A Passion for Physics

Abstract

### Contents #### News Special Relativity Reconsidered [Doubly Special, Twice as Controversial][1] We're So Sorry, Uncle Albert #### Viewpoints & Reviews [The Quantum Measurement Problem][2] A. J. Leggett [From Pedigree Cats to Fluffy-Bunnies][3] J. Dunningham et al. Time and the Quantum: Erasing the Past and Impacting the Future Y. Aharonov and M. S. Zubairy [Astrophysical Observations: Lensing and Eclipsing Einstein's Theories][4] C. L. Bennett Inflationary Cosmology: Exploring the Universe from the Smallest to the Largest Scales A. H. Guth and D. I. Kaiser See related [Next Wave material][5] and Book Reviews by Wilczek and [Bohannon][6] . T he World Year of Physics in 2005 celebrates the publication of Einstein's papers in Annalen der Physik that, 100 years ago, heralded the era of modern physics. Part of Einstein's legacy is that quantum mechanics and relativity forced us to accept notions of space and time, and of matter and energy, that do not square with our everyday experience. Given Einstein's passion for the deepest questions in physics, we highlight some of those challenges in this special issue. Of Einstein's many contributions, the work that has most gripped the public imagination boils down to a single word: relativity. Today physicists are still wrestling with the implications of this mathematically straightforward but surreal-sounding theory. Some hope to find subtle flaws in a key component of the special theory of relativity—flaws that, as Cho explains in his News story (p. [866][7]), could lead physics into realms even stranger than the ones that Einstein pioneered. In another News feature (p. 869), Seife and Lawler describe how NASA's new emphasis on exploration is affecting satellites designed to test whether the later general theory of relativity accurately describes spacetime. Despite being one of the fathers of quantum mechanics, Einstein was dismayed by its probabilistic nature. Leggett (p. [871][2]) explores the current status of the theory and discusses the controversy that still remains. Dunningham et al . (p. 872) look at two different categories: the fragile but useful and the robust but essentially useless. These two types of entanglement can perhaps explain the transition from the quantum to the classical worlds. Aharonov and Zubairy (p. [875][8]) discuss some of the stranger aspects of time in quantum mechanics, especially the “delayed choice quantum eraser” of Scully and Druhl, in which the erasing of “which path” information in two-slit experiments can restore interference patterns, even if that information comes “after the fact.” After the development of general relativity, Einstein spent many years attempting to unify the fundamental forces of the day: gravity and electromagnetism. Bennett (p. 879) discusses some of the current tests of Einstein's theories of relativity, including gravitational redshifts, gravitational waves, and the Lense-Thirring effect. He also discusses the role of dark energy and dark matter and the questions of the origin and ultimate fate of the universe. Guth and Kaiser (p. 884) overview inflationary cosmology, which helps bridge particle physics and gravitation, and they outline the experimental tests of inflation's mark on the present universe. They also discuss the theoretical efforts to use superstring theory to understand inflation and to determine the vacuum energy of the universe. In Books et al ., Wilczek (p. 852) reviews Penrose's comprehensive perspective on our understanding of the physical behavior of the universe and the mathematical theory that underlies it. Einstein's legacy includes the physicists who continue to take up his mantle. Science 's Next Wave ( ) profiles some European physicists as well as Canada's Perimeter Institute for Theoretical Physics. [1]: /lookup/doi/10.1126/science.307.5711.867 [2]: /lookup/doi/10.1126/science.1109541 [3]: /lookup/doi/10.1126/science.1109545 [4]: /lookup/doi/10.1126/science.1106444 [5]: http://www.sciencemag.org/sciext/einstein/ [6]: /lookup/doi/10.1126/science.1110157 [7]: /lookup/doi/10.1126/science.307.5711.866 [8]: /lookup/doi/10.1126/science.1107787