200 Palestinian scholar Judah ha-Nasi compiles tracts of the Mishnah, beginning the creation of Jewish Talmudic law. Rome boasts 1.5 million inhabitants, most living in 3- to 8-story-high insulae, apartment blocks made of brick, wood or rubble.

203 Origen, aged 22, succeeds Clement as leader of the Christian school in Alexandria.

213 Completion of the Baths of Caracalla, which contain reading rooms, running tracks, and public gardens covering 20 acres. Gunpowder invented by Chinese alchemists mixing saltpeter with sulfur at the right temperature.

219 Founding of the Sura Academy in Babylon.

226 Ardashir begins Sassanid Dynasty, rulers of Persia until the seventh century.

238 In this year there were 6 Roman Emperors: Maximin, Gordian I, Gordian II, Balbinus, Pupienus Maximus & Gordian III.

250 Greek mathematician from Alexandria, Diophantus, publishes Arithmetica, the first known algebra text, a treatise in 13 parts of which 6 survive. About 5% of Romans have become Christian.

258 Emperor Valerian beheads Cyprian in front of thousands; those near him throw pieces of cloth to catch his blood.

271 First form of compass used in China.

272 Three Christians beheaded near a hill outside of Paris. The hill will later be called Montmartre, the Mountain of the Martyrs.

276 Mani, a sage from Persia who calls himself a apostle of Jesus Christ, is executed for preaching Zoroastrian dualism with Christian theology, angering followers of both religions.

284 Diocletian becomes Emperor of Rome and proclaims himself the earthly representative of Rome’s supreme god, Jupiter.

299 Christians across Roman empire now about 10% of the population.