About the book: 1968 / It is probably impossible to find a more exciting and dramatic story in science than the story of Euclid’s fifth postulate. This problem has plagued mathematicians for over two thousand years; was solved by Lobachevsky and Bolyai, and then, quite unexpectedly, the development of their ideas by Riemann and Einstein led to a decisive change in our ideas about the universe. This book tells about the people who worked on this problem, people separated by centuries, who never knew each other, different almost in everything, but strikingly similar and close in the main thing. And about the problem itself. About two-thirds of the book can be read without knowing or liking mathematics at all; the rest is designed for those who have completed grades 7–8, although, formally speaking, to understand almost everything, you need to know almost nothing.