Hans C. Ohanian received his B.S. from the University of California, Berkeley, and his Ph.D. from Princeton University, where he worked with John A. Wheeler. He has taught at Rensselaer Polytechnic Institute, Union College, and the University of Vermont. He is the author of several textbooks spanning all undergraduate levels: Physics, Principles of Physics, Relativity: A Modern Introduction, Modern Physics, Principles of Quantum Mechanics, Classical Electrodynamics, and, with Remo Ruffini, Gravitation and Spacetime. He is also the author of dozens of articles dealing with gravitation, relativity, and quantum theory, including many articles on fundamental physics published in the American Journal of Physics, where he served as associate editor for some years. He lives in Vermont. John T. Markert received his B.A. in Physics and Mathematics from Bowdoin College (1979) and his M.S. (1984) and Ph.D. (1987) in Physics from Cornell University, where he was recipient of the Clark Award for Excellence in Teaching. After postdoctoral research at the University of California, San Diego, he joined the faculty at the University of Texas, Austin, in 1990, where he has received the College of Natural Sciences Teaching Excellence Award and is currently Chair of the Department and Professor of Physics. His introductory physics teaching methods emphasize context-based approaches, interactive techniques, and peer instruction. He is author or coauthor of over 120 journal articles, including many on experimental condensed matter physics research in superconductivity, magnetism, and nanoscience. He lives in Austin, Texas, with his wife and children.