Quantum physics, invented in the 1920s, describes an impossible world. Photons have wave-particle duality – they occupy two incompatible states simultaneously. They can be forced to choose between hese two conditions simply by being observed, and this seems to determine what has already happened. Imagine, Schrödinger proposed in 1935, a cat in a sealed box. The cat will be killed if a photon strikes a sensor. Open the box and you will find out if the cat is alive or dead; before you open the box the cat is both dead and alive because the previous behaviour of the photon depends on our observing it. Moreover, our observing one photon can alter the behaviour of another photon instantaneously, even if they are vast distances apart; and this despite the fact that news of the observation can only travel between photons at the speed of light.
The first person to understand that impossible worlds can be real was the Renaissance doctor, astrologer, and mathematician Girolamo Cardano (1501-1576). Cardano invented what we call imaginary numbers, the square roots of minus numbers, and demonstrated their mathematical power. He also made a lot of money gambling because he was the first to analyse the mathematics of chance events – another link to the world of quantum physics. However, in other respects he was unlucky: one of his sons was by profession a torturer and executioner, and (according to Cardano’s account) a murderer who set up his brother to take the fall. We know such things because Cardano wrote a frank and racy autobiography, only published long after his death.
The premise of Michael Brooks’s book linking Cardano and quantum physics is bonkers but curiously effective. Cardano believed that an angel or spirit guided him through life. Brooks imagines himself as that angel, talking with Cardano as he is held in a prison cell facing trial for heresy, and discussing with him the ways in which his own contributions to mathematics have been taken up within modern quantum physics. The book has a cunningly tricksy beginning and ending (spoiler alert): it begins with Cardano’s great rival, Niccolò Tartaglia, the first to study artillery projectiles as a problem in physics, denouncing him to the Inquisition and being present at his arrest. In fact, Tartaglia had long been dead by the time Cardano was arrested. We have been fed a fake fact, and precisely at the point where we think we are reading history not fiction. By telling us at the end of the book that the beginning was in fact fiction Brooks is trying to have his cake and eat it. This is postmodern cheating.
That’s OK; it’s even amusing. What disturbs me is that it doesn’t seem to have worried Brooks that he and Cardano would have had difficulty in communicating. Here are some words that Brooks uses happily without showing any awareness that they do not have any close equivalents in Cardano’s Latin or Italian, or in his mental world: fact, information, momentum, notation, experiment. Cardano’s algebra contained equations, but they were expressed with words. He had no equals, times, divide, plus or minus signs, or brackets, no letter to stand for an unknown. Imagine Cardano and Brooks communicating through Google Translate and you begin to get an idea of the scale of the problem.
It’s perfectly reasonable to claim that Cardano’s algebra is the beginning of something that leads in the end to the paradoxes of quantum physics. But we shouldn’t turn Cardano into our contemporary.
In a sense one can sympathise with Brooks. His real enterprise, you might argue, is explaining quantum physics not to Cardano, but to someone like me, whose algebra is inferior to Cardano’s and who starts with a Newtonian conception of space, time, and causation. But if he is going to write about Cardano he needs to explain some of the ways in which Cardano’s intellectual culture is radically different from ours; and instead what he does is keep trying to present him as a reasonable person by our modern standards.
I’ll go further in my sympathy with Brooks. He wants to talk to the dead, and history is a form of conversation with the dead – a strange sort of conversation, in which one side speaks a foreign language and only repeats what they have already said before, but a conversation nonetheless. Why, we ask, did Cardano think astrology was a rational undertaking? And we turn to what he wrote, and try to work out what his answer to the question (which he could surely have understood) would have been. But the whole point of the enterprise is that it involves entering a foreign world; Brooks, instead of struggling with Cardano’s texts, goes to a modern astrologer and has his own horoscope read, thus short-circuiting the whole endeavour of learning about Cardano by reading Cardano himself.
Policing genre boundaries is no fun, and I’ve been on the receiving end of the genre police, who tell me historians can’t write about progress. Yet the whole point of writing history is that historians don’t make things up. I once had an editor who made it clear that she would have liked recipes, sex scenes, accounts of the weather. And so would I, but I couldn’t find them in the sources. Unfortunately I wasn’t writing about Cardano, who in his autobiography, De vita propria liber, provides them all.
Brooks has permitted himself to mix fiction and fact, and left his readers unclear as to which is which; the result is a strange and innovative text – part popular science, part historical fiction, part history, part science fiction. For me it doesn’t work; but others will love it
David Wootton is the author of “The Invention of Science” (Penguin)
The Quantum Astrologer’s Handbook
Scribe, 256pp, £16.99