One of the wildest ideas in all of physics is quantum entanglement. It sounds like something out of a sci-fi movie, but it’s real, and scientists are still trying to figure it out.

Entanglement essentially says that all quantum particles experience strange behavior, across vast distances, they are able to interact with one another and behave. Imagine you have two tiny particles — like electrons — and you specially connect them so that they become entangled. After that, no matter how far apart they are (one could be on Earth and the other near Saturn), the other reacts instantly if you mess with the other. The most interesting aspect is that, even though this interaction happens instantly, energy transmission doesn’t travel faster than the speed limit of the universe, the speed of light. The behavior of one particle just happens to correlate with the other, and no information is being exchanged as nothing is traveling from one particle to another.

An example of entanglement is if a quark or electron spins one way, another may spin the other way or the same way. This correlation Einstein called “spooky action at a distance” because it made no sense to him. But tons of experiments since then have confirmed that entanglement is real.

Before particles can even get entangled, they first have to pull off another quantum trick called superposition. Superposition is when a particle isn’t doing just one thing — it’s doing everything possible at once. Picture flipping a coin, and instead of getting heads or tails, it’s both heads and tails at the same time, only when there is an observer does it decide. Quantum particles live in this weird probabilistic state. When two particles in superposition interact with each other, they can get locked together — that’s when entanglement happens. When you measure one, you instantly know what happened to the other, no matter how far apart they are.

To better understand this, you can’t really talk about quantum mechanics without mentioning Schrödinger’s Cat — the most famous (and confusing) thought experiment ever. The idea: Put a cat in a sealed box with a radioactive atom that might or might not decay. If it decays, it triggers a mechanism that kills the cat. If not, the cat lives. Now, because radioactive decay is a quantum event based on superposition, the cat is simultaneously alive and dead until you open the box. Encompassing all concepts of quantum entanglement and superposition.

Schrödinger made up this crazy scenario to show how strange quantum rules are when you apply them to regular stuff. It’s not that the cat is half-dead; at a quantum level, until you measure or observe something, it stays in all possible states, which is what superposition is conceptually.

In essence, quantum entanglement proves that reality is way more connected and weirder than we thought. Particles can stay perfectly linked no matter how far apart they are, and they seem to “talk” to each other instantly without sending any message at all.