The discovery of the expanding universe is one of the most exciting exploits in astronomy. This book explores its history, from the beginnings of modern cosmology with Einstein in 1917, through Lemaitre's discovery of the expanding universe in 1927 and his suggestion of a Big Bang origin, to Hubble's contribution of 1929 and the subsequent years when Hubble and Humason provided the essential observations for further developing modern cosmology, and finally to Einstein's conversion to the expanding universe in 1931. As a prelude the book traces the evolution of some of the notions of modern cosmology from the late Middle Ages up to the final acceptance of the concept of galaxies in 1925. Written in non-technical language, with a mathematical appendix, the book will appeal to scientists, students, and anyone interested in the history of astronomy and cosmology.

Since its foundation in 1904, the Mount Wilson Observatory has been at the centre of the development of astrophysics. Perched atop a mountain wilderness, two mammoth solar tower telescopes and the 60- and 100-inch behemoth night-time reflectors were all the largest in the world. Research has centred around two main themes - the evolution of stars and the development of the universe. This first volume in a series of five histories of the Carnegie Institution describes the people and events, the challenges and successes that the Observatory has witnessed. It includes biographical sketches of forty of the most famous Mount Wilson pioneer astronomers working during the first half of the twentieth century. Contemporary photographs illustrate the development and use of some of the innovative instruments that filled the observatory during this time. This story brings together the elements that formed modern theories of stellar evolution and cosmology.

Since its foundation in 1904, the Mount Wilson Observatory has been at the centre of the development of astrophysics. Perched atop a mountain wilderness, two mammoth solar tower telescopes and the 60- and 100-inch behemoth night-time reflectors were all the largest in the world. Research has centred around two main themes - the evolution of stars and the development of the universe. This first volume in a series of five histories of the Carnegie Institution describes the people and events, the challenges and successes that the Observatory has witnessed. It includes biographical sketches of forty of the most famous Mount Wilson pioneer astronomers working during the first half of the twentieth century. Contemporary photographs illustrate the development and use of some of the innovative instruments that filled the observatory during this time. This story brings together the elements that formed modern theories of stellar evolution and cosmology.