I've always wondered about Star Trek's phrase "the final frontier". Is the entire planet one fronteer? Is the earth a small set of fronteers, while the entirety of space, all of the planets and moons in all of the galaxies is just one fronteer, thus being the last?
Have we excluded alternate dimensions as a fronteer? We have established they exist, even by judging Van Dyke beards alone. Otherwise it's Earth -> All Of Space -> Other dimensions. "Space. The halfway frontier.".
Is that going too far? Is "the final frontier" just a catchy phrase? Maybe. Maybe the phrase is made up by a Van Dyke Beard Guy. Or an action planner.