THE EXPLAINER
WHAT IS A DYSON SPHERE?
A Dyson sphere is a hypothetical, large mechanical structure – a megastructure – designed to harness the energy of stellar nuclear furnaces. The basic idea is that a structure is constructed around a star which converts, stores or otherwise utilises, the star’s radiant energy. These facilities are postulated as the most likely, necessary and economical way of addressing the colossal energy needs of both future human civilisation and, possibly, advanced alien civilisations elsewhere in the cosmos.
WHO THEORISED THEM? AND WHEN?
The Dyson sphere concept is named after physicist Freeman Dyson (19➤3-➤0➤0) who, in 1960, discussed the idea in a short scientific paper concerning methods of detecting alien civilisations. However, Dyson admitted that he was inspired by the highly-acclaimed science fiction novel Star Maker (1937) by British author Olaf Stapledon. In Star Maker, Stapledon described “a gauze of light traps” surrounding every star in the Universe, which “focused the escaping solar energy for intelligent use”. Since then, many scientists have revisited the Dyson sphere concept, usually as part of SETI (Search for Extraterrestrial
Intelligence) research.
COULD THEY REALLY EXIST?
There is, as yet, no evidence that Dyson spheres, or anything similar, exist anywhere in the Universe. However, scientists can say something about whether they are ‘allowable’. Firstly, although such technology is way beyond what is currently possible for Earth-bound intelligence, there are no known insurmountable barriers to their construction. Given enough incentive, resources and technological advancement, Dyson spheres are certainly possible. One researcher estimates that humans could attempt such a feat within the next 100 years or so. Other researchers claim this is wildly optimistic.
Astronomers have actually placed some limits on how many Dyson spheres may be lurking out there in the cosmos. To do this, some assumptions are made about how these structures would affect the emergent starlight of the stars they surround. For example, most designs would block some of their host star’s light, leading to a drop in their optical brightness. They may also result in waste heat that would be emitted as infrared radiation. By looking carefully for such deficits or excesses in the light of thousands of stars, one estimate suggests up to 10,000 stars could host Dyson spheres within a radius of about 16,000 light-years of Earth (by comparison the distance to the Milky Way’s centre is about ➤6,000 light-years). Of course, that doesn’t mean that Dyson spheres do exist, only that they could.