The book is devoted to an eternal topic that can never be completely exhausted. However, you will not find strict scientific evidence in it. Guided by the method of most probable knowledge, the author leads the reader to the answer. The diverse factual material collected in the book reflects the latest scientific achievements and facts that modern science is not able to explain. The book is written in a fairly simple language, it is for those who are truly concerned about the issue raised in the book, for those who are capable of analysis and reflection. The author is a candidate of technical sciences, a specialist in the field of applied mathematics.