Who formulated the third law of thermodynamics in 1906?

Walther Nernst formulated the third law of thermodynamics in 1906.

Nernst’s work began as the Nernst heat theorem, developed during the period from 1906 to 1912. In broad terms, the theorem says that entropy changes associated with isothermal processes approach zero as temperature approaches absolute zero. This helped establish a thermodynamic framework for understanding matter at extremely low temperatures.

Later formulations refined the idea. Max Planck stated that the entropy of a perfect crystal approaches zero at 0 K, while the unattainability formulation says absolute zero cannot be reached through a finite sequence of processes. These versions are closely related but are not identical in scope or wording.

The historical attribution can become confusing because other scientists extended or reformulated the law. Francis Simon, Nernst’s doctoral student, made important contributions, and the name Nernst–Simon theorem is sometimes used. Gilbert N. Lewis and Merle Randall also gave a later formulation in 1923. Those developments do not change the standard quiz answer: Nernst is credited with formulating the third law.