This account of the scientific work that has created our modern picture of the origins of the universe was a best-seller in Britain; it deserves to be equally popular here. Chown, the cosmology consultant for New Scientist, begins by showing how scientists concluded that at some time in the distant past the universe, then very tiny, exploded. George Gamow was among the first to explore the consequences of the ``Big Bang,'' especially the fact that the early universe would have had an extremely high temperature. Two of Gamow's research students pointed out (in 1948) that the original explosion would in theory be detectable today as a residual layer of energy throughout the universe. More than 15 years passed before anyone attempted the measurement. Ironically, two teams worked on it within a few miles of each other--one at Princeton, the other at Bell Laboratories in Holmdel, N.J. The Bell team, composed of Robert Wilson and Arno Penzias, made the key discovery in 1965 and won the Nobel Prize for it. But a subtler measurement remained to be made. Theory implied that the Big Bang radiation would show irregularities--``ripples,'' as they were dubbed--to account for the present structure of the universe, which is far from uniform. In one of the largest scientific team efforts ever assembled, the COBE (COsmic Background Explorer) satellite was created to attempt the measurements, which Chown describes as the most difficult ever made. After rigorous testing, several redesigns, and unprecedented difficulties, COBE was launched. The results were stunning--including a measurement of the cosmic background radiation that matched the theoretical predictions within 0.25 percent. Chown concludes his account with a description of the resulting publicity and wrangling among team members who felt that one team leader, George Smoot (who had described a ``map'' of the ripples as ``like seeing the face of God''), was hogging the spotlight. A lucid account of the key developments in modern cosmology, especially good at capturing the human dimension of scientific work.