Why did Erwin Schrödinger choose a cat?

Erwin Schrödinger

Erwin Schrödinger

I’ll keep this short because it is not very interesting. Erwin Schrödinger was an Austrian Nobel Prize winning physicist. He is best known for what I will call a “theoretical experiment” concerning a cat.The experiment is also described as a “thought experiment”.

The experiment is news worthy because in celebration of Schrödinger’s birthday Google changed their fancy image on their search page to one that represented Schrödinger’s Cat. He would have been 126 years of age. Schrödinger  was born on 12 August 1887 and died on 4 January 1961.

This is the Google artwork:

Schrodingers Cat

Schrödinger’s Cat

Schrödinger’s Cat in the artwork is a tabby cat coming out of a box.

The experiment called “Schrödinger’s Cat” is almost impossible to describe unless you are a quantum physicist with a brain the size of a house so like other websites I’ll take the easy option and quote the man himself:

“A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer that shatters a small flask of hydrocyanic acid.

If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.”

“It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation.

That prevents us from so naively accepting as valid a “blurred model” for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.”

Got it? No, nor me. Well, I have discovered that when Schrödinger was working as a Fellow at Oxford University in 1933 he lived with two women and his cat, Milton! Great. He kept a cat called Milton. His living arrangements were frowned upon by the university. I think they were referring to the two women, not his cat.

Schrödinger left Oxford and went to Princeton University in America. I have no idea what happened to Milton. I have a sneaking feeling that he stayed behind to be looked after by his women friends.

So in answer to the question in the title, he chose a cat because he had a cat companion. The experiment was rather gruesome though.

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Why did Erwin Schrödinger choose a cat? — 19 Comments

  1. PBS had a documentary about this a few years ago. They showed a photo of Schrodinger and Milton, but I could not find it. In the United States he spent most of his time at home with Milton. He was trying to create a model that could explain a paradox. He was petting Milton when he came up with the idea. The point of the experiment is that you did not know if the cat was alive or dead until you opened the box. Up until that time both outcomes existed side-by-side. The ideas of parallel dimension and such come to mind from this model. It really was a big deal when he wrote the paper.

    His housekeeper was quoted (I assume she was dead when the documentary was created) as saying that he loved no one but himself and that damned cat! It seems the cat sat on his lap while he contemplated the mysteries of the universe and such. Sorry, I can’t find a link to the program. The part about the cat was very surprising to me. I think it shows how an analytically mind can place his cat in such a position, knowing that it wasn’t really his cat. I would use another animal, not my cat!

    If anyone finds that picture of him in his study with the cat in his lap I’d love to see it!

  2. I would say that this was a prime example of idiocy. The 2 different outcomes of experiment are so simple that there is no need to actually carry out the experiment. Either the cat dies or it doesn’t and the reason is known prior to the experiment one way or the other. It reminds me of the English mathematician who by the cunning ploy of miles of algebra and calculations proved that time does not exist. All he needs to do would be to go to catch the 7.30 train at 8 o’clock. He would soon learn that time does exist. Why does he have a watch and a clock on the wall in the kitchen? Do these people get paid for this kind of stuff?

    • You nailed it Harvey. A nut case. If he wanted to play his own version of Russian Roulette, he should have built a big
      enough box for himself not a poor cat.

      • Harvey and Dee: I don’t think you really read the article. He did not put his cat through this experiment. It was simply a thought experiment. He used a cat because he had a cat companion. However, I cannot understand how one can love a cat so much, then put that cat in such a horrible experiment even if it was theoretical.

  3. Thanks for explaining the reasons of a “CAT” named Milton being the model and subject of Nobel Laureate Physicist Erwin Schrödinger.I was surprised at seeing the same on “GOOGLE” yesterday in celebration of Erwin Schrödinger’s birthday.

    • It is not often that Google features a cat so I had to investigate! I had heard of Schrodinger’s cat but never investigated it because I knew it would be some heavy mathematical stuff.

  4. Well that’s all way above my head and horrible Schrödinger using a cat in the experiment, but you did make me laugh Michael:
    ‘I’ll keep this short because it is not very interesting’
    and Hsrvey
    ‘He was a nutcase’
    How true!
    We just never know what’s going to pop up on PoC next!

    • I tend to agree with Harvey. I don’t think he was that keen on cats. I pretty sure he left Milton behind when he went to America and he could have chosen a different way to make his point rather than a gruesome “thought experiment” whatever that is that incorporated his cat.

      Maybe we are being too serious. He would probably say we are.

  5. The only thing he was going to learn was that cyanide can kill a cat when a nutcase sets up a deeply flawed ” experiment” which depends on chance for it’s outcome. Very mathematical I’m sure!

  6. I think, no need any chemical like HCN,HCl or any radio active material. If we close the box (as they didnt mention that the box have any windoor)the cat will automatically die… some other mystery burried in this experiments…

  7. Also I think Mr. Schrodinger gave a Analogy to us regarding decay concepts of radioactive substances, i.e, we do not know & we can not predict when the radioactive substances get starts to decay. It may be now, tomorrow, next month or after 100 years. Not all the atoms decays at the same time. If it starts decay as in the Schrodinger’s cat experiments, the counter tube discharges and through a relay releases a hammer that shatters a small flask of hydrocyanic acid and kill the cat. If it does not decay the cat will be safe…..

  8. It’s a thought experiment to get people thinking. I believe he was quite clever to use a provocative (if shocking) example as it still has people thinking to this day. An elegant modern-day application is the episode of “The Big Bang Theory” where “Howard” was given the opportunity to know and not know the contents of a letter his long-lost father wrote without reading it. Pretty heavy stuff. Just as the socially awkward characters of that sit-com, most scientists are just matter-of-fact thinkers, not politically correct. I doubt Schroedinger advocated harming animals in such a way if he only cared about himself and his cat. Sometimes one can be blunt about something, confident in the fact that you’d never do it. Average people say extreme phrases all the time for effect, like: “I could have killed him.” or “I’m dying to see the new movie.” or “it was raining cats and dogs.” We use idiomatic phrases all the time for dramatic effect. I think the thought experiment is along those lines.

  9. It’s curious that so many people still can’t get with the apparent paradox of the quantum state – the possibility or probability wave before collapse through observation. This is rock solid in quantum mechanics. Calling Schrödinger a nutter doesn’t explain anything. The quantum world is so strange that we cannot understand it because of our experience of classical phenomena only. Physicist Amit Goswami cited Robert Oppenheimer who said that science is uncommon sense. Anyone who has to immerse himself in uncommon sense and have sensible people around him who have no clue about what he is discovering is bound to go a bit strange. If Schrödinger had a pet spider in a glass bottle and used this instead we wouldn’t be calling him a nutter. I’m a cat lover but I do see that greatest of minds are nevertheless confined within human emotional limitations and people who live in very circumscribed worlds physically tend to make do, in their imaginations, with what they happen to have around them.

    • Thanks a lot for your excellent comment, Arjun. I have not read the comments on this page. I presume one of them refers to him being a ‘nutter’. That is wrong of course and insulting.

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