Why do planets move in an elliptical orbit instead of a circular orbit?

Question

And how exactly did we find out how they move?

In: Planetary Science

Answer 1

We figured out they were ellipses through a lot of trial and error. We used to assume they were circular but whenever we calculated their positions based on them being circles we kept getting the wrong answer; the planets weren’t where we said they’d be based on the math.

Then a guy named Johannes Kepler decided to model them as ellipses seeing as how the previous thing wasnt working out and voila, the paths of the planets matched our observations.