Pierre Louis Maupertuis

Pier Louis Maupertius

In my spare times usually, I look at the work of mathematicians and physicists of old times and seek the original papers just to understand what was in the mind of the writer. It is still under debate who earns the credit, but Maupertius is the one who first formulated the Least Action Principle. After a little search, I found the English translation Accord between different laws of Nature that seemed incompatible (1744) and Derivation of the laws of motion and equilibrium from a metaphysical principle (1746).

Therefore, I would like to stress that even though the least action principle initially is formulated for the equation of motion of a mechanical system. Later by Hamilton and Lagrange developed the Hamilton and Lagrange formulation of classical mechanics. In 20th century Schrödinger used the principle to write down the famous wave equation for de Broglie waves which is Schrödinger Equation. The interpretation of the Schrödinger equation led to the probability waves in the atomic world and the birth of quantum mechanics. The same principle is also applied in the development of Relativity. Last but not least, it plays the essential role in the development of Quantum Field Theory.

Here the life of Pierre Louis Maupertuis, the one who formulated the Least Action Principle in Wikipedia.

It would also be nice to mention French mathematician Lagrange who formulated the known by his name the Lagrange formulation of classical mechanics. His original work in French (it would be really nice if somebody points to the English translation), and autobiography. Lagrange solves the system in 2nd-order differential equations in n-dimensional configuration space. The configuration space is simply defined as the degrees of freedom in the system.