For decades, scientists have grappled with a complex mystery of physics: Could the immense amounts of energy theoretically produced by rotating black holes ever be tapped by human hands?
If future societies were somehow able to deliver this amazing feat, the power supply of distant galactic civilizations would seemingly be assured – and now scientists have a new explanation for how such an exotic extraction could ever be possible .
“Black holes are usually surrounded by a hot ‘soup’ of plasma particles that carry a magnetic field,” explains Columbia University astrophysicist Luca Comisso.
“Our theory shows that when magnetic field lines are properly disconnected and reconnected, they can accelerate plasma particles to negative energies and extract large amounts of energy from the black hole.”
Comisso’s new work – co-authored by physicist Felipe A. Asenjo of Universidad Adolfo Ibáñez in Chile – offers a new prism for glimpsing how energy extraction from a spinning black hole might work.
Given their extreme mass, it is only natural to assume that black holes also contain an extreme amount of energy. Sadly, it’s all locked up at the bottom of a slippery space-time pit.
Under conditions where that mass rotates, it might be possible to dip a toe into this immense pool of energy while dragging the slopes of spacetime.
The physicist and mathematician Roger Penrose of the Emminent University of Oxford suggests an ingenious method. In what became known as the Penrose process, in theory energy could be extracted from the region outside a black hole’s event horizon, called the ergosphere, within which spacetime is distorted by the effects of the black hole’s rotation.
Penrose’s calculations suggested that if a particle splits in two in the ergosphere, with one piece falling into the event horizon and the other escaping the black hole’s gravity, the energy generated by the escaping object could theoretically be recovered, so practically impossible.
This famous idea was experimentally verified by scientists in an article published just a few months ago, but it’s not the only proposed way to harness the energy of a spinning black hole.
Hawking radiation, based on quantum mechanical emissions, is another way, known as the Blandford-Znajek process, in which energy can be extracted electromagnetically through the magnetic field around a black hole.
In Comisso and Asenjo’s analysis, magnetism also plays a central role – particularly as magnetic field lines break and reunite in the ergosphere – but it also reformulates part of the thinking of the Penrose process.
Since magnetic reconnections occur outside the event horizon – splitting plasma particles accelerated to speeds approaching the speed of light in two different directions – one plasma stream can fall into the event horizon while the other escapes.
From the perspective of the black hole, the falling particle would be drenched in a negative amount of energy. From outside the black hole, the exiting particle would have positive energy that could be put to work.
Through this method, escaping plasma streams of replenished energy could theoretically serve as an almost unlimited source of free energy, as long as the black hole swallows at least negative energy plasma.
“We have calculated that the plasma energization process can achieve 150 percent efficiency, much higher than any power plant on Earth,” Asenjo explains.
“Achieving more than 100 percent efficiency is possible because black holes leak energy, which is given away for free to the plasma escaping from the black hole.”
While it may be unlikely that we will ever be able to practically exploit this power generation in some way, that doesn’t mean it is completely useless.
From an astronomical perspective, the phenomenon could be the flares of black holes, representing massive emissions of radiant energy going into space unused.
“Unlike the Blandford-Znajek process, in which the extraction of rotational energy is obtained through a purely electromagnetic mechanism, the energy extraction mechanism described here requires a particle inertia that is not zero,” the authors write.
“This mechanism also differs from the original Penrose process as dissipation of magnetic energy is required to produce the negative energy particles. It is clear that all mechanisms extract the rotational energy of the black hole by feeding the black hole with negative energy. and angular momentum. “
The findings are reported in Physical assessment D.