Schrödinger’s cat: A thought experiment in quantum mechanics – Chad Orzel


Austrian physicist Erwin Schrödinger is
one of the founders of quantum mechanics, but he’s most famous for something he
never actually did: a thought experiment involving a cat. He imagined taking a cat and
placing it in a sealed box with a device that had a 50% chance
of killing the cat in the next hour. At the end of that hour, he asked,
“What is the state of the cat?” Common sense suggests that the cat
is either alive or dead, but Schrödinger pointed out that according
to quantum physics, at the instant before the box is opened,
the cat is equal parts alive and dead, at the same time. It’s only when the box is opened
that we see a single definite state. Until then, the cat is
a blur of probability, half one thing and half the other. This seems absurd,
which was Schrödinger’s point. He found quantum physics so
philosophically disturbing, that he abandoned the theory
he had helped make and turned to writing about biology. As absurd as it may seem, though,
Schrödinger’s cat is very real. In fact, it’s essential. If it weren’t possible for quantum objects
to be in two states at once, the computer you’re using to watch this
couldn’t exist. The quantum phenomenon of
superposition is a consequence of the dual
particle and wave nature of everything. In order for an object to have
a wavelength, it must extend over some region of space, which means it occupies many positions
at the same time. The wavelength of an object limited
to a small region of space can’t be perfectly defined, though. So it exists in many different wavelengths
at the same time. We don’t see these wave properties
for everyday objects because the wavelength decreases
as the momentum increases. And a cat is relatively big and heavy. If we took a single atom and blew
it up to the size of the Solar System, the wavelength of a cat
running from a physicist would be as small as an atom
within that Solar System. That’s far too small to detect, so we’ll
never see wave behavior from a cat. A tiny particle, like an electron, though, can show dramatic evidence
of its dual nature. If we shoot electrons one at a time at a
set of two narrow slits cut in a barrier, each electron on the far side is detected
at a single place at a specific instant, like a particle. But if you repeat this
experiment many times, keeping track of all the
individual detections, you’ll see them trace out a pattern that’s
characteristic of wave behavior: a set of stripes – regions with many
electrons separated by regions
where there are none at all. Block one of the slits
and the stripes go away. This shows that the pattern is a result of
each electron going through both slits at the same time. A single electron isn’t choosing
to go left or right but left and right simultaneously. This superposition of states also leads
to modern technology. An electron near the nucleus of an atom
exists in a spread out, wave-like orbit. Bring two atoms close together, and the electrons don’t need to
choose just one atom but are shared between them. This is how some chemical bonds form. An electron in a molecule isn’t on
just atom A or atom B, but A+ B. As you add more atoms,
the electrons spread out more, shared between vast numbers of atoms
at the same time. The electrons in a solid aren’t
bound to a particular atom but shared among all of them,
extending over a large range of space. This gigantic superposition of states determines the ways electrons move
through the material, whether it’s a conductor or an insulator
or a semiconductor. Understanding how electrons are shared
among atoms allows us to precisely control the
properties of semiconductor materials, like silicon. Combining different semiconductors
in the right way allows us to make transistors
on a tiny scale, millions on a single computer chip. Those chips and their spread out electrons power the computer you’re using to
watch this video. An old joke says that the Internet
exists to allow the sharing of cat videos. At a very deep level, though,
the Internet owes its existance to an Austrian physicist
and his imaginary cat.

100 thoughts on “Schrödinger’s cat: A thought experiment in quantum mechanics – Chad Orzel”

  1. What this tells me is that we can never make a conclusion of the universe until we've actually seen it. People who do so are just plain fools.

  2. But didn't Schrödinger disagree with the planetary model of atoms or the Bohr model and even made another atom model that opposes with that? And yet… 3:28 3:06 1:56

  3. Well if it meows and scratches the box, it’s alive, but if it’s not making any noise, then it’s dead. But I suppose cats are weird, they can be solid and liquid, so it may not be uncommon for cats to be dead and alive

  4. To: This Comment Section
    From: Minimal Grammar

    If you suggest any form of observation within the box, you should know that the decision happens when you detect the cat. So that wouldn't work.

  5. I imagine my last braincells will be put in a sealed box with my tablet playing this video my brain cells have 100000% chance that they are ded and hav a 0.0000000% chance that they are still alive

  6. Light has no dual nature within quantum mechanics tho correct? The wave like pattern is simply a probability distribution of the particles. This sounded as if it was conflated in the explanation

  7. so as molecules are able to connect and disconnect allowing transformation, such as lungs converting air molecules, electrons are not part of a molecule but instead part of all molecules and so all matter is then intrinsically connected ??

  8. ive been trying to find this for the last 5 months ive been drawing and thinking of all this but i had no idea what it was called, until now. what ive been thinking of and drawing relative to the magnetic field has been this the whole time, either im a genius or im a genius

  9. But the cat knows when they're about to die. When the cat experiences a life-ending experience, they don't exist as both dead and alive at the same time, instead, they are simply dead. The cat isn't in some impossible state of existence, and life does not center around a human's experience. The cat sees said radioactive element react and knows they will die. At least, a cat with the knowledge of a human will know they will die. Usually, the accepted theories require the least amount of explanation. Saying that said cat is dead after said life-ending experience is a lot simpler than saying that said cat is in the state of being both dead and alive simultaneously.

  10. I thought it was making Sence but at the end I either under stood it completely and at the same time under stood nothing at all

  11. I still like the story where schrodinger created a superhero cat who can never die because he's already dead but he never stops because he's also simultaniously always alive. An observable quantum cat. Of course I think if a large quantum object like that ever existed it would destroy physics around itself and eventually the universe.

  12. Ahhahah OMG you said "Atom" and I kept hearing "Adam" which threw me off so much and I already didn't understand much to begin with

  13. With a little though anyone can tell the the statement it self it wrong! The cat is not " half dead and half alive " the cat is EITHER dead or alive ! If it is both until the box is open, would it one or the over if the box is open by a deaf and blind person. The state of the box as no effect on the cat so logically the cat was EITHER dead or alive before the box was open not both.

  14. Part of the cat thing is that the possibilities separate once the box is opened, and the cat is observed. But why wouldn’t the cat be able to observe itself, or tell if it’s dead?

  15. * 1 hour has passed *
    Scientist: so before we open the box the cat is either de-
    Box:meow
    Scientist: ehem ehem… excuse me cocks gun and fuckin shoots the box
    Scientist: as i was saying, the cat is either dead or alive

  16. but that still don't make sesnse. If you did shoot a single eletron it's not gonna split in two, it's wither gonna go left or right … or am I missing something? T^T

  17. Actually both died,…
    1. Cat died because of toxic
    N
    2. Schrodinger died bc , cat pooped in that box…. Toxic smell KABooM……. 😷🤮💥💥💥

  18. I don't understand how the experiment with the holes in a barrier proves that electrons are existing in 2 places at the same time.

    I don't think I'm cut out to be a physicist.

  19. But what if you ARE the cat? You can look inside the box because you’re in the box. So are you alive or dead?

  20. 2‘55“one electron passes two slits simultaneously. Is this true? Does the law of conservation of charges not exist here?

  21. My guess is that the cat would still be alive, but very ill. I am glad that he never actually performed this experiment!

  22. Niels Bohr once said: if you are not confused by Quantum Mechanics then you havent fully understood it🤣😂🤣😂🤣

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