Camille Flammarion (1842-1925) - French astronomer, a well-known popularizer of this science. The most famous book of C. Flammarion "Popular Astronomy" was released in 1880 with a record circulation for that time of 100,000 copies and sold out within a month. The book has withstood many reprints and has been translated into all major European languages. In "The Sky of Christendom," the author describes views on the world order of the universe after the emergence of Christianity.