Cosmology and Astrophysics
Cosmology is a branch of astronomy that studies the structure and evolution of the universe from a holistic perspective.
In ancient China, there were three main theories about the structure of the universe, namely Gaitian said 、 Huntian said and Xuanye said 。 The theory of covering the sky believes that the earth is dry and flat, and the sky is like an umbrella covering the earth; Huntian theory holds that heaven and earth have a spherical structure, with the earth in the center and the sky around; Xuanye said that the sky is infinite and empty, and the stars are suspended in the emptiness. utilize Theoretical physics Methods A subject that studies the physical properties and processes of celestial bodies. In 1859 Kirchhoff according to thermodynamics Law interpretation Solar spectrum Of Fraunhofer lines , asserts that there are some chemical elements on the sun that are the same as those on the earth, which indicates that the inherent properties of celestial bodies can be analyzed from the astronomical observation results by using the general laws of theoretical physics Theoretical astrophysics The beginning of. The development of theoretical astrophysics closely depends on the progress of theoretical physics. Almost every important breakthrough in theoretical physics will greatly promote the progress of theoretical astrophysics. Early 1920s Quantum Theory The establishment of, which makes it possible to analyze the spectrum of stars in depth Stellar atmosphere System theory. the thirties Nuclear physics The development of, so that the question of star energy has been satisfactorily solved, so that Theory of stellar internal structure Rapid development; and based on Herotu The scientific theory of stellar evolution has been established based on the measured results. 1917 Einstein By analyzing the structure of the universe with general relativity Relativistic cosmology 。 In 1929, Hubble discovered Extragalactic galaxy The relationship between the red shift of spectral lines and distance of General relativity To analyze the observational data of extragalactic objects and explore the material structure and movement on a large scale modern cosmology 。 
