV programs popularizing the same. While I must admit the propaganda value of these media in helping to raise the general public's interest in Physics, I'm afraid that these books and media are extremely biased and give a skewed view of the state of theoretical physics today. An unsuspecting reader picking up this book will likely come away with the feeling that this is a summary of the status quo of theoretical physics nowadays, but nothing can be further from the truth.

While superstring/M theory is one of the active frontiers in theoretical physics, it is hardly the only active frontier, nor is it the most promising. Due to the almost complete lack of empirical evidence for superstring/M theory, plus the almost impenetrable math (even to many theoretical physicists!) within which superstring/M theory has wrapped itself, superstring/M theory stands out as a rather strange theory: it's an isolated self-perpetrating theoretical construct almost impervious to external checks and reviews. Such theories aren't uncommon in physics: throughout the history of physics they pop up every now and then, e.g. Eddington's numerology, Einstein's unified field theory and Finkelstein's theory of everything, to name just a few. The main difference between superstring/M theory and these other theories is that superstring/M theory is much more polished mathematically, and has a much larger following. This in turn has made superstring/M theory much more respectable in appearance, by patching any loopholes that appear with newer and higher orders of abstractions (as evidenced by appearance of the most anti-intuitive wild concepts like extra spacetime dimensions, parallel universes etc.), all of which were wrapped in the most exquisite and impenetrable mathematics. This in turn has attracted even more smart students to superstring/M theory, which in turn makes it appear even more respectable, which in turn... ad infinitum.

A theory in physics is only as good as the physical (not mathematical) foundation upon which it's built, and the physical foundation of superstring/M theory is shaky at best, non-existent at worst. As a purely mathematical theory, superstring/M theory may be able to stand on its own as an elegant and insightful theory which may even have applications in other exotic branches of mathematics. But a physical theory can never stand alone, it must have verifiable connections to experiments and to other more established branches of physics. A completely isolated theory in physics, however elegant and compelling it may be mathematically and aesthetically, is irrelevant and is doomed to suffer the fate of so many other fads and irrelevant theories in physics: to be forgotten in time.

I just hope that Brian Greene and other proponents of superstring/M theory can be a little more humble and admit that their theory is nothing but a spectacular but ultimately speculative theory in physics, just one among many many others, and stop preaching like it's the best and only candidate theory in physics.

Eleven-Dimensional Thinking

While much of this book is probably too dense for beginners, there is hardly a better source for informed laypeople to learn about the latest theoretical advances in astrophysics. In this particular informed layperson's view, Einstein's relativity explains the vast cosmology of stars and galaxies, while quantum mechanics explains the subatomic realms of quarks and electrons. Unfortunately these two theories of the cosmos come into conflict in extreme situations such as black holes and the big bang, with that pesky old gravity messing up the orderly theoretical functioning of the universe. Brian Greene's specialty, string theory, is the most audacious and currently believable candidate for Theory of Everything, though the theory has mostly been built from esoteric developments in bizarre mathematics and thought experiments, rather than direct observation.

Here Greene explains with remarkable precision and understandability how string theory works and where it currently stands, but the science is so complex that even his great writing leads to lots of head scratching. Early in the book Greene does a fantastic job of introducing string theory itself, remarkably in just two paragraphs, and in the next few chapters gives the most understandable non-mathematical explanations for relativity and quantum mechanics that I've ever seen. The rest of the book gets more complicated and the vast esoteric vagaries of string theory can be a real strain on the brain, but Greene deserves much credit for kicking off the reader's deep thoughts on some really extreme scientific concepts. And finally, Greene spends a sizeable portion of the book explaining that string theory is just that - a theory - which is not fully accepted by all physicists. Greene gives credit to all his colleagues where credit is due, openly admits to the weaknesses of the theory, and speculates on possible theoretical improvements. That makes many of the negative reviews here, which are obviously from some of Greene's more narrow-minded and professionally jealous university competitors, invalid and unworthy of further discussion. [~doomsdayer520~]

beautifuly written

Very good peice of work. Probably his best yet in fact. The book was illustrated so proportionaly and explicit, its very good updated peice of biblical refrence .. may be overwhelming at times but none the less an enjoyment.