Ringworlds

When the Earth is no longer enough

Art showing futuristic Ringworlds by Arkkus.

A Ringworld has three million times the living area of planet Earth. Artificial oceans and waterfalls gush around manmade chains of islands and lush green continents. They are roughly the same size as the ones on which we live today. Frosty mountains of brutal thousand-mile heights create a jagged landscape from where they trim the edges of the ring. And the mountains aren’t purely decorative, either — they serve as a kind of wall to contain the atmosphere of the Ringworld, home to every kind of environment from gold and grainy deserts to the sucking, slurring mud of the wetland swamps. The megastructure is so huge that — serving as the setting for Larry Niven’s 1970 science fiction novel — one of the characters goes on to proclaim that he must live forever in order to explore every inch of the never-ending terrain. Trillions of people can call this place home. To explore all 600 million miles of it requires much more than a human lifetime. And it also takes much more than a lifetime to build.

The resources required are so vast that by the time the Ringworld (also known as a Niven Ring) is constructed, there wouldn’t be much left of the Solar System but a few lingering rocky bodies and perhaps two or three planets that we could manage to spare. At the very least it would require as much matter as contained within the gas giant Jupiter.

After material had been sourced from the planets, machines would continue most of the work by forming it into plates that could be strung together into a ring. Efficient use of material is important in crafting the Ringworld. This might mean making mountains hollow or limiting how deep each ocean can reach. The above concept art shows a spacecraft capable of mining asteroids for their minerals.

But a good part of our material would come from the comets and asteroids of the Kuiper belt, extending a generous 1.86 billion miles (2.97 billion kilometers) in a region beyond Neptune. Here we’d find the raw material for the artificial world and its millions of tons in weight. The scope of the Ringworld is both what makes it beautiful to imagine and so challenging to engineer. If we are ever to create such an immense habitat then we will be exhibiting a deep control over nature and its laws of physics.

The ring circles the sun at a radius of 93 million miles, or about the distance from the Earth to our yellow star. Because the sun is at the center of the ring, its inhabitants will experience a perpetual daytime that lights and heats the land every hour of the day. It would be difficult even to distinguish one day from the next except by keeping a careful measure of time. To create an artificial nighttime, an inner ring of panels would be situated near Mercury. When a panel is in front of a section of the ring, that region will experience a period of darkness until they are once again between panels, allowing light to pour through into the artificial farmlands and beaches. The day and night cycles are not only more natural and comfortable for our bodies but are important for the growth of plant life as well.

The shadow panels also serve the purpose of collecting energy from the sun and powering the ring. Any energy they gather would be beamed to receivers on the edges of the Ringworld structure. Lasers from these shadow panels would help destroy incoming asteroids or other impactors that can wreak havoc either by causing an explosion or by creating a hole from which the atmosphere might seep into space. Art of the Ringworld and its inner shade panels by Eric Jones.

Really, the Ringworld is part of something much bigger.

Inspired by the concept of another megastructure — the Dyson sphere, which acts as an energy harvesting shell around a star — the Niven Ring is the middle slice of the Dyson sphere. It’s the slice of it we’d call the equator. The advantage of building this part of the sphere over any other is that it’s the only part that’s gravitationally stable. Until we innovate new technology the only way we have of creating artificial gravity is by use of the centrifugal force. Spin the ring fast enough and gravity for the artificial world will feel just like Earth’s as the inhabitants are pressed against the surface of the ring. Adjusting the rate of the spin and the size of the Ringworld will change the strength of gravity. And to get the ring spinning at the necessary 3 million miles per hour would take time. It’d be an incremental project, with the redeeming fact that once it was going at such a high speed it’d be easy to maintain. While space is not entirely frictionless, the amount of friction from ambient gas is so small it’s negligible. A ride on the ring structure would be quite a smooth one.

But the most expensive aspect of the megastructure isn’t the resources, the time, or the clever engineering that must go into it. The biggest cost comes from ingenuity in materials. To withstand the force of the spin and to hold the weight of all its oceans and continents would require a material stronger than any we have today. In fact that kind of strain would break most molecular bonds. It’s this characteristic which binds Niven Rings to old science fiction works and stories with visually astounding settings. A megastructure this ambitious requires using the most powerful of the universe’s four forces — the strong nuclear force. This is the force that keeps together subatomic particles which would otherwise repel each other with their like charges. The ability to influence and control the strong nuclear force would make possible for us architecture on the grandest scales. Even scales like the Niven Ring with its unending continent after continents: one rich, brazen Africa after the other, spaced with the familiar color of so many Americas or even the glassy ice of the Arctics.

To maintain the gravity and to keep the Ringworld in perfect position around the sun, it would be outfitted with rockets at the edges which would provide an explosive, stabilizing thrust whenever needed. The above concept art is from the movie “Elysium”, dir. Neill Blomkamp. In the movie a space station becomes a utopia for its inhabitants, having extracted all the best parts of society and created an artificial paradise. Poverty, pollution, and environmental disasters are left on Earth.

Because many of the challenges of the Niven Ring are due to its size, other ideas propose scaling down the floating habitats from millions of miles across to just over a thousand. These much smaller worlds could be made of carbon nanotubes and wouldn’t require consuming so much of the Solar System. Instead they’d rest at gravitationally stable regions above planets, like satellites at the Lagrangian points of Earth.

Still, Ringworlds aren’t what scientists consider to be the most efficient use of energy. If our descendants have gone as far as to create elaborate, spinning worlds in the generous stretches of space then they could just as well be terraforming planets. Both propositions ask that we progress our technology much further than it is today, for creating artificial worlds or large looming habitats is an act that’s divine in many ways. It’ll be a strange day when we can say we’ve designed an entirely new home on the plain of another planet or fashioned around an unsuspecting star. Something about that will be very monumental; it will generate both a feeling of awe and remorse to know too much of it will be left unexplored. Like the character in Niven’s novel perhaps we’ll look out over our own handmade landscapes and want for immortality. Just to see everything we’ve been able to build.