The statistical spread of energy values among the states of a system.Energy distribution describes how the total energy of a system is spread among its microscopic states—particles, modes, or configurations. In thermal equilibrium, this spread follows universal patterns, such as the Boltzmann distribution, where higher-energy states are exponentially less populated. The concept underpins statistical mechanics, linking the chaotic motion of atoms to macroscopic properties like temperature and entropy.
Ludwig Boltzmann formalized the statistical distribution of energy in the 1870s, building on Maxwell's earlier work on molecular velocities.
At a given temperature, particles constantly exchange energy through collisions or interactions. The probability of a particle occupying a state with energy E is proportional to exp(-E/kT), where k is Boltzmann's constant and T is temperature. This exponential weighting emerges from counting the number of ways energy can be shared among many particles, favoring configurations with energy spread as evenly as possible.
Energy distributions are used to model heat flow in materials, design efficient semiconductors, and interpret spectra from stars and quantum gases.
The same exponential law that governs energy distribution also describes how the density of Earth's atmosphere decreases with altitude.





