How We Know Ancient Science: Lost Books, Arabic Translations and Bronze Gears

Before you read

The Greek and Roman world, about 300 BCE – 500 CE

Some ancient scientific books survive complete in Greek, because they were copied again and again: Euclid’s Elements, Ptolemy’s great book of astronomy, and dozens of books by the doctor Galen. Many more are lost, and we know them only from later writers who still had them and described what was in them.

Some Greek books survive only in translation. In the ninth century, scholars in Baghdad translated hundreds of Greek books of mathematics, astronomy and medicine into Arabic. When the Greek copies disappeared, the Arabic ones survived, and some were later translated again, into Latin.

A few books have been found hidden underneath other books. Parchment was expensive, so scribes sometimes scraped old writing off and wrote something new on top. A page like this is called a palimpsest, and with modern light and cameras the old writing can sometimes be read again.

And sometimes the evidence is not a book at all, but an object: an instrument, a tool, a medical knife, a sundial. Objects cannot tell us their story in words, so scholars study them closely and deduce what they must have been used for.

We know ancient science from books, translations, hidden pages and things.

The story

Retold for this lesson; the events after Philo’s time are told by Sophia as things to come.

In Philo’s time, the Library holds the book in which Eratosthenes, librarian of Alexandria two centuries earlier, explained how he measured the size of the whole Earth. Things to come: the book will be lost. We will know his method mainly because a teacher called Cleomedes, who lived some centuries later (his dates are uncertain), described it in a simple textbook of astronomy. Cleomedes may have simplified the numbers, so scholars still argue about exactly how accurate Eratosthenes was.

Things to come: in Baghdad, in the ninth century, scholars such as Thabit ibn Qurra will translate Greek books into Arabic. Apollonius of Perga wrote eight books on the curves called conic sections. Four will survive in Greek, three only in Arabic, and the last one not at all. Without the translators of Baghdad, those three books would have disappeared for ever.

Things to come: in the tenth century, someone in Constantinople will copy several books of Archimedes onto parchment. In 1229, a priest called Ioannes Myronas will scrape the pages, cut them up and use them for a prayer book. Underneath the prayers lies the only surviving copy of Archimedes’s Method, in which he explains how he discovered his results. A Danish scholar will read part of it with a magnifying glass in 1906. Then the book will vanish, reappear at an auction in 1998, and be photographed with special light until the hidden words come back.

And in 1900, sponge divers sheltering from a storm near the island of Antikythera will find an ancient shipwreck full of bronze and marble statues. Among the finds is a lump of corroded bronze. In 1902 someone will notice a gear wheel inside it. More than a century later, X-ray scans will show dozens of gears and tiny inscriptions: instructions for a machine that showed the movements of the sun and moon and predicted eclipses. Nobody wrote about this machine in any book that survives. Who made it, and exactly when, is still debated.

Talk and write

Discussion and writing

Mystery object. Your teacher shows a picture of an unusual old tool or instrument. In groups, deduce what it was used for: It must have been… It might have been… It can’t have been… Then compare your ideas.

Discuss. 1. Which is better evidence: a book written centuries later, or an object with no words? 2. Why might a priest scrape a book of mathematics? 3. Which of today’s scientific knowledge do you think could be lost?

Write (100–130 words). How we know. Explain how we know about ancient science, using at least four examples and must have, might have and can’t have.