'''Physical cosmology''', as a branch of [[astronomy]], is the study of the large-scale structure of the [[universe]] and is concerned with fundamental questions about its formation and evolution. Cosmology involves itself with studying the motions of the celestial bodies and the [[first cause]]. For most of human history, it has been a branch of [[metaphysics]]. Cosmology as a [[science]] originates with the [[Copernican principle]], which implies that celestial bodies obey identical [[physical law]]s to those on earth, and [[Newtonian mechanics]], which first allowed us to understand those motions. This is now called [[celestial mechanics]]. Physical cosmology, as it is now understood, began with the twentieth century development of [[Albert Einstein]]'s theory of [[general relativity]] and better [[astronomy|astronomical]] observations of extremely distant objects. | '''Physical cosmology''', as a branch of [[astronomy]], is the study of the large-scale structure of the [[universe]] and is concerned with fundamental questions about its formation and evolution. Cosmology involves itself with studying the motions of the celestial bodies and the [[first cause]]. For most of human history, it has been a branch of [[metaphysics]]. Cosmology as a [[science]] originates with the [[Copernican principle]], which implies that celestial bodies obey identical [[physical law]]s to those on earth, and [[Newtonian mechanics]], which first allowed us to understand those motions. This is now called [[celestial mechanics]]. Physical cosmology, as it is now understood, began with the twentieth century development of [[Albert Einstein]]'s theory of [[general relativity]] and better [[astronomy|astronomical]] observations of extremely distant objects. |