00:00As far as we can tell in the subatomic world, everything is just so ridiculously and frustratingly
00:07random.
00:08You look at an electron and sometimes you look at it and it'll have a spin pointing
00:13up.
00:13And the next time you look at it, it'll have a spin pointing down.
00:16And you're like, can't you just pick one?
00:18Why do you have to be both?
00:20Why do you have to keep flipping back and forth?
00:23I'm Paul Sutter and this is Paul Explains, the show where I, you know, explain.
00:30The whole machinery of quantum mechanics is designed to translate the probabilities of
00:39what you might measure when you go to make an observation.
00:44In the case of an electron spin, the language that we use in quantum mechanics goes something
00:51like this.
00:51The spin of the electron is in a superposition of both spin up and spin down states.
01:00And then when you go to measure it, something happens and it chooses one of those states.
01:05And that's what you actually measure.
01:08But some of the founders of quantum mechanics didn't really like how this was being described.
01:15One of those people was Erwin Schrödinger, one of the founders of quantum mechanics.
01:20He looked at this example, this language, and developed a thought experiment to show just
01:26how lame this language is.
01:29He said, what if you put a cat in a box, you close the lid, and you put some radioactive
01:34element in there and just say that there's a 50-50 chance that the radioactive element
01:41will decay, it will poison the cat, and it will kill the cat.
01:45But there's a 50% chance that it won't decay, nothing bad will happen, and the cat will live.
01:50Now, as long as you have that box closed, you don't know what's going to go on.
01:56You don't know if the cat is alive or dead.
01:59And then you open up the box, you perform your measurement, and you see either a dead cat
02:04or an alive cat.
02:07Classically, non-quantum mechanically, we would think that at some point, the cat might or
02:12might not die.
02:14But our observation of it, our measurement of it, has absolutely nothing to do with what's
02:20going on inside the box.
02:21Either the cat is dead, or it is alive.
02:27But Schrodinger pointed out that in quantum mechanics, the way we're supposed to think
02:34about it is that the cat is both dead and alive.
02:40It exists in the quantum superposition of deadness and aliveness.
02:46And when we open up the box, that is the moment of the choice.
02:52That is the moment of the cat becoming dead or becoming alive.
02:57But until we open up the box, it is both dead and alive.
03:02And Schrodinger said, this sounds really dumb.
03:06Do you actually expect us to believe this when it comes to quantum mechanics?
03:11And everyone else who was working on quantum mechanics said, yes.
03:17How do you wrap your mind around this?
03:19Well, maybe you don't have to.
03:22Maybe reality is just weird.
03:25And we should leave the cats alone.
03:28Meow!
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