
A Dyson sphere is a hypothetical
megastructure
A megastructure (or macrostructure) is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enorm ...
that encompasses a
star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
and captures a large percentage of its
power output.
The concept is a
thought experiment
A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is ...
that attempts to imagine how a
spacefaring
Spaceflight (or space flight) is an application of astronautics to fly objects, usually spacecraft, into or through outer space, either human spaceflight, with or uncrewed spaceflight, without humans on board. Most spaceflight is uncrewed and c ...
civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Because only a tiny fraction of a star's energy emissions reaches the surface of any orbiting
planet
A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
, building structures encircling a star would enable a
civilization
A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
to harvest far more energy.
The first modern imagining of such a structure was by
Olaf Stapledon
William Olaf Stapledon (10 May 1886 – 6 September 1950) was an English philosopher and author of science fiction.Andy Sawyer, " illiamOlaf Stapledon (1886-1950)", in Bould, Mark, et al, eds. ''Fifty Key Figures in Science Fiction''. New York ...
in his science fiction novel ''
Star Maker'' (1937). The concept was later explored by the physicist
Freeman Dyson
Freeman John Dyson (15 December 1923 – 28 February 2020) was a British-American theoretical physics, theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrix, random matrices, math ...
in his 1960 paper "Search for Artificial Stellar Sources of
Infrared Radiation
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
".
Dyson speculated that such structures would be the logical consequence of the escalating energy needs of a technological civilization and would be a necessity for its long-term survival. A signature of such spheres detected in astronomical searches would be an indicator of
extraterrestrial intelligence.
Since Dyson's paper, many variant designs involving an artificial structure or series of structures to encompass a star have been proposed in
exploratory engineering or described in
science fiction
Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...
, often under the name "Dyson sphere". Fictional depictions often describe a solid shell of
matter
In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...
enclosing a staran arrangement considered by Dyson himself to be impossible.
Origins
Inspired by the 1937
science fiction
Science fiction (often shortened to sci-fi or abbreviated SF) is a genre of speculative fiction that deals with imaginative and futuristic concepts. These concepts may include information technology and robotics, biological manipulations, space ...
novel ''
Star Maker'' by
Olaf Stapledon
William Olaf Stapledon (10 May 1886 – 6 September 1950) was an English philosopher and author of science fiction.Andy Sawyer, " illiamOlaf Stapledon (1886-1950)", in Bould, Mark, et al, eds. ''Fifty Key Figures in Science Fiction''. New York ...
, the physicist and mathematician
Freeman Dyson
Freeman John Dyson (15 December 1923 – 28 February 2020) was a British-American theoretical physics, theoretical physicist and mathematician known for his works in quantum field theory, astrophysics, random matrix, random matrices, math ...
was the first to formalize the concept of what became known as the "Dyson sphere" in his 1960 ''
Science
Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
'' paper "Search for Artificial Stellar Sources of Infra-Red Radiation". Dyson theorized that as the energy requirements of an advanced technological civilization increased, there would come a time when it would need to systematically harvest the energy from its local star on a large scale. He speculated that this could be done via a system of structures orbiting the star, designed to intercept and collect its energy. He argued that as the structure would result in the large-scale conversion of starlight into
far-infrared radiation, an earth-based search for sources of infrared radiation could identify stars supporting intelligent life.
Dyson did not detail how such a system could be constructed, simply referring to it in the paper as a "shell" or "
biosphere
The biosphere (), also called the ecosphere (), is the worldwide sum of all ecosystems. It can also be termed the zone of life on the Earth. The biosphere (which is technically a spherical shell) is virtually a closed system with regard to mat ...
". He later clarified that he did not have in mind a solid structure, saying: "A solid shell or ring surrounding a star is mechanically impossible. The form of 'biosphere' which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star." Such a concept has often been referred to as a Dyson swarm; however, in 2013, Dyson said he had come to regret that the concept had been named after him.
Search for megastructures
Dyson-style energy collectors around a distant star would absorb and re-radiate energy from the star. The wavelengths of such re-radiated energy may be atypical for the star's
spectral type, due to the presence of heavy elements not naturally occurring within the star. If the percentage of such atypical wavelengths were to be significant, an alien megastructure could be detected at interstellar distances.
This could indicate the presence of what has been called a TypeII
Kardashev civilization.
SETI
Seti or SETI may refer to:
Astrobiology
* SETI, the search for extraterrestrial intelligence.
** SETI Institute, an astronomical research organization
*** SETIcon, a former convention organized by the SETI Institute
** Berkeley SETI Research Cent ...
has looked for such infrared-heavy spectra from
solar analogs, as has
Fermilab
Fermi National Accelerator Laboratory (Fermilab), located in Batavia, Illinois, near Chicago, is a United States Department of Energy United States Department of Energy National Labs, national laboratory specializing in high-energy particle phys ...
.
Fermilab discovered 17 potential "ambiguous" candidates, of which four were in 2006 called "amusing but still questionable".
Later searches also resulted in several candidates, all of which remain unconfirmed.
On 14 October 2015,
Planet Hunters' citizen scientists discovered unusual light fluctuations of the star
KIC 8462852 raising press speculation that a Dyson sphere may have been discovered.
However, subsequent analysis showed that the results were consistent with the presence of dust.
A further campaign in 2024 identified seven possible candidates for Dyson-spheres, but further investigation was said to be required.
Feasibility and science-based speculation
Although Dyson sphere systems are theoretically possible, building a stable megastructure around the Sun is currently far beyond humanity's engineering capacity. The number of craft required to obtain, transmit, and maintain a complete Dyson sphere exceeds present-day industrial capabilities.
