求翻译：The scientific theory which describes the origin and evolution of the universe is Big Bang cosmology, which describes the expansion of space from an extremely hot and dense state of unknown characteristics. The universe underwent a rapid period of cosmic inflation that flattened out nearly all initial irregularities in the energy density; thereafter the universe expanded and became steadily cooler and less dense. Minor variations in the distribution of mass resulted in hierarchical segregation of the features that are found in the current universe; such as clusters and superclusters of galaxies. There are more than one hundred thousand million (1011) galaxies in the universe,[1] each containing hundreds of thousands of millions of stars, with each star containing about 1057 atoms of hydrogen.是什么意思？

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