How far can we see into the past?

The farthest we can see into the past is determined by the speed of light and the age of the universe. Light from distant galaxies takes time to reach us, so observing these galaxies allows us to see them as they were when the light left them. For example, light from the most distant observable galaxies can take over 13 billion years to reach Earth, which means we are seeing them as they were shortly after the Big Bang. Thus, in principle, we can observe events and objects as they were up to about 13.8 billion years ago, the estimated age of the universe.