Laboratory systems simulating black hole properties using fluids, light, or quantum gases.Analogue black holes are laboratory systems that mimic the key properties of astrophysical black holes—such as event horizons, Hawking radiation, and thermodynamics—using entirely different physical media. These systems allow researchers to test predictions of gravitational physics that are otherwise impossible to observe directly, from quantum effects near horizons to the thermodynamics of spacetime itself.
The concept was proposed by William Unruh in 1981, who noted that sound waves in a moving fluid behave like fields in curved spacetime. The first experimental realizations came in the late 2000s with water waves and optical systems, followed by quantum gas experiments in the 2010s.
The idea exploits the mathematical analogy between the propagation of waves in a moving fluid (or other medium) and the propagation of light in curved spacetime. In a flowing fluid, if the flow speed exceeds the wave speed in some region, a 'sonic horizon' forms: waves cannot travel upstream past that point, just as light cannot escape a black hole. By engineering such flows in ultracold quantum gases, optical fibers, or even water tanks, physicists can create controllable analogues and study phenomena like Hawking radiation (the quantum emission from the horizon) in a tabletop experiment.
Analogue black holes are used to study Hawking radiation, quantum turbulence, and the thermodynamics of horizons, providing insights that may inform quantum gravity theories. They also serve as testbeds for understanding information loss in black holes.
In 2016, a team at the Technion in Israel created a sonic black hole in a flowing fluid of ultracold rubidium atoms and observed the first signature of Hawking radiation—phonons (sound particles) emitted from the horizon.
