The fundamental goal of astronomy and astrophysics is to understand how the universe and its constituent galaxies, stars, and planets formed, how they evolved, and what their destiny will be. To achieve this goal, researchers must pursue a strategy with several elements:

• Survey the universe and its constituents, including galaxies as they evolve through cosmic time, stars and planets as they form out of collapsing interstellar clouds in our galaxy, interstellar and intergalactic gas as it accumulates the elements created in stars and supernovae, and the mysterious dark matter and perhaps dark energy that so strongly influence the large-scale structure and dynamics of the universe.

• Use the universe as a unique laboratory for probing the laws of physics in regimes not accessible on Earth, such as the very early universe or near the event horizon of a black hole.

• Search for life beyond Earth, and if it is found, determine its nature and its distribution.

• Develop a conceptual framework that accounts for all that astronomers have observed.

Several key problems are particularly ripe for advances in this decade:

• Determine the large-scale properties of the universe: the amount, distribution, and nature of its matter and energy, its age, and the history of its expansion.

• Study the dawn of the modern universe, when the first stars and galaxies formed.

• Understand the formation and evolution of black holes of all sizes.

• Study the formation of stars and their planetary systems, and the birth and evolution of giant and terrestrial planets.

• Understand how the astronomical environment affects Earth.

These scientific themes, all of which now appear to offer particular promise for immediate progress, are only part of the much larger tapestry that is modern astronomy and astrophysics. For example, scientists cannot hope to understand the formation of black holes without understanding the late stages of stellar evolution, and the full significance of observations of the galaxies in the very early universe will not be clear until it is clear how these galaxies have evolved since that time. Although the new initiatives that the committee recommends will advance knowl-