What is
Schrödinger's cat,
really?
Can't play sound? The illustrated version is right below.
Read the transcript
The full narration of the video.
A lot of people think Schrödinger said: the cat in the box is both dead and alive. Actually, he told this story to poke fun at an idea. In 1935, the physicist Erwin Schrödinger described a box in a paper. He never built it. It was an experiment in his head.
Inside: a cat and a tiny bit of radioactive stuff. A detector, a little hammer, and a small vial of poison. Within one hour, there's a fifty-fifty chance that one atom suddenly breaks apart. If it breaks, the detector clicks. The hammer drops, the vial shatters, and the cat dies. If it doesn't, the cat lives.
Close the lid. Wait an hour. Is the cat dead or alive? You'd say: it's one or the other, we just don't know yet. Open the lid and look. But many physicists back then said that something as small as an atom, while no one is looking, is neither broken nor whole. It's both possibilities stacked together.
That's not a wild guess. Send electrons through two slits one at a time. The dots pile up into stripes, as if each one took both paths at once. So Schrödinger asked: fine, the atom is stacked. Then what about the detector, the hammer, and the vial that follow it? And the cat? By that logic, the cat is half living cat and half dead cat, smeared together until someone opens the lid.
He himself called it a ridiculous case. His point: move that idea up to a cat, and it falls apart. So the real question is: small things can be stacked, and cats seem not to be. Where exactly is the line? Many scientists today answer: a cat simply can't keep a secret.
A cat is made of countless atoms. They're constantly bumping into air and light. Every bump leaves a footprint. The stacked state falls apart in a blink, long before you open the lid. But why does it end up as this outcome and not the other? Scientists are still arguing about that. Here's the fun part: scientists keep making stacked things bigger. In 1999, it was a tiny ball made of sixty carbon atoms.
In 2023, a lab in Switzerland took a sixteen-microgram crystal and made it shake in two opposite rhythms at once. It weighs about as much as a fine grain of sand. That's still a long way from a cat. But this cat on paper, for over ninety years, has kept scientists moving forward. What science idea still makes no sense to you? Tell me in the comments.
"Dead and alive"
wasn't his point
A lot of people think the physicist Erwin Schrödinger said that the cat in the box is both dead and alive.
Actually, he told
this story to poke fun
at an idea.
In 1935, he described this box in a paper. He never built it — it was an experiment done only in his head, a "thought experiment."
Five things in the box
A cat, a tiny bit of radioactive stuff, a detector, a little hammer, and a small vial of poison.
How tiny is that bit of radioactive stuff? Within one hour, there's a fifty-fifty chance that a single atom suddenly breaks apart.
If it breaks, the detector clicks, the hammer drops, the vial shatters, and the cat dies. If it doesn't, the cat lives.
Close the lid. Wait an hour.
Is the cat dead or alive?
You'd probably say: it's one or the other, we just don't know yet. Open the lid and look.
That atom really can be
"two ways at once"
But many physicists back then said that something as small as an atom, while no one is looking, is neither broken nor whole. It's both possibilities stacked together.
That's not a wild guess. Send electrons through two slits one at a time, collect the dots one by one, and they pile up into stripes — as if each electron took both paths at once.
In 1989, Akira Tonomura's team at Hitachi in Japan filmed exactly that, one electron at a time. Tiny things do plenty of other strange stuff, too — like a magnet that moves electrons without touching them.
So are the hammer,
the vial and the cat stacked too?
So Schrödinger asked: fine, the atom is stacked. Then what about the detector, the hammer and the vial that follow it — and the cat?
By that logic,
the cat is half living
and half dead, smeared
together until someone
opens the lid.
He himself called it a "ridiculous case." His point: move that idea up to a cat, and it falls apart.
So the real question is: small things can be stacked, and cats seem not to be. Where exactly is the line?
A cat can't keep a secret
Many scientists today answer like this: a cat is made of countless atoms, constantly bumping into air and light.
Every bump is like leaving a footprint outside the cat. The world around it has already "taken note" of whether the cat is dead or alive.
The stacked state falls
apart in a blink, long
before you open the lid.
But why does it end up as this outcome and not the other? Scientists are still arguing about that.
Stacked things keep
getting bigger
In 1999, scientists in Vienna got a tiny ball made of sixty carbon atoms to make stripes too.
In 2023, a lab in Zurich, Switzerland, got a sixteen-microgram crystal to shake in two opposite rhythms at once — about the weight of a fine grain of sand.
from a cat.
scientists moving for over ninety years.
Quick check
Why did Schrödinger tell the story of the cat?
He called it a ridiculous case: an atom can be stacked two ways, but if the cat were stacked too, the idea would fall apart.
