# Portal:Systems science/Article

## Selected articles

Major features of the Solar System (not to scale)

The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, their 165 known moons, three dwarf planets (Ceres, Eris, and Pluto) and their four known moons, and billions of small bodies. This last category includes asteroids, Kuiper belt objects, comets, meteoroids, and interplanetary dust.

In broad terms, the charted regions of the Solar System consist of the Sun, four terrestrial inner planets, an asteroid belt composed of small rocky bodies, four gas giant outer planets, and a second belt, called the Kuiper belt, composed of icy objects. Beyond the Kuiper belt lies the scattered disc, the heliopause, and ultimately the hypothetical Oort cloud.

An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects a wide variety of pathogens, such as viruses and parasitic worms and distinguishes them from the organism's normal cells and tissues. Detection is complicated as pathogens adapt and evolve new ways to successfully infect the host organism.

To survive this challenge, several mechanisms have evolved that recognize and neutralize pathogens. Even simple unicellular organisms such as bacteria possess enzyme systems that protect against viral infections. Other basic immune mechanisms evolved in ancient eukaryotes and remain in their modern descendants, such as plants, fish, reptiles, and insects. These mechanisms include antimicrobial peptides called defensins, pattern recognition receptors, and the complement system. More sophisticated mechanisms, however, developed relatively recently, with the evolution of vertebrates.

The Manila Metro Rail Transit System is part of the metropolitan rail system in the Metro Manila area of the Philippines, the Strong Republic Transit System. Although it has characteristics of light rail, such as the type of rolling stock used, it is more akin to a rapid transit system. It is not related to the Manila Light Rail Transit System, a separate but linked system.

The MRT forms part of Metro Manila's rail transport infrastructure, known as the Strong Republic Transit System, and overall public transport system. One of its original purposes was to decongest Epifanio de los Santos Avenue (EDSA), one of Metro Manila's main thoroughfares and home to the MRT, and many commuters who ride the MRT also take road-based public transport, such as buses, to reach the intended destination from an MRT station.

A polar grid with several angles labeled in degrees

In mathematics, the polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by an angle and a distance. The polar coordinate system is especially useful in situations where the relationship between two points is most easily expressed in terms of angles and distance; in the more familiar Cartesian or rectangular coordinate system, such a relationship can only be found through trigonometric formulae.

As the coordinate system is two-dimensional, each point is determined by two polar coordinates: the radial coordinate and the angular coordinate. The radial coordinate (usually denoted as $r$) denotes the point's distance from a central point known as the pole (equivalent to the origin in the Cartesian system). The angular coordinate (also known as the polar angle or the azimuth angle, and usually denoted by θ or $t$) denotes the positive or anticlockwise (counterclockwise) angle required to reach the point from the 0° ray or polar axis (which is equivalent to the positive x-axis in the Cartesian coordinate plane).

Ecological analysis of CO-2 in an ecosystem.

Systems ecology is an interdisciplinary field of ecology, taking a holistic approach to the study of ecological systems, especially ecosystems. Systems ecology can be seen as an application of general systems theory to ecology. Central to the systems ecology approach is the idea that an ecosystem is a complex system exhibiting emergent properties.

Systems ecology focuses on interactions and transactions within and between biological and ecological systems, and is especially concerned with the way the functioning of ecosystems can be influenced by human interventions. It uses and extends concepts from thermodynamics and develops other macroscopic descriptions of complex systems.

In mathematics and physics, chaos theory describes the behavior of certain nonlinear dynamical systems that may exhibit dynamics that are highly sensitive to initial conditions (popularly referred to as the butterfly effect). As a result of this sensitivity, which manifests itself as an exponential growth of perturbations in the initial conditions, the behavior of chaotic systems appears to be random. This happens even though these systems are deterministic, meaning that their future dynamics are fully defined by their initial conditions, with no random elements involved. This behavior is known as deterministic chaos, or simply chaos.

Cybernetics is the interdisciplinary study of the structure of complex systems, especially communication processes, control mechanisms and feedback principles. Cybernetics is closely related to control theory and systems theory.

Contemporary cybernetics began as an interdisciplinary study connecting the fields of control systems, electrical network theory, mechanical engineering, logic modeling, evolutionary biology and neuroscience in the 1940s. Other fields of study which have influenced or been influenced by cybernetics include game theory, system theory (a mathematical counterpart to cybernetics), psychology (especially neuropsychology, behavioral psychology, and cognitive psychology), and also philosophy, and even architecture.

Management cybernetics is the field of cybernetics concerned with management and organizations. The notion of cybernetics and management was first introduced by Stafford Beer in the late 1950s.

Management cybernetics is the concrete application of natural cybernetic laws to all types of organizations and institutions created by human beings, and to the interactions within them and between them. It is a theory based on natural laws. It addresses the issues that every individual who wants to influence an organization in any way must learn to resolve. This theory is not restricted to the actions of top managers. Every member of an organization and every person who to a greater or lesser extent communicates or interacts with it is involved in the considerations.

Systems engineering is an interdisciplinary field of engineering, that focuses on the development and organization of complex artificial systems. Systems engineering is defined by INCOSE as "a branch of engineering whose responsibility is creating and executing an interdisciplinary process to ensure that customer and stakeholder's needs are satisfied in a high quality, trustworthy, cost efficient and schedule compliant manner throughout a system's entire life cycle, from development to operation to disposal. This process is usually comprised of the following seven tasks: State the problem, Investigate alternatives, Model the system, Integrate, Launch the system, Assess performance, and Re-evaluate. The systems engineering process is not sequential: the tasks are performed in a parallel and iterative manner."

Systems engineering techniques are used in complex projects: from spacecraft to chip design, from robotics to creating large software products to building bridges, Systems engineering uses a host of tools that include modeling & simulation, requirements analysis, and scheduling to manage complexity.

Systems art is art influenced by systems analysis, which reflects on natural systems, social systems and social signs of the art world itself. Systems art emerged as part of the first wave of the conceptual art movement extended in the 1960s and 1970s. Close related and overlapping terms are Anti-form movement, Cybernetic art, Generative Systems, Process art, Systems aesthetic, Systemic art, Systemic painting and Systems sculptures.

In systems art the concept and ideas of process related systems and systems theory are involved in the work and take precedence over traditional aesthetic object related and material concerns. Systems art is named by Jack Burnham in the 1968 Artforum article "Real Systems Art". Burnham had investigated the effects of science and technology on the sculpture of this century. He saw a dramatic contrast between the handling of the place-oriented object sculpture and the extreme mobility of Systems sculpture.