ELI5: Explain Like I'm 5

Universe

The universe is a pretty big place! It includes all of the planets, stars, galaxies, and everything else in space. The universe is so big that nobody knows exactly how big it is. Everything in the universe is constantly moving and changing. That might seem strange, but it's true! That's also why it's nearly impossible to explore the entire universe - it's just too big and there's so much happening at once.