Schrodinger's Cat, the explanation

COCK

For those of us who were on session 2 this year, you may have noticed several people wearing t-shirts bearing the slogan, "Schrodinger's cat is dead"

I, like most of us, am not a quantum physics nerd, so this obscure statement baffled me. Naturally, I ventured to learn the meaning behind this statement, but it was never properly explained.

So I did research, and found out what it means, here goes:

We place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, the hydrocyanic acid released, and the cat killed. Since we cannot know, the cat is both dead and alive according to quantum law, in a superposition* of states.








*The principle of superposition claims that while we do not know what the state of any object is, it is actually in all possible states simultaneously, as long as we don't look to check. It is the measurement itself that causes the object to be limited to a single possibility.

PurpleFistMixer

Is it just me, or is this entire experiment/theory/thing incredibly egocentric?
I mean, sure, one person may not know the outcome of the experiment, but that doesn't mean that the cat is both alive/dead/a toaster. The cat is probably quite aware of what's going on in there.

I suppose the only way you could justifiably argue that the cat exists in both states is that, for all intents and purposes to the observer (or not observer as the case would be), the cat might as well be dead/alive/neither/both/whatever, and thus it doesn't make a difference what the real truth of the matter is. However that doesn't strike me as a particularly scientific idea, rather something of a more philosophical basing.

Crash

Well it kinda rests first of all on how you view the idea of sentience, then how you typify the idea of observation (i.e. does observation rely on sentience etc.) - once you get into quantum mechanics a lot of the underlying philosophy of physics starts to bleed through.

Raphael

Shrodinger didn't regard the cat as an observer. The other way to look at it is to remove the cat and ask whether the acid is released or not. Answer being both and neither. The inclusion of the cat ads simplicity and dramatic effect

clearz

The way I looked at the Schrodinger's cat experment was to not even look at the acid as the observer. The Observer is any partical in contact with the decaying partical that the information about the event was passed to.

This experement cannot work because the partical involved would need to be not only away from humans or cats but not near any other particals either. And even space is full of particals popping in and out of existance. so where would you put it.

Mammy

PurpleFistMixer wrote:

Is it just me, or is this entire experiment/theory/thing incredibly egocentric?
I mean, sure, one person may not know the outcome of the experiment, but that doesn't mean that the cat is both alive/dead/a toaster. The cat is probably quite aware of what's going on in there.

I suppose the only way you could justifiably argue that the cat exists in both states is that, for all intents and purposes to the observer (or not observer as the case would be), the cat might as well be dead/alive/neither/both/whatever, and thus it doesn't make a difference what the real truth of the matter is. However that doesn't strike me as a particularly scientific idea, rather something of a more philosophical basing.

In quantum mechanics the role of the observer is fairly startling. Depending on the point at which observation is made, a quantum mechanical experiment will produce radically different results. The philosophical implications of this fact haven't been properly investigated yet.

cookiemonst3r

stephen should have a good explanation of this.he won a book about it in our class.

monkeyfudge

I think it was in one of the Dirk Gently novels by Douglas Adams, that they performed the experiment for real and the cat went missing and they hired Dirk Gently to find it.

StupidLikeAFox

Schrodinger should be reported to the ispca.

Anyway, in short hes basically saying that if you dont check the results of an experiment your not gonna know what happened. Isnt that a bit stupid?

andy1249

Schrodinger's cat is just an analogy to explain the situation when trying to observe sub-atomic particles. The situation is that to observe an electron , say , you need to shine light on it in some way , or bombard it with electrons or whatever , to know its position and velocity.
However the act of trying to observe the sub atomic particle alters it in some way , for instance illuminating it introduces photons , which are themselves sub atomic particles and these alter either the subjects position or velocity.

This being the case then depending on what way you try to observe quantum ( or very small ) particles the results will be different because you cant observe without altering the subject.
An example is light appears as a wave when looked at one way , and as a particle when looked at another , at the quantum level the way something is looked at matters!!

