The Acrobat and the Flea -- The Unexplored Science in Stranger Things

I just finished watching what is available of Stranger Things Season 4, and planning to watch the rest tonight.  I've been meaning to comment on the show for a while.  There are a lot of really neat ideas present in the series, that sadly I don't think get fleshed out as much as they could have been.

I was inspired to finally start writing some commentary by a scene near the end of vol 1 of season 4.  That is your spoiler warning.

In season 4, the older kids end up stuck in the Upside Down, and find a portal back in the ceiling of Eddie's house, where the younger gang is waiting for them.  It leads to an interesting geometry where to leave the Upside down, you must first go up into the ceiling, then fall down to the floor on the other side.  And this leads to an interesting physics illustration when Dustin throws a rope through the portal.

This scene is initially very cool.  The rope is spanning the portal.  On both ends it has gravity pulling it "down," which is two different directions across its length.  This means there is an equilibrium point where the gravity at both ends will be equal and the rope will simply float there between worlds.

You see this happen briefly when Dustin first lets go.

It sort of gets ruined when people then climb the rope and the rope stays there with no counter weights tied to it.  This is the part where I told my wife "that's not how it works," and she replied that it's a dimensional portal.  Fine, that is how it works, but that's not how it should work.  Initially it's a really cool application of physics, rather than just the principle that ropes magically stay in place inside a portal.

That leads me to two other things from way back in the first season.

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Seasons 2 and 3 were good and entertaining, but I think they lost track of the sci-fi element of the original season.  The mindflayer is clearly some kind of supernatural/spiritual entity that acts with magic.  It's made of swirling tornados, can pull people across to the Upside Down at will, and acts exactly like demonic possession.  This is unlike the demogorgon, which was simply an alien monster of flesh and bone posing a physical threat to the gang.

But season 1 is full of some great sci-fi nuggets, and I think has seeds for a much different run of seasons.

Eleven has psychic powers.  This is a classic sci-fi trope so doesn't usually require explanation, beyond that she can do magic with her mind at the cost of a nosebleed (more on psychic powers at the end).

One of her powers is remote viewing. With her mind she is able to see and hear people at long range.  This is shown as the black empty space with only her and a person she is looking for.  One day while looking far beyond her usual range, she encounters another presence in this empty space.  This is the monster.  She is sensing the psychic presence of creatures beyond our world.  She is initially afraid, but upon encouragement that it can't hurt her she returns to it and makes contact.  This is when a creature in the Upside Down first becomes aware of our world.  The psychic presence of Eleven reaching out to it drives the creature to cross over to our world to hunt her.  This creates the portal, opens our world to the Upside Down, and starts everything else in the series.

The psychic space where Eleven can sense other minds.

At the funeral for the fake body of Will, the boys ask Mr. Clarke to explain parallel dimensions.  This scene is great in so many ways.  

The science teacher pulling out a pen and scribbling on a paper plate is dead-on.  So many times friends and I would do the same thing with napkins, and when I worked teaching high school this was a common occurrence when the nerdy kids asked me something.  It was so dead-on I excused the over-used trope of folding a paper and stabbing a pen through it, even when it wasn't relevant, but of course I understand that this is a legal requirement for screen depictions of anything related to a wormhole.

The scene is also great because it sets up what the monster could be and how the Upside Down might work, and the setup has the potential to draw from some very deep math to create a multiverse of worlds that creatures like the demogorgon use for hunting.

After name dropping the requisite popular science words, Mr. Clarke lays out his theory, on the acrobat and the flea.

Our universe is like a high wire, and we are acrobats moving on it.  There are rules.  We can move forward or backward, but we can't turn over.  However, a flea also on the tightrope is not constrained to stay on top.  It can turn over to the side, or even upside down.  It's able to move around the circumference of the rope.  Unlike the acrobat.

It's a brilliant analogy that doesn't need me to break it down, but I'm going to anyway, so I can explain a part of the analogy implied, but not explicitly included, which I think is the most fascinating part.  Here's the breakdown.

The top of the rope is our world.  We are walking in our world.  The bottom of the rope is the Upside Down.  The flea is the demogorgon, walking in the Upside Down.  The flea, moving from the bottom to the top and back, is the monster moving through the portal and back again.  The part implied is all the side of the rope that the flea moves through.

The rope itself is a kind of object, in mathematics called a manifold.  A manifold is a generalization of the concept of space.  The space we occupy is a manifold, with three dimensions.  The spacetime of general relativity is also a manifold, with four dimensions.  The surface of a sheet of paper is also a manifold, with two dimensions.  Another very common example of a manifold is the surface of a sphere, this one also with two dimensions.  The surface of a donut (a torus) is also a two-dimensional manifold.

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When I draw a picture of a three-dimensional room, I am embedding that room into two dimensions.  I'm collapsing the full dimensionality to express the space with fewer dimensions.  Embedding is commonly used to illustrate curvature of four-dimensional spacetime in only two dimensions.  

For instance, you have likely seen an embedding of a black hole into two dimensions.  The image deceptively makes it look as though a black hole is a big literal hole in the floor. What it is instead showing is curvature in a four-dimensional space projected onto two dimensions in a way we can make sense of.  Each circle in the diagram is actually the surface of a sphere, and the "downward" dimension doesn't truly exist in the usual sense.

The rope of the analogy, as described, is an embedding into two dimensions of a five-dimensional manifold.

Four of the dimensions from the manifold are spacetime.  These four dimensions are collapsed into a single line, the tightrope the acrobat walks on.

But there is an additional dimensionality, which is a circle (also called a 1-sphere), made by considering the sides of the rope on a slice perpendicular to spacetime.  One point on this circle corresponds to a location in our universe (Steve's pool, say).  Another point on this circle corresponds to the parallel location in the Upside Down (the pool Barb wakes up in).  Movement through the portal corresponds to moving around this circle between our world and the Upside Down.  This is an additional degree of freedom (what I mean what I say "dimension"), that grants additional movement.

