Physics is a fundamental natural science that studies matter, energy, and the fundamental forces of nature—gravity, electromagnetism, and the strong and weak nuclear forces. It investigates the physical laws governing the universe, from the subatomic interactions described by quantum mechanics to the large-scale dynamics of celestial bodies. Core branches of the discipline include classical mechanics, which models motion and forces; thermodynamics, which addresses heat and energy transfer; and relativity, which describes the relationship between space and time. Modern physics further explores concepts such as wave-particle duality and particle physics, aiming to provide a comprehensive understanding of reality's underlying principles.