as a discrete element independent of the other chapters. The idea that elementary particles may constitute the bulk of the matter in the universe arises in several contexts—in discussions of both the evolution of the universe and the quest to unify the forces and particles, and in a chapter devoted to dark matter and dark energy. The committee hopes that readers of its report will thereby come to appreciate the many threads that connect the science of the quarks and the science of the cosmos.
Chapter 2, “Foundations: Matter, Space, and Time,” provides the intellectual foundation for the four chapters that follow and is by far the most challenging chapter for nonexperts. Chapter 3 addresses opportunities for deepening researchers’ understanding of the fundamental forces and particles and of how gravity can be taken beyond Einstein. Chapter 4 deals with the earliest beginnings of the universe. Scientists are poised not only to extend current understanding of the universe back to a time when even the largest structures in the universe were subatomic quantum fluctuations, but also to make profound advances in how matter, space, and time are viewed. The bulk of the stuff in the universe—dark matter and dark energy—lies between the stars and galaxies and is mysterious. As Chapter 5 discusses, the solution to the dark matter problem very likely involves one (or more) new particles of nature, and astronomers and physicists are now poised to solve this 70-year-old puzzle. At the same time, a joint effort is needed to tackle the dark energy problem. Chapter 6 deals with the opportunities that lie ahead to use the universe as a laboratory to study the physical laws—of nuclear physics, gravity, and electromagnetism—in regimes beyond the reach of terrestrial laboratories, and even, possibly, to discover new laws. Chapter 7, the final chapter, summarizes the scientific opportunities identified by the committee in the form of 11 questions that are deep in their content, crosscutting, and ripe for answering. The chapter goes on to recommend a strategy for realizing the opportunities. The strategy is summarized in the committee’s seven recommendations at the end of the chapter. Appendix D is a glossary that also contains definitions of acronyms.
This is a special moment. If we can take advantage of the opportunities that exist, we stand to make truly fundamental advances in our understanding of how the universe began as well as of the basic nature of matter, space, and time. Because of the deep and profound connections between quarks and the cosmos, advances in both are inextricably connected and taking will require a new approach that lies at the boundary of physics and astronomy.