There was this cat. It was in a box. There was this radioactive atom. It was in the box as well. I know it's Sunday and I'm only a mere mouton, but the obvious things to put in with the cat would be some food and water. However, this is science and science is weird.
Now then.......... The fate of this poor cat is dependent upon something called a 'wave function' and an 'observer'. Oh, I forgot to mention the hammer and a flask of cyanide, which is also in with the cat. Well I did say science was weird!
So, while this atom is waiting for the observer to wave at it, both the atom and cat are said to be in a 'superposition'. What might that be then, I hear you ask. Good question. A super position for the cat would be lying down and having a kip, no doubt. But no...The superposition for this cat is next to a geiger-counter. (Stay with me.)
Anyway, it seems that if this atom (Don't forget it's radioactive.) hangs about too long, it decays. (Well don't we all!) Also, if the hammer hits the flask of prussic acid, the cat will die. (But the cat will die if it is left in the box, anyway, so why all this additional paraphernalia!) Oh, I forgot. It's science.
It seems that an important part of this experiment is the wave function of the atom. (Sorry if I misled you about it being the observer waving............) Hence, according to Shroedinger, the atom remains in a 'superposition' of decay and undecay, up until the time the observer opens the box. (The lack of a space in the word 'superposition' as opposed to 'super' and 'position' is clearly crucial, here.) Because this possible dual state of potential pertains to the atom, Shroedinger claims the same can be said for the cat: it is in a 'superposition' of being both dead and alive.
So, the question is: Should the observer open the box? No need. It isn't a real experiment. It's just a Thought Experiment.
However, if you want to know more about atoms, particles, waves and observers, go to this fantastic animation and be truly amazed.
Now then.......... The fate of this poor cat is dependent upon something called a 'wave function' and an 'observer'. Oh, I forgot to mention the hammer and a flask of cyanide, which is also in with the cat. Well I did say science was weird!
So, while this atom is waiting for the observer to wave at it, both the atom and cat are said to be in a 'superposition'. What might that be then, I hear you ask. Good question. A super position for the cat would be lying down and having a kip, no doubt. But no...The superposition for this cat is next to a geiger-counter. (Stay with me.)
Anyway, it seems that if this atom (Don't forget it's radioactive.) hangs about too long, it decays. (Well don't we all!) Also, if the hammer hits the flask of prussic acid, the cat will die. (But the cat will die if it is left in the box, anyway, so why all this additional paraphernalia!) Oh, I forgot. It's science.
It seems that an important part of this experiment is the wave function of the atom. (Sorry if I misled you about it being the observer waving............) Hence, according to Shroedinger, the atom remains in a 'superposition' of decay and undecay, up until the time the observer opens the box. (The lack of a space in the word 'superposition' as opposed to 'super' and 'position' is clearly crucial, here.) Because this possible dual state of potential pertains to the atom, Shroedinger claims the same can be said for the cat: it is in a 'superposition' of being both dead and alive.
So, the question is: Should the observer open the box? No need. It isn't a real experiment. It's just a Thought Experiment.
However, if you want to know more about atoms, particles, waves and observers, go to this fantastic animation and be truly amazed.
3 comments:
Here's the thing, though, Monsieur M. The thing that makes this thought experiment interesting, and worthy of the ponderings of some of the finest minds of our times (and then mine), is that it only works if the determinant of the cat's survival is a radioactive atom. The significance of radioactive decay is that it is random; that is, it happens without a preceding cause. It's not just that we don't know the inner workings of radioactive decay well enough to say when an atom will decay, there are no inner workings to know. It isn't predictable; radioactive atoms decay on less than a whim.
If the cyanide flask's being broken (or not) depended on the state of, for example, a clockwork mechanism, then it would be possible to know (by examining the mechanism beforehand) whether the cat was still alive at a given point in the experiment.
However, since it is ourselves who set up the experiment, we would know what kind of atom we were using. And we do know the half-lives of the various radioactive elements. (The half-life is the amount of time it takes for half of a sufficiently large sample of atoms to decay.) So, we could say of the cat in the box: "We don't know whether the cat is dead or alive, but given that we're using an atom of Iodine-131, which has a half-life of 8 days, then 1 day into the experiment pussy is probably still alive, 2 weeks later it's probably dead, but neither of these is certain." If we used an atom of Carbon-14, with a half-life of 5730 years, we could assume that pussy would probably die a natural death before being killed by the cyanide, although some cats will just get unlucky...
Thought about in this way, there's no need to invoke an effect (the collapsing of the wave-function) which mysteriously involves the observer. In the world of quantum events, we can only talk about probabilities. Einstein's famous dice-throwing God that he didn't want to believe in. It's not often one gets the chance to say the great man was wrong.
Whether this experiment has ever been performed on sheep, imagined or, as in your case, real, I don't know.
Hey, O Venerable Occasional Stirrings.
I'm stunned and speechless and unbelievably impressed by your knowledge of the quantum world. How come you are so fluent in determinates, cats, the lives, half-lives and number IDs of atoms! Phew! And phew, again!
On the probability front, OS, I think there is a strong chance that an event of brain numbing dexterity occured, when you wrote your comment.
As for sheep, and speaking personally, I would refuse to go in the box, invoking the wave function directive.
Mouty
You're too kind, MM. These are just the musings of a lay scientist with too much time on his hands, reading far too many popular science books.
An extrapolation of Schrodinger's famous thought experiment is called Quantum Suicide, and (by implication) Quantum Immortality. This, in theory, allows the experimenter to determine the correctness or otherwise of the two interpretations of the weirdness of the quantum world - the Copenhagen interpretation (the 'collapse of the wave function') or the Many Worlds ('parallel universes') interpretation.
In this scenario, the experimenter takes the place of the cat, and one could argue that it is a more honourable experiment. The experimenter sits in front of a loaded gun, which fires (or doesn't) depending on the radioactive decay of an atom. As in the cat experiment, the apparatus and the experimenter are isolated from the rest of the world.
If the Copenhagen interpretation is correct, the wave function may or may not collapse (the gun will have fired or not), and the experimenter will be either dead or alive, when the outside observers checks the results. If the Many Worlds interpretation is correct, then after the experiment the observers will, as in the Copenhagen view, discover either a dead or living experimenter. However, if the gun has been fired it will also have resulted in the branching off of another 'world' in which the experimenter will find himself still alive. If he then repeats the experiment enough times to ensure that it is almost certain that the gun would have been fired at least once, and yet he still finds himself to be alive, he may consider himself to have proved the Many Worlds interpretation. He will also have shown himself to be immortal, at least in the situation where his survival depends on a random quantum event.
The main drawback to this experiment is that it is only the experimenter that will have proved the Many Worlds theory, and only to himself. Observers will remain uncertain unless they are brave or foolish enough to try it for themselves. Me, I'll leave it to the scientists.
Personally, I take the Many Worlds view. It agrees with some conclusions I reached concerning life and accidental death when I was about 12 years old. Precocious, moi?
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