For Star Wars fans, May 4 is a day to celebrate. The famous line — "May the force be with you" — was first heard when the movie was screened in 1977. It didn't take long for the Star Wars community to make a pun out of it. And so, May 4 came to be known as Star Wars day — "May the 4th be with you."

On May 25, 1977, the first Star Wars film was shown in cinemas. In the US, "Star Wars" was sold out for weeks. Hoping to snag a seat, audiences diligently lined up outside cinemas as shown here in Los Angeles. At that time, no one could have expected the series to span decades.

Obi Wan Kenobi utters this famous line to Luke Skywalker just before he is sent on a difficult mission. With the help of the "force," Luke is able to fight the empire on behalf of the Rebel Alliance. The empire has been threatening the entire galaxy with its planet-destroying Death Star space station. Forty years ago, audiences first heard the Jedi leader utter this unforgettable sentence.

Jedi master Yoda teaches Luke Skywalker how to harness the power of the "force." Using spiritual strength, it allows jedis to move objects with their minds. Yoda also trained Luke's father Anakin. Yoda sent him on his way with these wise words: "Fear is the path to the dark side. Fear leads to anger. Anger leads to hate. Hate leads to suffering."

Anakin ignored the wisdom of Yoda and allowed himself to be seduced by the dark side of the force. He became Darth Vader, the vicious right hand of the even more evil emperor. In "Star Wars - Return of the Jedi," Darth Vader fights Luke Skywalker and shocks him by saying: "Luke, I am your father."

He is the one responsible for manipulating young Anakin Skywalker and convincing him to join the dark side. "I can feel your anger. It makes you stronger," he says after killing a Jedi before Anakin's eyes. "Become my apprentice. Learn to use the dark side of the force." The emperor also assures him he will be a good Sith lord and gives him the name Darth Vader.

Golden C3PO and navigation droid R2D2 are the legendary robot pair featured in the Star Wars saga. Together, they sometimes resemble an old married couple, mainly due to C3PO, who takes every chance he can get to cheekily scold the smaller droid. "You'll be malfunctioning within a day, you nearsighted scrap pile," he tells R2D2.

This is what Luke Skywalker said about his twin sister Leia long before he knew that they were related. The droid R2D2 brought Obi Wan Kenobi a plea for help from Leia in the form of a hologram. "Help me Obi Wan, you're my only hope," she famously says. Luke is fascinated, and accompanies Obi Wan to Alderaan, Leia's home planet.

Star Wars fans have known for 40 years that the episode dates cause narrative confusion. After Episodes IV to VI were released between 1977 and 1983, George Lucas told the back-story in episodes I to III, which premiered between 1999 and 2005. The latest film "Rogue One" (2016), takes place between episodes III and IV.

George Lucas left the saga in the hands of Disney. The new series has won over new fans and places Episode VII (2015) in a familiar setting. Thirty years have passed since the rebels' victory over the empire and while new villains have appeared, so has Rey — a new heroine. It is assumed that she is the daughter of a Jedi knight, since she feels the force.