The Proceedings of the 17th International Cosmic Ray Conference held in Paris, July 15 to 25, 1981, appear in two sets. The Regular Volumes, 1 to 8, contain contributed papers received at the Secretariat by April 1st, 1981. They were issued at the opening of the Conference. The Late Volumes, 9 to 14, contain contributed papers received after that date, Invited and Rapporteur Talks, and the General Index. The assiduous reader will notice several changes with respect to the well-established traditions of the Conference. 1/ Following a recommendation of the Commission an Cosmic Rays of IUPAP, and although an increase in the total number of papers submitted was noticed as compared to the 16th ICRC (Kyoto, 1979), the total number of pages has been significantly reduced, thanks to introduction of three new rules for publication. (i) None of the first "Preliminary" Abstracts was published. These abstracts had to be confirmed, either by a new "Confirming Abstract" or by a Full Paper. The Confirming Abstracts are included in the Proceedings. (ii) The sum of the "fractional" contributions of each author should not exceed 3 papers, and each author should not appear in more than 10 papers. (iii) The maximum number of pages per paper was reduced from 6 to 4. The Organizing Committee thanks all authors who have, in their vast majority, very efficiently cooperated by kindly complying with these new rules. The papers we selected an the basis of the Preliminary Abstracts.

The Extravagant Universe tells the story of a remarkable adventure of scientific discovery. One of the world's leading astronomers, Robert Kirshner, takes readers inside a lively research team on the quest that led them to an extraordinary cosmological discovery: the expansion of the universe is accelerating under the influence of a dark energy that makes space itself expand. In addition to sharing the story of this exciting discovery, Kirshner also brings the science up-to-date in a new epilogue. He explains how the idea of an accelerating universe--once a daring interpretation of sketchy data--is now the standard assumption in cosmology today. This measurement of dark energy--a quality of space itself that causes cosmic acceleration--points to a gaping hole in our understanding of fundamental physics. In 1917, Einstein proposed the "cosmological constant" to explain a static universe. When observations proved that the universe was expanding, he cast this early form of dark energy aside. But recent observations described first-hand in this book show that the cosmological constant--or something just like it--dominates the universe's mass and energy budget and determines its fate and shape. Warned by Einstein's blunder, and contradicted by the initial results of a competing research team, Kirshner and his colleagues were reluctant to accept their own result. But, convinced by evidence built on their hard-earned understanding of exploding stars, they announced their conclusion that the universe is accelerating in February 1998. Other lines of inquiry and parallel supernova research now support a new synthesis of a cosmos dominated by dark energy but also containing several forms of dark matter. We live in an extravagant universe with a surprising number of essential ingredients: the real universe we measure is not the simplest one we could imagine.