Acoustic black hole — sonic horizon and phonon pair creation
Unruh (1981) showed that a fluid with a sonic point (where flow speed equals sound speed) is the acoustic analogue of a black hole. Phonons cannot escape the supersonic region, and quantum fluctuations at the sonic horizon produce thermal radiation with T_H = ℏκ/(2πck_B), where κ is the surface gravity (velocity gradient at the horizon). This was experimentally observed by Steinhauer (2016) using a BEC.