**THE HIDDEN REALITY: PARALLEL UNIVERSES AND THE DEEP LAWS OF THE COSMOS**

** By Brian Greene**

It was Galileo who said the book of nature is written in the language of mathematics, a bold claim since borne out by much of modern physics. Indeed the correspondence is so strong that recently some have even taken to arguing that reality is mathematics. And so anyone trying to write the book of nature in English is essentially taking on a job of translation. In order to make the complex mathematical formulas that describe the deep nature of reality comprehensible, explanation has to proceed by way of analogy.

Brian Greene, one of the best known popularizers of contemporary physics (both of his previous books, *The Elegant Universe* and *The Fabric of the Cosmos*, were bestsellers), has a real knack for analogies. We are told to imagine the universe as a baseball, a blimp, a patchwork quilt, a hunk of cheese, and a bedroom with a fly buzzing around it. No matter how difficult the concept Greene is able to come up with a familiar and easy way to visualize it, or the text introduces a simple graphic as an illustration.

These pictures and analogies remain, however, only very crude approximations of what are nearly incomprehensible theories. Greene’s subject in this book are parallel universes, which come in nine different flavours of multiverse (Quilted, Inflationary, Brane, Cyclic, Landscape, Quantum, Holographic, Simulated, and Ultimate). Of course there may be more, or less, or none, but these are the ones Greene presents for discussion.

As with the books by Stephen Hawking, one suspects the average reader will probably give up at some point, finding themselves in over their heads trying to understand a reality hidden in some very deep laws indeed. For example, people who have read any of Greene’s other books will know he is an enthusiastic proponent of string theory. This doesn’t make things easier, since while the basic concept of string theory can be simply stated (nature’s fundamental building blocks are tiny vibrating strings) the mathematics behind it – and string theory is “a wholly mathematical undertaking” – is highly sophisticated. There’s simply no way of explaining the stuff so that it can be grasped by a general audience. But Greene acknowledges this, and at several points he posts warnings and suggests skipping ahead, or pushes more advanced analysis into the endnotes.

In addition to being densely mathematical, the subject matter this time out is thoroughly speculative (like string theory itself, as Greene admits). In fact the scenarios presented are speculative to the point where Greene has to spend an entire chapter explaining why the study of parallel universes even counts as science, since in most cases the multiverse is by definition unobservable, inaccessible, and impossible of certain proof. Large differences of opinion exist among experts about the various theories, and it’s unclear if all of the questions up for grabs are capable of ever being resolved.

Still, the idea that, as e. e. cummings put it, “there’s a hell of a good universe next door,” is fun to indulge. Science is a creative exercise, something we are reminded of when we see it imagining worlds as rich and strange as these.

**Notes:**

** Review first published February 11, 2011.**