Open system

Open system may refer to:

Technical term

Paradigm shift

A paradigm shift is a phrase that was popularized by American physicist Thomas Kuhn to describe the nature of scientific revolutions, or fundamental changes in the basic concepts and experimental practices of a scientific discipline. Kuhn contrasts these shifts to the activity of normal science, which he characterized as scientific work done within a prevailing framework (or paradigm). In this context, the word "paradigm" is used in its original meaning, as "example" (Greek: παράδειγμα).

The nature of scientific revolutions has been a question posed by modern philosophy since Immanuel Kant used the phrase in the preface to his Critique of Pure Reason (1781), referring to Greek mathematics and Newtonian physics. In the 20th century, new crises in the basic concepts of mathematics, physics, and biology, revitalized interest in the question among scholars. It was against this active background that Kuhn published his work.

Kuhn presented his notion of a paradigm shift in his influential book The Structure of Scientific Revolutions (1962). As one commentator summarizes:

Open system (systems theory)

An open system is a system that has external interactions. Such interactions can take the form of information, energy, or material transfers into or out of the system boundary, depending on the discipline which defines the concept. An open system is contrasted with the concept of an isolated system which exchanges neither energy, matter, nor information with its environment. An open system is also known as a constant volume system or a flow system.

The concept of an open system was formalized within a framework that enabled one to interrelate the theory of the organism, thermodynamics, and evolutionary theory. This concept was expanded upon with the advent of information theory and subsequently systems theory. Today the concept has its applications in the natural and social sciences.

In the natural sciences an open system is one whose border is permeable to both energy and mass. In physics a closed system, by contrast, is permeable to energy but not to matter.