The foundation of Stranger Things is the Upside Down, and the foundation for the Upside Down is a heady blend of D&D, science fiction, and theoretical physics.

Weaving those elements together, the show has used Gary Gygax and Dave Arneson’s role-playing game in interesting ways since the beginning. The initial campaign in Mike’s (Finn Wolfhard) basement is not merely an ’80s nostalgia check or even solely a nod to his crew’s social status; it’s a motif that appears over and over as they embark on the mirrored, real-life adventure, launched because Mike wants to emulate Will’s selfless act during the game. Eleven (Millie Bobbie Brown) places the Upside Down literally on the D&D maze itself to explain its nature, complete with the Demogorgon figure standing in for the monster storing children in spider webs for midnight snacks.

In “The Flea and the Acrobat,” they expand on that connection when Dustin (Gaten Matarazzo) surmises that the Upside Down is like the “Vale of Shadows,” a realm invented for the show and shoved into their (fictionalized) D&D Expert Rulebook. “The Vale of Shadows is a dimension that is a dark reflection, or echo, of our world,” Dustin reads. “It is a place of decay and death, a plane out of phase, a place of monsters. It is right next to you and you don’t even see it.”

It helps the gang understand why Eleven took them to Will’s house to find him even though he’s not there (on their plane of existence).

Using the Expert Set and nerd currency to explain this haunted other world is clever and hip, but it’s also profound at a four-foot-tall level because it speaks the language of Mike and his friends. It fits perfectly into their world, intertwining creatively with their vision of the place they’ll have to save Will from and their vision of the adventure they’re on. They have a built-in shorthand for understanding the impossible.

That’s also the hidden connection D&D has to the Upside Down. Both feature physics-tearing doorways that connect the real world to a space of imagination, thrills, and danger. Where the gateway inside Hawkins Laboratory is a physical hole in space-time that allows passage between the two, D&D is a metaphorical door that allows plays to leave the real world behind (for 10 or more hours at a time).

After figuratively disappearing into a fantasy realm for entire weekends in that basement, Will has now disappeared for real into a world where you can’t hide your too-low dice role from the Dungeon Master.

Enter intrepid science teacher Mr. Clarke (Randy Havens), who drops some unfiltered theoretical physics on his middle school students during their friend’s funeral. The body in the casket is full of cotton wadding, but Mr. Clarke doesn’t know that. He’s just game to talk science anywhere, anytime, without the sugar coating.

“Science is neat, but I’m afraid it’s not very forgiving,” is epitaph material. It’s also the kind of thing that could get a middle school kid hooked on reading Sartre if he weren’t already freaked out about finding his best friend in a nether-region. Mr. Clarke basically just unloaded the Joker’s “chaos is fair” speech on the children with people tearing up all around them. No biggie.

Clarke’s illustration of the acrobat and the flea is meant to show the D&D-minded kiddos how travel to another dimension could theoretically work. The thrust being that we (the acrobat) don’t naturally have the physical tools to travel beneath the rope like the flea can.

Physicist Paul Steinhardt explains the concept using a sandwich. Imagine two slices of bread are two parallels dimensions connected by some tasty, space-time hummus. If you were the flea, you could walk on the bread just fine, but the space-time hummus warps according to Einstein’s general theory of relativity, so you can’t travel on it. Which is sad. But if you had an absurd amount of energy, you could potentially connect the two pieces of bread via a black hole or worm hole (like sticking a toothpick through the sandwich).

Voila. The road to the Upside Down. A delicious sandwich made with Dungeons & Dragons and theoretical physics with a fine layer of childhood trauma in the middle. The world comes from physics. The monsters that live in it come from D&D.

Images: Netflix

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