StefanBoltzmannGesetzgebung

Stefan-Boltzmann’s law is a fundamental principle in physical thermodynamics and radiative heat transfer, describing the total energy radiated per unit surface area of a black body across all wavelengths per unit time. The law is named after the Austrian physicists Josef Stefan and Ludwig Boltzmann, who independently contributed to its formulation in the late 19th century. Stefan initially observed experimentally that the total energy radiated by a black body is proportional to the fourth power of its absolute temperature, while Boltzmann later provided a theoretical derivation using thermodynamic principles.

The law is mathematically expressed as *j** = σT⁴, where *j** represents the total radiant emittance (energy per unit area per unit time), *σ* is the Stefan-Boltzmann constant (approximately 5.670374419 × 10⁻⁸ W·m⁻²·K⁻⁴), and *T* is the absolute temperature of the body in kelvin. This relationship holds true for ideal black bodies, which absorb all incident electromagnetic radiation and emit energy at maximum efficiency for a given temperature.

The law has broad applications in astrophysics, materials science, and engineering. For instance, it helps explain the energy output of stars, including the Sun, by relating their surface temperatures to their luminosity. In practical engineering, it aids in designing thermal management systems, such as radiators for spacecraft or cooling mechanisms for electronic devices. Additionally, the Stefan-Boltzmann law underpins the understanding of thermal radiation balance in Earth’s atmosphere and the greenhouse effect.

While the law provides a useful approximation for many real-world scenarios, actual surfaces often deviate from ideal black-body behavior due to material properties like reflectivity and emissivity. These deviations are accounted for by introducing an emissivity factor, *ε*, such that *j** = εσT⁴, where *ε* ranges from 0 (perfect reflector) to 1 (perfect emitter). Despite its simplifications, the law remains a cornerstone of thermal physics and continues to be a key tool in both theoretical and applied sciences.