What is Schrodinger's Cat

(And Can I Pet Him?)

What is Schrodinger's Cat and Can I Pet Him?

Don't be a silly sausage, you can't pet Schrodinger's Cat because he isn't real. He's a hypothetical cat in an 80-year-old thought experiment.

The famous cat was created by the Nobel prize-winning physicist, Erwin Schrodinger, to illustrate his objection to quantum uncertainty. But the thought experiment backfired. Instead of discrediting quantum theory, he popularised it by putting it in layman's terms.

Now, in this thought experiment, there's a 50 percent chance that Schrodinger's Cat will be fatally poisoned. So rather than make him cute and pettable, I decided to make him an arsehole. I mean, a really grumpy arsehole of a cat. Don't believe me? Just look at him.

Schrodinger's Cat Cartoon

Here he is stealing candy from a baby.

Schrodinger's Cat Stealing Candy From a Baby

And here he is trying to convince the baby's mother that the vaccines cause autism.

Schrodinger's Cat Posing as a Doctor

Like I say. Total arsehole.

Now let's take in a little background. In the year 1900, Max Planck gave birth to the theoretical study of quantum theory.

Planck had some smashing ideas about the nature of reality at the subatomic level. In particular, he said that when it comes to quantum scales, the traditional laws of physics no longer apply. This was a big problem for physicists.

Not only did Planck declare that Newton's classical laws break down in the tiny quantum world. But he also said that the new rules that apply are completely stupid and illogical. My words, not his.

An example of this is the infamous Double Slit experiment, first performed with electrons in 1927.

The Double Slit Experiment

The Double Slit experiment demonstrates how quantum particles behave differently based on whether or not physicists are looking at them. This nonsensical claim is based on two simple observations.

Observation #1: When a photon of light is being observed, it behaves like a particle with a definite point in space.

Paranoid Particle

So when you fire single photons of light at a screen with two slits, they either pass through one slit or the other and land predictably in two straight lines on the detector screen.

Double Slit Experiment Cartoon

So far, so good. This is reality as we know it. But look what happens when you turn your back on the quantum world.

Observation #2: When a photon of light is NOT being observed, it goes bonkers and behaves like a wave in many points in space.

Quantum Probability Wave

It's exactly the same procedure as before. The only difference is you're no longer measuring the photons in space. Yet now the photons leave an interference pattern on the detector screen, bouncing off each other like interfering ripples in a pond.

Double Slit Experiment Cartoon

This interference pattern reflects wave (water-like) behaviour instead of particle (solid-like) behaviour. Why?

Here's one explanation. When nobody's looking, the singly-fired photon splits into alternate versions of itself, creating a wave of possible alternate realities. It then travels through both slits at the same time, bumps off its alternate selves on the other side, and creates the interference pattern.

Let me explain that another way to be clear - because it's truly a bizarre conclusion.

At the quantum level, many alternate realities are played out for the path of each photon. In some realities it takes the first slit. In some realities it takes the second slit. In some realities it takes neither slit. The point is, all possible options play out at the same time. The many ghostly photons zapping around hit each other and create an inference patten.

If you think this is stupid and illogical, you'd be right. In fact, even the greatest physicists have admitted that the quantum world appears downright insane.

Get Heisenberg on The Case

To bring some order to this chaos, Werner Heisenberg came up with the Uncertainty Principle:

The Uncertainty Principle = it's impossible to know both the position AND the momentum of a quantum particle at the same time without affecting it. By measuring one trait, you automatically change the other and determine its path.

Albert Einstein famously struggled to accept the conclusion of quantum uncertainty. In fact it has long been the main reason why physicist's cry themselves to sleep at night.

Quantum Uncertainty

So quantum behaviour is a big hot mess. But what about Schrodinger's Cat?

I'm getting to that, but first this story gets weirder. Despite struggling with the dreadfully counter-intuitive nature of quantum mechanics, Einstein was still able to further the field with his theory of Quantum Entanglement.

Quantum Entanglement = quantum particles are invisibly connected and "talk" to each other instantaneously, even when separated by vast distances.

Quantum Entanglement Illustration

Einstein himself said that nothing can travel faster than the speed of light. That includes the simultaneous exchange of dinner plans between entangled particles on different sides of the planet.

Einstein referred to it as "spooky action at a distance" to stress the silliness of it all, and concluded the theory of quantum mechanics must be incomplete.

But he was wrong.

After Einstein's death, quantum theory was proven experimentally by John Stewart Bell. Its absurd conclusions and implications are very much real.

