There are certain advantages to being a cartoon. You only have to own one set of clothes, or none at all. You can fall from the highest buildings and smash through billboards, leaving you-shaped holes all over town. But we think the greatest advantage is the idea bulb. Imagine that appearing over your head every time you had a good idea.
"Are you sure that's a good idea?" someone would ask.
"Of course it is," you'd say, pointing to the top of your head.
Close Encounters' UFOs are basically giant idea bulbs in the sky, as the film uses light to symbolize, well, enlightenment. For the characters in the film, this knowledge is that we're not alone in the universe. But speaking more broadly, light represents the general idea of knowledge and the pursuit of it to better understand our place in the universe.
Light Bulb Moments
Of course, the movie isn't making this connection all by itself but borrowing an association that already exists in many cultural traditions.
The relationship between light and knowledge is coded into the English language. When someone is intelligent, we say they're bright. You can illuminate a subject when teaching someone. And if you really want to show off, you can even elucidate an idea, a word meaning "to explain" that comes directly from the Latin for "to make light or clear." (Source)
Many religious and historical traditions also link the idea of knowledge with light. When Buddhists discover the truth about life and reality, they are said to have reached enlightenment. Jesus called himself the "light of the world" and said those that followed his teachings needn't fear the darkness. And Western societies refer to the 18th century as the Age of Enlightenment, the time when Western culture moved out of its "Dark Ages" and made incredible advancements in politics, science, and philosophy.
Blinded by the Light
Close Encounters links light to knowledge in several scenes. Most obvious are the alien UFOs, which are visually defined by their striking light patterns. Roy and Lacombe follow those lights throughout the film.
When Roy first encounters the UFO on the back road, the otherworldly vehicle is represented by a bright light. Initially, Roy's terrified by the strange phenomenon, but when his curiosity gets the better of him, he chases after it. This chase represents the beginning of Roy's search for truth and knowledge, and the film represents it visually by having him literally chase after the lights.
This scene, by the way, is also a giant shout out to the Biblical story "The Road to Damascus," where Jesus appears before Saul as a bright light and grants the would-be apostle divine knowledge. Roy gets off a little easier than Saul as he only gets a sunburn instead of being blinded.
Lacombe's own search for knowledge also begins with a reference to light. When he interviews the local man about Flight 19, the local man tells him that "the sun came out last night" and "sang to him."
The film's finale follows up on this symbolism as both men find the knowledge they seek while simultaneously making contact with the source of light, the UFOs. The conversation of light and sound between the mother ship and the computer is referred to as "the first day of school"—again connecting the visual imagery of light with the idea of learning. And when the aliens appear before the humans, they are bathed in brilliant white background light.
In his search for knowledge about the extraterrestrials, Roy enters that very light-filled door. When Lacombe spies the man at the landing site, he goes up to him and asks:
LACOMBE: Monsieur Neary, what do you want?
ROY: [Sighs.] I just want to know that it's really happening.
Lacombe pulls some strings and secures Roy a place on Project Mayflower, a group of people chosen to leave with the aliens. Bathed in light, Roy enters the mother ship, where he'll finally learn what he's wanted to know.
Besides light's symbolic meaning in the film, we have to send a shout-out to Steven Spielberg's use of light as a visual motif. These kind of dramatic light/awe/amazement scenes are one of his many specialties.
One of Spielberg's earliest directing credits was the "Eyes" episode of Rod Serling's Night Gallery. (He was twenty-one.) He directed Hollywood legend Joan Crawford as a wealthy blind woman who pays a fortune to buy and surgically implant the eyes of a poor man just so she can have 12 hours of vision. After surgery, she takes off her bandages and revels in the light that surrounds her, only to have everything go suddenly black. The episode has all the hallmarks of Spielberg's later work.
TIME Magazine listed "streams of light" as #2 on their list of "The Five Ways to Know You're Watching a Spielberg Movie." (Source) In Shmoop's humble opinion, nobody does it better.