NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This project was supported by the National Aeronautics and Space Administration under Grant No. NAG5-6916, the National Science Foundation under Grant No. AST-9800149, and the Keck Foundation.

Front Cover: The image is a portion of the Hubble Deep Field, the deepest image ever taken of the universe. The most distant galaxies in the Hubble Deep Field emitted their light when the universe was less than 1 billion years old—in other words, when it was less than 6 percent of its present age. In this image, we can establish that the most distant and therefore earliest galaxies were quite different from those we study nearby. They were smaller and less regular, as if they were being built up from primordial clumps of gas. But we have still not seen the very first galaxies and stars that were created after the Big Bang. Seeing the very first galaxies is the primary goal of the Hubble Space Telescope’s successor, the Next Generation Space Telescope. Courtesy of the Space Telescope Science Institute.

Library of Congress Card Number: 00-112257

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0-309-07312-X (hardcover)

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