StefanBoltzmannligningen

The Stefan-Boltzmann law, in its original German form Stefan-Boltzmannligningen, describes the power radiated from a black body in relation to its temperature. Formulated by Josef Stefan in 1879 and later derived by Ludwig Boltzmann, it states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time is directly proportional to the fourth power of the black body's thermodynamic temperature. Mathematically, this is expressed as P/A = σT⁴, where P is the total power radiated, A is the surface area of the body, T is the absolute temperature in Kelvin, and σ is the Stefan-Boltzmann constant. The value of this constant is approximately 5.670374 × 10⁻⁸ W m⁻² K⁻⁴. This law is fundamental in astrophysics for calculating the luminosity of stars and in thermodynamics for understanding heat transfer. It is a key example of a universal law governing thermal radiation.