System

A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. Every system is surrounded by an environment that influences it. To understand a system, scientists define its boundaries, its structure, and its purpose. These characteristics are expressed through the system's functioning. Systems theory is the scientific study of these complex structures. By looking at systems, we can see how different parts work together to create something larger than themselves.

To study a system, researchers often create a model. A model is a simplified representation used to understand or predict how a system will behave. This process involves defining the system's boundaries. A boundary is a line that separates the entities inside the system from the environment outside. This allows scientists to decide which parts are part of the system and which are not. By using these models, we can analyze the structure and the behavior of the whole entity.

Systems are categorized by how they exchange things with their environment. Most systems are open systems. These systems have input and output flows, meaning they exchange matter, energy, or information with their surroundings. A car or the Earth are examples of open systems. A closed system is different because it exchanges energy but not matter with its environment. A computer or a project like Biosphere 2 are examples of closed systems.

Finally, an isolated system exchanges neither matter nor energy with its environment. The Universe is a theoretical example of an isolated system.

The study of systems has a rich history in science. In 1824, the French physicist Nicolas Léonard Sadi Carnot pioneered the concept while studying thermodynamics. He studied a "working substance," such as water vapor, in steam engines. He looked at how heat applied to this substance allowed it to do work. In 1850, the German physicist Rudolf Clausius expanded this by including the concept of surroundings. Later, the biologist Ludwig von Bertalanffy became a pioneer of general systems theory. In 1945, he introduced laws that applied to many different kinds of systems. In the late 1940s, Norbert Wiener and Ross Ashby used mathematics to study systems of control and communication, a field called cybernetics.

Systems can also be organized by scale through the use of subsystems. A subsystem is a set of elements that is a system itself, but also acts as a component of a larger system. For example, the IBM Mainframe Job Entry Subsystem is a group of components that handle input, scheduling, and output. These components work together within the larger computer environment. In many fields, researchers distinguish between "hard systems" and "soft systems." Hard systems are technical and can be studied with quantitative methods like systems engineering. Soft systems involve people and organizations, often requiring participatory designs.

We see systems applied across many different disciplines. In computer science, an information system uses hardware and software to manage data. This includes library systems like the Dewey Decimal Classification. In economics, an economic system is a social institution that handles the production and consumption of goods. It involves people, institutions, and the relationship to resources. Even in sociology, the human brain and mental processes are recognized as systems. These systems can be natural, like galaxies or living things, or artificial, like man-made structures or conceptual knowledge.

Understanding systems helps us connect different ideas. For example, an open system can be viewed as a transformation process. This is often called a "black box" where inputs are consumed and outputs are produced. A passenger ship is a system where the input is people at a departure point and the output is the movement of those people to a destination. By studying these connections, we can see how a change in one part of a system affects the entire structure. This interconnectedness is the core of how the world functions.