Structure and Evolution of the Universe-21/sup st/ century missions

The Structure and Evolution of the Universe (SEU) science theme at NASA centers on four cosmological quests: (i) to comprehend how matter in the Universe evolved from formlessness into the complexity of galaxies and galaxy clusters; (ii) to probe the ultimate limits of physics by searching for new behaviors of space, time, and matter close to black holes; (iii) to understand how matter behaves under extreme conditions, producing exotic objects such as quasars and gamma-ray bursters, and ripples of the space-time fabric called gravity waves; (iv) to study how stars create new elements, and to follow the cycles of mass and energy in stellar evolution, from star birth in giant interstellar clouds to the violent explosions that end some stars' lives but lead again to star birth. This paper discusses the variety of missions in the SEU theme, demonstrating how all the full electromagnetic spectrum must be surveyed to address these quests.