The answer to the simple question "What is time?" humanity has been looking for hundreds of years. According to the author, time is the energy state of matter, its manifestation and reflection in the gravitational field. The book for the first time reveals the reason for the unidirectionality of time and shows the factors that determine the pace of time of various bodies. The consequences of the hypothesis make it possible to explain such phenomena as poltergeist, levitation, teleportation, spontaneous combustion and the disappearance of objects and people. The book is addressed to specialists and a wide range of educated readers - everyone who wants to understand how the world works.