At the edge of science and imagination lies a question once posed by a Nobel laureate and now revisited with fresh eyes: could we one day power an interstellar civilization using the rotation of black holes?
In 1969, physicist Roger Penrose proposed that advanced civilizations might someday harness the immense energy swirling around spinning black holes. Over half a century later, physicist Jorge Pinochet of the Metropolitan University of Educational Sciences in Santiago, Chile, has dusted off Penrose’s idea and given it new life.
“In principle, extraction is possible,” Pinochet told science journalist Robert Lea from Space.com, “and it could be a clean and efficient solution to the complex energy problems we will likely face as a society in the distant future.”
His new paper doesn’t describe an engineering blueprint. Any such technology is well beyond our current reach. Instead, it asks us to look beyond the limitations of our current world — to a far future where black holes may serve as cosmic dynamos. The first step is always daring to push the boundaries.
Cosmic Spin Zones
At first glance, the idea sounds fantastical, impossible even. Black holes are known for their ferocious gravity and impenetrable event horizons. They don’t seem like natural partners for solar panels or power grids. You can’t just strap a turbine on it.
But something extraordinary happens around rotating black holes — also known as Kerr black holes — that separates them from the static variety.
“Kerr black holes are capable of spinning at speeds close to the speed of light in a vacuum,” Pinochet explained. “No other object in the universe could do this because centrifugal forces would tear it apart.”
As these black holes spin, they drag spacetime itself around with them — a phenomenon known as frame dragging, or the Lense-Thirring effect. This creates a swirling region outside the event horizon called the ergosphere, where anything — including light — is swept up in the rotation.
In this bizarre region, objects gain kinetic motion by virtue of simply sitting in the space-time fabric betting pulled by the black hole. So, the idea is to harness this region for energy.
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Nature’s Black Hole Batteries
In deep space, nature has already found a way to tap into this energy. Look no further than quasars — the brilliant jets of radiation beaming from the centers of galaxies. These luminous beacons are powered by supermassive black holes, whose swirling disks of gas and dust heat to millions of degrees as they spiral inward.
Some of that matter is devoured. But a portion is flung outward along the black hole’s poles as relativistic jets, accelerated to nearly the speed of light. This also happens on a much smaller scale with microquasars, where an accretion disk of gas and dust surrounds a smaller black hole with a mass between 10 and 100 times that of the sun.
The energy source behind both quasars and microquasars is the spin of the black hole itself. As they gradually give up this energy, they slow down — eventually becoming static, or what physicists call Schwarzschild black holes, defined only by their mass.
A Particle Trick from the ‘60s
Penrose’s original idea wasn’t about accretion disks, but rather about the ergosphere.
Imagine a carousel spinning without a motor, just from inertia. A child hurls a ball at it, and the ball rebounds faster than it came in. In the process, the carousel slows down a bit — the extra energy in the ball supposedly coming from the carousel’s rotation.
Now replace the child with a highly advanced civilization. Instead of a ball, they launch a particle toward a spinning black hole. Part of that particle escapes — carrying more energy than it arrived with. The black hole slows, ever so slightly.
“What Penrose imagined is that we launch a particle against the direction of rotation of a black hole,” Pinochet said in the interview with Space.com, “and a fragment of this particle returns to us with greater energy than the initially launched particle.”
It’s all real physics. But it’s also wildly impractical.
Engineering the Impossible
Today, we are not even a Type I civilization on the Kardashev scale, which ranks civilizations by their energy usage. We’ve yet to fully harness the energy of our own planet. Pinochet puts us at about 0.7.
To access the power of microquasars, we’d need to be Type II — able to exploit all the energy of our solar system. To tap into quasars, we’d need to leap to Type III, capable of wielding the energy of an entire galaxy.
“Perhaps the greatest difficulty is that to extract energy from a rotating black hole, we need to have one of these objects close to us,” Pinochet said. “As far as we know, there are no black holes in the solar system or its immediate vicinity.”
The closest known stellar-mass black hole, Gaia BH1, is 1,560 light-years away. The closest supermassive one, Sagittarius A*, sits at the center of our galaxy — 26,000 light-years from Earth. Unless we develop the ability for interstellar travel, black hole energy will remain a pipe dream.
So, why bother studying something so out of reach?
“It is important for students to think about black holes and related topics because it contributes to their educational process,” said Pinochet. “It whets their intellectual appetite, and it helps make them better scientists.”
He’s using black holes as a springboard. His upcoming papers discuss phenomena such as Hawking radiation, which shows that black holes emit heat.
“Personally, I study black holes and the universe for the intellectual pleasure it gives me, and because it instils a sense of profound humility in the face of the grandeur of the cosmos,” he said.
That may be the greatest energy of all: curiosity.
The findings were reported in the preprint server arXiv.