To date, no one has found evidence of intelligent extraterrestrial life elsewhere in the universe. However, if it exists, they might be soaring around Dyson spheres orbiting the shells of sun-like stars known as white dwarfs scattered throughout the Milky Way, a new paper argues.
And that is where we should focus our search for extraterrestrial life, says Ben Zuckerman, a co-author of the study and a professor emeritus of physics and astronomy at the University of California, Los Angeles.
Based on the results of such searches, astronomers could estimate how many advanced civilizations might be hiding in the galaxy, he states.
Advanced Civilizations
Dyson Sphere Simulation.
Any advanced civilization requires energy: for food, transportation, conflict, comfort, and convenience. Currently, 7.8 billion people on Earth use about 580 million trillion joules of energy each year, equivalent to the energy output of nearly 14,000 million tons of oil, according to The World Counts. Indeed, almost all human energy comes from fossil fuels, as we lack the understanding of technology to rely on the largest energy source in the solar system: the Sun.
If humanity covered every square inch of Earth’s surface with solar panels, it would generate more than 10^17 joules of energy per second. However, this would still capture only a fraction of the energy radiated by the Sun, approximately 10^26 joules per second.
This is the motivation behind the Dyson Sphere, named after the renowned physicist Freeman Dyson, who developed the idea in 1960. If an advanced civilization truly wanted to harness such vast energy output, they would need to construct a megastructure to capture it, blocking at least some light from the star and converting that energy into useful forms.
Dyson’s initial proposal for a solid sphere (with 100% coverage of the Sun) is unfeasible due to stability issues, as it would be impossible to keep the star at the center, and the entire sphere would disintegrate due to tidal forces and immense rotational stresses. Nevertheless, it is easy to imagine an advanced species constructing rings or a swarm of gigantic structures covered in solar panels to accomplish the task.
Not Viable
However advanced a species might be, and however many Dyson-like objects they construct, they will face the reality that every star has a finite lifespan. If a civilization arises around a typical sun-like star, that star will eventually become a red giant and leave behind a cold white dwarf.
This means that staying on the surface of a planet is not a viable long-term option. It implies that any extraterrestrial beings might pack up and move on, searching for a new system to call home, or establish a series of habitats that can collect radiation from the remaining white dwarf.
According to a new paper written by Zuckerman that was accepted in May for publication in the Monthly Notices of the Royal Astronomical Society, it seems unlikely that an extraterrestrial civilization would choose to undergo the difficulties of traveling to a new star just to build a Dyson Sphere. Thus, they would only construct these megastructures around stars, which will ultimately become white dwarfs.
This allows scientists to draw a direct connection between the lifespans of stars and the prevalence of Dyson Spheres. Therefore, Zuckerman argues that if astronomers search for Dyson Spheres around white dwarfs and find them empty, it could help estimate how many advanced civilizations might exist in the galaxy.
Current surveys of white dwarfs have found no evidence of any Dyson Spheres. Given the total number of white dwarfs we expect to inhabit the Milky Way, Zuckerman estimates that no more than 3% of habitable planets around sun-like stars could give rise to a civilization that chooses to build a Dyson Sphere around a white dwarf.
However, with so many planets surrounding sun-like stars, this calculation only provides an upper limit of 9 million potential Dyson civilizations around white dwarfs in the Milky Way, the researchers conclude.
