In a seminal 1981 paper, he showed that black hole event horizons and sonic horizons in systems like his waterfall – which are now referred to as sonic black holes – can be described by identical equations.
Researchers began plumbing the physics of sonic black holes for clues about actual black holes.
The measurement of the analogous effect in a sonic black hole – in this case, quantum units of sound radiating outward from a sonic horizon – therefore brings a long-standing question to a head: Are sonic black holes true analogues of black holes? More specifically, do Steinhauer’s findings indirectly validate Hawking’s calculation, proving that information is lost in black holes?
If sonic black holes serve as a true analogue, then Hawking’s approximation is correct, the event horizon is an uneventful place, and information gets destroyed in black holes, meaning that the probabilistic rules of quantum mechanics must be replaced by a more fundamental framework.
If Hawking’s approximation is wrong, then sonic black holes are not good proxies for black holes, and quantum gravity might somehow encode black hole histories in their radiation, preserving information as black holes evaporate.
From their perspective, an analogue to Hawking radiation in sonic black holes says nothing about true black holes because the two are categorically different; whereas the fluid approximation is accurate in the case of sonic black holes, space-time must not be approximately smooth at black hole event horizons.
In the majority opinion, the comparison with sonic black holes only reinforces how strange black holes and the theory of quantum gravity must be.