Whether Homer's fictitious island of "lotus-eaters" in the Odyssey, or Sherlock Holmes' habitual cocaine use, literature has never shied away from portraying drugs, and science-fiction is no different. But why do many modern authors and screenwriters go to such lengths to invent fake drugs when they have a virtually endless choice of real-world narcotics to choose from? It's all about finding the right metaphor — and occasionally an easy plot device — argues writer and artist Claire Evans.

In an article published by Motherboard earlier this week, Evans takes us through some of sci-fi's most powerful substances, from Scanners' Ephemerol, which when taken by pregnant women gifts their children with telekinetic and telepathic powers, to Dune's Melange, the life-enhancing spice that forms the economic basis of Frank Herbert's rich world. It's not an exhaustive list — who could forget Robocop 2's Nuke, or X-Men's Kick? — but makes for fascinating reading nonetheless.