Please, somebody explain this to me.

Somebody. Anybody.

4584191
It's a thought experiment about an aspect of something called Quantum Superposition. The idea that, on the quantum level, things aren't in a predictable, concrete state until you try to measure them.

You have four things. A cat, a tiny bit of a radioactive substance, a Geiger counter, and a flask of poison. They are put in a sealed chamber, which cannot be seen into. If one of the few atoms of the radioactive substance should happen to undergo radioactive decay, it will activate the Geiger counter, which will break the flask of poison and kill the cat. However, there are so few atoms of the radioactive substance that, say, in an hour, there is only a 50% chance the decay will happen.

We can't know if the cat is dead, after that hour. We can't know if the cat is alive. The cat is in some kind of blurry state of being alive and dead. It's in superposition, a collection of all states.
Until we open the container to find out, and measure the results. Then all the probability wave function collapses, and we end up with a live cat, or a dead cat.

It isn't meant to be what's literally happening, mind. The cat is not in some bizarre Lovecraftian state of dead but dreaming. It's just a way of looking at it. Quantum phenomenon don't seem to apply to the macroscopic world in all cases.

4584191

This post 4584221 did a very good job of explaining classic quantum mechanics, but there are a lot of other interpretations. One of the most popular is the quantum many worlds idea. That basically says that whenever the universe has a choice, it takes both options, and splits into two parallel universes, one for each option.

In the context of Schrodinger's Cat, that would mean the cat is both dead and alive, just in different universes. We live in one of them.

4584221

Couldn't this be applied to any uncertain thing?

Setup: I flip a coin and slap my hand over it so you can't see. I ask you "heads or tails?"

Is the answer "both"?
Isn't the proper answer to both the coin and the cat question: "I don't know"?

I realize that it's meant to be an analogy for a quantum mechanics phenomenon, but it doesn't do a very good job if the analogy doesn't make sense. I mean, if the cat isn't literally both dead and alive at the same time, then how does this apply to quantum superposition? And why construct such an elaborate setup such as the cat in the box with the radioactive stuff? Why not just use a coin toss?

4585376

Is the answer "both"?

No. Because we know that the coin, sitting on your palm, can only be either on one side or the other. Organic matter is completely different. With a sufficient level of radiation, <x> (in this case a cat) can be killed. But not all organisms, even the ones of the same species die with the same amount of radiation. Hence the question.

And even if you look at it and examine the cat, it can exists in 3 states: Alive, dead, or in the state between those, something we call "barely alive."

Isn't the proper answer to both the coin and the cat question: "I don't know"?

What's the fun in that?

~Twi

4585430

Organic matter is completely different.

Yes, but a cat is either alive or dead. It is a binary condition. The added variables may produce complexity in terms of the cause of whatever the current state is, but it does not produce any complexity in terms of the result. Similarly, many things can influence a coin in the air. Turbulence invokes chaotic mathematics, and the results are not predictable. This is especially true if you did not observe the coin toss as it happened.

What always bugged me about the cat question is that obviously the cat was still either alive or dead. Just because the observer did not know does not change the fact that it is in only one of two states. The state also does not change due to being observed.

And even if you look at it and examine the cat, it can exists in 3 states: Alive, dead, or in the state between those, something we call "barely alive."

Barely alive is still alive.

4584191

If you put a cat in a box with some poison, the cat is alive and dead up until the moment that you open the box and confirm if it is alive or dead.

However, Schrodinger made this theory to mock many popular theories that were out at the time as being ridiculous. Or, at least, that's how I interpreted it.

One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.

Edit: Wait, no. I was right. He was mocking the theories.

Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.

4585453

What always bugged me about the cat question is that obviously the cat was still either alive or dead. Just because the observer did not know does not change the fact that it is in only one of two states. The state also does not change due to being observed.

Just so you know, Schrodinger made the theory to mock popular theories at the time. He was never fully serious.

4585430
The cat is killed by poison, not radiation. The radiation is just a trigger for the poison.

Radioactive decay is used in the example because it's a truly random process. You can't predict when something will decay.

It's not about biology. It could be anything. Something dissolved when a flask of acid breaks, for example, when the decay triggers it. Or something changing colour due to a chemical reaction. Or being triggered and moving. Anything, really.

The point is that you can't know the state of it. It could go either way, probabilistically. And you never will know, until you check.

4585376
It could have been a coin toss, I suppose. It's just not quite as deep an analogy.

A coin toss isn't random in the way radioactive decay is. You could have the Geiger counter turn on a light, I suppose. But Schrodinger's Lamp doesn't have the same ring. Cats are the best. And you'd still be arguing that a light can't be both on and off. That's true. It can't be. Superposition doesn't exist at a macroscopic level. On the quantum level, stuff like the double slit experiment shows that seemingly something can be simultaneously both a particle and a wave. Or be in more than one place at once, and interfere with itself. And until something pokes it via measurement, it just happily doesn't settle in, and remains fuzzy.

4585478
That's a relief. I suppose he'd be at the knowledge that it is being taken seriously today.

Well, in the spirit of the thought experiment, I suppose it's pertinent to ask the question: In the case of quantum superposition, is it really true that something can exist in a stateless state until it is observed? To me, this seems nonsensical because perhaps your observation does change its state, but that does not necessarily mean that it did not have a definite state prior to being observed.

This goes back to the whole "if a tree falls down and no one is around to hear it, does it make a sound" question. The answer everyone should come up with is "yes, because sound does not require an observer to be factual".

4585484

Yes, perhaps.

But Schrodinger's cat does lend it self very easily to the Multi-verse theory.

That at that point in time, reality is waiting to split, and the instant you open the box, the reality you know is either the cat's dead, or the cat's perfectly fine.

However, the reality splits and creates an alternate reality in which the cat's the opposite of the reality you're aware of.

Of course, these are all just thought experiments, but they're fun ones.

4585480
Silly me.
It has been a looooooooooooooooooooooooooong time since I read up on that.

Sorry.
~Twi

4585484

In the case of quantum superposition, is it really true that something can exist in a stateless state until it is observed? To me, this seems nonsensical because perhaps your observation does change its state, but that does not necessarily mean that it did not have a definite state prior to being observed.

It's a rather... complicated subject.

But the nonsense appears to be what's true. Unless something forces a particle into a definite place by interacting with it, it'll take all the probabilistic paths there.

If you fire a single photon at a wall with two openings in it, it'll go through both openings, acting as a wave. You'll end up with an interference pattern on the wall, as the singular wave somehow destructively interferes with itself. It doesn't make sense on a macroscopic level. It would be like charging through one of two doors and slamming into yourself coming through the other door, before finally hitting the far wall as one person.

If you put a mechanism in place to directly check which one it specifically went through. It'll just go through one, as a particle. And you'll get a normal, happy glow on the wall as you'd expect. No interference pattern. Because hey, now it's just in one place. And something can interfere with itself, surely.

4585484

is it really true that something can exist in a stateless state until it is observed?

We have working quantum computers that rely on superposition being true. If the spin of an electron was set, but not known, the quantum computers wouldn't work.

And don't worry about it not being intuitive.

"If you think you understand quantum mechanics, you don't understand quantum mechanics."
-Richard Feynman