I have a quantum physics quandary (it could be multiple quandaries depending on current theory)

[innocent_lex]

So, Schroedinger's cat. There's this thought experiment where there's a cat in a box, and also in the box is a radioactive isotope and a vial of poison. If the isotope decays it will trigger the vial, the poison is released and the cat dies. So far, so... kind of gross, actually, but let's go with it. The experiment addresses the concept of quantum superposition, whereby a sub-atomic particle is in all states until it is measured / observed, whereupon it collapses into one particular state.

With me so far? The thought experiment goes that due to the bizarre nature of the physics the cat is both dead and alive until someone opens the box and observes the experiment, at which point the superposition collapses and you see the cat as either alive or dead.

Which is extremely odd all on its own, and gets even odder when you ask: why are we excluding the cat from the experiment as an observer? Yes, that's what's been bothering me for days now. And also, the cat is not a sub-atomic particle. And also, how does the particle-cat know it's being observed and therefore have to choose a state (and what if it can't make up its mind?). And quite frankly, extending that experiment into the real world brings all kinds of problems for people who live alone, as they would spend their nights floating around at home like some disembodied and indecisive cloud of particles unless someone else happened to look in the window and see them. Yes, fine, so I'm possibly exaggerating and in reality the single person could become multiple single people in different universes, some of whom watch Torchwood and some don't. Or not.

I think the point of the experiment (this was back in the 1930s) was to remind people that quantum physics was (and still is) incomplete and that people should start thinking a little more intelligently about the problems and how they'd work in reality and not get blinded by pretty maths. But then I've never actually been taught nor studied any quantum physics and am apparently out of my depth on this one. Where's Rodney McKay when you need him?

Comments

[readerjane]

(why are we excluding the cat from the experiment as an observer?)

*G*

The cat would like to know, why does the human observer think he can safely open a box with a 50% chance of poison gas inside?

Silly human.

[innocent-lex.livejournal.com]

See! Another excellent question. Although, I think it's not a 50% chance, it's something weird and quantumy.

[sg1jb]

Oooh, ooh, I love this paradox ;-). I don't know much of anything about quantum physics (a pin-head is the size of the grand canyon, compared to the space what I know would take up).

However...

Wasn't Schroedinger's goal, in presenting the quandry of the Schroedinger's Cat paradox, to point out that there were problems with a particular line of thinking/theory in Quantum mechanics? It's my impression that the paradox never was intended to put forward that the cat's state may only be determined upon outside observation. Almost just the opposite, actually. No?

>"...why are we excluding the cat from the experiment as an observer?"<

Yeah; I believe, from what I can recall, that's one of the flaws his paradox highlighted: What constitutes 'observation'? Apparently the word 'observation' used in the theory that the paradox was created to question wasn't exactly comprehensively operationally defined. I can't remeber what I read, but I'm thinking it might have mostly been accepted as observation via scientific measurement? I dunno.

>"...and also, the cat is not a sub-atomic particle."<

Doesn't that 'subatomic particle' reference apply to the state of the radioactive isotope? I always thought it meant that the isotope's state (upon which the state of the cat is dependent) doesn't 'collapse' into a definitive state until it is observed/measured?

On the other hand, there's a little niggle at the back of my brain about that ... something about that being part of Schroedinger's point? That when applied to the state of things other than sub-atomic / atomic particles, the quantum mechanics theory he was questioning poses some real problems?

99% of this stuff is well, well, way, way far beyond me, but that 1% sure is fun to contemplate ;-).

[innocent-lex.livejournal.com]

You could well be right about everything you say. Quantum mechanics is silly and makes no sense to people who have an ounce of logic (or who want to hang onto that logic). But it's apparently true and that bothers me - why does the universe have to be so complicated???

[sailorsueuk.livejournal.com]

I never got why the state of the cat was determined solely on the state of the isotope. Presumably it would die of thirst, starvation, heart attack, lack of air, etc long before the isotope reached the infinity state of certain decay.

Still, I'd never considered the observation part of your post, which is a really good point.