The book consists of 37 letters to the unnamed woman. They serve as vehicles for discussion of the history of astronomy, climatology and science. In writing the letters, Milanković remembers his early life, from birth in
Dalj, through his education, to successes and failures at a professional level. The work takes inspiration from his travels through Germany,
Hungary,
Istanbul and Europe, and his return to his birthplace, which seems to him desolate and dilapidated in contrast. The writer uses a personal approach to science, traveling with a friend through time and space. In the appropriate attire, they roam the ancient world. Unseen by the natives, they spy Babylonian priests,
Aristotle,
Eratosthenes and other great scholars and figures of antiquity and modern history. The letters describe experiments, development of scientific instruments, ancient architecture and new cities, and an epic voyage on the seas. The history of scientific ideas is explored, including basic knowledge about the Sun, planets and their orbits. In the central part of the book, the writer discusses climate change and cyclical ice ages throughout the history and future of the Earth. In the final letters, Milanković describes the formation of the Earth and the stages through which it passed until it became the cradle of life, then presents its future, following the dying stages of the
Sun and planets. Finally, the book deals with travel to the
Moon,
Mars and
Venus, and a pilgrimage to the universe. ==References==