Third Law of Thermodynamics

The third law of thermodynamics states that the entropy of a system at thermodynamic equilibrium approaches a constant value as its temperature approaches absolute zero, zero itself for a perfect crystal with a single ground state, though systems without a unique ground state, glasses among them, can retain some residual entropy even there. Walther Nernst developed the principle between 1906 and 1912, giving it the alternate name the Nernst heat theorem, with contributions from his doctoral student Francis Simon; in 1912 Nernst stated it as the impossibility of reaching the isotherm at absolute zero in a finite number of steps, an unattainability that follows directly from the law itself.