ArticlesBlog

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

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.

Comments (100)

  1. See that's a thought experiment.

  2. ok but what if the box was made of glass :/

  3. Yeah cat can be ket and ket… vectors.

  4. How do they even remotely think this video makes any sense whatsoever

  5. Did anyone else watch this because they didnt get that part of bunny girl senpai?

  6. The only bit I understood was the covalent bonds bit because…school.

  7. So is the cat dead
    Schrodinger: yesn't

  8. This is the dumbest thing ever. Is the cat dead or alive? Who gives a damn?

  9. Quantum Physics?

    That's sakuta's favorite subject 😁

  10. Lol i got an ad for the musical movie cats

  11. ok. musk bring u here blablablabla

  12. I try to understand but i can’t

  13. i just heard chips

  14. This is how D4C works

  15. If you don’t like to think of dead cats think of the light in your refrigerator. Is it on when the door is closed or is it off? I know there’s a switch but how do you know the door being fully shut doesn’t bypass that switch?

  16. Actually i'm here cuz of Seishun Buta Yarou

  17. Who's here from the teen Titans episode?

  18. Dint quite understand completely apart from the cat logic. But thats ok for the first time of even knowing there is a theory like this.

  19. What still confuses me is that the cat has any percentage of dying and living not just 50/50. If you open the box, it doesnt matter if its alive or dead, if you dont know the statistics of if it was going to die or stay alive. Im so puzzled.

  20. I understood everything until he talked about the electrons

  21. So this is where the Copenhagen Interpretation comes from? … A thought experiment based on our inability to understand/observe the subatomic?

  22. I understand it but I also don't understand it

  23. I saw this first in Big Bang Theory…………

  24. ok ma g. how you get from cats to atoms

  25. Thats cool and all but im watching this on my phone

  26. I just came here from an anime

  27. paradox: the cat has a slit that can be closed by it and a screen. if the cat is closing it and looks at the screen he either sees his own death or schrodinger not finding him.

  28. In that case, our brain may and may not exist. Nonsense.

  29. But he can HEAR it die inside the box? Cat must make a noice when it dies.

  30. Put a camera in the bunker

  31. What if you don't decide to open the box because you fear it will be dead and after few days you smell your cat's body rotting away?

    How are you going to explain this?

  32. yes that makes sense but at the same time it doesn't

  33. Trees don't fall until you witness them fall.

  34. disclaimer: this part of my comment was written before i finished watching the video
    so we just gonna watch a youtube video about some dudes cat? bruh ok sure i'll watch.

    this part of my comment was written after i finished watching
    ok nevermind the cat was imaginary and the guy was a scientists and its interesting

  35. To be honest though in my opinion either the cat will be alive yet it will be dead for either a couple of days or so, because I have a theory that radiation will continue to grow and spread to the cat's body, or it will be dead instantly

  36. I just want to watch cat,but what i saw was the atom???

  37. Me: fails physics in all previous exams

    Also me: watches this video and low-key hoped that I would understand

  38. You all should go watch Rascal does not dream of Bunny Girl Senpai

  39. Utter nonsense based on particle based physics that is not valid today. Interesingnly he knew that in the early 20th century

  40. Who is here because of Aobuta?
    |
    /

  41. If you put a cat in a sealed box for an hour it would be dead when you opened the box. No death device necessary. Because I'm a very simple person, who understands nothing about quantum theory, but I know enough to tell you a cat in a box with no air for an hour is going to die miserably. I'll call that Practical Theory. Works for me.

    Besides, just because you don't know if it's dead or alive does not mean it is both at once, it means you lack information, education, and common sense. Open the box. Your cat is dead. It has been dead. It wasn't alive just because you didn't know about it being dead. It was still just dead. The cat was never in question of that. This is a problem with the person opening it, they are the one uncertain. The one in two states of mind is them. Cat is still dead, the person is just a confused, sad mess of a human being.

    Seriously? This is like a fancy description with a full theory for that thing kids do where they put their fingers in their ears and hum, then assume if they didn't hear it that it isn't real and does not exist. Ask any parent how well that one ends for the child in question (hint: it usually involves extra chores at best). Schrodinger was a famous physicist with many contributions and degrees. Who also never grew up. Then everyone who came along after thought this was perplexing because they didn't grow up either. Sounds about right from I've seen of humanity.

    This is what stumps intelligent minds across the world? Here's a theory. We're all on this rock with these people. Many of us are even worse at a lot more things than scientists who study this are. With this in mind consider the future of the human species. What's in that box of possibilities? Because we might all just be cats watching the lid shut above us. A far more pressing question to answer if you ask me.

  42. "To be or not to be…"

  43. How dare you do this to an innocent cat!

  44. Big Bang theory anyone ?

  45. I get that the cat is either dead or alive and can only be determined once we've open the box but I don't understand how we can say that it's both dead and alive. While its true that we are not certain about its condition the fact of the matter is that it is confirmed. For example, if it died it's dead. We just do not know or do not have confirmation until we check. What point is there to say it is alive. Just because we didn't check doesn't make it alive.

