The variational calculus deals with optimum finding problems.
This approach to physics, others than the familiar Newtonian one, starts with optimum- and symmetry-principles instead of tracing back local changes in the motion to local force effects. The local view actually follows from the global optimalization. This way the basic equations of classical mechanics, optics, electrodynamics, thermodynamics, relativity and quantum mechanics are treated in a unified framework; the correspondences become more conscious.
The Newtonian causality and the Galilean relativity principle in the description of physical motion led to a mathematical model based on the variational principle a century later. This was worked out by many; among others by Euler, Lagrange and Hamilton. The basic laws of later disciplines, like the theories of special and general relativity by Einstein or the Schrödinger equation, or the Maxwell equations describing electromagnetic waves including radio waves, light and X-rays, as well as thermodynamics, all can be derived from variational principles.
Tamás Sándor Biró, physicist, Doctor of the Hungarian Academy of Science, lectures at the Technical University in Budapest. He is affiliated to the KFKI Rsearch Institute for Particle and Nuclear Physics in Budapest. As a theoretician he investigates quark matter produced and to be produced at the largest accelerators of the world (CERN, RHIC, FAIR).