The time is of the emergence of the age of reason when Galileo was teaching young students the incredible account of how the earth moves around the sun, rather than the other way around.
His heretical announcement, that both the moon and Jupiter only reflect the sun's light, is brought to the attention of the church and Galileo is summoned to the Vatican. His friends abandon him and his appeal to the Pope is intercepted by the inquisitor. Galileo recants, but even while imprisoned continues his writings surreptitiously.
"Unquestionably Brecht's masterpiece." New York Daily News