I follow you everywhere but you can never touch me or catch me. What am I?

The elusive companion that follows you everywhere but can never be touched or caught is your shadow. This is because a shadow isn't a physical object at all; instead, it's an area where light is blocked. Light travels in straight lines, and when an opaque object, like your body, stands in the path of a light source, it prevents those light rays from reaching the surface behind it. The resulting region of darkness is what we perceive as a shadow, and since it lacks any material substance, it's impossible to physically interact with it or grasp it.

Shadows are formed by the interplay of a light source, an opaque object, and a surface for the shadow to appear on. The shape and size of your shadow are constantly changing, depending on the position of the light source relative to you. For instance, in the early morning or late afternoon, when the sun is low in the sky, your shadow will appear long and stretched out. As the sun climbs higher towards midday, your shadow shortens, often appearing directly beneath you.

Beyond simply following us around, shadows have played a significant role throughout history and science. Ancient civilizations utilized the predictable movement of shadows cast by the sun to create sundials, which were among the earliest devices for telling time. Scientifically, shadows can be divided into different regions: the umbra, which is the darkest central part where all light is blocked, and the penumbra, a lighter, partial shadow around the umbra. The study of shadows even helps us understand celestial events like solar and lunar eclipses, which are essentially large-scale shadows cast by the Earth or Moon.