At the turn of the 20th century, scientists generally thought the universe was essentially timeless and unchanging. In 1915, with the publication of Einstein's general theory of relativity, there were implications of the cosmic role of gravity, but these were generally unappreciated. Even after Edwin Hubble proved that the spiral nubulae are other galaxies at vast distances, astronomers were slow to recognize the implications.

Astronomers study the farthest objects because they are the oldest and tell us about the earliest stages of the universe.