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In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course ...
There are two main interpretations for this disparity: either the universe began with a small preference for matter (total baryonic number of the universe different from zero), or the universe was originally perfectly symmetric, but somehow a set of phenomena contributed to a small imbalance in favour of matter over time. The second point of ...
c. 16th century BCE – Mesopotamian cosmology has a flat, circular Earth enclosed in a cosmic ocean. [1]c. 15th–11th century BCE – The Rigveda of Hinduism has some cosmological hymns, particularly in the late book 10, notably the Nasadiya Sukta which describes the origin of the universe, originating from the monistic Hiranyagarbha or "Golden Egg".
According to theory, the energy density in matter decreases with the expansion of the universe, but the dark energy density remains constant (or nearly so) as the universe expands. Therefore, matter made up a larger fraction of the total energy of the universe in the past than it does today, but its fractional contribution will fall in the far ...
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. [1]
As a result, a variety of logical arguments for the universe having a finite past were developed by John Philoponus, Al-Kindi, Saadia Gaon, Al-Ghazali and Immanuel Kant, among others. [3] English theologian Robert Grosseteste explored the nature of matter and the cosmos in his 1225 treatise De Luce (On Light). He described the birth of the ...
In physical cosmology, the photon epoch was the period in the evolution of the early universe in which photons dominated the energy of the universe. The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang. [1]
His son John Herschel repeated this study in the southern hemisphere and found a corresponding increase in the same direction. [93] In addition to his other accomplishments, William Herschel is noted for his discovery that some stars do not merely lie along the same line of sight, but are physical companions that form binary star systems. [94]