Quantum entanglement has been proven experimentally with photons, neutrinos, electrons and even buckyballs. The phenomenon may have uses in communication and computation, and is an active area of research today.

And yet we still don't know how it works. Entangled particle communicate within 0.01% of the travel time of light between them. How can we get to grips with this absurd carry-on?

There are two conflicting theories which hold a lot of ground today.

1. The Copenhagen Interpretation

In 1927, Niels Bohr hypothesised that quantum particles simply don't exist in any fixed location until we measure or observe them.

The Copenhagen Interpretation = reality only exists in hypothetical states of quantum superposition until it's observed. This act forces deterministic outcomes of one way or another.

Einstein agreed with Bohr's maths on quantum superposition but refused to accept the conclusion. Since everything is made up of quantum particles, it means that nothing is real until we measure it.

"I like to think the moon is there, even if I am not looking at it." Albert Einstein
Einstein vs The Moon

Despite Einstein's scathing indictment, the Copenhagen Interpretation remains one of the most commonly taught explanations of quantum mechanics today.

2. The Many Worlds Interpretation

Proposed by Hugh Everett in 1957, the Many Worlds Interpretation claims the complete opposite of Copenhagen.

Many Worlds Interpretation = every possible outcome of every possible event truly exists - inside an infinite number of alternate universes.

Kanye West as a Proctologist Cartoon

The Many Worlds theory states that you die horribly an infinite number of times before breakfast. This extraordinary theory has been favoured by Stephen Hawking and Richard Feynman and whoever created the cutest science fiction show ever.

Schrodinger's Cat Explained

Now you have the elevator pitch of quantum mechanics, Schrodinger's Cat will make a lot more sense.

Amid the quantum hullabaloo of the 1930s, Erwin Schrodinger came up with a thought experiment to illustrate the problem with quantum uncertainty. He started by imagining a cat inside a lead box. A real arsehole of a cat, if you recall.

Beside him there's a hammer, suspended over a glass vial of poison. Triggering the hammer to fall is a Geiger counter, and a single atom of radioactive material that has a 50:50 chance of decaying in the next hour.

That may sound like a convoluted set-up, but being a man of scientific rigour, Schrodinger's idea was to create a set of circumstances in which the cat has a completely random and unknowable chance of being dead or alive.

Schrodingers Cat Cartoon is Alive

So now we have two possible outcomes, largely speaking:

Outcome #1. The atom DOESN'T decay. The Geiger counter doesn't detect any radiation, doesn't trigger the hammer to fall, and doesn't smash the vial. Schrodinger's Cat lives.

Outcome #2. The atom DOES decay. The Geiger counter detects the radiation, triggers the hammer to fall, and smashes the vial. The poison escapes and Schrodinger's Cat dies. Sad face.

If you're an animal lover (and what kind of cold-blooded psychopath isn't?) then consider an alternative victim in your quantum-murder fantasy. Someone who actually deserves to be put in the box, like a racist, narcissistic megalomaniac?

Schrodinger's Trump Cartoon

That's the spirit. Now, according to Bohr's Copenhagen Interpretation, your victim is in a superposition of two states. He's both dead and alive in a ghostly way, but neither state actually exists until an observer detects it.

Schrodingers Cat Cartoon is Dead and Alive

In other words, if a tree falls in the forest and there's no-one around to hear it, does it make a sound? Better yet, if a tree falls in the forest and there's no-one there to hear it, did it even fall in the first place?

It's only when you look inside the box (or shake it, according to Gisby's attempt to circumvent quantum law) that you break the superposition and the cat becomes dead or alive.

We all know it's incorrect to declare that something "becomes dead". It's just bad grammar. But that's the whole problem with quantum superposition, isn't it? It breaks all our comfortable rules.

Schrodinger thought so too. He insisted that it was impossible for a living organism as large as a cat to be both dead and alive at the same time. He took a familiar object and stuck it in a scientifically controlled setting and then called up quantum law.

"This is bullshit," Schrodinger pointed out. Except he was Austrian so he would really have said, "Das ist Kuhscheiße".

Most people assume Schrodinger's Cat was created in support of Bohr's Copenhagen Interpretation as a way to better visualise it. But in fact he was vigorously against it.

Unfortunately for Schrodinger, experimental data continue to show that quantum superposition does actually exist, rendering the whole cat scenario moot.

Becky Casale Bio

ABOUT THE AUTHOR: Becky Casale is the writer, illustrator, marketer, spellchecker, accountant, lunchlady and janitor at Science Me.