If you type “Why are millennials” into Google, the top result completes the question with “obsessed with astrology”. Never mind the answer; the question alone is likely to incite exasperation among scientists, most of whom would condemn astrology as pseudoscience at its most fatuous and infuriating. Astrology may have long been debunked – there is no reason to suppose that our fate is written in the stars – but it still endures, endorsed by countless trashy magazines and newspapers (and some supposedly serious ones), feeding off our own, self-absorbed vanity.
But the truth, however annoying, is that astrology played an important role in the history of science. Many of today’s scientists might be embarrassed to acknowledge, for example, that the 17th-century German mathematician Johannes Kepler, who discovered the laws of planetary motion, also cast horoscopes for his boss, the Holy Roman Emperor Rudolf II.
A new book by American data scientist Alexander Boxer, who has a doctorate in physics, aims to shift that view. A Scheme of Heaven: Astrology and the Birth of Science explores how astrology was a regular part of what was then called natural philosophy, at least until the time of the so-called scientific revolution in the 17th century that Kepler and Galileo heralded.
Boxer explains how a belief in the “astral influences” of the celestial bodies – the stars, constellations and planets – on events and people on Earth had motivated careful studies of the night sky since ancient times. The extraordinary detail and accuracy of the astronomical observations of scholars such as the Greek mathematician Hipparchus, in the second century BC, were due at least in part to a conviction that only with excellent data could astrological forecasts and diagnoses be reliable.
“The sun, moon and stars were useful for navigation,” Boxer tells me. As for planets, he says, in early times “the motivation for planetary observations had always been astrology”.
There’s no doubt too that astrology had useful spin-offs, much like those often claimed for big science projects such as the Apollo missions and the Large Hadron Collider. Astrological calculations by the ancient Babylonians led them to make new discoveries in geometry. The importance of observing and measuring the heavens helped stimulate the development of accurate instruments such as the astrolabe – a treatise on the subject by Geoffrey Chaucer was the standard reference work throughout the middle ages. The exquisite astronomical data collected by the Dane Tycho Brahe (used partly for drawing up those horoscopes for Rudolf II) was essential to the discoveries of his protege, Kepler.
Boxer is understandably nervous about how his book will be received by his peers. “Invoking the rallying cry of science for a book about astrology, the arch-pseudoscience, may come across as a little preposterous,” he writes.
So will it undermine his credibility as a hard-headed data analyst? “It is a worry, and I’m still worried about it!” he admits. But he adds: “If you’re interested in science and ideas, it always behoves us to recognise that we’re a part of a much longer tradition.”
Boxer became curious about astrology because “it occurred to me that it can be seen as the antecedent of modern data science. If astrology is garbage, how do we know? It seemed to me that a lot of these questions are data questions.”
Astrology proved amazingly resilient as science evolved. You might imagine it would have been dealt a sucker punch when Copernicus rearranged the heavens in the early 16th century by replacing the Earth with the sun at the centre of the cosmos, relegating our home to a mere planet. That idea remained much disputed until the early 17th century, but the observations and arguments put forward by the likes of Kepler and Galileo, and later Isaac Newton, helped to make the Copernican model generally accepted by the end of the century. And what did astrology do? “It didn’t miss a beat,” says Boxer – it just adapted to the new cosmology.
“This wasn’t the first time astrology had faced what should have been an existential crisis,” he explains. The discovery of the so-called precession of the equinoxes by Hipparchus – the roughly 26,000-year rotation of the constellations relative to the Earth – should have profoundly challenged it too. Cynics might say this just shows how unscientific astrology is: it can be adapted to fit anything. But you might see it instead as a reflection of how tenaciously our minds cling to ideas deemed useful.
Boxer points out that astrology as we know it today – those columns predicting what your star sign has in store for you this week – was an invention of the late 19th and early 20th centuries. “Modern astrology is a fascinating social phenomenon,” he says. “It changes from being a scientific and mathematical pursuit to something more social.” This shift, he suggests, was driven by communications media: “The modern 12-sign horoscope is so perfect for a newspaper or magazine.” But with the internet, things may be changing back, he says, because websites and apps make it possible to obtain more personalised astrological predictions based on your personal data – a more “boutique, bespoke” astrology, as it used to be.
Boxer argues that traditional astrology fitted perfectly with a scientific worldview of impersonal cause and effect, where anything becomes “scientific” as long as you can express it in numbers. “Astrology was an expression of a deeply mathematically deterministic view of the human condition,” he says. “That seems to be the direction many of our current technologies are heading – the idea that we can be described pretty well with certain fairly simple algorithms that predict what you’re going to buy, how you’re going to vote, where you’re going to go, when you’re likely to keel over and die.” Boxer sees a direct link between the algorithms used by ancient astrologers for drawing up horoscopes and making predictions, and those used today by companies and data analysts to anticipate our behaviour and life trajectory.
The idea of “astral influences” became untenable, however, once we understood that the only known way the stars and planets could exert a physical effect on us here on Earth is by the force of gravity. But while the gravitational fields of the moon and sun do both cause the tides, their effects on our individual bodies can be calculated to be utterly negligible. Even more so for the other planets; and as for stars many light years away… forget it.
oxer understands why a lot of people don’t find this reasoning convincing. “Purely theoretical arguments tend not to be very persuasive,” he says – people want to see hard evidence. But this has always been hard to get. For one thing, astrological forecasts could be vague enough to fit many outcomes (that, of course, is what the shallow and silly horoscopes in magazine pages rely on). And the existence today of big data sets doesn’t necessarily help. As a data scientist, Boxer knows how perilously easy it is to find spurious correlations in complex figures.
Besides, some links that might seem to vindicate astrology are real. “Are there correlations between people’s profession and their sun sign?” Boxer asks. “In certain cases, yes.” This had been noted in professional sports for decades. But it has nothing to do with the planets – it reflects age differences at the cutoff dates used for junior sports competitions. Still, it means the times of the year at which we were born can influence our lives.
Yet probably the ultimate reason people clung to astrology is one that is not going to go away: it offered hope of making sense of a bewilderingly complicated cosmos, and reassured us that we are a part of its grand design. And though Boxer remains noncommittal on whether there is a smidgen of truth in astrology, it’s not because he thinks there really is some way of reading your fate in the stars, but because the fundamental intuition of astrology is unambiguously true: “Astrology embodies a sense that life on Earth is affected by events in the wider universe” – as shown, for example, by discoveries in the 20th century about the cycle of the sun’s activity, the flux of cosmic rays, and the influence of meteorite impacts on evolution. It’s just that today we call all that astronomy.
• A Scheme of Heaven is published by Profile. To order a copy, go to guardianbookshop.com
How the planets got us talkingAstrology was once thought by almost everyone to reflect how the world works: as the ancient phrase put it, “As above, so below.” It’s not surprising, then, that it infiltrated our languages. Here are some common words with astrological origins:
Disaster From the Greek for “bad star” (dys aster), this word of medieval origin signifies the way stars and planets were thought to be responsible for catastrophic events on Earth.
Influenza Italian for “influence”, this nasty viral disease tends to appear in outbreaks (often seasonal) that were thought to be caused by the influence of an evil star.
Consideration Once, a big decision demanded careful consultation with the stars (Latin: con sidus).
Desire You know when you wish upon a star? That’s when you wish de sidus.
Saturnine A gloomy, melancholic disposition was typical of people governed by Saturn.
Lunacy Temporary bouts of insanity were believed to be induced by changes in the cycle of the moon (Latin: luna).
