Throughout recorded history,several cosmologies and cosmogonies have been proposed to account for observations of the Universe.The earliest quantitative geocentric models were developed by the ancient Greeks,[citation needed] who proposed that the Universe possesses infinite space and has existed eternally,but contains a single set of concentric spheres of finite size – corresponding to the fixed stars,the Sun and various planets – rotating about a spherical but unmoving Earth.Over the centuries,more precise observations and improved theories of gravity led to Copernicus's heliocentric model and the Newtonian model of the Solar System,respectively.Further improvements in astronomy led to the characterization of the Milky Way,and the discovery of other galaxies and the microwave background radiation; careful studies of the distribution of these galaxies and their spectral lines have led to much of modern cosmology.
