On Certainty



I’m looking at an old map of the moon – a plump, pitted disk on thick yellowish paper. This is the first scientifically accurate lunar map. The astronomer Giovanni Domenico Cassini made it in around 1679, after years of peering at the moon through telescopes. His map gave a clearer understanding of the moon’s surface than we had of the Earth at that time. You could say it’s a masterwork of certainty.

And for me, certainty is what makes maps so seductive. Maps edit and order the tangled chaos of reality. They solidify the facts from a world of flux. Even as my eye wanders across the moon’s dustbowls, I feel I’m on solid ground.

But there’s something in Cassini’s moon that startles me. If you look closely at the edge of the Sea of Rains [Mare imbrium] where the cliffs of the Heraclides Promontory should be, you’ll see instead the tiny head of a woman. Frustratingly there’s no reason recorded for it being there. So why is there a miniature fiction inside this picture of what seems to be perfect fact?

Some believe the map’s engraver put it there. But surely hawk-eyed Cassini would have noticed. Maybe it’s just a joke. Many have thought that’s all it is. But my itch to know won’t leave it there. And I suspect, by leaving a little mystery intact in his unmasked moon, that’s what Cassini wanted – to tease us with the never-knowing.

When you look at the cliffs and shadows of the Heraclides Promontory through a telescope today it does vaguely resemble a woman’s head. It seems all Cassini did was to exaggerate that resemblance to show how the mind can see things that aren’t there.

And so, impossibly, Cassini’s map is two things at once – an essay in certainty and ambiguity. It seems to be saying that the one can’t be free of the other, that I shouldn’t let the tidy static surface of the map blind me to fluctuating, complex, random reality.

Reason and sanity requires us to accept what is unpredictable and unknown. There are times of course when we need clarity, decisive judgement, plain facts. I want my dentist to know for sure which tooth needs drilling. And I prefer my politicians to be free of doublespeak. But the drive for absolute certainty means not being able to tolerate ambiguity, difference, change. At its most extreme that’s the mindset of the totalitarian and the tyrant who violently force reality to conform to the plan. At its most dreary, it’s the person who wants a world free of questions.

This makes me wonder how much I’ve started playing a part in an economy of certainty where facts and opinions are traded like commodities, stockpiled for status – and where good questions are devalued in favour of neat answers. But Cassini’s mysterious little figure in the map poses questions that I can’t answer with fact. I can only wonder and speculate why it’s there. And that, ultimately, feels like a liberation. This splendidly unfathomable thing throws me back on my imagination. It opens up a universe of possibility and dreaming in place of the mental poverty of total certainty.

Cassini was an early pioneer in the drive to map, measure and know the universe. But to me it’s just as important that his great achievement also contains a petition for dreaming, wonder and doubt. The mysterious figure in his moon seems to stand for acknowledging the limits of certainty, and that the fullness of existence exceeds the maps we make of it. As we measure and account for everything in ever-closer detail, I hope that’s something we never forget.

Now looking at the map again I’m caught in a curious tension between wanting to know and hoping I never find out why Cassini put a figure in his moon. So, I hesitate to ask this, do you think you know?

This essay was commissioned and recorded as the leader piece for BBC Radio 4’s Human Zoo programme on the theme of Ambiguity (Series 1, ep. 6, 9Apr13). You can listen to the whole the programme, and hear me reading the essay, here.

Image: Carte de Lune by Giovanni Domenico Cassini, c. 1679 (reissued 1787). Copyright: The British Library Board [Maps K.Top.1.88].