What causes the Earth's axis of rotation to tilt at a specific angle relative to the elliptic?

Question

What causes the Earth's axis of rotation to tilt at a specific angle relative to the elliptic?

Answer 1

That angle varies over time.  Precession is the change in orientation of the Earth's rotational axis.  The moon helps stabilize it.  It could have been the collision of the planetoid that formed the moon that shifted the axis.

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