eli5: why are the orbits of celestial bodies elliptical?

Question

eli5: why are the orbits of celestial bodies elliptical?

In: 1

Answer 1

Because f=gmm/r2

Orbits are elliptical because the force of gravity decreases as the square of the distance between objects. Newton proved this.

Edit: to clarify a bit, Kepler showed that the orbit of Mars and other objects was elliptical, based on observations mostly from Tycho Brahe. Newton proved that only a square-diminishing force would produce such orbits.