I don’t understand..
When we observe it, we can define it’s state right? But it was never in both states. It was only in one, we just didn’t know which one it is. It’s not like if I go back in time and open the box at a different time, that the outcome will be different. It is one of the 2 outcomes, we just don’t know which one until we look. And when we look we discover which one it was, it was never the 2 at the same time. This is what’s been bugging me. Can anyone help explain it? Or am I thinking about it wrong?
In: Physics
I think that the only part you’re missing is that it was an example by Schrodinger to show how absurd the results of quantum mechanics are. It’s supposed to not make sense. How on Earth can it be dead and alive at the same time? **Of course it can’t actually be,** ***and that’s the point.***
You’re thinking about it wrong. It was never an actual experiment done as far as I understand, but a thought experiment for understanding quantum superposition. Quantum theory is extremely weird and doesn’t follow the rules we use for everyday objects, aka classical physics. It’s saying that until the observation is made, the result of the cat being absolutely alive or dead literally didn’t happen. It takes observation, which involves interacting with the quantum system, to “collapse” it into a single state.
>It’s not like if I go back in time and open the box at a different time, that the outcome will be different.
It could be though, that’s the whole point.
The thought experiment involves a quantum process that is indeterminate, typically, the radioactive decay of a single atom. With such quantum processes, we can make estimations of the average time that it takes for them to happen, but we can’t actually predict when it will happen for any given atom. In a large number of atoms undergoing radioactive decay, we can use statistical averages and tell when half the sample will have decayed, but it is impossible to predict when any given atom will decay. It’s completely random. If you go back in time, you very much could get a different outcome – we think, at least.
There’s lots of other quantum phenomena at the particle level that is uncertain in a similar way, and making observations of these things change the outcomes. This is very annoying to scientists! Physicists using mathematical models said well, okay, there’s lots of stuff we can’t know about the quantum states of these individual particles until we have observed them, so let’s just model it mathematically as if the particle is in multiple states at once up until we observe it. And the math works, so fine.
Schrodinger thought that this was kind of stupid. That’s the whole point of the thought experiment: if we apply the logic that these mathematical models use to larger objects, like cats, we come up with a nonsensical conclusion that the cat is both alive and dead. You’re right to think that this seems nonsensical because that’s the whole point; the whole thing is a joke, basically.
In reality, in practice, quantum uncertainty can’t be extended to large objects like cats. In the real world, the cat is being “observed” constantly, whether we look in the box or not, and the quantum state isn’t uncertain and the cat is always actually alive or actually dead, and never both. When the cat dies is a random process that we can’t predict, but it certainly will happen at one point in time.
Schrödinger gave the cat example as a way of criticizing a certain interpretation of quantum mechanics. According to that interpretation, before you make the measurement, the cat is neither alive nor dead, but somehow in superposition of both. Schrödinger was saying that’s absurd, so that interpretation of QM should be rejected.
Then popular culture misunderstood the point as being that physics says cats are sometimes both alive and dead before they’re observed.
Logically, common sense wise, yes you’re correct. But, the whole point of it isn’t to be taken literal, but more to show how weird QM (quantum mechanics) are, especially with the whole idea of superposition.
The whole thing of course goes
*”A cat in a sealed box with a radioactive atom, a Geiger counter, and some poison. If the atom decays (random process), the Geiger counter detects it, releases the poison, and the cat dies. If the atom doesn’t decay, the cat is alive.”*
It’s hard to eli5 with quantum mechanics, and yeah from here, the cat is either alive or dead, but we just simply don’t know until we open the box and actually see it, it’s one of those outcomes already. But, with quantum mechanics, particles like atoms can exist in superposition, they can be in MULTIPLE states at once, and in this case it can be decayed and not decayed, which both lead to different outcomes, those are the multiple states. Until we actually observe the particle, the atom is in a *superposition state* of **both**.
In the end, the whole point is to show that quantum mechanics are weird. The idea is that the cat exists in both states until it’s observed. When we open the box, the superposition ‘collapses’ and we find out which outcome it truly is. It’s not really about whether we didn’t know the state it’s in, it’s that the cat exists in both states until it’s finally observed.
I guess one way you can think about it in a more ELI5 way is that, let’s say you have a box. The box is magical, there is a coin inside. The box is a special magic box, because until you open it, the coin is both heads and tails at the same time. It’s not like.. It’s heads and we don’t really know, or tails, it’s both and neither while the box is closed. Only when you finally open the box to see if it’s heads or tails does the whole thing collapse and you figure out the answer. Schrodinger’s cat is basically the same thing, before we actually open it and take a look, the cat is in a ‘mysterious’ state where it just so happens to be alive AND dead, just like how the coin can be heads AND tails at the same time. You, as the observer, open the box and see what the true answer is. Until then, it’s both.
* It’s just a thought experiment. *It isn’t real*.
* Shrodinger thought that quantum mechanics *didn’t* make sense, and came up with this thought experiment to show how absurd it would be if it applied to a macro scale.
it was a super simple thought experiment to explain something that isn’t simple.
in superposition, a quantum system is in all states at once. or you could say it’s not in any states. say when you hit the enter button a computer tells you “yes” or “no” at random. The computer is holding these in superposition where until the point you hit enter (observe it) the outcome is both yes and no.
essentially, the computer is holding all possible outcomes at the same time and only the act of you observing it forces it to collapse down to one of the possible outcomes.
So the cat experiment was that an alive cat is placed in a box, and a thing exists in that box which at some random time in the future kill the cat.
Because it could be a second or a millenia before that thing transpires, we have to consider that until the box is opened the cat is both alive and dead, because it could truly be either.
We can interact with the box, move the box, and the box surely exists in our universe, but we don’t know the state of the box and that doesn’t impact how we feel about it.
When we open the box, we will either be met with an alive (and quite angry) cat, or a dead cat. And that act of knowing will now impact us. Before we opened the box, we didn’t know what would greet us, but on observing the box is when it is changed in our mind, and for quantum mechanics, in the universe.
At the quantum scale, the starting atom’s particles are in a superposition of having both decayed and remained stable. It is not a matter of not knowing whether or not it decayed it is in both a state of having decayed and not decayed at the same time. When the radiated particle interacts with another particle, that particle too is in a state of superposition, having interacted and not interacted with the radiating particle. This is accepted physics.
Now continue this chain reaction until it scales up into the world we observe. Everything should be in a state of superposition, but it’s not. There is one definite measured outcome. The idea of this thought experiment is to take the theory of how particles interact and scale it up to the macro sized world that we understand. Clearly this doesn’t happen at the macro scale.
So how can physics explain how and why something that starts in a superposition of many states ends up in a single state? That’s called *the measurement problem* and is an open, unanswered problem in physics.
Another way to look at is to ask the question from a different perspective. How is the thought experiment wrong? As of right now, physics is not able to explain how it’s possible for the cat to be in a single state of alive or dead before “opening the box.”
Nope. No one can explain it. The underlying reality of superpositions is one that, at least as of 2024, unexplained.
I know that sounds snarky, but it’s not. It’s something called the Measurement Problem. When you observe the cat and it collapses to one state, nobody knows for sure what’s making it do that or why.
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