Of all the unanswered questions in modern science, perhaps the most talked about is whether we are alone in the universe. A new paper looks at another way we might be able to detect advanced civilizations, and at its center is the need for energy.
The more advanced a civilization becomes, the greater their need for energy and one of the most efficient ways, according to current theories, is to harness the energy from an actively feeding black hole. The paper suggests a civilization feeding matter into a black hole could harvest energy from it; more excitingly perhaps, the process could be detectable within 17,000 light years.
The search for intelligent life beyond Earth has been of fascination to scientists, philosophers and even inspired artists over the centuries. With hundreds of millions of stars in our galaxy and billions of other galaxies across the cosmos, it seems the odds are in our favor of finding some other civilizations out there.
The discovery of thousands of exoplanets in latest decades adds to the excitement, so researchers have directed radio telescopes and space probes in the search for aliens. SETI, the Search for Extraterrestrial Intelligence, has been scanning the sky looking for unusual patterns or messages that could reveal an advanced civilization, but despite the effort, there is a distinct lack of success.
A different approach is to search for advanced civilizations based upon their energy signatures. It’s an innovative idea that seeks to identify civilizations based upon artificial patterns in the electromagnetic spectrum. We have certainly seen how human energy demand has increased as we have become more advanced, and so theoretically, any more advanced civilizations would need to harness energy on a scale far in excess of what we currently use. It may be that civilizations use giant megastructures like Dyson spheres to harness energy from stars and it’s the output from these or their impact on the light from a star that may be detectable.
In a paper authored by Shant Baghram and published in The Astrophysical Journal, the team began by categorizing civilizations on the Kardashev Scale. It categorizes advanced civilizations by measuring their technological advancement based upon the amount of energy they are capable of harnessing and using. They also propose an alternate scale based upon the Kardashev scale and the distance a civilization is able to explore space, suggesting the more advanced can explore further from their host planet.
As a paper based purely on a theoretical model, they take the advanced civilization’s category and explore the idea that they may use Dyson spheres around primordial black holes as an energy source. The team also propose observational techniques that may be employed to detect such structures using infrared and sub-millimeter signatures.
They do assert, however, that telescopes like ALMA (the Atacama Large Millimeter/Sub-millimeter Array) is well placed to make observations and even to detect signatures and maybe even megastructures at distances of approximately 5.4 kiloparsecs.
More information: Shant Baghram, In Search of Extraterrestrial Artificial Intelligence Through Dyson Sphere–like Structures around Primordial Black Holes, The Astrophysical Journal (2025).