Appearance
2.2 — The First Fifteen Centuries
The years from 1 to about 1500 contain the two events that most shape how you think — the invention of zero as a number, and the printing press — separated by a thousand years and connected by a trade route.
The Roman centuries
79 CE — Vesuvius buries Pompeii
The eruption on 24 August (or possibly in October — the evidence is contested) killed perhaps sixteen thousand people in Pompeii and Herculaneum and preserved both towns under metres of ash.
What makes it historically enormous is what it preserved: not monuments, but ordinary life. Bread still in ovens. Election slogans painted on walls. Graffiti — insults, love notes, advertisements for gladiator fights, a boast about who slept with whom. A snack bar with the food residue still in the counter jars. Almost everything else we know about the Roman world comes from what the elite chose to write down; Pompeii is the exception, and it is why we know what a Roman shop smelled like.
Pliny the Elder, the naturalist, sailed towards the eruption to rescue people and died on the shore. His nephew Pliny the Younger watched from across the bay and wrote the only eyewitness account, describing a cloud shaped like an umbrella pine — which is why the most violent class of eruption is now called Plinian.
313 and 380 CE — Rome adopts Christianity, in two steps
In 313 the Edict of Milan made Christianity legal, one tolerated religion among many, ending three centuries of intermittent persecution. That is the step usually credited to Constantine.
The step that mattered more came in 380, when Theodosius I made Nicene Christianity the state religion, and other beliefs — including the older Roman religion and rival Christian interpretations — went from tolerated to suppressed. Legalisation and establishment are very different things, and collapsing them into one date hides the sixty-seven years in which the outcome was genuinely uncertain.
476 CE — the date historians dislike
The last Western Roman emperor, a teenager named Romulus Augustulus, was deposed by the Germanic commander Odoacer, who did not bother appointing a replacement and sent the imperial regalia to Constantinople.
Nothing much happened that year. The western empire had been effectively governed by Germanic generals for decades, its territory had been shrinking for a century, and the eastern half — which we now call Byzantine, though its people called themselves Romans until 1453 — continued for another thousand years without interruption. Contemporaries did not experience 476 as an ending.
It is in every textbook because a millennium later scholars wanted a boundary between the ancient and medieval worlds, and this was the tidiest available. Almost every famous date for the "fall" of something is a line drawn afterwards by people who needed a chapter break.
About 500 CE — Aryabhata, and India's mathematics
Aryabhata completed the Aryabhatiya in 499 CE at the age of 23. In 121 verses it gives a value of π accurate to four decimal places, a table of sine values, methods for solving certain equations in integers, and the statement — a thousand years before Copernicus and against every authority of his time — that the apparent daily rotation of the stars is caused by the Earth turning on its axis.
He also explained eclipses correctly as shadows, in a culture where the standard account involved a demon swallowing the sun.
Zero, and the number system you use
628 CE — Brahmagupta writes down the rules for zero
The digit zero as a placeholder existed earlier, in Babylon and in India, and a dot for it appears in the Bakhshali manuscript and in a Gwalior temple inscription of 876 CE. But a placeholder is only punctuation.
Brahmagupta was the first person known to treat zero as a number you can calculate with, and in the Brahmasphutasiddhanta he sets out the rules: a number minus itself is zero, zero added to a number leaves it unchanged, zero times anything is zero, and — importantly — he defines operations on negative numbers, which he calls debts, at a time when most mathematical traditions refused to accept that a quantity less than nothing could exist.
He got one thing wrong, and the mistake is illuminating: he claimed zero divided by zero is zero. It took another five centuries and Bhaskara II to argue that division by zero produces something unbounded rather than a number.
About 820 CE — al-Khwarizmi, and two words you use constantly
Muhammad ibn Musa al-Khwarizmi worked at the House of Wisdom in Baghdad, where scholars were systematically translating Greek, Persian and Indian texts into Arabic. He wrote two books that changed European mathematics.
One described the Indian decimal number system, and the Latin translation of his name — Algoritmi — became the word algorithm. The other, al-Kitab al-mukhtasar fi hisab al-jabr wa'l-muqabala, gives methods for solving equations by moving terms across the equals sign; al-jabr, "the restoring", became algebra.
So the numerals on your keyboard travelled from India to Baghdad to Muslim Spain to Italy, which is why Europe calls them Arabic numerals and Arabic calls them Indian numerals. Both are right about the leg of the journey they saw.
1202 — Fibonacci brings the digits to Europe
Leonardo of Pisa grew up around his father's trading post in North Africa, learned the Indian-Arabic system there, and published Liber Abaci arguing that European merchants should abandon Roman numerals.
The argument is entirely practical. Try multiplying MCMXLVII by XXIII. Roman numerals have no place value, so arithmetic requires either an abacus or a specialist. The new system made calculation something a merchant could do on paper, check, and file — which is a precondition for double-entry bookkeeping, credit, and everything built on them.
Some cities resisted. Florence banned the new numerals in 1299, on the grounds that a 0 could be altered into a 6 or a 9 while an X could not — an early and correct observation about fraud in a new technology.
The rabbit-breeding puzzle that gives the Fibonacci sequence is a minor example in the book, and the sequence was known in India centuries earlier from studies of Sanskrit poetic metre.
The medieval world
1054 — the Church splits, and a star explodes
Two unrelated things, in one year, both worth knowing.
