As the Oppenheimer trailer countdown clock nears zero, a fan realizes the historical event the clock is actually counting down to. Renowned as the filmmaker behind such acclaimed based-on-fantasy movies as The Dark Knight, Inception and Interstellar, Christopher Nolan has now trained his cinematic eye on a subject of real and massive historical import: the explosion of the first atomic bomb. Starring Cillian Murphy as the vaunted “father of the A-bomb,” Nolan’s Oppenheimer is a 3-hour epic that promises to blow minds in classic Nolan style, while tackling the story of one of the 20th Century’s most important and enigmatic figures.

As part of the marketing ahead of the Oppenheimer release date, a countdown clock trailer has been running on a loop on Universal’s YouTube page, but the countdown doesn’t actually end with the movie’s release (as many have already noticed). As pointed out by...