March 25 (Bloomberg) -- The most precious substance on Earth isn't gold or platinum. It's antimatter, valued by physicist Michio Kaku at $62.5 trillion a gram.

Antimatter, which is like ordinary matter except with the charges of its subatomic particles reversed, powered spaceships in ``Star Trek'' and in real life is one possible key to allowing travel between planets or galaxies, Kaku writes in ``Physics of the Impossible.''

A professor at the City University of New York, Kaku appears to have read every major tract by Albert Einstein, Werner Heisenberg and Kurt Godel, plus a mountain of comic books and science-fiction novels. His own book assesses whether phasers, teleportation and other technologies used by Flash Gordon and Captain Kirk could really be developed.

Kaku is no stranger to his subject. In high school, he photographed antimatter tracks. He went on to become a pioneer of string field theory, which aspires to improve on Einstein in explaining the universe. He also wrote earlier science books aimed at the broader public, including ``Hyperspace.''

Kaku knows, and conveys, that both physics and science fiction are thrilling. In the beginning, the book is kind of a ``Whole Earth Catalog,'' or perhaps ``Whole Universe Catalog,'' of technologies. For each, Kaku describes how they appear in fiction, summarizes the relevant real-world science, and makes a prediction, albeit a loose one.

Cloaking Devices

``A form of invisibility may become commonplace'' within a century, if not a few decades, according to the author, who cites advances in nanotechnology and holograms. So-called metamaterials that make part of the light spectrum invisible already exist, possibly pointing the way to cloaking devices. But using the power of the unproven ``fourth dimension,'' the method favored by H.G. Wells's ``Invisible Man,'' isn't likely to pan out, according to Kaku.

The discussion of gadgets sometimes drags, and in later chapters the author wisely turns his attention to what's really fascinating in this enterprise: people and ideas. This is a book of enormous sweep, crammed with science and its history. His portraits of such figures as Erwin Schrodinger (of the fabled cat paradox in quantum mechanics) and Paul Dirac, the ``founder of antimatter,'' are immensely readable.

Seeing the Future

Some phenomena, such as precognition, or seeing the future, Kaku rules out as impossible under the known laws of physics. But he regards many other things that appear impossible today as likely to come about in thousands or millions of years.

The terms and concepts, arriving faster in later chapters, are often challenging. If you stop to ponder each idea too long, the book may have the effect of one of the so-called black holes in space discussed along the way: You may get in, but never get out. Otherwise, it's a rewarding trip.

``Physics of the Impossible: A Scientific Exploration Into the World of Phasers, Force Fields, Teleportation and Time Travel'' is published by Doubleday (329 pages, $26.95).

(Jeffrey Tannenbaum is an editor for Bloomberg News. The opinions expressed are his own.)

To contact the reporter on this story: Jeffrey Tannenbaum in New York at jtannenbaum@bloomberg.net.

Last Updated: March 25, 2008 00:01 EDT