An outrageous new paper by a mathematician at Kansas State University does just that, positing that a sufficiently advanced alien civilization would likely build starships powered by the radiation thrown off by small black holes — and speculating that astronomers could use gamma telescopes to spot evidence of these black hole starships.

The basic idea, according to mathematician Louis Crane, is that a spaceship powered by a black hole would leave distinctive spillover from gamma rays. He suggests astronomers could detect that spillover using a telescope like the orbital Fermi Gamma-ray Space Telescope.

"If some advanced civilization already had such starships, current [very high energy] gamma ray telescopes could detect it out to 100 to 1,000 light years if we were in its beam," Crane said in a press release. "They could be distinguished from natural sources by their steadily changing redshift over a period of years to decades."

In the course of looking for possible signs of extra-terrestrial intelligence (ETI), scientists have had to do some really outside-of-the-box thinking. Since it is a foregone conclusion that many ETIs would be older and more technologically advanced than humanity, those engaged in the Search for Extra-Terrestrial Intelligence (SETI) have to consider what a more advanced species would be doing.

A particularly radical idea is that spacefaring civilizations could harness radiation emitted from black holes (Hawking radiation) to generate power. Building on this, Louis Crane, a mathematician from Kansas State University (KSU), recently authored a study that suggests how surveys using gamma telescopes could find evidence of spacecraft powered by tiny artificial black holes.

The study, "Searching for Extraterrestrial Civilizations Using gamma Ray Telescopes," recently appeared online. This is the second paper published by Dr. Crane on the subject, the first of which was co-authored by Shawn Moreland (a physics grad student with KSU) and published in 2009 – titled "Are Black Hole Spacecraft Possible?"

In the first paper, Crane and Westmoreland explored the possibility of using Hawking radiation from an artificial black hole. They concluded that it was at the edge of possibility, but that quantum gravity effects (which are currently unknown) could be an issue. In her most recent paper, Crane took things a step further by describing how the resulting gamma-rays such a system would produce could aid in the search for ETIs.

This concept was described by Prof. Philip Lubin in a 2016 study, where he suggested that evidence of ETIs could be found by searching for signs of directed energy. Consistent with Lubin's own research involving lasers for planetary defense and laser propulsion (for NASA and as part of Breakthrough Starshot), Lubin suggested that errant flashes of laser energy (aka "spillover") could indicate a technologically advanced civilization.

In the same way, SETI researchers could rely on gamma-ray telescopes to search for signs of spillover from gamma ray lasers. Dr. Crane said, "If some advanced civilization already had such starships, current VHE gamma ray telescopes could detect it out to 100 to 1000 light years if we were in its beam. They could be distinguished from natural sources by their steadily changing redshift over a period of years to decades. To investigate this, astronomers would need to keep time series of frequency curves of the point-like gamma ray sources. This does not seem to be something they currently do."

What is perhaps most exciting, though, is the fact that astronomers may have already found signs of some Type II Kardashev civilizations that use this type of method for energy production. As Dr. Crane explained, several point-like gamma ray sources have been detected in the universe for which no natural explanation has been given.

Crane also said, provocatively, that he believes astronomers may have already spotted several gamma ray sources "for which no natural explanation has been given."

He also speculated about what it would mean for a civilization to be capable of creating an artificial black hole — and it sounds absolutely epic.

Future observations using space-based telescopes like the Fermi Gamma-ray Space Telescope, and ground-based facilities like the High Energy Stereoscopic System and the Very Energetic Radiation Imaging Telescope Array System, could reveal whether these sources could actually be artificial in nature.

Coupled with next-generation instruments that have greater resolution and imaging capabilities, gamma-ray laser spillover and other potential technosignatures could be out there, just waiting to be identified. In the meantime, humanity still has a long way to go before it can begin to contemplate building this kind of technology.

Much like Dyson spheres, Alderson disks, space elevators, and the ability to move stars, this kind of Type - 2 megaproject is just going to have to wait humanity can tackle a few smaller challenges. Something more our speed, like finding ways to settle on other planets in our solar system, or learning how to use Earth's resources sustainably