Scientists Built a ‘Toy Model' of a Black Hole Bomb—and Brought a 50-Year-Old Theory to Life
An experimental setup mimics a 'black hole bomb' first theorized in 1971.
The spinning cylinder with circuitry is true to the original idea, showing that it can be plausible.
Electrical waves spin off in random ways until they compound and create a runaway effect.
There's nothing some physicists love more than an outlandishly impossible sounding idea, from nuclear fusion power plants to Star Trek's warp drive. (Fusion people, don't come for us—we'll happily share when a plant makes net energy over its operating costs, whenever that may be.) And recently, in a study uploaded to the preprint server arXiv, a team of scientists claimed to have made a very simplified 'toy model' of something known as a black hole bomb. Could this particular decades-old idea be making a move toward real life? The answer is complicated.
A black hole bomb is not a true black hole, obviously, but it is heavily inspired by the massive gravity wells. In 1971, Yakov Zeldovich iterated on Roger Penrose's groundbreaking observations about black holes and wondered if the conditions seen in these structures could be harnessed as energy. Unlike a space superstructure, a black hole bomb might be a graspable human size.
But scientists like Stephen Hawking predicted that, under some conditions, this energy would be too small to measure and verify the theories. Zeldovich, therefore, suggested adding a resonator in the form of a cylindrical mirror surrounding the original cylinder. Like an insulated coffee cup, the added metallic layer would reflect energy back into the black hole, and that energy would accumulate until it exploded outward and shattered the mirror. Others have iterated on these designs ever since.
In this recent study, the research team attempted to take that black hole bomb concept from idea to reality—or, at least, take the first step towards reality by creating a toy model. A toy model is a very boiled down version of a theorized system, as the name suggests. Today, toy models explore things like quantum information theory or nanomaterials—in other recently published research, scientists used one to help model the strength of mismatched shapes and study how a particular arrangement of quantum qubits performs in computing.
To create their toy model, the scientists nested a conductive aluminum cylinder—solid and just four centimeters in diameter—inside three concentric layers of circuitry. The setup was then rotated by an attached direct current motor (not that different from what powers an electric drill or rotating cake plate). As the assembly spun, the waves it produced grew more and more unstable until they achieved a runaway chain reaction effect.
As the spinning cylinder generated positive energy radiating outward, the black hole effect created in its center absorbed all the negative energy, and the positive energy increased even more as the cylinder continued to rotate. But, instead of resulting in the predicted explosion, the team designed their assembly to switch itself off once it reached a certain point, ensuring that it did not explode (a good call, because it sure seems like it could have otherwise).
'[T]he physical ingredients are as proposed more than 50 years ago,' the scientists explained. 'The results show that extraction of rotational energy can be observed at low-frequencies, where the conditions for negative energies (or negative resistances) can be met. Furthermore, it also shows how this unstable regime can be switched on and off as predicted for the black hole bomb.'
In other words, this setup realizes—almost exactly—what the 'golden age' black hole pioneers of the 1960s and 1970s were theorizing. The rest of the way toward a true black hole bomb, the team concluded, is a matter of when, not if. In the meantime, these results must be evaluated and recreated by others.
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