Legacy of Hawking, Penrose and Zeldovich: US Laboratory Recreates Rotating Black Hole Physics with Synthetic Superluminal Rotation
Physicists have made a stationary electronic circuit behave as though it were rotating faster than light, successfully amplifying radio waves through artificial rotation. The experiment reproduces the fundamental mechanism long associated with attempts to extract energy from spinning black holes and was published in the journal Nature.
More than half a century ago, British physicist Roger Penrose proposed that energy could be extracted from a rapidly rotating black hole. A particle entering the ergosphere—the region where the black hole drags spacetime itself—would split into two parts. One part falls into the event horizon while the other escapes with more energy than the original particle possessed, the additional energy coming from the black hole’s rotation.
Soviet physicist Yakov Zeldovich later extended the same principle to waves. According to his calculations, a wave with appropriate characteristics can be amplified when it interacts with a sufficiently fast-rotating object, extracting part of the object’s rotational energy and returning with greater amplitude. This phenomenon is known as rotational superradiance.
Testing these predictions mechanically proved extremely difficult because any physical object would need to be spun at speeds beyond the capabilities of real laboratory equipment. Researchers at the Advanced Science Research Center of the City University of New York bypassed this limitation by replacing actual mechanical rotation with a synthetic analogue.
The team constructed a ring-shaped network of electronic resonators. Although the physical structure remained completely stationary, scientists rapidly and sequentially altered the parameters of individual elements. This created an artificial moving pattern around the ring, causing electromagnetic waves passing through the device to interact with the system as if it were an extremely fast-rotating medium.
The speed of this synthetic pattern could formally exceed the speed of light. Relativity is not violated because neither matter nor any physical component of the apparatus moved faster than light; only the electronically generated pattern of changes traveled at a superluminal rate.
Radio waves possessing the correct angular momentum—a property describing how the electromagnetic field rotates around an axis—gained energy from the periodically modulated medium and were amplified. Waves with different parameters were either amplified differently or not amplified at all, turning the circuit into a selective, broadband amplifier.
The installation did not create energy from nothing or draw it from an actual black hole. The additional energy supplied to the radio waves came from the electronic control system that continuously changed the resonators’ properties. The experiment faithfully reproduced the central physical principle of the Penrose–Zeldovich process without requiring gravity, an event horizon, or a real cosmic rotating body.
The method belongs to Floquet engineering, in which system parameters are periodically varied in time. This approach enables the creation of artificial motion and the study of physical regimes that are inaccessible to conventional mechanical devices. In this case, synthetic rotation established the precise conditions needed for energy transfer to waves carrying specific angular momentum.
The laboratory platform will allow physicists to investigate superradiance, extreme Doppler shifts, and wave interactions with rapidly rotating media under fully controlled conditions. The authors also envision applications in wireless communications, photonics, signal processing, and quantum technologies, although further development is required to transfer the principle to more compact and efficient platforms.