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Physical cosmology is the branch of physics and astrophysics that deals with the study of the physical origins of the Universe and the nature of the Universe on its very largest scales. In its earliest form it was what is now known as [[celestial mechanics]], the study of the [[celestial sphere|heavens]]. The Greek philosophers [[Aristarchus of Samos]], [[Aristotle]] and [[Ptolemy]] proposed different cosmological theories. In particular, the [[geocentric]] [[Ptolemaic system]] was the accepted theory to explain the motion of the heavens until [[Nicolaus Copernicus]], and subsequently  [[Johannes Kepler]] and [[Galileo Galilei]] proposed a [[heliocentric]] system in the [[16th century]]. This is known as one of the most famous examples of [[epistemological rupture]] in physical cosmology.

'''Physical cosmology''' is the branch of physics and astrophysics that deals with the study of the physical origins of the Universe and the nature of the Universe on its very largest scales. In its earliest form it was what is now known as [[celestial mechanics]], the study of the [[celestial sphere|heavens]]. The Greek philosophers [[Aristarchus of Samos]], [[Aristotle]] and [[Ptolemy]] proposed different cosmological theories. In particular, the [[geocentric]] [[Ptolemaic system]] was the accepted theory to explain the motion of the heavens until [[Nicolaus Copernicus]], and subsequently  [[Johannes Kepler]] and [[Galileo Galilei]] proposed a [[heliocentric]] system in the [[16th century]]. This is known as one of the most famous examples of [[epistemological rupture]] in physical cosmology.

With [[Isaac Newton]] and the 1687 publication of ''[[Philosophiae Naturalis Principia Mathematica|Principia Mathematica]]'', the problem of the motion of the heavens was finally solved. Newton provided a physical mechanism for [[Kepler's laws]] and his [[law of universal gravitation]] allowed the [[anomalies]] in previous systems, caused by gravitational interaction between the planets, to be resolved. A fundamental difference between Newton's cosmology and those preceding it was the [[Copernican principle]] that the bodies on earth obey the same [[physical law]]s as all the celestial bodies. This was a crucial philosophical advance in physical cosmology.

With [[Isaac Newton]] and the 1687 publication of ''[[Philosophiae Naturalis Principia Mathematica|Principia Mathematica]]'', the problem of the motion of the heavens was finally solved. Newton provided a physical mechanism for [[Kepler's laws]] and his [[law of universal gravitation]] allowed the [[anomalies]] in previous systems, caused by gravitational interaction between the planets, to be resolved. A fundamental difference between Newton's cosmology and those preceding it was the [[Copernican principle]] that the bodies on earth obey the same [[physical law]]s as all the celestial bodies. This was a crucial philosophical advance in physical cosmology.