The new millennium marks a turning point in the history of efforts to understand our place in the universe. The heavens have been a source of fascination for humanity for thousands of years, but only in the last few centuries has it been possible to take the measure of the stars—and only in the last few decades, to take the measure of the entire universe. The scientific and technical revolution that has enabled this enormous progress is accelerating. We can anticipate major new discoveries in the early decades of the new millennium, but more importantly we can anticipate major advances in our understanding of the universe—its origin, its evolution, its ability to support life, its destiny. What is the nature of the matter and energy in the universe? What happened at the dawn of the modern universe, when the first stars and galaxies formed? How are black holes formed? How do stars and planets form, and how do planets evolve to create habitats suitable for life? How does the astronomical environment affect Earth? These questions are all part of the fabric of science, cutting across traditional disciplines and government agencies and connecting the universe from the smallest to the largest scales. Addressing them will require interactions of astronomy with many other disciplines, including physics, mathematics, computer science, and biology. The interaction with physics is particularly important since all objects in the universe—and indeed the universe itself—are governed by the same fundamental physical laws. Answering these questions will alter the perception of our place in the universe, just as the advent of the heliocentric theory did centuries ago. The search for the answers can also capture the imagination of the public and inspire interest in science, thereby helping to create a more scientifically literate citizenry.
The past decade saw an unprecedented number of important astronomical discoveries. Some highlights include:
Discovery of planets orbiting other stars; about three dozen are now known.