It seems even small things in the normal world are instantly represented in Upside-Down, such as the Christmas lights. Are the changes two-way?

In Upside-Down, the Demogorgon

Finds Will hiding out in his fort, and destroys it

Does that mean that change is reflected in the real world?

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    Consider all the empty cars in the upside down. If things changed in real time wouldn't the cars be moving? I think the upside down was like snapshotted manifestation somehow and stays the way it was when it was created. I have no credible source for that idea though. So I don't think they are two way. I think it was a one time creation where some things still communicate, like energy
    – Kai Qing
    Oct 7, 2016 at 0:11
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    @JackBNimble I'd actually be really interested if you could provide an exact reference for the Christmas lights being replicated in the Upside Down. I looked specifically for that and never could see them at all. Unless you're just inferring their existence there from the fact that Wil could interact with them? Oct 7, 2016 at 14:28
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    @Jack - Maybe Will could see the currents of electricity but you do bring up a good point related to the lights - The paint. How would he have seen the letters if it wasn't real time? Unless there's some kind of exception to the house for whatever reason... Like - the writers not really thinking that through all the way. Other things like why doesn't the pool have water in it, etc. Maybe there's something about that house that attracts attention
    – Kai Qing
    Oct 7, 2016 at 16:58
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    It seems that the Upside-Down is not a true reflection of the material world, but rather a warped version of it. While not strictly applicable, the words of the (fictionalized?) D&D sourcebook are probably pertinent: “The Vale of Shadows is a dimension that is a dark reflection or echo of our world. It is a place of decay and death.” Not everything is going to get copied.
    – Adamant
    Oct 17, 2016 at 7:37
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    There is absolutely some difference between Will and Hopper/Joyce. They both can affect the real world by passing near the lights, but don’t seem to be able to perceive it equally. It’s definitely possible that spending more time in the UD has sensitized him enough to see past the barrier. My personal theory.... Don’t forget, Will’s character is a wizard. Who else has been described as a wizard? Eleven. Who else can perceive things in one realm while present in the other? Eleven. Is it possible that Will is just a little bit psychic?
    – Adamant
    Oct 17, 2016 at 7:55

4 Answers 4


Probably not

Changes in the Upside-Down likely do not affect the normal world—nor the other way around.

  1. The Upside-Down does not affect the “Material Plane”

    This isn’t very likely. We don’t have a long list of changes to the Upside-Down to compare, but….

    There are seemingly a number of large creatures moving through the Upside-Down (the Demogorgon, the Demo-dogs, and of course the Mind Flayer). Surely they’d be causing large changes that people would notice, if the Upside-Down affected the Material Plane?

    The Mind Flayer sends vines through to dig tunnels and infiltrate the normal world. Would it have any need to do so if it could affect the world directly from within the Upside-Down? It could simply dig the tunnels there, rather than risk exposing itself. It could collapse the institute. It could collapse a tunnel on Hopper. It has a malign, if unknowable, intelligence—that it doesn’t avail itself of such techniques suggests that they are not available.

    Why would anyone (e.g. Will) have such difficulty communicating from the Upside-Down if changes propagated to the normal world? They could just smash a wall, or carve letters into the ground.

    The one exception, of course, is that people passing through the Upside-Down can affect lights on the other side. However, this is more a unique effect—they don’t have any way of turning the lights on in the Upside-Down.

  2. The “Material Plane” does not affect the Upside-Down.

    Contrary to the premise of the question, changes in the normal world likely do not get reflected in the Upside Down. The Upside-Down doesn’t seem to have seasons (we see it during various times from summer to winter, and it looks roughly the same), even though these changes are occurring in the real world. Moving objects, like cars in the normal world, are stationary.

    Nor did putting up the Christmas lights make them appear in the Upside Down. Going back to the episode where Joyce and Hopper were walking through Joyce’s house in the Upside Down in the first season, the Christmas lights don’t seem to appear (though they could be covered by the plant matter). Since they were all over the house, this would be a clear sign that changes to the real world don’t go into the Upside-Down.

    Rather, Will could perceive the Christmas lights from the Upside Down. In Season 2, he’s shown to have developed some connection with the Upside Down from having spent time there, being able to see (and even perhaps enter) into it:

    WILL: You know on a View-Master, when it gets, like—

    MIKE: Caught between two slides?

    WILL: Yeah. Like that. Like one side’s our world, and the other—the other slide is the Upside Down.

