Physics is an exact science of nature. It is the study of the outside world and the laws of evolution. Systems modeling ignores the special characters to living beings. It exists in the practice of scientific work necessary to distinguish between experimental physics, theoretical physics and mathematical physics. Physics provides to other natural science methods and techniques: it intervenes in chemistry and physics, astrophysics, geophysics, biophysics.

The old divisions of mechanics, heat, acoustics, optics, electricity, magnetism are supplemented or replaced by: the size of structural elements at the center of modeling: elementary particles, nuclei, atoms, molecules, macromolecules or polymers, grains of material. Characters interact with the origin of phases or states of matter: plasma, gas, liquid, solid. Classical physics is based on earlier theories of relativity and quantum. It is often a limiting case where: either the speed is much lower than the speed of light in vacuum is the discontinuity of the energy levels is impossible to identify.

Physics born with repeated experiences of Galilee does, beyond the principles and conventions emanating from the mathematical patterns as a result that is measurable and reproducible by experience. The method chosen to confirm or disprove the hypothises is based on a given theory. It describes in quantitative models and fundamental things in the universe, seeks to describe the motion by the forces that are exerted and their effects. It develops theories using the tool of mathematics to describe and predict the evolution of systems.

The word natural has a long history, it comes from φυσικη formed on the Greek etymon φυσις, nature. The physica Physika or Greco-Roman is etymologically that relates to the nature or precise knowledge harmonious and cyclical nature called φυσις. It corresponds to the natural sciences or natural philosophy. The significance of this ancient physics no longer suitable for current sciences such as physics, chemistry and biology.

Includes a physical form, usually by field of study, tools and appropriate mathematical formulas. The need for such a form is that most forms physical, and especially when we work in coordinate systems exotic are impressively complex.

Physics is a science that one expression most accurate and useful for making predictions is the language of mathematics. Physical laws reflect the phenomena and observation, and their mathematical expression is often short and explicit …

Physics formulas are expressions that show the relationships between matter, energy, movement, and forces in this mathematical language.

In classical mechanics, there are : general quantities, mass and inertia, moment of inertia theorems, newtons laws, galilean transforms, derived kinematic quantities, derived dynamic quantities, collisions, general planar motion, mechanical energy, work-energy equations, potential energy and work, transport mechanics, friction, stress and strain, fluid dynamics, thermodynamics laws, law of gravitation, law of electromagnetism, electric circuit, light, diffraction / interference, relativity.

The history of physics seems to show that it is illusory to think that we will eventually find a finite corpus of equations that can never be contradicted by experience. Each accepted theory at a time eventually reveal its limits, and is integrated into a broader theory. Newtonian theory of gravitation is valid under conditions where speeds are small and that the masses involved are small, but when the speeds approaching the speed of light or the masses (or equivalently in relativity, energy) become important, it must give way to general relativity. Moreover, it is incompatible with quantum mechanics when the scale of study is microscopic and under conditions of very high energy.

Many philosophers, including Immanuel Kant, have warned against any belief that human knowledge of phenomena may coincide with the real, if it exists. Physics does not describe the world, its findings do not relate to the world itself, but the model deduced from a few parameters studied. It is an exact science in that the basic assumptions and parameters considered leads to an accurate conclusions.

The modern conception of physics, particularly since the discovery of quantum mechanics, is not given more generally as the ultimate goal of determining the root causes of physical laws, but only to explain how a positivist approach. We may also retain the idea of Albert Einstein on the work of physicist doing physics is like issuing theories on the workings of a watch without ever being able to open.