Peter Jackson’s Lord of the Rings trilogy converted J.R.R. Tolkien’s monumental fantasy epic into an action-adventure saga spanning more than nine hours across three films. But Tolkien’s work is so expansive that even the extended editions of the Jackson films couldn’t possibly cover all the questions people are bound to have about how the world of Middle-earth works. Many viewers still ask “why didn’t they just take the eagles to Mordor?” in reference to the movies. There’s a reasonable answer to that question, but viewers have to dig deep into Tolkien’s mythos to find it.