As the Earth spins, the angle at which the Sun’s rays strike the Earth changes

Model of the sun (torch) rays hitting the Earth (globe).

During the day, we perceive the Earth’s spin as the Sun’s apparent movement across the sky. As this occurs, the shadows cast by objects on Earth change in length because the angle at which the Sun’s rays hit the object changes.

This effect becomes more pronounced in the different seasons, due to the tilt of the Earth’s axis relative to the Sun. Noon shadows in winter – when the viewer’s part of the Earth’s surface is tilted furthest away from the Sun – are longer than noon shadows in summer.