Eli5: How could humans tell the difference between a planet and a star in the nightsky, before telescopes where invented?

Question

Eli5: How could humans tell the difference between a planet and a star in the nightsky, before telescopes where invented?

In: Planetary Science

Answer 1

Stars follow a regular path through the sky, whereas planets appear to make loops.

The word ‘planet’ comes from the Greek ‘planan’ (to wander) because of this movement.

When they thought the earth was at the centre of the universe, [they had to invent complex paths for the planets to explain their movement](https://i.imgur.com/FlkiyQw.jpg).

Of course, once you realise that the sun is at the centre of the solar system, and that the earth is one of several planets going around it, the patterns seem a lot simpler!