ELI5: How did the Moon form?

The Moon was formed when a giant space rock crashed into the very young Earth, blasting out melted pieces that stuck together to make a whole new ball in the sky.

Imagine playing with two balls of soft clay on the floor.

You have a big blue ball of clay, which is the young Earth. Suddenly, someone rolls another red ball of clay right into it, very hard and fast. Scientists call this colliding rock Theia.

When the two clay balls smash into each other, a few things happen:

• The Big Splash: Tiny bits and splatters of clay tear off from the impact and fly all over the room. In space, this crash was so violent that the rocks melted into super-hot, glowing liquid.
• The Swirling Ring: Gravity, which acts like an invisible rubber band, stopped all those splashed-out pieces from floating completely away. Instead, they spun around the Earth in a giant, glowing ring of dust and melted rock, just like the rings you see around Saturn.
• Rolling the Snowball: Over time, these floating melted rocks bumped into each other. Just like when you roll a tiny snowball across the yard and it picks up more snow until it becomes a giant snowman body, these space rocks stuck together. They clumped into one giant sphere, cooled down over millions of years, and became the Moon.