Rotational superradiance detected for the first time in a water...

Rotational superradiance detected for the first time in a water vortex flow which may mimic the effect of some kind of black holes (rotating black holes).

From the paper’s abstract:

We observed that waves propagating on the surface of water can be amplified after being scattered by a draining vortex. The maximum amplification measured was 14% ± 8%, obtained for 3.70 Hz waves, in a 6.25-cm-deep fluid, consistent with the superradiant scattering caused by rapid rotation. We expect our experimental findings to be relevant to black-hole physics, since shallow water waves scattering on a draining fluid constitute an analogue of a black hole, as well as to hydrodynamics, due to the close relation to over-reflection instabilities.

Picture (from one of the authors, Silke Weinfurtner) via Science News: Water circling a drain provides insight into black holes