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. What’s more, there’s a 50/50 chance he’s about to succumb to a fatal poisoning. 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.
Here he is stealing candy from a baby.
And here he is, pretending to be an expert, and trying to convince the baby’s mother that vaccines cause autism.
Like I say. Total arsehole.
How Does Schrodinger’s Cat Fit into Quantum Mechanics?
In 1900, Max Planck gave glorious birth a new field of theoretical study called quantum theory: reality at the subatomic level. Planck tried to explain the nature of the universe on the smallest conceivable scales, where the traditional laws of physics don’t apply.
This is a problem for physicists. Not only do Newton’s laws break down in the quantum world, but the new rules are spooky and illogical, to say the least. For instance, quantum particles literally behave differently depending on whether or not you’re measuring them.
Here’s how a single photon of light appears when you measure his position or momentum. He’s a fixed particle at a definite point in space:
The Double Slit experiment famously illustrates how, when measured, single photos fired one at a time through a screen with two slits must act as particles. The particles pass through one slit or the other (or neither, bouncing off) and land predictably in two straight lines on the rear detector screen.
So far, so good. This is reality as we know it. But wait and see what happens when you turn your back on the quantum world. When you stop measuring a photon’s movements, he goes bonkers and behaves like a wave of probabilities:
Despite being fired one at a time, the photons now behave like a wave, leaving a complex interference pattern on the detector screen.
There’s only one conclusion. And it’s freakishly disturbing. Each individual photon of light travels through both slits simultaneously as a wave of probabilities. On the other side, he bounces off his alternative possible selves, leaving a predictable interference pattern on the detector. The photon of light exists in all possible states at once. But crucially, only when no-one’s looking.
The quantum world is downright insane.
Get Heisenberg on The Case
To bring some order to this chaotic observation, Werner Heisenberg (Walter White’s hero) came up with the Uncertainty Principle. This says it’s impossible to know both the position and the momentum of a quantum particle at the same time. By measuring one trait, you automatically affect the other. Albert Einstein famously struggled to accept the conclusion of quantum uncertainty, and it has long been the main reason why physicist’s cry themselves to sleep.
So quantum behaviour is a big hot mess. But what about Schrodinger’s cat? I’m getting to that. Keep your hair on.
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. In entanglement, quantum particles become invisibly connected and “talk” to each other, instantaneously, even when separated by vast distances.
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. What the hell, universe?
Einstein found it so mysterious, he referred to it as “spooky action at a distance” to stress the silliness of it all. The only explanation was that the accepted theory of quantum mechanics must be incomplete. But he was wrong. After Einstein’s death, quantum theory was proven experimentally by the Irish physicist John Stewart Bell. Modern experiments have measured entangled particles communicating within <0.01% of the travel time of light between them.
Quantum behaviour is breaking the universe. How can we get to grips with this absurd carry-on? The answer is we can’t – but some very famous physicists have certainly tried. Here are two theories which hold a lot of ground today.
The Copenhagen Interpretation
Niels Bohr said that quantum particles simply don’t exist in a fixed location until we measure them. Until they’re observed or measured in some way, such tiny bits of reality only exist in hypothetical states of quantum superposition: across all the possible states at the same time, like overlapping waves.
Einstein agreed with Bohr’s maths on quantum superposition, but he 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,” quipped Einstein.
Despite Einstein’s scathing indictment, the Copenhagen interpretation remains one of the most commonly taught interpretations of quantum mechanics today.
The Many Worlds Interpretation
If you think that’s disturbing, this next explanation is really no better. Proposed by Hugh Everett, the Many Worlds interpretation claims the complete opposite of the Copenhagen interpretation. Everett suggested that every possible outcome of every possible event does exist – but in an infinite number of alternative universes.
The Many Worlds theory says that I have already died an infinite number of times, which doesn’t sit too well with me. Still, this extraordinary theory has been favoured by Stephen Hawking and Richard Feynman and whoever created perhaps the cutest science fiction show ever.
And The Cat?
Now that you have the elevator pitch of quantum mechanics, Schrodinger’s cat is going to 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 imagined 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 sounds like a convoluted setup. But, being a man of scientific rigour, Schrodinger’s idea was to create a set of circumstances where the cat has a completely random, unknowable chance of being dead or alive.
If the atom doesn’t decay, the Geiger counter doesn’t detect any radiation, trigger the hammer to fall, or smash the vial. Schrodinger’s cat lives. If the atom does decay, the Geiger counter detects 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, which you absolutely should be, why not consider an alternative victim in your quantum murder fantasy? Someone who actually deserves to be put in the box, like a racist, narcissistic megalomaniac?
That’s the ticket. According to Bohr’s theory, the victim is in a superposition of two states. He is both dead and alive in a ghostly but also literal sort of way. It’s only when we look inside the box (or shake it, according to our friend Gisby’s attempt to circumvent quantum law) that we break the superposition and the cat becomes dead or alive. We both know that 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 tried-and-tested laws.
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 in the same universe. And that is what Schrodinger’s cat is really all about. 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”.
Ironically, many people think Schrodinger’s cat was created in support of Bohr’s Copenhagen interpretation as a way to better visualise it. I bet he hated that. Unfortunately for Schrodinger, experimental data continue to show that quantum superposition does actually exist, rendering the whole cat scenario moot. And you didn’t even get to pet him.