Our physical universe is 1.5×1010 years old. It began with the Big Bang. There is some debate about what happened in the first tenth of a second! The first 3×105 years were radiation dominated. Since then it has been matter dominated. (This in accordance with the first law of thermodynamics which states that total mass-energy is conserved.) The universe has continuously expanded in space and in the future either this may continue, or expansion may stabilise at a fixed size or the universe may contract in the Big Crunch (depending on the spatial curvature). At a certain scale the universe is spatially isotropic and homogeneous. Its trajectory exhibits increasing entropy in accordance with the second law of thermodynamics. These statements are in accordance with certain models and empirical data: distant galaxies are receding from us at a velocity proportional to their distance; there is greater spatial uniformity at greater distances from us; there is uniform presence in space of radiation with a temperature of 2.7K; etc.
Burt, G. (2010), "Chapter 14 World history: The growth and distribution dynamics of power, truth and value", Burt, G. (Ed.) Conflict, Complexity and Mathematical Social Science (Contributions to Conflict Management, Peace Economics and Development, Vol. 15), Emerald Group Publishing Limited, Bingley, pp. 221-242. https://doi.org/10.1108/S1572-8323(2010)0000015017Download as .RIS
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