Representatives of the Pope and the Patriarch of Constantinople excommunicated each other, formalising the Great Schism between what became the Roman Catholic and Eastern Orthodox churches. The stated dispute was over a single clause in the creed and the authority of the Pope; the real one had been building for centuries over language, politics and the fact that the two halves of the empire had grown apart.
And in July of the same year, Chinese and Japanese astronomers recorded a new star in Taurus so bright it was visible in daylight for 23 days. It was a supernova, and what is left of it is the Crab Nebula, still expanding at about 1,500 kilometres per second and still visible in a small telescope. European records of it are almost absent, which is a data point about who was watching the sky.
1215 — Magna Carta
English barons forced King John to seal a document limiting his power at Runnymede. It failed immediately: John asked the Pope to annul it within weeks, the Pope did, and civil war followed.
Most of its 63 clauses concern feudal grievances that mean nothing now — fish traps in the Thames, the treatment of forests, the debts owed to Jewish moneylenders. Only three remain on the statute book in England. But one of those is the reason the document is famous: no free man shall be imprisoned or stripped of his rights except by the lawful judgement of his equals or by the law of the land.
Its real career began four centuries later, when English lawyers and then American colonists reinterpreted a baronial deal as a general statement that the ruler is under the law rather than above it. That reading is a creative misreading, and it built two constitutions.
1347–1351 — the Black Death
Yersinia pestis arrived in Europe on ships from the Black Sea and killed somewhere between a third and half the population in four years. Some regions lost sixty per cent. It had already devastated Central Asia, the Middle East and North Africa.
The medical story is in Volume V. The economic consequence belongs here, and it is brutal and counter-intuitive: the survivors got richer. With a third of the workers dead and the same amount of land, labour became scarce and wages rose sharply. Landlords tried to freeze wages by law and largely failed. In Western Europe serfdom weakened and in places collapsed, because a peasant who could walk to the next estate and be hired had leverage for the first time.
It is the clearest historical demonstration that the price of labour is set by supply and demand rather than by custom or by law — a fact that took economists another four hundred years to state.
1453 — Constantinople falls, and a chain reaction begins
Mehmed II took the city after a seven-week siege, using among other things a cannon so large it needed sixty oxen to move and could fire three times a day. The walls that had held for a thousand years came down. The last Roman emperor died in the fighting.
Three consequences ran outward. Greek scholars fled west with manuscripts, feeding the Italian Renaissance. The overland trade routes to Asia came under Ottoman control, which sharpened European interest in finding a sea route — Columbus and da Gama are downstream of this. And the fall demonstrated that gunpowder artillery had made the tall stone wall obsolete, which redrew the map of European fortification and, with it, the balance between kings and castle-holding nobles.
The machine that changed reading
About 1440–1455 — Gutenberg's press
Printing was not new. China had woodblock printing by the seventh century and Bi Sheng made movable type from clay around 1040; Korea printed with metal type in 1377, decades before Gutenberg.
What Johannes Gutenberg invented was a system, and the crucial part was not the press. It was a hand mould that could cast identical metal letters quickly and cheaply in a durable alloy of lead, tin and antimony — an alloy chosen because it expands slightly as it sets, so it fills the mould completely and gives a sharp face. Add an oil-based ink that would stick to metal rather than run off it, and a press adapted from wine and olive presses, and you have a process that can produce hundreds of identical copies.
The scale of the change is easiest to see in numbers. Before 1450, Europe produced a few thousand manuscript books a year. By 1500 the presses had produced something like twenty million volumes, and by 1600, perhaps two hundred million. A book's price fell by a factor of hundreds.
Everything downstream follows: the Reformation, which was a pamphlet war Luther won because he understood printing; the scientific revolution, which requires that a result published in one country be exactly reproducible in another; standardised spelling; and the very idea of a reading public.
Gutenberg himself was sued by his financier Johann Fust, lost the case, lost the press and the type, and died in relative obscurity. Fust and Gutenberg's foreman took over the business and it made them wealthy.
1492 — Columbus, and the year that gets two entries in one
He was looking for Asia, he had the size of the Earth badly wrong — he used an underestimate that made the westward journey to Japan look feasible — and he died insisting he had reached the Indies. Educated Europeans already knew the Earth was round; the flat-Earth myth about his voyage was largely invented by Washington Irving in a novelistic biography of 1828.
The consequence that matters has a name: the Columbian Exchange. Two biological worlds that had been separate for ten thousand years were connected in a few decades. Westward went wheat, horses, cattle, sugar — and smallpox, measles and influenza, which killed something like ninety per cent of the population of the Americas within a century. Eastward went potatoes, maize, tomatoes, chillies, cacao, tobacco and rubber.
Reset your mental picture of world cuisine accordingly. There were no chillies in India before the sixteenth century, no tomatoes in Italy, no potatoes in Ireland, no chocolate anywhere outside Mesoamerica. The food that now defines those places is four hundred years old at most.
The same year, Spain expelled its Jewish population and completed the conquest of Granada, ending eight centuries of Muslim rule in Iberia and the scholarly transmission that came with it.
What comes next
The next page runs from 1500 to 1800 — the three centuries in which Europe went from a peripheral region to a global power, in which the way knowledge is checked changed permanently, and in which two revolutions decided that a government must answer to the people it governs.