13.7 billion years ago: Universe, which includes time and space, begins with Big Bang. The Big Bang is dated according to NASA. 300 thousand years after the Big Bang, hydrogen nuclei capture electrons, forming the first atoms. 600 million years after the Big Bang: formation of first galaxies, see Galaxy formation and evolution. 5 billion years ago: formation of the Sun. 4.5 billion years ago: formation of the Earth.