George Dvorsky has advocated the use of
self-replicating robots to overcome this limitation in the relatively near term.
Some have suggested that Dyson sphere habitats could be built around
white dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
s and even
pulsar
A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...
s.
Stellar engines are hypothetical megastructures whose purpose is to extract useful energy from a star, sometimes for specific purposes. For example,
Matrioshka brains have been proposed to extract energy for computation, while
Shkadov thrusters would extract energy for propulsion. Some proposed stellar engine designs are based on the Dyson sphere.
From May until June 2024, speculation grew that potential signs of interstellar Dyson spheres had been discovered. The seven objects of interestall located within a thousand light-years of Earthare
M-dwarfs, a class of stars that are smaller and less luminous than the Sun. However, the authors of the findings were careful not to make any overblown claims. Despite this, many media outlets picked up on the story. Less fantastical alternative explanations have been made, including a proposal that the infrared from the discoveries was caused by distant dust-obscured galaxies.
Fictional examples
A precursor to the concept of Dyson spheres was featured in the 1937 novel ''
Star Maker'' by
Olaf Stapledon
William Olaf Stapledon (10 May 1886 – 6 September 1950) was an English philosopher and author of science fiction.Andy Sawyer, " illiamOlaf Stapledon (1886-1950)", in Bould, Mark, et al, eds. ''Fifty Key Figures in Science Fiction''. New York ...
,
in which he described "every solar system... surrounded by a gauze of light-traps, which focused the escaping solar energy for intelligent use"; Dyson got his inspiration from this book and suggested that "Stapledon sphere" would be a more apt name for the concept. Fictional Dyson spheres are typically solid structures forming a continuous shell around the star in question, although Dyson himself considered that prospect to be mechanically implausible.
They are sometimes used as the type of plot device known as a
Big Dumb Object.
Dyson spheres appear as a background element in many works of fiction, including the 1964 novel ''
The Wanderer'' by
Fritz Leiber
Fritz Reuter Leiber Jr. ( ; December 24, 1910 – September 5, 1992) was an American writer of fantasy, horror, and science fiction. Along with Robert E. Howard and Michael Moorcock, Leiber is one of the fathers of sword and sorcery.
Life ...
where
aliens enclose multiple stars in this way.
Dyson spheres are depicted in the 1975–1983 book series ''
Saga of Cuckoo'' by
Frederik Pohl and
Jack Williamson, and one functions as the
setting of
Bob Shaw's 1975 novel ''
Orbitsville'' and its sequels.
In the 1992 episode "
Relics" of the TV show ''
Star Trek: The Next Generation'', the finds itself trapped in an abandoned Dyson Sphere; in a 2011 interview, Dyson said that he enjoyed the episode, although he considered the sphere depicted to be "nonsense".
Michael Jan Friedman who wrote the novelization observed that in the TV episode itself the Dyson sphere was effectively a
MacGuffin, with "just nothing about it" in the story, and decided to flesh out the plot element in his novelization.
Other science-fiction story examples include
Tony Rothman's ''The World Is Round'',
Somtow Sucharitkul's Inquestor series,
Timothy Zahn's ''Spinneret'',
James White's ''Federation World'',
Stephen Baxter's ''
The Time Ships'', and
Peter F. Hamilton's ''Pandora's Star''.
Variations on the Dyson Sphere concept include a single circular band in
Larry Niven
Laurence van Cott Niven (; born April 30, 1938) is an American science fiction writer. His 1970 novel ''Ringworld'' won the Hugo Award for Best Novel, Hugo, Locus Award, Locus, Ditmar Award, Ditmar, and Nebula Award for Best Novel, Nebula award ...
's 1970 novel ''
Ringworld
''Ringworld'' is a 1970 science fiction novel by Larry Niven, set in his Known Space universe and considered a classic of science fiction literature. ''Ringworld'' tells the story of Louis Wu and his companions on a mission to the Ringworld, an ...
'',
a half sphere in the 2012 novel ''
Bowl of Heaven'' by
Gregory Benford and Niven,
and nested spheresalso known as a
Matrioshka brainin
Colin Kapp's 1980s
''Cageworld'' series and
Brian Stableford's 1979–1990
''Asgard'' trilogy.
Stableford himself observed that Dyson spheres are usually MacGuffins or largely deep in the backgrounds of stories, giving as examples
Fritz Leiber
Fritz Reuter Leiber Jr. ( ; December 24, 1910 – September 5, 1992) was an American writer of fantasy, horror, and science fiction. Along with Robert E. Howard and Michael Moorcock, Leiber is one of the fathers of sword and sorcery.
Life ...
's ''The Wanderer'' and
Linda Nagata's ''Deception Well'', whereas stories involving space exploration tend to employ the variants like Niven's Ringworld.
He gives two reasons for this: firstly that Dyson spheres are simply too big to address, which Friedman also alluded to when pointing out that the reason his novelization of "Relics" did not go further into the sphere was that it was only four hundred pages and he had just shy of four weeks to write it; and secondly that, especially for hard science-fiction, Dyson spheres have certain engineering problems that complicate stories.
In particular, since gravitational attraction is in equilibrium inside such a sphere (per the
shell theorem), other means such as rotating the sphere have to be employed in order to keep things attached to the interior surface, which then leads to the problem of a gravity gradient that goes to zero at the rotational poles.
Authors address this with various modifications of the idea such as the aforementioned Cageworld nesting,
Dan Alderson's double sphere idea, and Niven's reduced Ringworld (discussed in "
Bigger Than Worlds").
See also
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References
Further reading
*
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External links
Dyson sphere FAQFermiLab: IRAS-based whole sky upper limit on Dyson sphereswith an appendix on Dyson sphere engineering
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