Einstein's theory of general relativity is a cornerstone of modern physics. It also touches upon a wealth of topics that students find fascinating - black holes, warped spacetime, gravitational waves, and cosmology. Now reissued by Cambridge University Press, this ground-breaking text helped to bring general relativity into the undergraduate curriculum, making it accessible to virtually all physics majors. One of the pioneers of the 'physics-first' approach to the subject, renowned relativist James B. Hartle, recognized that there is typically not enough time in a short introductory course for the traditional, mathematics-first, approach. In this text, he provides a fluent and accessible physics-first introduction to general relativity that begins with the essential physical applications and uses a minimum of new mathematics. This market-leading text is ideal for a one-semester course for undergraduates, with only introductory mechanics as a prerequisite.

As physics has progressed, its most fundamental theories have become more distant from everyday experience posing challenges for understanding, notably with quantum mechanics. This volume contains twenty-five essays written to address such challenges. The essays address issues in quantum mechanics, quantum cosmology and physics in general. Examples include: How do we apply quantum mechanics to the whole universe when all observers are inside? What do we mean by past, present, and future in a four-dimensional universe? What is the origin of classical predictability in a quantum universe? Could physics predict non-computable numbers? Short personal recollections of Murray Gell-Mann and Stephen Hawking are included.The essays vary in length, style, and level but should be accessible to most physicists.

The subject of Quantum Cosmology is concerned with providing a quantum mechanical description of the universe as a whole and, within that description, to constructing a theory of the universe's initial condition whose predictions can be compared with observation. The recent progress in this area has profound implications for physics at all scales. The lectures at this School describe these theories and their implications. They cover basic quantum mechanics of cosmology, proposals for theories of initial conditions, and their application to the prediction of the large scale features of our universe. A special emphasis of the School is the implication of topological fluctuations of spacetime (wormholes, baby universes) for the observed coupling constants of the low energy interactions of elementary particles and as a potential explanation for the vanishing of the cosmological constant.