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Basic Human Intuitions That Are Left Completely Shaken By Quantum Mechanics

Our experiences help build our assumptions about the world. They form our intuition.

Einstein may have believed that human intuition is our greatest gift, but as we make our advancements in science, that intuition isn’t much of a help. You would be surprised to know that some scientific experiments even leave some of our most basic intuitions completely violated, which we so easily take for granted in our daily lives.

(Correction — The above quote must actually read ‘The only real valuable thing is intuition.’)

Let’s discuss 3 of such human intuitions that you would very easily relate to. Technically they are called —

  1. Object Permanence
  2. Realism
  3. Locality and Causality

The terminology might sound a little overwhelming and as if some really nerdy stuff is about to come your way; but honestly, they’re so simple to understand that you can even tell it to a young school kid.

The only reason most of us feel uncomfortable with those terms, is because nobody ever bothered to teach us about them, very conveniently believing that we already understand them because they are part of our intuition after all. That is, our teachers and elders at home, everybody felt that these 3 ideas are so deeply intuitive that we don’t even need to learn about them, they just come to us naturally as humans.

Well by now you’re probably craving to know what these terms really mean and how have you never come across them if they’re so simple to understand. So let’s get to them!

Object Permanence — A Peekaboo Universe

You might have played “Peekaboo” with babies and toddlers. It’s a simple game where you cover a baby’s eyes with your hands so that he/she is unable to see you and then suddenly you take away your hands to let him/her see you again. The baby laughs! (or cries if not particularly sporty) But you get the point.

Now think —
What makes the babies laugh? Why is this game so funny for them?
The answer is pretty simple. The moment you cover the baby’s eyes, the baby starts to believe that you are gone, that you have disappeared. The moment you remove your hands, the baby believes you just appeared from thin air. And this is quite funny for the baby to handle.

You were like that too once upon time! But by the time you were 12 months old, you had already built

an intuition that objects & people (of course) keep existing even when you are not looking at them.

When objects are hidden from you behind a curtain, you still tend to reach out for them, believing strongly that you will find them where they were behind the curtain. That is you showing the earliest signs of ‘Object Permanence’. And in no time, this idea of objects existing permanently whether you are looking at them or not is embedded deeply within you. So much so that when you are old enough, you never question it. And for quite the same reason, no one else cares to question your intuition either.

Well hoping that you have now discovered this Intuition Number 1 inside you, let’s move on to the next.


This is somewhat similar to our intuition of Object Permanence. Realism means that —

Nature exists independently of man’s mind. (source)

Properties of an object (say its mass, position or momentum, etc.) are real even when we are not measuring their value.

Okay! This might have sounded a little absurd and confusing. So let’s understand this with an example. Wherever you are at the moment, close your eyes and imagine that there is a fly behind you buzzing around. Let’s say we even take away your power of hearing for now. So you cannot see, hear or touch the fly (that is cannot measure it) in any way.

The Big Question!
Considering there is a fly behind you, are you just imagining that it has a speed? Or does it actually (“in reality”) have a speed with which it moves ?

If you take some time to internalise this, you’ll realise it is a profound question for someone to even come up with. Only someone who is able to completely detach himself from his intuitions, and stop taking for granted even his most basic beliefs, can ask such a radical question.

So what’s the answer to our question? Well people who believe in ‘Realism’ would say, that it’s not just in our mind, the fly actually moves with some speed.

You’re probably thinking this is so absurd, that it is obvious that the fly must have some speed in real. But then again, that’s precisely what you have to understand, that this idea is so basic, so intuitive, that we just take it for granted, that we consider it “so obvious”. What if it’s not!? What if this reality of the world that we perceive is just in our mind. (Remember the movie The Matrix. The character Neo used to believe that the computer generated artificial world called the ‘The Matrix’ is real, until he was unplugged.)

But let’s not get too lost here. Let’s give you your hearing back and move on to Intuition Number 3.

Locality And Causality

These two are comparatively easier to understand and not as mind-boggling.

The concept of Locality says that —

An object is only directly influenced by its immediate surroundings. (source)

Well this is understandable. If we imagine people standing in a queue, and the last person trying to push the queue forward, his push only affects the person right after him. The first person in the queue doesn’t receive the push directly from the last person, but instead from the second person in the queue. Something similar is observed in most events in our daily lives, for example, the propagation of sound waves across air molecules, the transfer of heat from molecule to molecule, etc.

