The changing universe

Light from nearly all galaxies is redshifted, showing they're moving away, with distant galaxies receding faster. Evidence shows that galaxies were all in the same place about 14 billion years ago, showing their movement apart since. The Big Bang Theory suggests that the universe began from a very small region that was extremely hot and dense. A scientific theory is our best understanding based on all evidence and is subject to rigorous testing. We do not fully understand dark matter or dark energy.