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It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...
In quantum chemistry, size consistency and size extensivity are concepts relating to how the behaviour of quantum-chemistry calculations changes with the system size. Size consistency (or strict separability) is a property that guarantees the consistency of the energy behaviour when interaction between the involved molecular subsystems is nullified (for example, by distance).
This metric has only two undetermined parameters. An overall dimensionless length scale factor R describes the size scale of the universe as a function of time (an increase in R is the expansion of the universe), [152] and a curvature index k describes the geometry.
where t is the age of the universe, is the speed of light and r e is the classical electron radius. Hence, in units where c = 1 and r e = 1, the age of the universe is about 10 40 units of time. This is the same order of magnitude as the ratio of the electrical to the gravitational forces between a proton and an electron:
According to inflation theory, the universe suddenly expanded during the inflationary epoch (about 10 −32 of a second after the Big Bang), and its volume increased by a factor of at least 10 78 (an expansion of distance by a factor of at least 10 26 in each of the three dimensions).
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 ...
As such, the observed size of the universe always increases. [ 1 ] [ 3 ] Since proper distance at a given time is just comoving distance times the scale factor [ 4 ] (with comoving distance normally defined to be equal to proper distance at the present time, so a ( t 0 ) = 1 {\displaystyle a(t_{0})=1} at present), the proper distance to the ...
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]