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In the realm of cosmology, understanding the nature of gravity is crucial for unraveling the mysteries of the universe. The current cosmological models are built based on general relativity. The solutions of the specific equations, Friedmann-Lemaître-Robertson-Walker, allow to model the evolution of the universe starting from the Big Bang. Some of the parameters of the universe have been established by observations. Based on these, and other observational data, the models can be tested. Predictions include the initial abundance of chemical elements formed in a period of nucleosynthesis during the Big Bang period, the subsequent structure of the universe, cosmic background radiation, and so on.