Having read Langley, in 1888, Russian physicist V.A. Michelson published a consideration of the idea that the unknown Kirchhoff radiation function could be explained physically and stated mathematically in terms of "complete irregularity of the vibrations of... atoms". At this time, Planck was not studying radiation closely, and believed in neither atoms nor statistical physics. Michelson produced a formula for the spectrum for temperature: I λ λ = B 1 θ θ 3 2 exp ⁡ ⁡ ( − − c λ λ 2 θ θ ) λ λ − − 6 , where I λ denotes specific radiative intensity at wavelength λ and temperature θ, and where B 1 and c are empirical constants.