We can't move in this way.  But the demogorgon can.

The creators of the show have said, the name "demogorgon" is what it is called in-universe.  It's what the kids call it.  In the creators' notes it is called a "shark," and at least once explicitly related to a shark in the show.  Like a shark, the demogorgon has ways it can detect living beings around the circle of the rope, and then pass through the circle to reach those beings.

Prior to Eleven making contact, we were too separated along the rope-edge for the demogorgon to sense us.  It was presumably content to hunt in its own spaces, closer to the Upside Down.  After contact, it became aware of us and hunts between our worlds.

One point on the rope-edge circle is our universe, another the Upside Down... but this is a circle.  There are a lot of points.

What other things are lurking in the rest of the rope?

This is where I think the show could have gone.  The first season introduces (maybe without knowing it) this cosmology of worlds of horrible monsters lurking just beside us.  It implies interdimensional hunters, and possible worlds of thinking beings similar to ourselves plagued by war with these beasts.  It implies perhaps the Upside Down is just one particularly horrible location, but passage through portals could create contact with other races of beings, some benign, others far worse.  It sets a landscape for cosmic horrors, of beings completely indifferent to human life except as a food source.

The first season reminded me of a Lovecraft-themed board game I used to play with my friends, called Arkham Horror.  It's not a family board game, or good for parties, and is the kind of board game you should only play with people who really really like board games.  In the game, you play a team of adventurers individually investigating strange occurrences throughout a small university town, fighting monsters and closing portals and searching through creepy abandoned houses.  Or the first season was like a mix of Scooby Doo and Call of Cthulhu.  And mixed into it were science fiction themes, not merely magical, supernatural ones.

The later seasons weren't bad, and built more on the characters and their relationships than the world created or the original tone.  I think audiences will always prefer strong characters and friendships over intricate world-building.  It became more psychological and supernatural horror, and the Upside Down became more of a spiritual than literal space.  I think there was a lot of lost potential that was built-up in the first season, and the later seasons lost their way from it.

Psychic Powers

I mentioned that Eleven has psychic powers.  And I mentioned that this is an established enough trope that I don't have to explain what that means or how it works for most audience members to accept that she does.  But let's think about what it actually means.

A fellow grad student once raised the question with me, how far beyond our skull does our mind extend.  I originally thought it was a stupid question, but maybe it's not.  The brain itself is complicated, but the mind even more so, and we don't exactly understand how it does what it does.  But we do know that your mind is related to your brain, and related at least partially to the interconnectedness of neurons in your brain.

I'm being very careful with my language here.  The mind and brain are correlated, but we don't actually know what the correlation is.  Some people think your mind is like a software that runs on your brain, so that the brain makes the mind.  But it is equally possible that your brain is just the physical tool your mind uses to think with.  But the mind and brain are not completely independent, and so correlated.

The brain works by transmitting electrochemical signals (currents of positively charged ions) across neurons, and these signals are related to your thoughts, memories, and emotions.  The transmission of these electrochemical signals depends on electromagnetic forces inside your brain which are driving the charged ions through neurons causing interaction of different signal pathways.  And those electromagnetic fields extend beyond your skull though their intensity very, very quickly dies down.

To the extent to which it can be said your mind is formed by the interactions within your brain, then it can also be said that your mind extends beyond your skull, as those interactions are not limited to your skull.

You can add in, then, how external stimuli interact with the neurons that interact with your brain.  Light from an external object strikes your retina.  The light is an electromagnetic signal, it strikes nerves in the eye, triggering another electromagnetic signal that is correlated to your mind.  Smell is similar.  But what about direct interactions of external electromagnetic fields with the signals within the brain.  There are things like the "God Helmet" that can induce psychedelic experiences using electromagnetic waves.  

What other possibilities are there?

You could imagine (imagine), that if someone had a powerful enough brain, the brain's field could extend far enough beyond the skull to interact tangibly with other objects, to the extent of pushing things.  It would not be as simple as thinking really hard about pushing a chair and the chair would push.  It wouldn't be simply "reaching out" to the chair.  It would require training your brain to think in a certain way so that an "unintended" consequence of your thoughts would be a strong electromagnetic field in an area capable of knocking over an object.

The object so manipulated would have to either be ferromagnetic, have a net charge, or else the field be so strong it also induces a dipole charge in a neutral object.

You could also imagine (imagine), that if someone had a powerful enough brain, the brain's field could extend and overlap with another brain's field, and then incorporate those signals back into its thinking.  It would not be a simple as seeing images and thoughts and hearing a voice.  It would initially register as confusion, and would take careful training to decipher what it means.

You could also more easily imagine (imagine) someone with a strong brain field simply zapping another person's brain field, inducing "psychic damage" in this way.

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This is how I think psychic powers would work, if there were such a thing.  I don't think human brains are powerful enough generators of electrical signals to qualify.  I don't think most power transform stations are powerful enough generators to qualify.  For a human, it would require metabolizing enormous amounts of Calories in a very short period of time.  More Calories than I think you could store in food.  It would also require far more blood flow than human vessels could support.

But for fantasy purposes, those are some guidelines.  The nosebleeds are good, and Eleven should also become ravenously hungry every time she uses her powers.  She might require a specialized food made in Hawkins Lab that is ridiculously energy-dense and allows her to metabolize quickly.  Mike should feel his fingers tingle and his hair stand on end when he's elevated (since he's receiving an induced charge).  Lucas should get a static shock when he hits the side of the car after Eleven pushes him.

So those are some of my thoughts on the science of Stranger Things.