megastructure

Megastructure is a term used to describe artificial structures of a scale far exceeding ordinary buildings, often spanning kilometers or more, and sometimes designed to serve planetary or stellar-scale functions. In discussions of future technology and speculative engineering, megastructures encompass constructs that would require resources, energy, and fabrication capabilities beyond conventional infrastructure.

Most commonly discussed forms include Dyson structures for harvesting stellar energy, such as a Dyson swarm (a dispersed collection of satellites) or a Dyson shell (a single enclosing shell around a star); ringworlds, a fictional megastructure proposed by Larry Niven that forms a ring around a star; Matrioshka brains, nested shells used as enormous computational resources; and large orbital habitats or artificial planets built to house populations.

Feasibility remains theoretical and technologically speculative. Proposals face challenges in materials and energy economics, structural stability, thermal management, propulsion and assembly in space, and long-term maintenance. Even starting construction would require advances in mining, manufacturing at scale in space, autonomous construction, and risk management for mega-scale systems.

In science fiction, megastructures are used to explore societal, ecological, and ethical questions about civilization scale, resource use, and the survivability of life in space. In scientific and futurist discourse, they are tied to concepts such as the Kardashev scale, energy capture at stellar scales, and solar energy as a primary driver of civilization.