Megastructures

Megastructures are hypothetical artificial constructs built on astronomical scales designed to interact with stars, planets, or galaxies. They are typically conceived to harvest energy, provide habitat, or enable computation, and are discussed in both speculative science and science fiction. In real-world discourse they are used to explore the limits of technology and energy management, often in the context of the Kardashev scale, which ranks civilizations by energy consumption.

Types and examples commonly considered include Dyson structures around a star, such as a Dyson swarm (a collection of separate energy-harvesting units), a Dyson shell or bubble (a continuous enclosure), and variations thereof. A ringworld is a large, habitable ring encircling a star. Habitat megastructures like Bernal spheres or Stanford toruses are cylindrical or spherical habitats intended to maximize living area. Computational megastructures such as a Matrioshka brain consist of nested shells designed to provide enormous processing power. Stellar engines, including the Shkadov thruster, are proposals to move or alter a star’s trajectory by redirecting part of its energy.

Feasibility and observational status remain uncertain. Building such structures would require resources, materials, and technologies far beyond current capabilities, and no confirmed megastructure has been observed. Infrared searches for waste heat from large-energy-harvesting systems have not yielded conclusive evidence, though technosignature research continues. Megastructures serve as thought experiments in energy economics, thermodynamics, and civilizational scalability, and they feature prominently in speculative scenarios about future advanced civilizations.