Oh! One more thing, before we forget. Earth has seasons because our planet's axis of rotation is tilted at an angle of 23.4 degrees, relative to our orbital plane (the plane of earth's orbit around the sun).
Now that we've defined a parent Earth-Moon object, we can also tilt the earth without affecting the position of this whole celestial pair system:
- Select Earth and change its Transform Rotation to (0, 0, 23.4).
- If you use the rotate gizmo in the Scene view, be sure to set it to Local (not Global).
- Make sure Transform Position is still (0,0,0).
- Save the scene and the project.
The following screenshot shows our Scene view with the sun, tilted earth, and orbiting moon:
