Why does a shadow follow your feet?

On a sunny walk, a dark shape stretches across the path beside you. You take a step, and the shape moves too, right along with your shoes. Why does a shadow follow your feet?

The answer starts with light, the brightness that helps you see things. The sun gives us light during the day. Some of that light reaches the path and makes it bright.

Light travels in straight lines until something gets in its way. When you stand in the sunshine, your body gets in the way of some of those lines. Sunlight cannot go straight through you to reach the ground behind you.

That leaves a shadow, a darker patch where something blocks the light. Your body blocks some sunlight, so the ground there looks darker than the sunny ground around it. That dark patch has a shape a little like you!

But why does your shadow meet your feet? When you stand on the path, your feet touch the ground. You block sunlight right down to that spot, so your shadow starts at your feet and stretches away from the sun.

Imagine you take one step to the side in the sunshine. Will your shadow stay in the old spot, or move to the side too?

It moves too! Your body now blocks sunlight in a new spot, making a shadow there. Sunlight can reach the ground you no longer block, so that part becomes bright again.

Your shadow does not pull itself along the path. As you walk, you keep changing where your body blocks the light. The dark patch changes places with you, which makes it look as though it follows.

Your shadow is not actually stuck to your shoes. When you lift one foot, that foot no longer touches the ground, so a sunny gap can appear between your foot and its shadow. The foot's shadow still falls on the ground because your foot still blocks sunlight.

Here is the whole chain: light, your body blocking it, a shadow on the ground, your feet touching the ground, and a new shadow spot as you move. Your shadow follows your feet because your body keeps blocking light in a new place as you walk.

On your next sunny walk, you can carry that little answer with you, right beside your shadow.