A Dyson Sphere is the natural consequence of an advancing civilisation with growing energy needs. It is a megastructure that harnesses the entire energy output of a star. The concept was initially dreamed up by Freeman Dyson, a British-American mathematician and physicist in 1960. It has been a science fiction staple, that is also well studied by scientists. Such a megastructure would be a marvel of engineering that even the brainiest aliens may not be able to pull off.
A structurally solid, homogenous Dyson Sphere is mechanically impossible. The stresses would tear it apart. In the 1970 novel Ringworld, Larry Niven described an artificial ring constructed around a star, with a habitable interior surface. Such spinning hoops are called Niven Rings and are a stability nightmare. Swarms or loose, free-moving orbiting collectors are much more feasible, but collecting the material necessary would require the disassembly of entire planets.
A solid Dyson Sphere about the size of Earth’s orbit, with a shell about a metre thick would require as much mass as Jupiter. Only the remote cores of gas giants are solid, and they may well be diamonds the size of Earth, difficult to extract and use. For a rigid sphere at least, the material will have to be tough enough to withstand pressures of 10¹³ N/m², tougher than diamonds. Terrestrial worlds could be ripped apart to construct a shell made up of free-floating platforms. A far more practical approach to reduce the material costs is to construct a Dyson Sphere around a White Dwarf star, the core of a dead star glowing in leftover heat.
Thicker shells would allow for lower densities but would require more material, and could buckle under the influence of gravity. Such a design would require a shell 100 km in thickness. The thermal and optical properties of any construction materials have to be carefully evaluated. Graphene, with its high melting point, is a viable option. Very thin Dyson Spheres with low mass densities in the range of 0.8 g/m² would be less mechanically unstable because of radiation pressure balancing gravitational forces. Opaque metallic metamaterials in films only a few nanometres thick embedded with dipole antennas can reduce the amount of material required. Dyson Swarms could also use photovoltaic panels or microscopic antennas. Dyson Sphere tiles could also be designed as light sails, which could easily escape the system.
The structure would be a microgravity environment, especially if the material is thin. One approach is to genetically engineer the residents for life in microgravity. It is possible to increase the speeds of the platforms to provide simulated gravity, but the poles would still be in microgravity. Complex designs with multiple nested, rotating rings might work, if positioned at different latitudes around the star. Different angular velocities can create usable regions, allowing for more energy capture than a single ring. Dyson Disks maintaining a constant orientation towards the host star can be the scaffolding for the construction of a Dyson Sphere. A Dyson Bubble could be made up of a large number of thin collectors, a stationary array of light sails. Nested Dyson Shells operating at different temperatures to maximise energy use for computational purposes is an advanced concept called a Matrioshka Brain.
Dyson spheres may be like unicorns, beautiful and mythical. Dyson Swarms and Rings may be more practical because they bring down the steep material costs. A spinning heliocentric hoop may provide the right amount of gravity. Around pulsars, the rings can have even lower material costs. The construction of a Dyson Sphere is a monumental undertaking that can allow a civilisation total energy dominance. Such Dyson Spheres would leak waste radiation in infrared light, detectable over astronomical distances. Automated surveys have picked up stars that are glowing in more infrared light than expected. A fraction of these may be hosting Dyson Spheres. Humans may have already spotted alien megastructures.
Image Credits: GPT 4o, Qwen
Sources:
Dyson Spheres around White Dwarfs
Interstellar Objects from Broken Dyson Spheres
Sunscreen: Photometric Signatures of Galaxies Partially Cloaked in Dyson Spheres
On the possibility of the Dyson spheres observable beyond the infrared spectrum
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