Reports of the discovery of Kepler-16b, a planet that inhabits a binary star system, have been quick to compare it with Tatooine in the film Star Wars. Apparently the image of Luke Skywalker contemplating his planet’s double sunset for the last time before escaping to a life of interstellar adventure is deeply inscribed in our generation’s collective psyche, even for astronomers and science reporters. But there is a far better sci-fi analogy for planets with more than one sun.
In Isaac Asimov’s 1941 short story Nightfall, a planet that basks in the light of six suns faces one of the rare moments of darkness that bedevil its history. Because one of the suns always shines, night is unknown to this advanced civilisation. There is no such thing as electric light.
Except there is a flaw in this sunny outlook. Only a handful of astronomers have worked it out, and as they barricade themselves in their observatory, they are reviled as cranks. They have calculated that once every 2,049 years a solar eclipse plunges the planet into darkness. Why is this not in any history books? Because every time it happens, the shock of nightfall is so sudden, so inexplicable to the people who live in permanent daylight, that the entire population goes insane. In minutes, society tears itself apart and retreats to the stone age. And today the eclipse is due …
I won’t give away more. This is one of the greatest sci-fi stories ever written. It is profound because it is about us; it casts new light on how our identity is shaped by our sun.
In imagining a world without regular nightfalls, Asimov makes the reader recognise how phenomena we take for granted define everything about us. The earth, as it spins, turns each person away from and towards the sun, inscribing night and day as the fundamental reality of our lives. We rise with the sun, reach the height of activity at noon, and retreat to bed when it abandons us. Seasons, tides, months, years – all are as they are because of our one sun and one moon. It could all be so different.
Early human culture was more immensely aware of these realities than we are today. Neolithic people who aligned monuments according to the winter solstice or ancient Egyptians who built solar boats for Pharaohs to ascend to the heavens lived in constant admiration and dread of the one great light in the sky. What if the sun abandons us for ever? The Aztecs feared it too. Their response – human sacrifice – rivalled the terrors of nightfall in Asimov’s story.
Science and science fiction are apparently inseparable. And as Asimov’s great story of the psychology of light reveals, so are astronomy and art. In Raphael’s painting the Mond crucifixion, a personified sun and moon divide the sky between them. Two suns, or six, would not just mean a more crowded painting, but a totally different conception of life. We face the sun. To face two, we might need two heads. Thinking would be different. Perhaps we would see too much, and no longer open our eyes. Art owes much to our sun, and its regular disappearance.