Stranger Things just revealed the true origins of the Upside Down (and it’s not what anyone guessed)

For five seasons, we’ve thought we’ve known what the Upside Down was in Stranger Things, but it turns out that everything we thought we knew was wrong. 

In simplistic terms, the longstanding belief has been that the Upside Down is a parallel dimension which exists alongside the real world. It’s basically a mirror version of Hawkins, Indiana, but one where a bunch of terrifying creatures happen to live. However, that is not the case. 

As we learn in the second part of Stranger Things’ final season, everything they’ve assumed about the Upside Down has been wrong this entire time. The real origin of the Upside Down is something no one expected, or at least not until season 5 began to subtly tease the true explanation of what the Upside Down is. 

Stranger Things season 5 episode 7 fully explains what the Upside Down is

After discovering some of Brenner’s old journals in the Hawkins Lab within the Upside Down, Dustin discovers that the world was actually created by science. 

Dustin explains that they’ve always assumed that the Upside Down was another dimension opened by Brenner, but it turns out it’s actually a bridge. More specifically, an interdimensional bridge that rips through space-time. This bridge is wildly unstable, but held together by exotic matter, which they found dead center right above the lab in the Upside Down. 

In theoretical physics they call this type of bridge a Wormhole, and this wormhole connects Hawkins to another world which Dustin coins the Abyss. Dustin theorizes that this Abyss is the true home of the Demogorgons, the vines, the Mind Flayer, and all the other supernatural beings they’ve found in the Upside Down. This is where, all those years ago, Eleven banished Henry. He was lost for years and would’ve stayed lost if not for Brenner. 

Eleven deduces that Brenner had her find Henry, and Dustin notes that when she made remote contact with the Abyss all those years ago, the bridge formed and thus the Upside Down was officially born. Ever since its creation, Henry and his army of monsters has been using it to cross into Hawkins.

This entire time, we’ve been led to believe that Henry reshaped the Upside Down into this twisted reflection of Hawkins after he was banished there by Eleven. However, it seems that Henry had nothing to do with shaping the Upside Down and this isn’t where the creatures who have haunted Hawkins originated. The Upside Down is simply a bridge connecting these two worlds.

There are essentially gates to both worlds that are connected through the Upside Down, with the Abyss essentially on one side of the bridge and Hawkins on the other. This bridge was created and is held together by exotic matter, which leads Dustin to devise a plan to drop a bomb in the Upside Down after they rescue Holly and the rest of the kids from Vecna. Doing so will destroy the bridge to the two worlds, with the Upside Down ceasing to exist and the creatures of the Abyss no longer being able to cross over into Hawkins. 

This twist was definitely an unexpected surprise, but one that makes the endgame much more clear for the show. There is no longer a mystery of how they can close the gate once and for all. They simply need to destroy the Upside Down/bridge, and doing so will separate these two worlds once and for all.