Extraterrestrial Megastructures and the Dyson Sphere
Exploring Freeman Dyson's Conception of Advanced Civilizations That May Obscure the Light of Stars
Imagine a colossal, artificial shell encompassing an entire star system—designed to capture and harness all of the energy emitted by the star. Or perhaps humungous rings surrounding a star system with geoengineered surfaces inside (much like in Larry Niven’s Ringworld or the Halo series of games). Maybe even something grander in scale—could there be a structure that literally spans across lightyears of spacetime somewhere out there in the cosmos?
Seems farfetched, but also entirely plausible.
The concept of extraterrestrial megastructures has long been in the imagination of science fiction and the speculations of astrobiology. There’s a good chance that anyone reading this would have heard of the idea of a Dyson Sphere. One of my personal favorite examples is in an old episode of Star Trek: The Next Generation where the Enterprise gets trapped inside of a colossal sphere in space:
The concept of the Dyson Sphere was famously proposed by the late Freeman Dyson. But how might such a structure be discovered from Earth? Could humanity one day create such a sphere or other megastructure ourselves?
Freeman J. Dyson, a renowned physicist and mathematician, made significant contributions to a variety of scientific fields, including astronomy, quantum electrodynamics, and solid-state physics. Beyond his technical work, Dyson was also known for exploring speculative ideas related to the origins of life, evolution, artificial intelligence, space exploration, and extraterrestrial life. And perhaps his most enduring legacy (at least for the general public) remains the groundbreaking concept he introduced in a 1960 article—an idea that has since come to define what we now call the Dyson Sphere.
.png){kind=link}
Dyson’s 1960 Article: The Birth of the Dyson Sphere
In his original paper, “Search for Artificial Stellar Sources of Infrared Radiation,” Dyson proposed a radical thought experiment aimed at advancing the search for extraterrestrial intelligence (SETI).
During the 1960s, SETI was primarily focused on detecting alien signals through radio waves. Dyson, however, offered a novel approach that extended beyond the familiar pursuit of extraterrestrial signals, drawing inspiration from earlier science fiction works, such as those of Olaf Stapledon.
Dyson’s central premise was simple but profound: As civilizations advance, they inevitably require more energy to fuel their growth.
From the earliest days of our own human society—when we relied on fire for warmth and cooking—our increasing need for energy has driven technological and societal progress. Over time, we’ve harnessed steam, electricity, and nuclear fission, and have now ourselves started exploring the space environment within our own star system. We may one day wish to expand even further. But our advances have come with challenges—especially today as the new developments in AI and quantum computing have been ramping up our need for more sources of energy (having grown up near Three-Mile Island, it’s pretty crazy to think that they might restart the power plant just to power data centers for Microsoft).
In the 1960 paper, Dyson speculated that any advanced civilization, after passing through an industrial phase, would likely face similar challenges to what we have and might develop technology to meet their growing energy needs. He suggested that one conceivable solution could involve constructing a vast structure—a shell—completely surrounding the star of that civilization, capturing all the energy it radiates. This theoretical megastructure would become known as the Dyson Sphere.
The Hypothetical Colossal Sphere
In the original article, Dyson presented a hypothetical star system similar to our own, in which a civilization could build a Dyson Sphere.
For this thought experiment, Dyson assumed that the shell would have roughly the mass of Jupiter—an object so massive that the combined mass of all the other planets in our solar system is only about 40% of Jupiter’s mass. The star in this system would emit energy similar to our Sun, and the radius of the shell would be approximately 2 AU (astronomical units)—about 372 million miles or 598 million kilometers. Dyson also calculated that, even with efficient use of energy, such a shell would naturally heat up and begin emitting infrared radiation—and that’s really one of the most important parts of the concept.
This emitted infrared radiation, Dyson proposed, could offer a specific kind of target in the search for alien life.
An advanced civilization, using a Dyson Sphere, would likely be detectable by the excess infrared emissions from their star. Thus, Dyson’s paper, titled Search for Artificial Stellar Sources of Infrared Radiation, proposed that such civilizations might be found not through radio signals, but through the infrared signatures of their energy-harvesting structures.
Searching for Dyson Spheres: Challenges and Possibilities
A full-scale sky survey to detect infrared signatures from Dyson Spheres remains technologically daunting even today. We’ve done full sky infrared studies (like NASA's Wide-field Infrared Survey Explorer (WISE) and ESA’s Planck Spacecraft) and even the James Webb Space Telescope is an infrared space telescope, but so far we haven’t seen any signs of a Dyson Sphere and might not even have been looking well enough to find them yet (if they could be out there).
Dyson also outlined two potential methods for identifying these colossal structures more easily than just doing surveys in infrared.
One possibility is that the sphere might not fully capture all of the star’s energy. Limitations in construction materials could result in a structure resembling a series of bands, rather than a continuous shell. This partial Dyson Sphere might appear more like the concept of ringworlds and halos, which have now certainly entered the sci-fi lexicon.
Alternatively, Dyson considered the possibility of a binary star system, where the star surrounded by the Dyson Sphere could be part of a pair of stars in orbit around each other. In such a system, the second star’s gravitational interactions would reveal the presence of an unseen companion—a clue to the presence of the artificial structure. Searching for infrared sources near binary systems could therefore help scientists detect Dyson Spheres (pretty nifty thinking, right?! Of course, if the megastructure is so big that it encompasses the entire binary system, then we’d still need to be looking in the infrared).
The Search for Dyson Spheres: The Case of Tabby’s Star
Although no Dyson Sphere has been discovered to date, one intriguing anomaly captured the attention of astronomers and enthusiasts alike starting in 2015: Tabby’s Star.
Observations showed irregular dimming patterns in the light emitted by the star, leading some to speculate that a megastructure or even a constellation of megastructures might be responsible. While subsequent research suggests that the dimming is likely due to clouds of dust or debris from destroyed exomoons, the idea of a mega-structure around the star remains a tantalizing possibility (it still is possible that we have already observed a megastructure out there—but we don’t know for sure and should be cautious before jumping to conclusions).
As our technological capabilities continue to improve, the search for Dyson Spheres and other megastuctures may become more fruitful.
With more sensitive instruments and better survey methods, we may one day detect these immense artificial constructs.
Here’s an awesome video from Kurzgesagt – In a Nutshell that explores the idea of Dyson Spheres a bit more:
Freeman Dyson’s Legacy
Freeman Dyson passed away in 2020 at the age of 96—a lifetime filled with groundbreaking work and insatiable curiosity.
While many of his ideas may be relegated to the annals of history, Dyson’s vision for the future of space exploration, energy, and extraterrestrial intelligence remains influential. His conception of Dyson Spheres may one day become more than just a theoretical idea—it may one day become a reality. Not just for us finding some alien neighbors who’ve built megastructures, but perhaps even for ourselves (or whoever/whatever comes after us here in our solar system).
In closing here, we might reflect on Dyson’s own words from his 1960 article:
One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.
Perhaps one day, we’ll make that discovery—and perhaps we’ll even create our own Dyson Sphere.
I’m still personally wondering if we may one day discover that not only are Dyson Spheres and megaconstellations possible, but perhaps they could even allow some civilizations to migrate their entire star systems across the galaxy and perhaps between galaxies. That’d be pretty groovy, right?!
This essay is an improved and expanded version of my original article, "Looking Back on Dyson Spheres," published on Sciworthy in 2020.