In one minute

Weinfurtner, Tedford, Penrice, Unruh and Lawrence use the mathematical analogy between fields in curved spacetime and long surface waves on moving water. Long waves moving upstream over a streamlined obstacle are blocked in the fast flow and converted into short waves, the analogue of stimulated emission at a white hole. Measured amplitudes of the converted waves follow a Boltzmann distribution, showing the conversion is thermal. The ratio stays thermal even though water waves have a different dispersion relation from the one Hawking used, which strengthens trust that the effect does not depend on short-wavelength physics. The effect survives turbulence and viscosity, attesting to the generality of the Hawking process.

Measurement of Stimulated Hawking Emission in an Analogue System