This Curved Earth

The Mindletter posted on 25/04/25 written by Dr Kitty Wheater

the earth as seen from space
Full Disk Earth, Apollo 17, 1972

For the many months that I was in the south, with family, recovering from illness, I thought of the curved earth between me and Edinburgh. I trod clay mud underfoot and pictured the sandy soil up north. In the autumn, I wondered about the light falling over Arthur’s Seat and Portobello beach; would it have the apricot glow of a south-eastern September afternoon, or the elegant pallor of a Nordic sunrise? Over winter I thought about how the wind would be harsher, the daylight fade sooner. It was a matter not just of north and south but of a different dimension, a subtle tilting of the land. Home and health were out of sight, around a bend in the road.

To keep myself afloat, I turned to a new and unexpected interest: space. I listened voraciously to the audiobooks of Pulitzer Prize-winning Carl Sagan, and consumed science programmes on Radio 4. Slowly, I gained strength; rapidly, as when one’s private conversation with a friend gives rise to the weirdly apposite on Facebook, space and its science rushed upon me from all directions. Space, time, and gravity bent my mind into all sorts of new shapes, even as I discovered the different sizes, curves, orientations, and consistencies of things I had always taken for granted. I wrapped up warm at nightfall to look up at the starlit sky; I found a fuzz of distant galaxies; I wondered at a daytime moon. I thought about my life, and what I would do when I was better. I paid attention to new things in new ways, and it changed me.

I was well by the time Jeff Bezos’s rocket Blue Origin touched into space for ten minutes a couple of weeks ago, with its all-female crew including Katy Perry. The place that it reached – more than a hundred kilometres up – was described as that where you might see the curve of the Earth. It was striking to me that this was definitional: this was the internationally-recognised boundary with space. Definitional, too, was the weightlessness of the crew. It is almost as if distance begets a kind of unreality, a dissolution of body from world, whereby world is far away and body begins a journey back to stardust. Or, perhaps, it is the dissolving of one real, and the emergence of another around the corner.

In Sagan’s seminal 1980s TV series, ‘Cosmos’, he described the discovery over two thousand years ago that the Earth was curved. The Greek Eratosthenes had heard that at noon, a stick placed into the earth at Syene, in modern Egypt, would cast no shadow. But at Alexandria, several hundred miles north, when a stick was held in the earth a shadow remained. If the earth had been flat, the sun’s rays would have struck the equally upstanding sticks at precisely the same angle. The only possible explanation was that the sticks were oriented to the sun in slightly different directions, and that therefore, the earth was curved. 

Eratosthenes then did what any self-respecting Greek scholar would do: he hired a man to pace out the distance of eight hundred kilometres between Alexandria and Syene, so that he could estimate, from the distance and the curvature, the circumference of the entire Earth. His conclusion, 40,000 kilometres, was pretty much bang on. ‘Eratosthenes’ only tools were sticks, eyes, feet, and brain,’ says Sagan. ‘Plus a zest for experiment.’ Yet it would be a long time before the curvature of the earth was uncontested. Indeed, in some places, that time is still to come.

It is dizzying when things are not as we think they are, when the shadow over here and the shadow over there are different, when we find ourselves occupying a space that is distant from the one we had come to know, when the world curves in a manner we did not expect. Discombobulation is hard work; eight hundred kilometres is a long walk; illness is a world apart. There are times when the future seems out of sight, lurking in an unfriendly vastness. And so we might find ourselves overtaken by feelings as big as the ocean, as dark as the great void of outer space. We forget that difference, distance, and change are intrinsic to life, to being a body in motion, whether our own or the Earth’s. We forget that even if we have fallen out of the world, we are still here.

So is the world, all its 40,008 kilometres around, most of which we’ll never see. Choose it for your sticks, eyes, feet, and brain; find a zest for experiment; walk its winding roads that always, inevitably, disappear behind the horizon. Find a reality big enough to contain your life, and find, too, that it was there all along.

Warm wishes

Kitty

Carl Sagan giving a talk
"Carl Sagan (Cosmos)" by trackrecord is licensed under
CC BY-NC-ND 2.0.
To view a copy of this license,
visit https://creativecommons.org/licenses/by-nc-nd/2.0/?ref=openverse.
earth as seen from voyger 1 as a pale blue dot
"Pale Blue Dot — Earth from Voyager 1" by Lights In The Dark is licensed under
CC BY-NC-SA 2.0.
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visit https://creativecommons.org/licenses/by-nc-sa/2.0/?ref=openverse.