What are bell tests?

A bell test is like asking two friends to play a game from far apart and seeing if they can guess each other’s choices correctly more often than chance would say they should.

Imagine you have two friends, Luna and Leo, who love playing a guessing game. They’re in different rooms and can’t talk to each other. Every time the game starts, they both pick a number, either 1 or 2, without knowing what the other picked.

Now, here’s the fun part: if their numbers match more often than just by luck, it means something special is happening between them, like they’re sharing some kind of secret signal that helps them guess right even when they can’t talk!

In a bell test, scientists use this idea but with something called particles instead of friends. These particles act like Luna and Leo, even if they're far apart, they still seem to know what the other is doing.

Sometimes, these tests show that the particles match in ways that feel almost too perfect, as though they were sharing a secret signal all along!