Question

What causes axial tilt?

Answer 1

Two factors: the initial tilt provided by the nebulae that formed the solar system and any subsequent impact by planetoids.

Explanation:

When the solar system is forming, gravity tends to attract lumps of matter together that later form planets. However, this eventually gives the early solar system a rotational spin. All planets in our solar system revolve around the sun in the same direction. If a planet forms without any subsequent impact, the axial tilt is pretty much a random factor.

However, if like Earth, an early forming planet gets smacked by another smaller forming porto-planet, this can cause the axial tilt to flip further. For example, Uranus, is tilted about 83 degrees or almost spinning on its side!