Thats the whole point of the story , the cat cannot be determined to be alive or dead until you look , but the mechanism that allows you to look alters the situation so you can never know for sure what the original situation was?

The analogy only applies to illustrate quantum effects and was never meant to apply philosophically as far as I know.

There you are , relatively simple !!


This also forms part of the " uncertainty principle " but thats another for another day maybe !!

Undergod

It's a thought expiment only. Schrodinger was using it to riducule the absurdity of quantum theory.


Vaguely on the topic, a physics experiment in switzerland showed there is either human free will or an actual reality, but both can't exist.

Liquorice

Undergod wrote:

It's a thought expiment only. Schrodinger was using it to riducule the absurdity of quantum theory.

Exactly, he didn't actually believe it himself. And a lot of the people I explain it to just say 'the cat will be dead at some point 'cause all cats die' *slaps forehead*

Zounds

I have that t-shirt and yeah, so many people mention that the cat will die of starvation inside the box....*shakes head*

elephamt king

Undergod wrote:

Vaguely on the topic, a physics experiment in switzerland showed there is either human free will or an actual reality, but both can't exist.

you should tell that to a priest.

Mammy

Undergod wrote:

Vaguely on the topic, a physics experiment in switzerland showed there is either human free will or an actual reality, but both can't exist.

Elaborate.

Blitzkrieger

Did the cat prefer whiskas?

clearz

Undergod wrote:

Vaguely on the topic, a physics experiment in switzerland showed there is either human free will or an actual reality, but both can't exist.

Yea im interested also. Couldn't find anything on google worth talking about.

Flashling

That's saying that there is some kind of Higher Power that is controlling our ways if there is an actual reality, right? So there is, if that possibility is correct, some kind of God? (And with God there can be no free will, so the other possibility is that there is no God?) So really it's "there has been an experiment to show that there either is, or isn't, a God." Ingenious.

Undergod

Mammy wrote:

Elaborate.

Make me.

Undergod

But actually, it's to do with quantum entanglement, photon 'spin' and really deep theory. I didn't understand it as such, but the results differed depending on whether the scientists set the parameters, or something. It was in new scientist a few weeks ago.

Mammy

Undergod wrote:

But actually, it's to do with quantum entanglement, photon 'spin' and really deep theory. I didn't understand it as such, but the results differed depending on whether the scientists set the parameters, or something. It was in new scientist a few weeks ago.

Sounds interesting. I'll ask my supervisor about it. He's a particle physicist who's part of a project at CERN to figure out CP violation (I'm guessing CERN is where the experiment was carried out). I'd be cautious though about listening to scientists pontificate on philosophy/theology. They (we!) have a tendency to spew out terms like 'free will' and 'actual reality' as if they were as well defined and easily understood as terms like 'force.' Physicists, it seems to me, are probably the most intellectually arrogant species of academic (mathematicians are potentially moreso, but noone knows as they never leave their rooms... :cool: <= here's a mathematician wearing sunglasses cos he's allergic to light).

Dalamar

From Wikipedia:

Schrödinger's cat is a seemingly paradoxical thought experiment devised by Erwin Schrödinger that attempts to illustrate the incompleteness of the theory of quantum mechanics when going from subatomic to macroscopic systems.

Ta da! wikipedia knows everything.

Crash

That would be right actually - with my experience of mathematicians and physicists - the physicists are insane and talk a lot of ****e 80% of the time - the mathematicians just huddle and rock in the feotal position sucking their thumbs and singing "its a long long way to tipperary" off key.


....man that was a weird party.

Undergod

No, I don't think it was in CERN. If I remember correctly the article specifically stated somewhere else, but I might have imagined that.


You're probably right though, I wouldn't entirely accept what they say, but I just thought it was interesting.

andy1249

Further reading , especially on the copenhagen interpretation,

http://www.benbest.com/science/quantum.html

http://www.mtnmath.com/cat.html

For the record , I agree that the copenhagen view , is definitely not science !