What explains the variation in shadow length throughout the day?

The variation in shadow length throughout the day is primarily influenced by the position of the sun in the sky. As the sun moves from east to west during the day, its angle relative to the horizon changes significantly. When the sun is low in the sky during the early morning or late afternoon, shadows are longer because the light strikes objects at a more oblique angle. Conversely, when the sun is at its highest point around noon, shadows are shorter since the light hits more directly overhead.

This phenomenon is a direct result of the sun's trajectory across the sky and is consistent regardless of the season, though it might be slightly affected by the tilt of the Earth's axis, which influences the sun's path over the year. However, it is the sun's position at any given time of day that most directly impacts shadow length.