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Save Schrödinger’s cat – dead or alive!

28 December 2011

I’ve always had a problem with Schrödinger’s cat. Not his actual cat, you understand (as I never met it), but his thought experiment designed to highlight the flaws of the Copenhagen interpretation of quantum mechanics. Hold on, don’t panic! There’s no reason to reach for that ‘close browser tab’-button. It’s only a little bit of quantum physics. Just like grammar is the basis of language, quantum mechanics is the basis of the universe. What’s that? You rather read about grammar instead? Why, of course; go right ahead! The Lucy’s football post is a really good one, I’ll wait for you here.

“I’m a quantum cat, me!”

You back? Good. Anyway, I’m sure you’re already familiar with the Schrödinger’s cat paradox, but let me just recap to show off my own (limited) knowledge in quantum theory:

A cat is placed in a sealed box together with a minute amount of radioactive matter. A Geiger-meter in the box will detect if any of the radioactive atoms decay and emit radiation. The Geiger-meter is connected to a relay that will release a hammer crushing a vial containing poisonous cyanide gas. According to the Copenhagen interpretation, the likelihood of an atom actually decaying and triggering the hammer is represented by a probability waveform, and until and external observer open the box and look inside, the cat will exist in both states simultaneously – i.e. it’s both dead and alive at the same time.

Obviously, no physicists ever conducted such an experiment. They tend to leave such cruelty to us biologists. But the point here is the dual state of the whole system prior to observation: Since we haven’t observed the Geiger-meter, the atom hasn’t collapsed to a state of decayed/not-decayed yet. There seem to be some kind of ‘magical’ connection between the state of a quantum system and whether we observe it or not. If this sounds absurd, it’s because it really is, but it has been proved countless of  times experimentally. Here’s an (only slightly condescending) animated video illustrating just such an experiment:


But back to my problem with Schrödinger’s cat. The idea that the cat would just sit in the box perfectly happy with being both dead and alive is obviously absurd. The cat would naturally observe first hand if the vial was crushed by the hammer (by hearing the glass of the vial being smashed, if nothing else), and would therefore collapse the quantum system to one of its probable outcomes. So, regardless of us opening the box to observe the outcome or not, the system has already collapsed and the cat is already dead or alive.


“Save Schrödinger’s cat – dead or alive!” T-shirt now available in the shop

This whole magical power of the observer is all down to the concept of entanglement, and it relates to coupling systems together. By observing a quantum system, we connect our observing apparatus to it. The observing apparatus contains billions upon billions of quantum particles/waveforms, and the probability of one of them spontaneously collapsing is very high. This will trigger a chain reaction and force all other connected particles to collapse as well, including the coupled quantum system we’re trying to observe. So, by observing a quantum system we inadvertently couple it to our – already collapsed – macro-system, and forces it to collapse.

This is also the explanation for why the world doesn’t behave in that weird quantum way, but in the familiar way we’re used to, i.e. if you drop a ball you expect it to end up on the floor, not to become suspended in a probability wave until we actually observe what happened.

So, collapsing probability waveforms into particles has got nothing to do with whether we observe them or not. It’s by coupling them to a much larger system that entangle them to the already collapsed part of the universe that forces them to collapse. See? No magic. Just probability. Isn’t science awesome?

26 Comments leave one →
  1. 28 December 2011 19:24

    i like schrodinger’s cat. but then i am happy with a bit of ambivalence, and see it as a kind of existential poetic.

    it’s not going to help a scientist along, but it’s just how i roll.


    • 28 December 2011 19:50

      It’s always annoyed me. It just felt like we missed something essential, but most physicists just adhered to the philosophy of “shut up and calculate!”. Now, however, we seem to finally get to a logical explanation of the duality of quantum objects – and it only took 90 years!


  2. 28 December 2011 20:59

    This has nothing to do with Schrodinger’s Cat, really. I’m just amazed that you’re this intelligent AND also fun and personable. You’re the best.

    Also, just try to get a cat to sit in a box for a while without ripping that box to shreds or yowling until you open the box just to get the noise to stop. FACTOR THAT IN, SCIENTIST TYPES.

    I’m also on the poetic side of things – I like the idea of something being both dead and alive at once, and the not-knowing of it all. There’s a poem in there for me to write, somewhere, I think.


