ELI5: Explain Like I'm 5

Equatorium

An equatorium is like a special kind of calculator that people used a long time ago to figure out exactly where the stars and planets were in the sky.

Imagine you're outside at night and you look up at the stars. You might see one star that is really bright, and another that is more faint. But how do you know which one is which and where they are in the sky?

Well, back then, people used something called an equatorium to figure that out. The equatorium had a bunch of moving parts and pieces, kind of like a puzzle. You would adjust the pieces to match up with the position of the stars and planets you were looking at, and then the equatorium would tell you exactly where they were in the sky.

Sounds pretty cool, doesn't it? But just like how you need to learn how to use a calculator to do math problems, you would need to learn how to use an equatorium to figure out where the stars and planets were in the sky.