 Despite favorable reviews, however, the episode received a 1.5/4 in the 18-49 rating/share demo, with 3.91 million Americans watching it live on Fox, showing a steady decline from the series premiere.Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years ago.Tyson further explains how modern astronomy has used such analysis via deep time to identify the Big Bang event and the age of the universe.