A new approach for the determination of the temperature of rotating bodies is described, which makes use of the fact that the sample is rotating with virtually no friction. The basic principle is that a temperature change causes thermal expansion, and hence a change in the moment of inertia which, due to conservation of angular momentum, results in a change of rotational frequency. The method was used to determine the temperature of a magnetically suspended cylinder of pure iron within ±5 K while cooling down from 800 to 300 K. The contact‐free suspension is ideally suited to study the radiative interaction of the sample with its environment. It is shown that on the basis of the Stefan–Boltzmann equation the time constant of radiation exchange and the emissive power of the sample can be evaluated. From the results of these investigations the measuring limit of a spinning rotor vacuum gauge due to temperature fluctuations can be estimated.