This book came out in Russian in 1988, the centenary of the birth of Alexander Friedmann, an outstanding Soviet scientist. The anniversary was widely marked by the scientific community with national and international conferences and symposia dedicated to this event as a tribute to the enormous contribution A. A. Friedmann made to the development of hydrodynamics, meteorology and, particularly, relativistic cosmology. Very little has been written about Friedmann. The present book is the first detailed biography of the scientist. The material is generally given chronologically and is based on the scientific works of Friedmann, documentary records and reminiscences by his contemporaries published in the late 1920s. The book also includes unpublished reminiscences about Alexander Friedmann.

The division of the work between the authors was as follows: Chapters 1–3, 5, 6 and 10, as well as the last section of Chapter 9, have been written by V. Ya. Frenkel; Chapters 4, 7 and 11 by E. A. Tropp; Chapters 8, 9 and 12 by A. D. Chernin. Given this clear division, in some chapters the material is presented in the first person singular. As to the method of citation, given that the book is popular science, the authors decided not to overburden it with footnotes. Quotations are either from archives or from the literature given at the end of the book.

The authors would like to thank the staff workers of the Leningrad archives for their assistance. We are grateful to Professor G. A. Grinberg and Professor L. G. Loitsyansky, and also to S. Ye. Malinina, O. N. Trapeznikova and A. B. Shekhter who shared their reminiscences with us.