Richard Chace Tolman (March 4, 1881 – September 5, 1948) was an American mathematical physicist and physical chemist who made many contributions to statistical mechanics and theoretical cosmology.

Tolman attended the local public schools before matriculating at the Massachusetts Institute of Technology (MIT), where he earned his bachelor's degree in chemical engineering 1903.

[2] In a 1916 experiment with Thomas Dale Stewart, Tolman demonstrated that electricity consists of electrons flowing through a metallic conductor.

"[2] Tolman was a member of the Technical Alliance in 1919, a forerunner of the Technocracy movement where he helped conduct an energy survey analyzing the possibility of applying science to social and industrial affairs.

[2] In 1927, Tolman published a text on statistical mechanics whose background was the old quantum theory of Max Planck, Niels Bohr and Arnold Sommerfeld.

[13][14] In his work on the subject, Tolman built heavily upon the key contributions of Ludwig Boltzmann, J. Willard Gibbs, Paul and Tatyana Ehrenfest.

[2] In his 1934 monograph titled Relativity, Thermodynamics, and Cosmology,[15] Tolman demonstrated how black body radiation in an expanding universe cools but remains thermal – a key pointer toward the properties of the cosmic microwave background.

[16] His investigation of the oscillatory universe hypothesis, which Alexander Friedmann had proposed in 1922, drew attention to difficulties as regards entropy and resulted in its demise until the late 1960s.

[2] During the 1930s, Tolman obtained solutions to the Einstein field equations describing the static spherically symmetric perfect fluid.

[19][20] During World War II, Tolman served as scientific advisor to General Leslie Groves on the Manhattan Project.

[2] At the time of his death in Pasadena, he was chief advisor to Bernard Baruch, the U.S. representative to the United Nations Atomic Energy Commission.