Tell me how often you’ve seen this – a sci-fi movie needs to justify its plot so in a 30-second scene some “scientist” in a lab coat throws the word quantum in an overlong sentence and the movie just moves on. WELL SCREW THAT! The movie can’t continue until I know exactly what the word quantum even means, much less if that made sense! I am that guy who ruins movie nights, and they let me write an article!

Quantum mechanics has a reputation, of being obtuse and unintuitive. While these claims may have some truth to them, I want to prove that it’s actually fairly simple. All so that we can criticize movies better together!

Quantum Mechanics is the branch of physics that deals with atoms and their interaction with light. Prior to the 19th century, the model used by physicists to describe the world was called classical mechanics; it assumed that all things were made up of particles (minute portions of matter, like atoms and their constituents, protons, neutrons and electrons). Quantum mechanics instead said that these particles were capable of behaving both as particles and as waves simultaneously. This decidedly weird behaviour could then be described by a special equation called the wavefunction, which, in the simplest terms possible, describes the likelihood of a thing to be found in a certain place while moving with a certain speed.

In short, what the word “quantum” means is distinct. It describes things that can only be in distinct states, like electrons and their orbit around a nucleus. Imagine it like this – when you go to an ice-cream shop you can ask for 1 or 2 scoops of whatever. You can’t ask for 3/7ths of vanilla and 0.46 scoops of mint (ew, vanilla and mint together, you reprobate). The same goes for electrons. They can’t just orbit anywhere around a nucleus; they need to be found in a certain area of space, moving with a certain speed, which is defined by their wavefunction. Unfortunately, because of something called the Heisenberg uncertainty principle, we can’t pinpoint a particle’s position or speed exactly. If we knew one of these properties with perfect precision, we would have literally no clue about the other. This is where a lot of the weirdness of quantum mechanics starts to emerge.

Because of this inherent uncertainty, quantum objects (anything roughly smaller than a few atoms) are in a state of superposition; until they are observed, which causes the superposition to collapse into a steady quantum state. So that was a brain-wrinkling sentence, huh? Let’s explain it! 

Superposition means that a thing isn’t quite in one state or another, but rather both at the same time. For instance, I could spin either clockwise or counterclockwise, but an electron can spin in both directions at once! That’s a concept which we cannot possibly fathom, due to the classical way in which our brains work. But thankfully, the moment you take a look at an electron it somehow decides which one of the two ways it wants to spin and just sticks with that. That is all that the big, scary sentence meant – things are in all their possible states until something makes them choose one state by observing them. When you’re buying a single scoop of ice-cream, that scoop is all the possible flavours at once, all at the same time, until you actually make a choice and all of the possibilities, except the one you chose, are eliminated – this is superposition and collapse.

An interesting effect of superposition is the “many-worlds interpretation” of quantum mechanics. What it states is that no choice is made to the detriment of any other – you didn’t pick a single flavour of ice-cream, you picked them ALL. Except for each flavour, an entirely new reality was created where that is the only difference to this one! This idea tends to send most people into an existential panic and most screenwriters into fits of joy because they just found an excuse to create an apocalyptic timeline of Earth. Thankfully, what the happy writers often ignore, is that these alternate realities cannot actually interact. So, you don’t have to live paralyzed by fear that your decisions could destroy a whole other reality because even if they did, you’d never know...yayyyyy! Most physicists in fact insist that if the many-worlds interpretation is true it has absolutely no effect on how we ought to live our lives – any choice you make will only define your own reality and nobody else’s.

Another interesting effect caused by quantum mechanics is called “quantum tunnelling” and it’s the idea that quantum objects have a small probability of travelling through solid matter, given that the barrier placed in front of them is thin enough and they have enough energy. Imagine that you’re bouncing a ball against a window and it doesn’t bounce back. It doesn’t break the window, it just kind of passes through. This is what quantum tunnelling is like – seemingly impossible, yet observable and even necessary for our very survival! It is what allows for nuclear fusion to occur in stars and is the basis for a lot of electronics. But only for very small objects (size of an electron)!

So the next time you see a kooky university professor explain how they travelled between realities, through time or solid matter using the strange and wonderful powers of a “quantum” googah, end any fun that might be had, with the comfortable knowledge that none of it is possible. Screenwriters have all the scientific literacy of a flock of caffeinated seagulls and your alternate-dimension self isn’t coming to kill you because you forced them to eat vanilla and mint ice cream (though you would deserve it if they did).