    Stranger Things, “Trick or Treat, Freak” (S02E02)

    It’s plausible that his sojourn, or previous innate abilities, or both, enabled the opposite—for him to see the normal world from the Upside Down.

    He was also able to hear his mother talking in the Material Plane, even when Joyce and Hopper couldn’t hear Nancy, Jonathan, or Steve talking during their excursion.

    As for why this is, Will might be a tad psychic. In Season 2 (“The Mind Flayer”), he is possibly able to make lights flicker while in the normal world. While this could be the Mind Flayer’s doing, it could also be evidence of innate talents on Will’s part.

In conclusion, most changes to the Upside-Down have next to no effect on the real world, and vice versa.

Why is all this? Speculation warning!

The true nature of the Upside Down has not been revealed yet (and may not be until the fourth and final season), but there’s a telling little clue.

DOCTOR OWENS: How’s it looking out there, cowboy?

SOLDIER: Uh, you know, Doc. The usual. Nice and nasty with a chance of radioactivity.

Stranger Things, “Trick or Treat, Freak” (S02E02)

The mention of radioactivity is bit odd. Not that the Upside-Down is a hospitable place, but it’s not even as if whatever radioactivity is there is immediately lethal. It’s more like the sort of thing that you’d expect from…hmm, from a place where a lot of nuclear bombs had been dropped.

I do not believe that the Upside Down is any sort of “shadow” of the normal world, where the effects of one world propagate to another. All that about the Vale of Shadows in the first season was a bit of a red herring. I believe it is a full alternate Earth, one where there was a nuclear war (don’t forget the constant references to Russia, the Soviet Union, and the Cold War in this series). A place like Hawkins likely wouldn’t have been bombed directly, but there’d be a lot of radioactive fallout. And the idea of radiation causing supernatural mutations has been around for a long time….

This also explains why the Upside-Down looks like the town of Hawkins, but has its own peculiar attributes. If it’s a Plane of Shadow, why doesn’t adjust to look like the current world, albeit slowly? What’s up with the positions of cars?

Thus, there is communication between the two worlds—they’ve been drawn closer together—but one doesn’t determine the other, because neither one was directly created from the other.

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    The "bombed out" appearance of the Upside-Down, radioactivity, and the ash/fallout in the air would support the theory that the Upside-Down is an alternate Earth that experienced a devastating nuclear war & nuclear winter. Perhaps in future seasons, explorers of the Upside-Down will find newspapers, human corpses, or other clues to the Upside-Down's true nature.
    – RobertF
    Oct 31, 2017 at 21:10
  • “The Upside-Down doesn’t seem to have seasons... we see it during various times from summer to winter” — do we? I thought both series 1 and 2 were set between late October and Christmas of their respective years and that we don’t get any Upside Down flashbacks. Nov 17, 2017 at 22:23

The Upside Down is actually like an echo of the real world. In the book Stranger Things: The Other Side (2019), we actually get to see how Will tries to survive in the Upside Down.

Will was affecting the Christmas lights even though the lights weren’t there. In the scene where Joyce tries to talk to him, Will was confused about blinking once for 'yes' and twice for 'no'. So he actually blinked trying to convert energy around him and saw the Christmas lights’ aura of light form next to him. While he fell asleep when Joyce was setting up the alphabet, he woke up and saw like a distorted version fade in to the Upside Down. He did not see the Christmas lights though. So that shows that after a long period of time, SOME things form in the Upside Down, like the hole in the wall from The Body.

When he concentrates, Will can also see when the aura of light appear, just like he can hear people in the normal world if he is close enough to them. It's just like how things can affect the Upside down, but not the other way around (except for electricity), so Will could not do anything like make a message or break something in the Upside Down.

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    – Skooba
    Aug 21, 2021 at 16:00

Season 4 answers this more clearly: The upside down appears to look like how it was when opening the rift in season 1. We know this due to Nancy Wheeler's diary.


if you look at the very end of season 2, while the view of the snow ball falls through to the upside down version of the building, you can see the snow ball decorations on the building in the upside down, which means the decorations they put up transferred to the upside down. maybe the upside down updates or something when there's nothing and nobody around to see it?

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    Hi, welcome to SF&F. This question is actually about changes transferring the other way; if someone changed those decorations in Upside-Down, would they be changed in the real world?
    – DavidW
    Oct 9, 2020 at 20:20

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