Complex system

A complex system is a system made up of many parts that interact with each other. Examples include Earth's global climate, living organisms, the human brain, and large organizations like cities. Because these parts are connected and influence one another, the behavior of the whole system can be very hard to predict.

Complex systems have special properties that come from how their parts work together. These properties include unexpected patterns, self-adjusting behaviors, and feedback loops. Scientists study these systems to understand how the whole is more than just the sum of its parts.

The study of complex systems brings together ideas from many different areas of science and knowledge. It includes concepts from physics, biology, mathematics, computer science, and social sciences. This wide approach helps us solve problems in many fields, from weather forecasting to understanding how societies change.

Types of systems

Complex systems can be different kinds, such as complex adaptive systems, which can change and learn over time. Others are polycentric systems, where many parts work together but also make their own decisions. There are also disorganised systems, where many small interactions happen without forming a clear pattern, and hierarchical systems, which are made of smaller parts that fit together like pieces in a puzzle. Lastly, there are cybernetic systems, which use information to adjust and respond, like when a robot corrects its movements based on what it senses.

Key concepts

Complex systems are made of many parts that interact with each other. Some of these systems can change and learn from experience, called complex adaptive systems. Examples include trade markets, ant colonies, the biosphere, the brain, the immune system, cells, embryos, cities, and human groups like political parties or communities.

A system is decomposable if its parts do not affect each other much, like in a model of a perfect gas. In a nearly decomposable system, the parts do affect each other a little, which is common in social systems. These systems can be separated into groups that work mostly independently but still influence each other.

Features

Complex systems are usually open systems, meaning they are always changing and using energy. They often stay stable even while this change happens.

These systems can sometimes change very quickly when conditions shift, like when a lake suddenly freezes or an economy crashes. Parts of complex systems can also be complex themselves — for example, a city is made of many smaller groups, which are made of people, and each person is made of tiny cells.

Complex systems can show surprising behaviors that aren't obvious from looking at their parts alone. For instance, a group of insects can work together to build something amazing that no single insect could create by itself. Small changes in these systems can lead to big results, for better or worse. Finally, complex systems often have loops where actions affect the system in return, either calming it down or making it grow.

History

In 1948, Dr. Warren Weaver wrote about how science deals with complicated problems that have many connected parts. The serious study of complex systems began in the 1970s, and the first special research center, the Santa Fe Institute, opened in 1984. Many famous scientists have worked there to learn more about these systems.

Later, scientists who study math and physics began looking at economic problems in new ways, mixing ideas from physics with economics. In 2021, the Nobel Prize in Physics was given to three scientists for their important work on understanding complex systems, which helped improve climate change predictions.

Applications

Complexity in practice

When dealing with complicated things, one old way is to break them into smaller, easier parts. For example, companies split their work into different groups, and engineers build things from separate pieces. But this can cause problems when issues happen between those pieces.

Complexity of cities

Cities are very complicated places with many parts that affect each other. If we try to make cities too simple, it can cause big problems. Learning to understand cities' complexity helps us build better, more supportive spaces.

Complexity economics

New tools have been made to help understand how economies grow. These tools come from studies done by groups like the Santa Fe Institute and work by people such as Cesar A. Hidalgo and Ricardo Hausmann.

Complexity and education

Scientists are looking at how ideas from studying complex systems can help in teaching and learning, especially in subjects like physics.

Complexity in healthcare research and practice

Healthcare is a great example of a complex system. It includes many people and groups working together, such as doctors, patients, and governments. Understanding these connections helps improve how we share knowledge and apply research to real medical problems.

Complexity and biology

Scientists also use ideas about complex systems to study living things. For example, they look at heart rates and brain activity to understand health and find illnesses.

Complexity and chaos theory

Complex systems are related to chaos theory, which studies systems that seem very unpredictable. Even though these systems can be hard to forecast, they follow certain rules. Complex systems sit in a middle place between order and randomness, called the "edge of chaos."

Complexity and network science

Complex systems often have many parts that connect to each other, like networks. For example, the Internet is a network of computers connected by links. Other examples include social networks and biological systems.

Notable scholars

Many smart people have studied complex systems to understand how they work. Some famous scholars include Nikola Tesla, known for his work with electricity, and W. Ross Ashby, who explored how systems stay balanced. These scholars helped us learn more about how different parts of a system interact and affect each other. Their work shows how complex systems, like the weather or living things, behave in surprising ways.