According to the "Big Bang" expansion theory of the universe, the universe began in a sort of explosion, starting from infinite density and temperature and then expanded, thinned out, and cooled, while being controlled by gravity. The appearance of its expansion can be likened to the surface of a balloon being blown up: the galaxies all recede from one another.
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According to the "[[Big Bang]]" expansion [[theory]] of [[the universe]], the universe began in a sort of [[explosion]], starting from infinite [[density]] and [[temperature]] and then expanded, thinned out, and cooled, while being controlled by [[gravity]]. The appearance of its expansion can be likened to the [[surface]] of a balloon being blown up: the galaxies all recede from one another.