A shadow is a dark area or shape produced when an object blocks light from a source, such as the sun or a lamp. Shadows are typically seen on surfaces like the ground or walls and can vary in size and shape depending on the angle and intensity of the light source. The length and direction of a shadow change throughout the day as the position of the sun moves across the sky. In the morning and late afternoon, shadows are longer, while they are shorter and more defined at noon. Shadows can also be used in art and photography to create depth and contrast.