The fields inhabiting a given dimension have infinitely many degrees of freedom. Penrose has two major objections to the extra-dimensional program of string theory. In string theory, there are at least eleven and as many as twenty-six space-time dimensions. The idea that the laws of physics can be made simpler by the expedient of multiplying dimensions has never lost its appeal to physicists. In 1907, Hermann Minkowski unified space and time into a four-dimensional Minkowski manifold, and in 1921, Theodor Kaluza attempted to reconcile electromagnetism with general relativity by moving to a five-dimensional space. If Penrose is critical of the proliferation of elementary particles, he still more critical of the proliferation of spatial dimensions in string theory.
“Given the alarming nature of this proliferation of basic particles (and, perhaps, the seeming absurdity of the proposed terminology),” Penrose observes, “the reader may be relieved to hear that no such supersymmetric sets of particles have been yet observed!” 3 Penrose thinks it unlikely that they exist and even if they do, he claims, they will not do much to help string theory. Its “stranglehold on developments in fundamental physics,” he argues, “has been stultifying.” 2 He objects, in particular, to supersymmetry, or SUSY, which pairs elementary particles to entirely imaginary partners, bosons to charginos, photons to photinos, and quarks to squarks. P enrose is passionate when criticizing string theory. The epilogue is reserved for some of Penrose’s personal thoughts on theoretical physics. In the third chapter, “Fantasy,” he argues against inflationary theories in cosmology, offering in its place his own theory of cyclic conformal cosmology. In the second chapter, “Faith,” Penrose questions the near-religious devotion to quantum mechanics of most physicists, arguing that gravitational effects must be included in any picture of the quantum world. Penrose views string theory in particular as fundamentally wrong, but, as he notes, it has monopolized the attention, funding, and students of a generation.
The first chapter, “Fashion,” introduces particle physics. The book is organized into four chapters and an epilogue.
1 In Fashion, Faith, and Fantasy in the New Physics of the Universe, Penrose considers some recent developments in theoretical physics, appearing both as a stodgy conservative, reacting against flights of mathematical fantasy by string theorists, and as a maverick, with idiosyncratic ideas about quantum mechanics, gravity, and cosmology. He is also known for his argument that human consciousness is non-algorithmic. R oger Penrose is well known for the Moore–Penrose pseudoinverse, the Penrose diagram, the Penrose–Rindler books on spinors and space-time, and the Penrose tile.
Princeton University Press, 520 pp., USD$29.95. Fashion, Faith, and Fantasy in the New Physics of the Universe