stars and that our souls are a part of heaven’. Ptolemy was also an advocate. Alongside the Almagest, he wrote another epic and hugely influential work, Tetrabiblos, in which he summarised the methods of astrology and tried to arrange them in a logical system. Personal qualities ‘which concern the reason and the mind are apprehended by means of the condition of Mercury’, he wrote, ‘and the qualities of the sensory and irrational part are discovered from . . . the moon.’ Ptolemy’s approach differed from the Babylonians in that rather than seeing celestial signs as divine warnings, he believed powers emanating from stars and planets, such as ‘humoral shifts’, could trigger effects on Earth, influencing everything from the weather to personality and health. But he too was driven to achieve mathematical accuracy at least partly because he wanted to read human secrets in the stars.
It took more than a thousand years before scholars in western Europe superseded Ptolemy’s system and constructed our modern, heliocentric view of the heavens. In 1543, Copernicus suggested that the sun, not the Earth, is at the centre of the cosmos, a theory supported by Galileo when he turned his telescope skywards and found, for example, that Venus has phases like the moon. Then, in 1609, Johannes Kepler banished epicycles and equants when he realised that celestial orbits are not circular but elliptical.
For these founding fathers of astronomy, the idea that the stars influence our fate was still embedded in their motivation and world-view. Galileo regularly made astrological predictions for rich clients, and drew up horoscopes for his illegitimate daughters. Kepler hoped to strengthen and reform the discipline, describing himself as ‘throwing out the chaff and keeping the grain’. He discounted the idea that cultural inventions like names or zodiac signs could affect earthly events. But he firmly believed that different qualities of light from the various planets could influence climate and health, and he suggested that just like human beings, the Earth has a soul, sensitive to the harmonies of the stars.
Ultimately, though, astrology was incompatible with the scientific revolution. In 1641, the French philosopher René Descartes famously separated mind from body, consciousness from the material world – part of an inexorable shift in the West towards physical causation as the only acceptable type of explanation. Astronomy and astrology had to go their separate ways: the former making sense of the universe based on objective measurements; the latter emphasising intangible connections and subjective meaning. There could only be one winner. Without an obvious physical mechanism by which distant celestial bodies might affect our lives, the intellectual standing of astrology slowly collapsed.
While scientific astronomy soared, astrology was left to ‘stumble along’, as Nicholas Campion, director of the Sophia Centre for the Study of Cosmology in Culture at the University of Wales, puts it: ‘a system that is dislocated from its cosmology’. For many scientists, it’s a threat that needs stamping out. In the UK, celebrity physicist Brian Cox has described astrology as ‘undermining the very fabric of our civilisation’, while biologist and sceptic Richard Dawkins complains that it is ‘shrivelling and cheapening the universe’.
And yet despite (or perhaps because of) the lack of scientific support, the interest in zodiac signs and horoscopes persists. In fact, astrology is now reportedly rising in credibility and popularity, particularly among millennials seeking guidance, escape and even ambiguity in a stressful, ultra-rational world. Astronomy and astrology might seem complete opposites, even enemies. But in a way they are twins, reflecting two essential sides of our nature, and born of the same fundamental human desire to see patterns, order and meaning in the sky.
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In February 323 BC, Alexander once again approached Babylon with his army. The city’s envoys included an astronomer-priest, Bel-apla-iddina, who warned him that, according to the celestial omens, his life was in danger if he entered the city. The details given by different ancient writers vary: according to one, the priest advised that Alexander should approach Babylon facing east, to avoid catching sight of the setting sun. But the marshy terrain was too difficult for his troops, so the king turned back, and arrived facing westwards after all.
Once in Babylon, Alexander made plans for his next military campaigns – he wanted to attack Arabia in the south, Carthage and Italy in the west. Several Greek and Roman writers recount a story that in May that year, while the king was away from his throne – Diodorus says he went for a massage; Plutarch says he was exercising – an escaped prisoner entered the palace, crowned himself and sat on the empty chair. Alexander’s Babylonian advisers told him to put the man to death. The classical authors seem mystified by this strange event. But recent scholars have suggested that the priests, concerned for Alexander’s life, may have tried to enact the substitute king ritual to save him.
A few weeks later, Alexander attended a drinking party and afterwards fell seriously ill. An astronomical diary for the evening of 11 June 323 BC is the only contemporary record of what happened next. ‘The king died,’ wrote the scribe. ‘Clouds.’
Aged just thirty-three, the career of one of the world’s greatest generals was over and the city’s fate was sealed. Alexander had made Babylon his capital, and was rebuilding Marduk’s temple and the Etemenanki tower. But after his death, his kingdom was split between his generals. Seleucos, who took Mesopotamia, built himself a new capital and forced Babylon’s citizens to move there. Only the priests stayed, diligently recording their nightly observations in the abandoned city.
The region was next conquered in 125 BC by the Parthians from modern-day Iran, and shortly afterwards was subsumed into the Roman Empire. Within a few centuries, Babylon, like the great cities of Nineveh and Uruk, lay buried under the sand, forgotten until the nineteenth-century exploits of Layard and Rassam. It was the end of humanity’s first civilisation, a flourishing of armies and empires, temples and towers, myths and magic, which created many of the foundations from which our own society is built. Its dying breath – the very last cuneiform tablets ever found – date from the first century AD. They are astronomical almanacs, forecasting future events in the sky.
As far as we can tell, people have recognised star constellations and followed the annual cycles of the sun, moon and stars as far back as the Palaeolithic. By the Neolithic, they were starting to shape their cosmos, building monuments to create and capture key moments and effects. But the ability to keep written records – and the administrative system that writing supported – offered the opportunity to vastly extend that control. In a centuries-long effort, the Babylonians transformed a wandering, whimsical sky, plaything of the gods, into a predictable, mathematical universe.
Many civilisations through history have developed mathematical models to describe the sky. Chinese emperors employed teams of astronomers to draw up sky maps and predict events such as eclipses. The Mayans, whose leaders associated themselves with heavenly bodies, counted celestial cycles that lasted millions of years. But the scribes of Enuma Anu Enlil were the first we know of to move from an analogue cosmos to a digital one; the first to swap the messy complexity of reality for the simplicity and power of numbers.
1 Mesopotamia, from the Greek for ‘land between the rivers’, stretched from southern Turkey down to the Persian Gulf.
2 Rassam and Layard didn’t record where they found the different tablets, and the crates became mixed up further after arrival in London, so they are all now treated as one collection.
3 As at Nineveh, the find-spots of these tablets weren’t recorded, and many of them were damaged during recovery and transport. By the time the German team started work, barely any clay tablets were left.
4 Its first appearance before sunset and last appearance before sunrise.
5 This is because Earth and the other planets are all orbiting the sun. Mercury and Venus are closer to the sun, so they always appear close to it in the sky. When they move behind the sun (as seen from Earth) they appear to be going backwards. The other planets (Mars, Saturn, Jupiter) are further from the sun than we are, so sometimes we overtake them on the inside.
6 Rather than tracking celestial bodies through the zodiac, the priests were most interested in computing the times and positions of key events – such as a new moon or lunar eclipse, or the moment at which a planet stops or changes direction – as these were what