    • 28 December 2011 21:43

      Stop it! Please! *blushing* It’s not like I discovered quantum mechanics or anything! I just recently found out the answer to something I’ve always perplexed me.

      The quantum duality is poetic, I guess. But the whole ‘reality doesn’t exist until we look at it’ thing has always felt a bit too anthropocentric for my taste. Why should the universe care if a monkey on planet Earth can be bothered to watch something before it snaps into existance? And now of course we know it doesn’t. *phew*


      • 28 December 2011 23:22

        Andreas DID discover quantum mechanics. Don’t let him tell you any different. Also, he isn’t that personable. He pays people to do that for him. Lots of them.


        • 28 December 2011 23:24

          Also, I suspect lucysfootball only likes this post because it mentions a hammer.


          • 29 December 2011 00:11

            And vials of poisonous gas. Don’t forget those. Without vials of poisonous gas you’re not really a mad scientist. And what would be the fun in that?


          • 29 December 2011 13:58

            It mentions my blog, cats, AND a hammer. It’s really the perfect post.


        • 29 December 2011 00:08

          Well, that’s what you do when you don’t have the time to micro manage – you delegate.


  3. 28 December 2011 23:21

    But when you isolate things down to the very small, they start behaving in that weird quantum way. I enjoy wondering if the world could be performing in an entirely different manner than what we are perceiving. I keep thinking that if I turn around fast enough, I will catch it at its mischief.


    • 29 December 2011 00:19

      That reminds me of an experiment some physicists conducted recently (I forget their names): they managed to get a macroscopic blade of metal to behave like a quantum probability waveform by suspending it in a dark vacuum. So quantum mechanics apply to all matter, as long a it’s decoupled from the rest of the world.


    • 2 January 2012 12:34

      She’s right. This post makes no mention of subatomic cats. Subatomic cats behave very differently than conventional cats. Subatomic cats, for example, are very affectionate.


  4. 29 December 2011 08:57

    Cats have nine lives. QM can’t let the cat out of the box.


  5. 29 December 2011 11:31

    It means that the cat can only be both dead and alive after she has reached her ninth live, which moment has nothing to do with QM.


  6. 5 January 2012 00:13

    No matter how often I read about Schrodinger’s cat (and more than once I have actually sought out explanations of the whole theoretical cat/box/collapsed quantum system debacle,) I never get it. I love Science, (at the Discover Magazine level as opposed to raw data from CERN,) but there are some areas, particularly in physics, where I enjoy listening, but get nothing whatsoever out of it. Like French. In my version the cat contrives to expel the poison gas into the room, killing the scientists, then licks its ass for the laboratory camera before going on to world domination.


  7. Andrew Lawrence permalink
    8 January 2012 16:18

    Its amazing that Schrodinger’s cat causes so much confusion considering he was using the analogy to explain to his class that counter intuitive nature of quantum physics.

    By making the analogy he was trying to show how different the micro world functions to that of the macro world. however all it has done is confuse the world, many people mistaking if for some sort of philosophical existential quandary, to the point where Schrodinger himself is quoted as saying “i wish i’d never mentioned that damned cat!”

    One thing we can be sure of, however, is given Schrodinger’s ability to further confuse anybody looking for clarity on a subject, never ask him for directions!

    you’d probably end up on the wrong continent.


    • 8 January 2012 16:21

      I’m just glad I live in a time where we finally are getting some answers on why macro-systems don’t behave like quantum systems. Exciting times!


  8. 15 January 2012 13:25

    My girlfriend found this hilarious picture of Schrödinger’s cat:


  9. Sharmila permalink
    22 December 2015 23:04

    I enjoyed reading your posts and especially loved the cat in the box image. I also read the book, “The Age of Entanglement” by Louisa Gilder. Philosophy is also a favorite subject of mine. I like how the uncertainty principle applies to real life. Can I use the picture of “the cat in the box”? Please let me know. Thanks.


    • 23 December 2015 07:40

      Glad you liked the post! Haven’t read Louisa Gilder’s book, but might look it up.

      The cat-in-the-box picture isn’t originally mine, and I can’t seem to remember how I got hold of it all those years ago. I think it was made from a picture of a cat in an Amazon box in Japan or something, but not by me. So feel free to use my copy, but keep in mind that I’m not the original creator.



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