The exploration of the first billion years of the history of the Universe represents one of the great challenges of contemporary astrophysics. During this time, the first structures start to form the first stars, galaxies, and possibly also soon the first quasars. At the same time, light comes to the dark, neutral Universe. This book contains the worked out lectures given at the 36th Saas-Fee Advanced Course "First Light in the Universe" by three eminent scientists in the field.

This book represents the proceedings from the NATO sponsored Advanced Research Workshop entitled "Observational Tests of Inflation" held at the University of Durham, England on the 10th-14th December, 1990. In recent years, the cosmological inflation model has drawn together the worlds of particle physics, theoretical cosmology and observational astronomy. The aim of the workshop was to bring together experts in all of these fields to discuss the current status of the inflation theory and its observational predictions. The simplest inflation model makes clear predictions which are testable by astronomical observation. Foremost is the prediction that the cosmological density parameter, no, should have a value negligibly different from the critical, Einstein-de Sitter value of 00=1. The other main prediction is that the spectrum of primordial density fluctuations should be Gaussian and take the Harrison-Zeldovich form. The prediction that n =l, in patticular, leads to several important consequences o for cosmology. Firstly, there is the apparent contradiction with the limits on baryon density from Big Bang nucleosynthesis which has led to the common conjecture that weakly interacting particles rather than baryons may form the dominant mass constituent of the Universe. Secondly, with n =l, the age of the Universe is uncomfortably short if o the Hubble constant and the ages of the oldest star clusters lie within their currently believed limits.

One of today's leading astronomers takes readers inside the decades-long search for the first galaxies and the origin of starlight Astronomers are like time travelers, scanning the night sky for the outermost galaxies that first came into being when our universe was a mere fraction of its present age. When Galaxies Were Born is Richard Ellis's firsthand account of how a pioneering generation of scientists harnessed the world's largest telescopes to decipher the history of the universe and witness cosmic dawn, the time when starlight first bathed the cosmos and galaxies emerged from darkness. In a remarkable career spanning more than forty years, Ellis has made some of the most spectacular discoveries in modern cosmology. He has traveled the world to conduct observations in locales as beautiful and remote as the Australian outback, the Canary Islands, Hawaii, and the Chilean desert. In this book, he brings to life a golden age of astronomy, describing the triumphs and the technical setbacks, the rivalries with competing teams, and the perennial challenge of cloudy nights. Ellis reveals the astonishing progress we have made in building ever larger and more powerful telescopes, and provides a tantalizing glimpse of cosmic dawn. Stunningly illustrated with a wealth of dramatic photos, When Galaxies Were Born is a bold scientific adventure enlivened by personal insights and anecdotes that enable readers to share in the thrill of discovery at the frontiers of astronomy.

The exploration of the first billion years of the history of the Universe represents one of the great challenges of contemporary astrophysics. During this time, the first structures start to form the first stars, galaxies, and possibly also soon the first quasars. At the same time, light comes to the dark, neutral Universe. This book contains the worked out lectures given at the 36th Saas-Fee Advanced Course "First Light in the Universe" by three eminent scientists in the field.

This book represents the proceedings from the NATO sponsored Advanced Research Workshop entitled "Observational Tests of Inflation" held at the University of Durham, England on the 10th-14th December, 1990. In recent years, the cosmological inflation model has drawn together the worlds of particle physics, theoretical cosmology and observational astronomy. The aim of the workshop was to bring together experts in all of these fields to discuss the current status of the inflation theory and its observational predictions. The simplest inflation model makes clear predictions which are testable by astronomical observation. Foremost is the prediction that the cosmological density parameter, no, should have a value negligibly different from the critical, Einstein-de Sitter value of 00=1. The other main prediction is that the spectrum of primordial density fluctuations should be Gaussian and take the Harrison-Zeldovich form. The prediction that n =l, in patticular, leads to several important consequences o for cosmology. Firstly, there is the apparent contradiction with the limits on baryon density from Big Bang nucleosynthesis which has led to the common conjecture that weakly interacting particles rather than baryons may form the dominant mass constituent of the Universe. Secondly, with n =l, the age of the Universe is uncomfortably short if o the Hubble constant and the ages of the oldest star clusters lie within their currently believed limits.

Scientists in the late twentieth century are not the first to view galaxy formation as a phenomenon worthy of explanation in terms of the known laws of physics. Already in 1754 Kant regarded the problem as essentially solved. In his Univerlal Natural Hutory and Theory 0/ the H eaven$ he wrote; "If in the immesurable space in which all the suns of the Milky Way have formed themselves, we assume a point around which, through some cause or other, the first formation of nature out of chaoo began, there the largest mass and a body of extraordinary attraction will have arisen which has thereby become capable of compelling all the systems in the process of being formed within an enormous sphere around it, to fall towards itself as their centre, and to build up a system around it on the great scale . . . . Observation puts this conjecture almost beyond doubt. " More than 200 years later, a similar note of confidence was voiced by Zel'dovicb at an IAU symposium held in Tallin in 1911; "Extrapolating . . . to the next symposium somewhere in the early eighties one can be pretty sure that the question of the formation of galaxies and clusters will be solved in the next few years. " Perhaps few astronomers today would share Kant's near certainty or feel that Zel'dovich's prophecy has been fulfilled, Many, however, will sympathize with the optimistic olltlook of these two statements.

From the reviews: ..". Each chapter of the book is followed by a notes section and by a problems section. There are over 100 problems, many of which have hints. The book may be recommended as a text, it provides a completly self-contained reading ..." --S. Pogosian in Zentralblatt f r Mathematik