In mathematics, an equation is a formula that sets one or more numbers or mathematical symbols equal or unequal to another set of set of one or more numbers or mathematical symbols whose operation is governed by specific rules. In 1918, American historian 1918 William Thayer, in commentary on the previous work of American physical historian Henry Adams, posited the future would see the arrival of a “common formula” that would unite history and thermodynamics: [1]

“The time may come when human affairs may be described no longer by words and sentences, but by a system of symbols or notation similar to those used in algebra or chemistry … then it may be possible to invent a common formula for thermodynamics and history.”

The best candidate for this common formula, to note, as things currently stand, is the Goethe-Helmholtz equation, shown below:

Famous equations
A few of the biggest or most-famous equations in thermodynamics are listed below:

Equation	Name	Date	By	Description
(add)	Gibbs-Helmholtz equation
● PV = nRT	Ideal gas law	1893	Walther Nernst
● S = k ln W	Planck entropy (statistical entropy)	1901	Max Planck
● E = mc²	Mass-energy equivalence	1905	Albert Einstein
● ΔG < 0	Lewis inequality (for a natural process)	1923	Gilbert Lewis
● ΔG° = –RT ln K	Standard free energy of formation	1923	Gilbert Lewis
● ΔG = –nFE	Electric work (Galvanic free energy change)	1923	Gilbert Lewis
● A = –ΔG	Goethe-Helmholtz equation	1923 1936 2007	Gilbert Lewis Theophile de Donder (Libb Thims)

See also
● Equation of love
● Equation of state
● Equation overlay method
● Bridgman’s thermodynamic equations

References
1. Thayer, William R. (1921). “Vagaries of Historians”. Annual Report of the American Historical Association (pgs. 77-88, esp. pgs. 80-84). G.P.O.

External links
● Equation – Wikipedia.