The Lord of the Rings is just one story in an entire world of tales that Tolkien created for his Middle Earth. Because of this, a viewer will have tons of questions after watching the trilogy since there are details in the story that aren’t explained in the trilogy, but are explored in other books that Tolkien wrote.
One of those questions might be “why does the Ring turn everyone except Sauron invisible?” When watching the extended version of The Fellowship of the Ring, viewers will see several beings put on the Ring. The first is Sauron, who was the creator of the Ring. After that, Isildur puts on the Ring and turns invisible. The Ring was next worn by Sméagol who gets his origin story of finding the Ring and becoming Gollum explored in The Return of the King, and he also turns invisible. Then Bilbo puts the Ring on and becomes invisible at his birthday party—the event that led Gandalf to discover the Ring had been found. And after that, Frodo becomes the Ring Bearer and puts the Ring on several times. He too becomes invisible. There are other characters in the book who wore the Ring, but it is not shown in the movies.
So, after watching The Lord of the Rings trilogy, it may be interesting to some to find out why Sauron is the exception to the invisibility rule. In an interview with WIRED, Tolkien expert Cory Olsen answered this question. Olsen said that the reason Sauron does not turn invisible when he puts on the Ring is because, quite simply, he does not have a body. At least, not in the normal sense anyway. Sauron was a Maia. Maiar spirits are angel-like beings that are very powerful and have existed since the beginning of time. In Tolkien’s work, there is the physical world and then there’s the spiritual world. Maiar spirits are of the spiritual world, and so they don’t have bodies. They can embody any being they want (like a Balrog, Elf, serpent, vampire, old Man, etc.), but they do not need to interact with anyone in the physical world and thus can remain invisible.
When Bilbo first discovered the Ring, he was not aware of what it was or how powerful and important it was. The only thing he understood was that he had a magical ring capable of turning him invisible. Because Tolkien wrote The Hobbit first, he did not know exactly where the story would lead to. The Tolkien expert Cory Olsen implied that the story of the Ring and its owner were both afterthoughts, and not only was the Ring just “a magical invisibility ring” to Bilbo, but that’s all it was to Tolkien at the time, too. The Hobbit (1937) was written 17 years before The Lord of the Rings (1954), so Tolkien didn’t have all the details yet because he hadn’t created them. It was only after Tolkien decided that this ring Bilbo found would be The Ring that he decided to give the Ring more powers, and sort of treat the invisibility the Ring offered the wearers as a side effect.
In the interview, Olsen said Sauron “can give himself a body and interact with the physical world.” When someone puts on the Ring, they enter into the Wraithworld. A wraith is a ghost or ghost-like image of someone, sometimes defined as a wisp or faint trace of something. So the Wraithworld is like a ghost or spirit world. When wearing the Ring, beings of the physical world are transported into the spiritual world through a direct link to Sauron and his evil. In the spiritual world, beings are invisible to those in the physical world.
This is why Isildur, Bilbo, and Frodo become invisible when they wear the Ring—because they are no longer in the physical world. As Olsen said, Sauron does not have a real body, so he is not affected in the same way. The Ring only affects mortal beings, and because Sauron is an immortal Maia spirit, he doesn’t experience the same side effect of invisibility. The “mortals are being drawn into Sauron’s world. But he lives there,” so he has control over everything.
Because Sauron chose to manifest a body, he chose to present himself to the physical world. He wants to be seen and feared by all. “That manifested body doesn’t become invisible, because he doesn’t want it to be.” Sauron wanted to be a present threat, and control all who dwelt in Middle Earth, and his desire to control them all required he maintain a physical and menacing form. His last physical form before being defeated was a nine-foot tall and powerful monster-like, massive figure that was shown in the prologue of The Lord of the Rings: The Fellowship of the Ring.