The Big Bang

The Big Bang is the leading scientific explanation for the origin of the universe. About 13.8 billion years ago, all matter, energy, space, and time were concentrated in an extremely hot, dense state. Then, a rapid expansion, called the Big Bang, occurred, causing the universe to grow and cool. Over time, particles combined to form atoms, stars, galaxies, and planets. This expansion continues today, with galaxies moving away from each other. The Big Bang helps explain the universe's large-scale structure, cosmic microwave background radiation, and the observed redshift of distant galaxies.