In one minute

Sushkov, Kim, Dalvit and Lamoreaux report the experimental observation of the thermal Casimir force, driven by thermal rather than quantum fluctuations of the electromagnetic field. Earlier measurements had not settled whether the Drude model or the plasma model correctly describes the low-frequency dielectric response. They measured the attraction between a flat and a spherical gold plate at separations from 0.7 µm to 7 µm, including the electrostatic force from surface potential patches. The data agree excellently, with a reduced χ2 of 1.04, with the Drude-model Casimir force including the 300 K thermal force. The thermal force dominates the quantum one beyond 3 µm, and the plasma model is excluded across the measured range.

Observation of the thermal Casimir force