  46. Rick and Morty talking cat brought me here.

  47. Me: so is the cat alive?

    Schrödinger: um yes and no

  48. Or, like Hamlet said, 'To be, or not to be'.

  49. Watch 2:06 and than this: https://www.youtube.com/watch?v=pznWo8f020I from 25:48

  50. thought I was understanding but then I sneezed and lost where I was

  51. Rascal does not dream of bunny girl senpai anyone?

  52. i come here after watching seishun buta yarou and myriad colors phantom world

  53. the only thing that I understood that I understood and not

  54. I still don't understand it. I realize that this is a thought experiment, but it's not applicable to anything. In fact, it's rather silly to even suggest such a thing. Just because you can't see the cat doesn't mean it's simultaneously alive and dead. The cat is either alive or dead.

  55. I no longer take much interest in science getting my belief it’s not the same electron is in two places at one time but yet The result of that electron is not the end result of what you’ve caused but a chain reaction to cause the same result

  56. This makes no sense, but you can't stop watching it cause it's so interesting

  57. am i the only person who's actually feeling bad for the cat 😡

  58. For some unknown reason, this topic make me remember of the Teen Titan talking about quantum mechanics

  59. Mamma’s Spaggehti

    (A better version of Scrodinger’s cat?)

    So your mamma puts poison in your spaghetti then tells you to go in the box with the spaghetti. Then there is a 50 percent chance that it will harm you and a 50 percent chance it won’t. So you eat it and your mom opens the box and your either ded or alive.

  60. Brain has left the chat

  61. But what if you didn’t open the box and the cat just dies of dehydration or starvation…

  62. TED-Ed : Do you understand?
    Me: yes but no!
    .
    .

  63. I just remember shrodinger vat from "the unadulterated cat" terry prach

  64. 4346477645798366306374475375706764356675657

  65. Person: Hey cat, are you alive?

    Cat: Yesn’t

  66. Why not use a clear box

  67. God, im not really for all these knowledge

  68. What a cat-astrophe Theory.
    Lol😁😁😁😁😁

  69. This is like Mumbo Jumbo talking about redstone

  70. G͞et in͞ t̸h͘e̡ ҉b́o͠x͠

  71. "sir is the cat alive or dead?"

    Shrodinger: YESN'T

  72. Is the cat dead, or is it alive? I have an answer. Probably actually.

  73. First of all, the easiest experiment is to say whether 0 is a negative number or a positive number.
    Second, it is to say whether a tossed coin will result head or tail.
    Why Shrödinger chose such a complicated way to explain superposition?
    Conclusion :—
    Neutral = superposition

  74. correction
    I'm on a phone

  75. Dont trouble cat, here is the thig.
    Watch "Smallest particle" on Youtube
    https://youtu.be/A3SSf-PoBg4

  76. I've been reading about atoms and I'm a bit confused. According to the internet "electromagnetic force" holds the protons of the nucleus and electrons together while kinetic force of the electrons pulls them apart. But isnt this just general relativity?

    As in; at first sight electrons and protons dont appear to be perfect opposites because an electron behaves differently (whizzing around outside the nucleus) and is also 1832 times less massive. But its energy is also comparably more massive than the proton per unit mass (MEv)

    This is in line with the Energy – mass equivalence (E=mc2) suggesting that an electron is the antithesis of a proton but one has converted the majority of its mass to energy (electron), the other remains mainly mass and less energy.

    So what is electromagnetic force? And assuming the the electron uncertainty cloud could be "cooled" to a state of equal mass/ energy as the proton (reducing its ability to stay away from the proton – kinetic energy) would they come together and annihilate eachother? Or leave just neutrons (0).
    Wouldnt this mean that at absolute zero kelvin (heat death) atoms would vanish or at least leave neutrons?

  77. so the cat is dead and alive and if the cat is dead by now the cat is now double dead?

  78. ok this is what i got from this video (and another vid) my sister (at the time of me writing this) is in her room sopossedly "reading". bit i wouldnt know what she was doing unless i opened her door. but behid the closed door nothing in the room exists. and whatever she was doing didnt exist until i open the door. but the wierd thing is, she still does exists along with everything in her room. but i wouldnt know unless i open the door.
    idk if that was roght but i think i got the idea of it

  79. It was fun not until he stopped saying cat. 😕

  80. I, uhhh, yeah I don’t understand

  81. "Two states at once" — this shows they trying to explain QM they don't understand themselves. There is no at once in quantum system.

  82. it's dangerous for mind try to understand the quantistic physics , i prefer use the Copenhagen interpretation , shut up and calculate , but for human spirit this isn't enough , this is the problem .

  83. So… what happens if you put a camera into the box and do the test again?

  84. Very well explained by Indian Film Maker Thiagarajan Kumararaja in the movie "Super Deluxe" by the character Gaaji's shirt.

  85. This makes sense since I equal parts understand it, and don’t at the same time

  86. Shane Dawson has entered the chat

  87. Schrodinger : thinking about quantum theory
    his cat : sweat

  88. Two beams of Light pass through each other without hitting each other like a wave.
    If it were a particle it would have bounced off each other.

    But it also transferred packets of energy to metal plate called quanta. Quantum physics

    0:40
    2:10

  89. "Who shot Johnny Joestar?"

    YES

  90. 2:28 how did the electron end up in the middle?

  91. Me: expects a reference from the big bag theory in the comments
    Comments: none

    Me: 😕

  92. Wow this is just bs lol

  93. so its neighboring dimensions?

  94. I only searched this up to see if it help explain D4C from JoJo's Bizzare Adventure…

  95. Who's here from Will Grayson, Will Grayson?

Comment here