The ‘Effect’ from a ‘Cause’ is always local and it takes time to propagate.

Locality has a very interesting outcome that was taken into consideration very closely by Einstein, called ‘Causality’. Causality is taken as an assumption in most of his theories.

The concept of Causality says that —

The effect cannot happen before its cause. And that the effect created by a cause cannot travel faster than the speed of light.

The reason Causality can be thought of as an outcome of Locality, is because we believe that an object is affected only by its immediate surroundings, the speed of the effect travelling from object to object thus gets automatically limited, and as per Einstein’s theory of relativity, this speed cannot be faster than the speed of light. Why the effect cannot travel faster than light is a discussion meant for another time.

What’s important to realize at this point is that we have grown to consider Locality & Causality quite intuitively as well; in a very taken for granted manner. We almost always realize that the effect takes a bit of time to propagate. Even if the effect appears instantaneous, intuitively we realize that there is some time-delay.

For example, the effect of the TV channel getting changed on clicking of the remote button (the cause). It looks immediate but we internally realize that the two events did not occur at the same time. And the idea that the change of channel can happen before the button is clicked is completely out of question. Intuitively we believe, that the effect would have happened only after the cause.

Hopefully, you’ve gotten in close touch with these 3 basic human intuitions inside you by now. Because its time we discuss how the Quantum world completely shatters these intuitions.

Welcome To Strange World of Quantum Mechanics

If you’re completely new to the idea of Quantum physics, it’s not a big deal. It’s just studying how things behave in the world of sub-atomic particles (Quantum World) like electrons. And Quantum Physics comprises of the various theories that scientists have built or are working on to explain the various phenomenon in this world of the small. Here’s a brilliant guide for beginners on Quantum Physics —

Without getting too deep into the why, here are the weird phenomenon in the quantum world that leave our intuitions violated.

  1. Particles (like electrons) may or may not exist at a specific location when not being observed. They might be present at a range of possible locations when not being observed. But the moment the particles are observed or measured using a device (like a screen), they take up one definite location out of the many probable locations.
    ViolationThis is different from our normal macroscopic world where our basic intuition of ‘Object Permanence’ makes us believe that the particle should be present where we last saw it. It can’t be at multiple probable locations when we are not looking at it. However the observation of a wave-like interference pattern on the screen created by particles shot in a double-slit experiment, can only be explained by considering that particles behave like a wave of probabilities when not being observed. It’s completely unintuitive!
  2. Particles possess a range of probable values for each property like location, speed, momentum, spin, etc. when not being observed. When observed or measured, the properties take up one definite value out of a range of probable values.
    ViolationThis is different from our macroscopic world where our intuition of ‘Realism’ makes us believe that the particle must have definite single values for each of its properties when not being observed. Just like the fly having a specific speed even when we are not looking. Its speed is not an imaginary wave of probabilities, but one very real and specific number as per our intuition. However in the quantum world experimentations show us that when not being observed each property of a particle is a probability wave with multiple possible values.
  3. We observe that the collapsing effect of the wave function (probability wave) of an entangled system of particles, is observed to take place at the same time without any delay even when the system is stretched (particles are taken away from each other) to very far distances in the universe. The collapsing effect is seen immediately at the individual locations of each particle.
    ViolationThis violates our intuitive concept of locality and causality that effects cannot travel faster than the speed of light. But here a particle in the entangled system immediately collapses to one specific state as soon as a measurement is made at the other end separated by very far distances. This has even been proved to happen experimentally.

By now you probably have realized that the Quantum world is really weird and it has baffled scientists for years because of experiments in the quantum realm that violate our normal everyday intuitions. While many scientists have accepted this un-intuitive nature of quantum particles and taken up the challenge to explain them, some famous scientists including Einstein kept serious reservations about quantum theories (like the Copenhagen Interpretation).

However un-intuitive, quantum mechanics definitely has opened up a vast new field of science and given us a new perspective to challenge and question the reality as we perceive it.

Thanks for taking out time to read this.

I’m a co-founder of Clerro — a publishing platform for educators to explain intellectually compelling topics from math, science, art, history, philosophy, etc — away from news, opinion, personal stories and marketing speak.

Clerro is a . Away from news, personal stories and marketing speak.

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Utkarsh Sinha

Utkarsh Sinha

Programmer. Cat lover. Cofounder @ Betaflux

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