AnThere’s a sealed box, inside the box is a cute cat and a device that can kill it as soon as a radioactive atom decays. Were we to open the box, would the cat be alive? And how is it doing while the box is still closed?
In extreme synthesis, this is the idea of the famous “Schrödinger’s cat” experiment (thought experiment! no actual cats actually harmed! what kind of sicko would do that?!), named after German physicist Erwin Schrödinger, one of the fathers of quantum mechanics.
As you may have heard, as long as we don’t open the box, quantum mechanics allows the cat to be both dead and alive at the same time.
The reason behind this weirdness is one of the founding principles of quantum mechanics: the superposition principle. Simply put, in the microscopic world of quanta, some properties can have several values simultaneously. For example, an electron can be in two places at once, until we go measure it. Then it “picks” a position to be found at. Until then, it really is in several places at the same time.
The superposition principle is a real thing. For real. They did experiments. Quantum theory, then, describes a world fundamentally different than the macroscopic, classical one we know and love.
Our rules don’t work for microscopic particles, and quantum rules don’t work for, like, cats.
Using the rules of one world in the other we get in trouble: a cat cannot be both dead and alive, but an atom can be both decayed and not.
That’s exactly what Schrödinger was trying to do putting a quantum thing (the atom) together with a classical one (the cat).
Precisely those different rules are where the wonderful and magical weirdnes of quantum mechanics comes from.