Physics is the natural science that studies matter, its motion, and behavior through space and time, and that studies the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves.
Physics is divided into two main branches: classical physics, which studies the behavior of matter and energy in the macroscopic world; and quantum physics, which studies the behavior of matter and energy in the microscopic world. Classical physics includes mechanics, heat, electricity and magnetism, light, and sound. Quantum physics includes atomic and subatomic physics, condensed matter physics, nuclear physics, and particle physics.
Physics is essential to the understanding of how the universe works. It has been integral to the development of essential technologies like the telephone, television, computer, and the Internet. Physics is also involved in important medical applications like MRI and CAT scans, and in the development of new materials and energy sources.