text: Globes are tilted -- the angle is about 23.5 degrees -- because that is the angle between the axis of rotation of the Earth and the normal of the Ecliptic. The Ecliptic is the orbital plane of the Solar System.\n\nThe tilt is responsible for the seasons. If the angle was zero degrees, the Sun would always travel the same apparent path through the sky (over the equator, of course) and there would be no seasons. The reason the seasons change is in summer, the pole of the Earth is tilted toward the Sun and more light falls on that hemisphere, warming it up. On the opposite hemisphere, pointed more away from the sun, less light falls and it's colder. Since the tilt of the axis remains more or less constant, the seasons change as the Earth orbits the sun, warming up opposite hemispheres alternately.