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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 ...
While the Big Bang model in cosmology is sometimes said to derive from the Copernican principle in conjunction with redshift observations, the Big Bang model can still be assumed to be valid in absence of the Copernican principle, because the cosmic microwave background, primordial gas clouds, and the structure, evolution, and distribution of ...
In cosmology, the anthropic principle, also known as the observation selection effect, is the proposition that the range of possible observations that could be made about the universe is limited by the fact that observations are only possible in the type of universe that is capable of developing observers in the first place.
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]
The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, [2] and in 1731 taken up in Latin by German philosopher Christian Wolff in Cosmologia Generalis. [3] Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and ...
[3]: 25.1.3 To apply the metric to cosmology and predict its time evolution via the scale factor a ( t ) {\displaystyle a(t)} requires Einstein's field equations together with a way of calculating the density, ρ ( t ) , {\displaystyle \rho (t),} such as a cosmological equation of state .
One class of solutions to the Boltzmann brain problem makes use of differing approaches to the measure problem in cosmology: in infinite multiverse theories, the ratio of normal observers to Boltzmann brains depends on how infinite limits are taken. Measures might be chosen to avoid appreciable fractions of Boltzmann brains.
[3]: 62 The basic model makes two simplifying assumptions: until the temperature drops below 0.1 MeV only neutrons and protons are stable and; only isotopes of hydrogen and of helium will be produced at the end. These assumptions are based on the intense flux of high energy photons in the plasma.