Warning: This article covers minor plot points of Stranger Things Season 4.
The final two episodes of season 4 of Netflix's hit streaming show Stranger Things have come and gone, and the stage is set for the final season. The Battle for Hawkins and the rest of the world will be epic. Additionally, it will feature the remaining beloved characters in one place and all-together.
Before that occurs, though, audiences were left with new information regarding The Upside Down and some of its inhabitants, as the origins of both unfolded a little more throughout a terrifying season 4. Some new information appears to have created a plot hole of sorts, which is odd because it was an issue that the Duffer brothers appeared to have stated in an interview with Variety would be answered with Season 4. This has not been the case for the question of how Will Byers and some of his communication from The Upside Down in season 1 of Stranger Things. Some of his methods most certainly make sense, but one in particular does not.
The Lights Make Sense
One of the earliest forms of communication to The Upside Down and the real world was the discovery of lights, dimming and turning off and on in particular. This method was used by Will Byers (Noah Schnapp) to communicate with his mother Joyce (played by Winona Ryder), in the show's first season. Joyce notices the lights acting oddly, and since that moment, the method of using of lights has been a mainstay of communication and general location throughout the show. Recently, members of the Hawkins gang used lights to determine the location of season 4's big bad, Vecna in his childhood home. What you may not have known is this is actually based on sound paranormal research. Paranormal Investigators, such as Jason Hawes, Grant Wilson, Keith Age, and more, commonly use trigger items to welcome a spirit to communicate using the 'yes-no' method. Additionally, a spirit can use a trigger item, such as a flashlight, to simply acknowledge they are present. The trigger item, also in this case a flashlight, can be 'tapped' by the unseen being to have the light blink on, off, or even to dim in response to questions.
The Stranger Things gang's science teacher Scott Clarke (Randy Havens) also explains how electromagnetic fields play into this. In Season 3, Joyce's magnets fell off her fridge and she seriously and comically endeavors to answer the question of 'why' the entire season. Electromagnetic fields came into the fold in season 1 when Dustin (Gaten Matarazzo) notices the compasses the kids own are not pointing true north.This also has scientific accuracy within the paranormal, as paranormal investigators often use electromagnetic field detectors(EMF for short) to find and locate spikes of electromagnetic influxes to determine a spot where a spirit may manifest. A lot of what the team uses to communicate does in fact have legitimate scientific roots in the paranormal community as actual methods of research, and are therefore valid methods of communication that one might be able to use from one dimension to another.
The Letters Don't Make Sense
The method that Will uses in season 1 that potentially creates a plot hole is lettering. Once Joyce figures out that Will can communicate using lights, a valid method of simple communication, she then paints letters in the present, corresponding to a light on the wall. Once again, the lights would be a valid form of communication, but here is the catch: Season 4 has confirmed The Upside Down is stuck in the past by about four years. This means the lights and the letters especially would not be painted on the wall in The Upside Down's corresponding time in the present.
The lights are ok in this example because they seem to trigger — at least a little — when a being, human or not, is at least near the lights (and not necessarily right on top of them) and the corresponding real world location. Since the lights and the letters would not have been visible for Will to see in The Upside Down, and even though he can validly communicate through lights, it would have been impossible for Will to see which letters Joyce had painted on the wall corresponding to a particular light that he also couldn't see in his current present.
This was still used as an important plot point, the fact that communication from the other side is possible. Fans of the show theorize that Will could have identified the particles which would have been illuminated. While that may be true, it still would not have been accurate to the degree that WIll was spelling out small words and sentences. All in all, as fun as this communication was back in season 1 of Stranger Things, especially in the moments leading up to the Demogorgan emerging from the wall, the mode of communication shouldn't be possible to the degree of accuracy depicted by the Duffer brothers own current mythos.