Wigner's theorem

Wigner's theorem is like a magic wand that helps us predict what will happen when we measure things in the tiny world of atoms and subatomic particles.

Imagine you have a toy car that you want to measure, like its speed or its position on the floor. You can do this easily by looking at it or touching it. But in the world of atoms and particles, things get a lot trickier because we can't see them with our eyes or touch them with our hands. We need special tools like microscopes and detectors to measure them.

Wigner's theorem helps us predict how particles behave when we measure them. It says that when we measure a particle, we change the way it behaves in a very fundamental way. It's kind of like when you watch your toy car and it slows down because it knows you're looking at it.

But here's the really cool part: Wigner's theorem also says that particles can exist in multiple states at once, like a toy car that is both moving and not moving at the same time. This is called "quantum superposition." And when we measure a particle in one state or the other, we also change the state of all the other particles that are connected to it, like a row of toy cars that all stop or start moving at the same time.

So Wigner's theorem helps us understand how particles behave when we measure them, and it also helps us predict how other particles connected to them will behave. It's like a secret code that unlocks the mysteries of the tiny world of atoms and subatomic particles.