Is Schrödinger’s cat -
[ol]
[li]Simultaneously alive and dead[/li][li]Neither alive or dead[/li][li]Simultaneously (alive and dead) AND (neither alive or dead)[/li][li]OpalCat[/li][/ol]
Depends on which interpretation you are using. Wikipedia has a good article.
“Erwin! What have you done to that poor cat? He looks half dead!”
– Frau Schrödinger, an ailurophile
The cat is either alive or dead.
The idea that it exists in some sort of in-between state until the moment the box is opened is a fallacy exposed in Murray Gell-Mann’s book The Quark and the Jaguar.
The Quantum Mechanical concept of indeterminate states can’t be applied to macroscopic objects like cats (although mine does seem to to be unable to decide whether it wants to go in or out).
It’s either alive or dead. Schrodinger’s point was that a macroscopic object like a cat obviously can’t be in a superposition, that there’s no such thing as a cat that’s both alive and dead, and so there must be something wrong with the quantum mechanical interpretation of the experiment he proposes.
The experiment often gets mischaracterized as Schrodinger trying to explain superposition, when in reality he was proposing a paradox to illustrate a problem with the concept.
We don’t know. Why don’t you open, take a look, and get back to us?
My first “real” exposure to the Schrödinger equation and cat was in learning about the measurement problem. See, it’s one thing to describe a particle in this weird state–we have no direct experience with it. It’s only mildly disturbing to talk of it being in neither one, the other, both, or either state. But from personal experience, we know (or believe we know) that macroscopic items don’t exist in superpositions, they exist in discreet states. And if you take a familiar binary state --alive or dead–and make that dependent on a particle in superposition (a state which will collapse into a more familiar concept ostensibly upon observation), then you have a thought experiment that, instead of nice, abstract particles, uses a much more tangible situation to demonstrate just how fucking weird the subatomic world is.
Wikipedia, John? I’m disappointed.
The best explaination of Schrödinger’s Cat is much closer than that.
This is what I was told - the point of Shrodinger’s cat is that the cat is obviously either alive or dead, and that it’s silly to apply quantum-level phenomena to macroscopic objects, so therefore there must be some stage at which objects get too big to be in a quantum superposition. So the answer is that the cat is none of those 4 options; it’s either alive or dead, in the same way that any other cat is.
But, if I understand the experiment correctly, when it comes to the decaying subatomic particle that decides the cat’s fate, it’s number 1 - both decayed and not decayed - until it’s “observed”. The experiment is a paradox designed to show that even though:
- The subatomic particle is both decayed and not decayed, and;
- The cat’s fate depends on whether the particle has decayed;
Nevertheless, it’s impossible that the cat can be both alive and not alive. “So where has the thought experiment gone wrong?” is the thinking.
Just one of the things I love about the Dope is that whenever the subject of quantum mechancis (or cats, for that matter) comes up, Schrondingers cat is always mentioned with some amusing remarks. Or some erudite discussion.
Thanks, Poluycarp, that is really funny.
I’d like to see some justification for saying that quantum mechanics doesn’t apply to macroscopic objects. I don’t believe there is any.
Not so much that it doesn’t apply, but that at the macroscopic level, it gives results identical to what you’d expect classically. The Correspondence Principle I believe, is actually usually taken as a postulate of quantum theory.
The Correspondence Principle is more of a matter of giving direction to the development of quantum mechanics than a postulate. Regardless, being in a superposition of dead and alive, until observed, does give a result identical to to the classical result that would be observed.
Yeah, what he said.
Seriously, though. As far as I know the thought experiment highlights the Copenhagen interpretation, so what are the currently viable alternatives to that?
Schrödinger put out the thought experiment because he hated that the Copenhagen interpretation required such a paradox. That may be what you meant by “highlights it,” but I thought it needed to be stately directly.
Wikipedia has a page of the main alternative theories. Take your pick.
“Excuse me, Professor Schrödinger, but have you seen my cat?”
“Maybe I have, and maybe I haven’t…”
I thought the whole point of the experiment being a paradox was that a cat could never really be both dead and alive, so that there must be something wrong with the experiment’s conclusion? If the cat could in fact be dead and alive at the same time and the maths all works, then what’s wrong with the conclusion of the thought experiment?
Except that the cat is an Observer. That’s why it’s a false paradox. Schrödinger knew that, and wrote it up to show that it’s a false paradox.
Doesn’t matter. To another Observer outside the box, the cat/Observer is still in a superposition of dead cat/Observer and live cat/Observer.
Von Neumann held that all matter is composed of quantum particles and so all you ever had was a never ending chain of superpositions. So, in order to break the chain you needed something that wasn’t composed of quanta - he held that this was human consciousness.
How could you prove that anything is objectively there if you’re not observing it?
I was under the impression that Schrödinger’s Cat was essentially a failed thought experiment in the sense that Schrödinger intended it to show that the Copenhagen interpretation is flawed (because surely anyone would agree that a cat can’t really be both alive and dead), but that Bohr and most other proponents of the Copenhagen interpretation responded (like ZenBeam above) “Yep, alive and dead! Sounds right to us! Long as it’s in the box, what’s the problem?”
No one knew quite what to say to this, and so the Copenhagen interpretation went on to become the dominant interpretation among physicists.