Kugler, from a landowning family in Königsbach, Bavaria, was square-jawed, determined and difficult. Another ex-student of Epping, he was appointed as maths professor at a Jesuit college in the Netherlands, and taught himself Akkadian in order to take over analysis of Strassmaier’s drawings in 1897, a few years after Epping died. He had a strained relationship with Strassmaier, complaining that his colleague’s frequent linguistic suggestions were not helpful for his astronomical analysis. He was also a scathing critic of ‘Panbabylonism’, a school of thought that emerged in the late nineteenth century which argued that the Hebrew Bible was directly derived from Babylonian culture and mythology, and that the Babylonians had developed highly sophisticated astronomy as early as the third millennium BC.
It was Kugler who worked out much of the detail of the astronomical theories that Epping had unearthed. And he noticed something odd about the period relations that the Babylonians used to calculate the behaviour of the moon.
This was the priests’ most complex theory. To fully describe the moon and predict all-important lunar eclipses, they had to combine several different lunar cycles: the moon’s variation in speed (anomalistic month); progression through its phases (synodic month); and the time it takes to travel between the ‘nodes’ where it crosses the sun’s path (draconitic month). To do this, the Babylonians ultimately used a cycle of nearly 350 years, from which they derived the average length of the synodic month as precisely 29.5306 days.8 Kugler noticed that the numbers in this theory were identical to those used by Hipparchus. In other words, Hipparchus didn’t derive the numbers in his theories from observations at all. He took them from the astronomers in Babylon.
In fact, over the last few decades it has emerged that pretty much all of the numbers on which Hipparchus’s theories were based, including his period relations for the planets, come from Babylonian tablets. Historians already knew that some aspects of Babylonian maths and astronomy had filtered to the Greeks, including the zodiac signs and the base-60 number system (which Hipparchus was one of the very first Greeks to use). But the Babylonians were still seen as primitive stargazers, inferior to the scientifically minded Greeks. The French Assyriologist George Bertin, for example, responding to Epping and Strassmaier’s findings in 1889, insisted that even if the Greeks had adopted some of the priests’ terminology, it was the Babylonians who had learned astronomy from the Greeks: ‘The Babylonians . . . soon discovered the accuracy of their new masters in science.’
The discovery of Hipparchus’s numbers embedded in older Babylonian models turns that view upside down, proving that the fundamental ingredients for his theories came from the temple tablets. More evidence is still being uncovered. In 2017, Australian researchers claimed that a Babylonian tablet from the second millennium BC contains a trigonometric table: perhaps the priests helped to inspire Hipparchus’s invention of trigonometry too. Hipparchus’s reliance on Babylonian astronomy is so extensive, in fact, some scholars think he must have visited the Esagila temple himself and worked with the priests there, copying observations and equations from their tablets and converting them into Greek. More than that, contact with the priests may have transformed his very approach. After the hand-waving philosophical discussions back home, Hipparchus must have been ‘shocked’, says Evans, to discover that the Babylonians were accurately predicting future positions of the sun, moon and planets in the sky. No wonder he made it his mission to make the Greek models just as precise.
In Hipparchus, then, two opposing worldviews collided. The Babylonian arithmetic progressions yielded precise predictions but included no three-dimensional structure, while the Greeks had geometric models but no accurate numbers. Neither approach on its own could produce a complete description of the sky. When they came together, the science of astronomy was born.
Of course, that wasn’t all the Babylonians helped to forge. Entwined with astronomy from the beginning was the parallel discipline of astrology.
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In September 1967, French archaeologists excavating near a Roman sanctuary at Grand in northeast France found broken fragments of ivory at the bottom of an ancient well. Along with pottery, jewellery, fruit stones and shoes, the team eventually recovered nearly 200 pieces from two pairs of ivory tablets, smashed and discarded around AD 170. Their surfaces still hold traces of gold leaf and coloured paint, and they’re beautifully carved with a circle of figures still intimately familiar today, from a crab and scorpion to two scaly fish. They were used for casting horoscopes.
Before Alexander conquered Babylon, the Greeks had plenty of ways to foretell the future, from dream specialists to temple oracles, but there was no particular tradition of reading someone’s fate in the sky. Without the ability to calculate the positions of the sun, moon and stars, the idea of casting a horoscope simply didn’t exist. But some time in the second century BC, after contact with Babylon, a craze for astrology swept through the Greek and Roman world. It reached throughout the Roman Empire but was particularly popular in Greco-Roman Egypt. Elaborate zodiacs start appearing on Egyptian temple ceilings, and papyrus fragments found in ancient rubbish dumps have yielded hundreds of briefly scrawled horoscopes, noting details of the sky at the moment of a person’s birth. James Evans suggests these were astrologers’ notes, summarising information about a client that would be displayed during a consultation on a board like the tablets from Grand. These have portraits of the sun and moon carved in the centre, surrounded by a zodiac circle. Around that are thirty-six decans, groups of stars that the ancient Egyptians used to divide up the sky.
A narrative poem called the Alexander Romance (a fictional version of Alexander the Great’s life, which exists in several versions and originates from the second century AD) includes a passage describing how a similar tablet was used. In the story, the last native Egyptian pharaoh, Nectanebo II, travels to the Macedonian court after being defeated by the Persians, posing as an astrologer as part of an elaborate plan to trick Queen Olympias – who would later give birth to Alexander – into sleeping with him. He tells the queen that the horoscope reveals a ram-horned god will visit her during the night; Nectanebo subsequently disguises himself as this deity. During the consultation, Nectanebo uses a ‘princely and costly board’ made of ivory, ebony, gold and silver, decorated just like the Grand tablets. He opens a small ivory case and carefully pours out gemstones to represent the celestial bodies – crystal for the sun, sapphire for Venus, a blood-red stone for Mars – placing them on the board to show their positions in the heavens at the moment of the queen’s birth. In Greco-Roman times, wealthy clients probably had such consultations in temples and sanctuaries, says Evans. For everyone else, street astrologers may have cast horoscopes in squares and markets, drawing their charts in sand trays or on the ground.
The inspiration for astrology based on birth charts and zodiac signs – the kind we recognise today, popular in New Age websites and self-help books – is often credited to the ancient Egyptians; classical writers say it was invented by a seventh-century pharaoh called Nechepso. Greek astrology did incorporate traditional Egyptian elements – not least groups of stars called decans, originally used to tell time at night – and added features such as the ‘horoscopic point’, the part of the ecliptic rising at the time of birth after which the entire chart was named. But as with mathematical astronomy, the fundamental ingredients of western astrology come from Marduk’s priests.
Since around 400 BC, the Babylonian scribes had been branching out. Instead of just giving predictions for king and country, they made forecasts for individuals based on the position of celestial bodies in the sky at the time of birth. Epping and Kugler deciphered the first Babylonian ‘horoscopes’; a few dozen are now known. One of the earliest, dating from 410 BC, records the birth of a child on the fourteenth night of the month Nisannu, when Jupiter was in Pisces, Venus in Taurus, and the moon was beneath the ‘Horn’ of the Scorpion (the stars of our constellation Libra). ‘Things will be good for you,’ the tablet says.
While the Babylonians’ astronomical techniques enabled Greek astrology, the desire to study horoscopes was in turn a key motivation for Greek astronomers. Hipparchus wrote a now-lost treatise on astrology, with the historian Pliny the Elder remarking that he