Do we know much about our ancestors? How little we know about them! Moscow schoolchildren have been reported to remember at best the names of their grandfathers. Adults who care to think about their roots know the names of their great-grandparents and the names and patronymics of their grandparents.

It is different with people who have left their mark in politics, science or culture. So, what is known about the hero of this book – Alexander Alexandrovich Friedmann? A sample opinion poll among physicists showed that his works of 1922–24 on relativistic cosmology are included among the two or three most outstanding achievements of Soviet physicists. It would seem that interest in his personality would be heightened and therefore satisfied. Yet, it is not the case. His biography was published only once, in a thin brochure put out by Znanie (Knowledge) Publishers. The massive volume of Classics of Science, devoted to Friedmann and published in 1966, contains his short autobiography – “Curriculum Vitae.” It also contains Friedmann's major works in hydromechanics, dynamic meteorology, atmospheric physics and relativistic cosmology. The “Addenda” to the volume have a few reminiscences of his contemporaries about him, reprinted mainly from journals and magazines of the 1920s. There are also Friedmann's extremely interesting letters to Vladimir Steklov, his teacher, whom he so much revered, and to Boris Golitsyn – two outstanding Russian scientists with whom he was associated for many years. These materials are a source for biographical notes on Friedmann. No biographical dictionary of science or Soviet encyclopaedia fails to mention his name, starting with the first edition of the Great Soviet Encyclopaedia, in the preparation of which he himself took part.