The History of the Universe:
The Big Bang Cosmology

It is believed that our universe began about 14 billion years ago with a huge explosion called the Big Bang. It is thought that the universe started at an unimaginably high temperature and high density, and that the temperature decreased as a result of expansion over time, leading to its current state. The universe is thought to have changed its configuration over time following the Big Bang based on investigations into redshift in distant galaxies\which is known as Hubblefs Law, cosmic background radiation, and the nucleosynthesis ratio in the early universe. Particles were generated by the decrease in temperature resulting from the expansion of the high-temperature and high-density state shortly after the Big Bang, and light elements were formed three minutes after the Big Bang. After 300,000 years, the universe was in an electrically neutral condition under a plasma state, and the universe became transparent to radiation because of the dramatic decrease in interaction between electromagnetic waves and materials. It is thought that Hubblefs Law came into being at this time as galaxies were also formed around the same time.

The Graduate School of Pure and Applied Sciences, University of Tsukuba Program for
the History of the Universe