" ... remarkably accessible... ." ("Sky & Telescope, February 2005)

" Halpern dug out some historical details that other writers miss and this helps make the string picture more complete" ("Focus, December 2004)

Many physicists are continuing to work toward the fabled goal of a " theory of everything." A successful theory would unify the four known physical forces - gravity, electromagnetism, and the nuclear strong and weak forces - and case some light upon newly discovered cosmological phenomena and puzzles. Quite a few theoreticians are attempting to use postulated extra dimensions to come up with a workable product; fantastic as it may seem, a universe containing ten or 11 dimensions offers considerable promise. Halpern (physics & mathematics, Univ. of the Sciences, Philadelphia) takes a historical approach to examining the advancement of multidimensional theory. Kaluza, Klein, Einstein, and many other contributors over the past 100 years are discussed, and their work is described at a level appropriate for a general audience. Only Halpern's terminology and the pace of the discussion in the last few chapters will challenge nonspecialists. Recommended for academic and large public libraries. - Jack W. Weigel, Ann Arbor, MI ("Library Journal, July 2004)

Ever since Plato first told his students the allegory of the cave, people have wondered whether dimensions exist beyond the three we immediately perceive. An extra dimension-- time-- played a role in Einstein's work, although he saw it only as a necessary evil to get his equations to work. Other scientists were morereceptive: mathematical physicists Oskar Klein and Theodor Kaluza made higher dimensions an integral part of their attempts to discover a " theory of everything" that would tie together strong and weak nuclear forces, electromagnetism and gravity. Halpern explains that over the past century gravity has been the shadow flickering on the walls of the cave hinting at other realms. Why is it so weak compared with electromagnetism? With string theory, and its successor, M-theory, physicists speculate that gravity " leaks" back and forth between our reality, an 11-dimensional " brane" (or membrane) and other branes, perhaps as close as a millimeter away. Halpern masterfully creates word pictures to illustrate mind-bending scientific theories, and he paints highly detailed sketches of the scientists involved-- sometimes too detailed, leading readers to lose the thread of the narrative. Science buffs won't find much new here, but for average readers, this is an accessible account of the search for what lies behind our dim perception of reality. B& w photos. "Agent, Giles Anderson. (July 16) ("Publishers Weekly, June 7, 2004)