What is Schrodinger's Cat?

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 50/50 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 literally stealing candy from a baby.

Schrodinger's Cat Stealing Candy From a Baby

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

Schrodinger's Cat Posing as a Doctor

Like I say. Total arsehole.

Quantum Theory Explained

Now, let's take in a little background on quantum theory so all of Schrodinger's Cat makes sense.

In the year 1900, Max Planck gave glorious birth to the theoretical study of quantum theory.

Planck said that when it comes to infinitesimal quantum scales, the classical laws of physics no longer apply.

This created a big problem for physicists.

Not only did Planck declare that Newton's laws don't apply at the quantum level, he also said the new rules that apply are stupid and illogical. My words, not his.

An example of this is the Double Slit experiment.

The Double Slit Experiment

This experiment demonstrates how quantum particles behave all silly depending on whether physicists are looking at them.

This 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.

I like to think of such particles as paranoid.

Paranoid Particle

When you fire individual photons of light at a screen with two slits, they predictably pass through either one slit or the other. They accumulate, if you like, to create two straight lines on the detector screen.

Double Slit Experiment Cartoon - Particles

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 behaves like a wave in many points in space.

Just look at this dude.

Quantum Probability Wave

You use exactly the same procedure as before. The only difference is you're no longer measuring (observing) the photons in action.

Yet now the photons leave a completely different image on the detector screen, in the form of an interference pattern.

Double Slit Experiment Cartoon - Waves

This interference pattern reflects wave-like behaviour instead of particle-like behaviour. But why?

For reasons we still don't understand, the individual photons turn into probability waves by splitting into alternate versions of themselves and travelling en masse.

The ghost-photons then take all possible routes through the screen—the top slit, the bottom slit, both slits, and neither slit—all at the same time.

Once through the slits, the ghosts bounce off their alternate selves to create an interference pattern. A bit like ripples in a pond.

If you think this is insane, you'd be right. How can the behaviour of photos change depending on whether we're measuring them?

Get Heisenberg on The Case

To bring some order to this chaos, Werner Heisenberg came up with 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. I assume it's one of the top three reasons why physicists cry themselves to sleep at night.

Quantum Uncertainty

So the quantum world 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 counter-intuitive nature of quantum mechanics, Einstein was still able to further our understanding with his theory of quantum entanglement:

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

Quantum Entanglement Illustration

Einstein already 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.

Even though it was his own theory, Einstein referred to it as "spooky action at a distance" to stress the woo-woo of it all.

He 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 all very much real.

Since then, quantum entanglement has been proven experimentally with photons, neutrinos, electrons and even buckyballs. The phenomenon may have real-world applications in communication and computation, and is an active area of research today.

And yet we still don't know how it works.

Somehow, entangled particles communicate at 99.99% of the speed of light. How can we get to grips with this absurd carry-on?

There are two conflicting theories which hold precedence today.

1. The Copenhagen Interpretation

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

The Copenhagen Interpretation says that reality only exists in hypothetical states of quantum superposition until it's observed.

Einstein agreed with Bohr's maths but refused to accept the conclusion: since reality is made up of quantum particles, it means that nothing is real until we observe 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

Hugh Everett claims the complete opposite of the Copenhagen Interpretation.

The Many-Worlds Interpretation says that every possible outcome of every possible event exists in an infinite number of parallel universes.

Kanye West as a Proctologist Cartoon

The Many-Worlds Interpretation implies that you die horribly an infinite number of times before breakfast.

This extraordinary theory has been favoured by Stephen Hawking and Richard Feynman and the creators of the cutest science fiction show ever.

But What is Schrodinger's Cat?

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. There's also 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

There are two possible outcomes for Schrodinger's Cat:

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.

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.

Now, if you're an animal lover (and who 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 quantum superposition of two states. He's both dead and alive in a hypothetical realm, but neither state actually exists until an observer checks in on the cat.

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?

Or better yet—if a tree falls in the forest and there's no-one around, 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 nonsense 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.

Harking to classical physics, he said it was impossible for a complex organism as large as a cat to be both dead and alive at the same time. He took a non-quantum object, stuck it in a controlled setting, and called up quantum law.

"This is bullshit," Schrodinger pointed out.

Except he was Austrian, so he would have said, "Das ist Kuhscheiße".

We might assume that Schrodinger's Cat was created in support of the Copenhagen Interpretation as a way to better visualise it. But in fact, Schrodinger was vigorously opposed to it.

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

Becky Casale Bio

ABOUT THE AUTHOR: Becky Casale is a science freak and a writer who pooped out Science Me. She is studying for a BSc and writing her first sci-fi novel.