ringworld

A ringworld is a hypothetical artificial habitat consisting of a massive ring that encircles a star at roughly Earth’s orbital distance. The ring’s inner surface is designed to be habitable, providing extensive land and seas. Gravity on the inner surface is produced by the ring’s rotation, creating a comfortable, Earth-like environment for inhabitants. The ring is not a small space station; it is a world-scale structure with far more surface area than a planet.

The concept was popularized by Larry Niven in his 1970 novel Ringworld, where a ring with a radius near 1 astronomical unit and a width measured in millions of kilometers circles a sunlike star. The inner face contains continents, oceans, and weather systems, with a day-night cycle generated by the ring’s rotation and tilt. The Ringworld’s interior is described as an engineered environment maintained by ancient builders in the story.

Ringworlds are distinct from Dyson spheres or Dyson rings; they are not shells around a star but wide rings whose inner surface forms a habitable landscape. Variants and related concepts include cylindrical habitats and other rotating megastructures. The idea continues to appear in science fiction and discussions of future habitat design.

Feasibility remains speculative; such structures require unprecedented materials, energy, and stability management. Real-world discussions treat ringworlds as thought experiments illustrating megastructure challenges, orbital dynamics, and the astronomical scale of future engineering.