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Outline of physics

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Physics is the natural science that studies matter and its motion through spacetime. It also explores related concepts like energy and force. At its most basic level, physics is a general analysis of nature. Scientists use it to understand how the entire universe behaves. In this context, the universe includes everything that physically exists. This means all of space and time, all forms of matter, energy, and momentum. It also includes the physical laws and constants that govern them. Physics is an academic discipline with its own departments, degrees, and specialized journals. It is a scientific field that uses specific terminology to describe the world.

To understand the core of physics, we can look at the atomic hypothesis. The scientist Richard Feynman suggested this was a very compact way to share scientific knowledge. He proposed that all things are made of atoms. These are tiny particles that are in constant, perpetual motion. Atoms behave in a specific way based on their distance from one another. They attract each other when they are a little distance apart. However, they repel each other when they are squeezed too close together. This movement and interaction of particles form the basis of much of physical science.

Physics is divided into many specialized branches. Astronomy is a major branch that studies the universe beyond Earth. It includes the study of the formation and development of the cosmos. This field covers celestial objects like galaxies and planets. It also looks at phenomena like cosmic background radiation. Within astronomy, there are even more specific areas. Astrometry involves precise measurements of the positions of stars. Astrodynamics applies mechanics to the motion of rockets and spacecraft. Physical cosmology focuses on the largest-scale structures of the universe. These sub-fields help scientists tackle different scales of the cosmos.

Other branches of physics focus on smaller or more specific systems. Atomic, molecular, and optical physics studies how matter and light interact. Optics is the specific study of the behavior and properties of light. If we look at non-living systems, we study physical science. However, physics also connects to living things through biophysics. This is an interdisciplinary science that uses physics to study biological systems. Some parts of biophysics are very specific, such as neurophysics. Neurophysics deals with the study of the nervous system. There is even quantum biology, which applies quantum mechanics to biological phenomena.

Mechanics is another fundamental area of study. It is concerned with how physical bodies behave when subjected to forces or displacements. Mechanics is often split into two major sub-fields. Classical mechanics describes the motion of bodies under a system of forces. Kinematics is a part of classical mechanics that describes motion without looking at the causes. Dynamics, however, is the study of the causes of motion and changes in motion. Within mechanics, there is also fluid mechanics. This branch studies fluids and the forces acting upon them. It includes fluid statics, which studies fluids at rest, and fluid dynamics, which studies how forces affect motion.

Physics also explores the very small and the very powerful. Nuclear physics studies the building blocks and interactions of atomic nuclei. Particle physics looks at the fundamental constituents of matter and energy. Quantum physics deals with phenomena that occur on the scale of the Planck constant. This field includes quantum field theory, which applies quantum theory to systems with infinite degrees of freedom. There is also a search for quantum gravity. This is the attempt to find an account of gravitation that is compatible with quantum theory. These fields help us understand the rules that govern the tiniest parts of our world.

The history of physics is a long and global journey. Different cultures have contributed to our understanding of the natural world. There is a history of physics in the medieval Islamic world. European science also developed through the Middle Ages. China and India have long histories of science and technology. Many specific fields have their own histories to trace. For example, we can study the history of atomic theory or the history of astronomy. These historical paths show how our knowledge of matter and motion has grown over time.

Finally, physics is deeply connected to many practical and modern applications. Medical physics applies physical principles to medicine. This includes tools like PET scans, NMR imaging, and radiotherapy. In the environment, geophysics studies the Earth and its surroundings in space. There is even agrophysics, which applies physics to agroecosystems. Some researchers use physics to solve problems in other areas, such as econophysics. This field applies physics methods to the study of economics. Whether studying the motion of air in aerodynamics or the properties of soil, physics is everywhere.

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