A team of researchers has succeeded in recreating for the first time in a laboratory experiment a phenomenon that until now only existed as a theory in the realm of black holes. The experiment demonstrates that the rotation of an object can exponentially amplify electromagnetic waves, mimicking the behavior of a black hole bomb, a concept proposed more than 50 years ago.

It all began in 1971 when physicist Yakov Zel’dovich predicted that a rotating metallic cylinder could amplify electromagnetic waves if it spun fast enough. The idea was inspired by rotating black holes, which theoretically can extract energy from their spin and transfer it to the surrounding waves.

Zel’dovich thought that if a mirror were placed around the rotating object, the amplified waves would bounce back and feed themselves, growing uncontrollably until becoming unstable, turning the device into a sort of “bomb.” Until now, no one had managed to demonstrate this effect in a real experiment.

The Experiment: A Rotating Cylinder and Magnetic Fields

The team, led by researchers from the universities of Southampton and Glasgow, used an aluminum cylinder spinning at high speeds, surrounded by coils that generate a rotating magnetic field. When the cylinder spins faster than the magnetic field, something extraordinary happens—instead of absorbing energy, it amplifies it.

Black hole bomb
Concept and scheme of the experiment. Credit: M. Cromb et al.

The system acts as an amplifier, but when the electrical resistance in the circuit is reduced, something even more curious occurs: the electromagnetic waves begin to grow exponentially on their own, fueled by the background noise of the system.

The Self-Destructing “Bomb”

Under normal conditions, this uncontrolled growth would cause the system to collapse, but the scientists were able to observe another phenomenon predicted by theory: as the cylinder loses rotational energy, its speed decreases until the amplification effect stops, as if the bomb shuts itself off before exploding—a behavior consistent with what would be expected from a black hole losing energy until it stabilizes.

Although the experiment was conducted at manageable scales in a laboratory, it serves to validate physical theories such as the connection between the rotation of objects and the amplification of waves. It also opens the door to future investigations to observe even more exotic effects, such as the generation of waves from quantum vacuum energy—a phenomenon that Zel’dovich also predicted but that has yet to be directly detected.

The study suggests that this principle could be used to develop new types of electromagnetic signal amplifiers or even innovative energy storage systems.

Although the system is far from the scale of a black hole, it shows that the physical principles governing these cosmic monsters also apply in our everyday world. The next challenge, according to the team, is to observe this effect amplifying the tiny fluctuations of the quantum vacuum—something that will require even greater technical advances.

SOURCES

Marion Cromb, Maria Chiara Braidotti, et al., Creation of a black hole bomb instability in an electromagnetic system. arXiv:2503.24034 [quant-ph]. doi.org/10.48550/arXiv.2503.24034

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