'A Ringworld will tend to drift off whenever it gets a chance,' Sandberg says. Any perturbing force from, say, a meteorite strike or a close encounter with another star could throw the Ringworld out of attractive equilibrium and onto on a cataclysmic collision course. Managing the SunĪlthough it would be equidistant from its central star at all points, the Ringworld would not, in fact, be gravitationally stable. The ring could work up to that speed over time and then maintain it with little additional thrusting. But in a frictionless space environment, it could be doable. To get Earth-like gravity, the Ringworld would need to spin at nearly three million miles per hour. 'So,' Niven tells PM, 'I just used the equator.'Ī Niven Ring, then, can be thought of as the slice of the habitat-friendly section of a Dyson Sphere.

Rotating the sphere would create gravity via centrifugal force, but only the equatorial regions would reap the benefits. In its usual science fiction presentation as a 'ping pong ball around a star,' Niven said, a solid Dyson Sphere lacks gravity. When imagining the ring, Niven had started with the concept of a Dyson Sphere, an idea explored by physicist Freeman Dyson a decade prior to Ringworld's publication. According to Anders Sandberg, a research fellow at Oxford University's Future of Humanity Institute who has studied megastructure concepts, a Ringworld 'is an amazingly large structure that's way beyond what we can normally imagine, but it's also deeply problematic.' Establishing Gravity The inner surface could be sculpted like Earth's surface-full of great (though shallow) oceans, soaring mountains, and prodigious farmland-or whatever its builders desired.Ĭould a Ringworld ever be made? While the concept does not bend physics past the point of breaking, it would require truly extreme engineering and an utter mastery of the forces of nature. Mountain 'walls' a thousand miles high would line each rim, preventing the atmosphere from leaking into space. Niven figured a Ringworld would have a thickness of a few thousand feet, and require raw materials with a mass equal to that of Jupiter. It will be some time before anyone complains about the crowding,' Niven wrote in a 1974 essay entitled 'Bigger Than Worlds.' 'The thing is roomy enough: three million times the area of the Earth. The vast landscape could comfortably support perhaps trillions of humans (or another similarly ambitious, technologically advanced race). The ring' would reach 600 million miles across and a million miles tall. Niven imagined a ring with a radius of 93 million miles-the sun-Earth distance-with the sun placed at the center. Sci-fi author Larry Niven conjured up such a megastructure for his award-winning 1970 book Ringworld. Someday, when humankind outgrows planet Earth, we might aim to build a habitat so vast we could never overpopulate it. Play icon The triangle icon that indicates to play

The ringworld engineers