For much of the 20th century, research in astronomy was dominated by the United States. Today, the globalization that has influenced so many facets of our society is transforming astronomy as well—see Box 3.1. Over the past 50 years astronomy has expanded dramatically in Europe, which has achieved parity with the United States in many areas, as well as in Australia. A similar, more recent expansion in Asia—Japan and China in particular—is likely to influence the future of our subject for decades to come (Figure 3.1). South America also continues to increase its impact on the field, and South Africa is becoming a presence. In this new era it is imperative that planning for the U.S. research enterprise be done in an international context. We all share one sky and similar science agendas, and there are significant gains to be made by increasing international coordination and cooperation. This is a challenging task, because our early leadership means that many U.S. researchers, institutions, funding agencies, and policy makers are unaccustomed to long-range scientific planning with an international perspective.

Astronomy is among the most international of research disciplines, in part because the best ground-based observing sites (e.g., Antarctica, Australia, Chile, Hawaii, southern Africa), and of course space, are not necessarily located in places with the largest human and fiscal assets. Although the U.S. investment in astronomy has grown, that of the rest of the world has grown even faster. While this outcome should be celebrated, it does underscore that it is no longer possible for the United States or any other country to assume that it is an unquestioned leader across the whole field. Given the growing scale, cost, and complexity of major projects and the convergence of national scientific agendas, astronomy is becoming increasingly collaborative and cooperative—essential and desirable features for the field in the 21st century.

As astronomy research has blossomed in recent decades, the complexity has grown proportionately, as has the expense of the facilities necessary to explore the universe. The launch of the Hubble Space Telescope (HST) marked the entry of astronomy into large-scale transformative scientific facilities. A salient feature of the HST and other large space facilities in this class, such as Chandra, Fermi, Herschel, Kepler, Planck, Spitzer, and XMM-Newton, is that many are collaborative with other nations. The same is true of recent large ground-based astronomy and astrophysics facilities such as the NSF-funded Gemini telescopes, LIGO, and IceCube, and the NSF/DOE astrophysics projects Dark Energy Survey (DES), Auger, and VERITAS. The forthcoming flagships of the 2001 decadal survey AANM¹—JWST