How does the universe work?

The universe is like a giant, never-ending playground where everything is made of tiny building blocks that keep moving and changing.

Imagine you're playing with Legos. Each Lego piece is like a particle, and when you put them together, you make something bigger, just like how atoms become molecules, and then things we can see, like trees or cars.

Everything in the universe is always moving, even if it looks still. Think about your toy car: when you push it, it goes forward. That’s like gravity, a hidden force that pulls things toward each other, just like how your toy car is pulled back to the floor after you let go.

Sometimes, things in the universe grow or shrink. Like when you blow up a balloon, it gets bigger, and the air inside pushes against the rubber. That’s like expansion in the universe: everything is moving away from each other, just like the balloon stretches out.