Physical cosmology is the branch of astrophysics dedicated to studying the origin, evolution, and large-scale structure of the universe. It examines the fundamental physical laws and mathematical models that govern the cosmos, addressing questions such as the initial state of the universe and its ultimate fate. Key observational pillars include the measurement of the cosmic microwave background radiation, which provides a snapshot of the early, hot universe, and the analysis of galactic redshift, which confirms the uniform expansion of space over time. Modern models incorporate concepts such as dark matter and dark energy, theorized components that dominate the universe's energy density and dictate its expansion dynamics, providing a comprehensive framework for understanding the evolution from a hot, dense beginning to its current state of structured expansion.