Rock 'n' roll has always, on some level, been about the outsiders and outcasts, and the same can be said about what may be the defining literary and cinematic genre of the 20th and early 21st centuries: science fiction.

While early sci-fi often envisioned a bright, sparkling utopia in which humanity has achieved peace and harmony among the stars, let's be real - the best and most engaging sci-fi is often found in novels and films that warn of the dystopia or even extinction that awaits humanity if we aren't careful with the natural forces we've tamed and harnessed for our benefit.

Hey, I absolutely love Star Trek and the vision of peaceful space exploration it's brought us, but most days it feels like The Expanse portrays the more likely future.

As rock music became a worldwide phenomenon, more artists starting pushing the limits of the themes the genre could explore both lyrically and musically. I was born in 1986, the same year my favorite Iron Maiden album, Somewhere in Time, was released. I'm told the band's heavy use of synthesizers on that album was pretty controversial at the time, but it really lends every song the feeling of somehow having fallen through a time warp from the future and into our ears.

Sci-fi was ripe for rock artists to plunder for inspiration, especially given its rebellious nature and the tumultuous century from which it emerged.

Let's take a look back (and forward) with 12 of the Greatest Classic Rock Songs With a Sci-Fi Theme in no particular order. If your favorite didn't make our list, let us know in the comments!

LISTEN: 12 Best Classic Rock Songs with a Sci-Fi Theme