November 19, 2007
In this latest effort to popularize the sciences, City University of New York professor and media star Kaku (Hyperspace
) ponders topics that many people regard as impossible, ranging from psychokinesis and telepathy to time travel and teleportation. His Class I impossibilities include force fields, telepathy and antiuniverses, which don't violate the known laws of science and may become realities in the next century. Those in Class II await realization farther in the future and include faster-than-light travel and discovery of parallel universes. Kaku discusses only perpetual motion machines and precognition in Class III, things that aren't possible according to our current understanding of science. He explains how what many consider to be flights of fancy are being made tangible by recent scientific discoveries ranging from rudimentary advances in teleportation to the creation of small quantities of antimatter and transmissions faster than the speed of light. Science and science fiction buffs can easily follow Kaku's explanations as he shows that in the wonderful worlds of science, impossible things are happening every day.

Starred review from January 15, 2008
The best science fiction writers strive to render even their most fanciful visions of future technologies consistent with known physical facts. But, in some ways, the history of science shows that what is impossible must frequently be reconceived as new discoveries are made. Physicist and renowned science popularizer Kaku ("Hyperspace") classifies the impossible into three categories. "Class I Impossibilities" are those believed impossible today but violate no known laws of physics, including force fields, invisibility, teleportation, psychokinesis, intelligent robots, and starships. Accordingly, "Class 2 Impossibilities" are technologies at the far boundaries of what we know of the physical worlde.g., time travel, parallel universes, and faster-than-light travel. "Class 3 Impossibilities," those that violate known laws of the universe, constitute the smallest category and include precognition and perpetual motion machines. In these discussions, Kaku not only explores impossibilities but, in doing so, elucidates some basic physics, so this book both teaches and challenges. Finally, in the epilog, the author concedes that nobody may yet have even imagined tomorrow's impossibilities. This tour de force of science and imagination is for advanced high school students and up. [See Prepub Alert, "LJ" 10/1/07.]Gregg Sapp, Science Lib., SUNY at Albany

Copyright 2008 Library Journal, LLC Used with permission.

March 15, 2008
The imagination of science fiction faces up to the laws of physics in this prognostication of future technologies from a high-profile string theorist. Kaku wrote about his specialty in Parallel Worlds (2004); here he covers a gamut of sf gadgets. Interestingly, most things Kaku turns over, such as ray guns, deflector shields, invisibility, and interstellar travel, are theoretically possible, provided one harnesses energy on a titanic scale. But until somebody can arrange atoms at will, and black holes, too, early adopters might have to cool their heels for decades or untold millennia before being able to buy the latest gizmo. Meanwhile, they can revel in Kakus amble through the technological stars of sf books and movies. Referencing a scene, as when the Death Star of Star Wars blows up a planet, Kaku spells out the mass-energy requirements necessary to replicate the destruction in reality. Excluding only perpetual-motion machines and precognition from the realm of possibility, Kaku entertains techno-dreamers through his clarity about the physics of mind reading and time machines, yielding a high popularity quotient in the process.(Reprinted with permission of Booklist, copyright 2008, American Library Association.)

"[Kaku explores] what we still do not quite understand, those grey areas that are surely the most fascinating part of physics."

--New Scientist

"Kaku's latest book aims to explain exactly why some visions of the future may eventually be realized while others are likely to remain beyond the bounds of possibility. . . . Science fiction often explores such questions; science falls silent at this point. Kaku's work helps to fill a void."

--The Economist

"A fascinating exploration of the interface between science and science fiction, extremely well researched, lively, and tremendously entertaining."

--Fritjof Capra, author of The Tao of Physics and The Science of Leonardo

"Mighty few theoretical physicists would bother expounding some of these possible impossibilities, and Kaku is to be congratulated for doing so. . . . [He gets] the juices of future physicists flowing."