The Hour of the Bull (Russian: Час Быка, Chas Byká) is a social science fiction novel written by Soviet author and paleontologist Ivan Yefremov in 1968.

Six months after its publication in book form in 1970 Soviet authorities attempted to remove it from libraries and bookshops[1] after realizing that it contained a sharp criticism of the current state of affairs in the USSR disguised as a critique of "Capitalism" and Chinese-style communism of that time.

The actual story is told as an answer to a question asked in school at a lesson about the patterns of the development of societies.

And prior to it there was a period of great ecological degradation and pollution resulting in widespread diseases, genetic and otherwise, increase in cancer rates and planet-wide epidemics (that's when the progenitors of Tormancian human population had left the "doomed" Earth on a starship flotilla that subsequently "fell through a space-time anomaly", and found itself near the inhabitable planet of Tormance, by pure chance).

The novel was first published in 1968 in the Soviet popular science magazine Tekhnika Molodezhi (Technology for the Youth).