You hold your hand in the air, nowhere near the wall. The wall suddenly shows a giant dark hand. Your real hand is not black, and it is not touching the wall. So what is that dark shape? If the lamp is the only bright light, why does the wall look like a giant copy of your fingers? And why does the copy get bigger when you move your hand toward the lamp? That dark patch is a shadow. Today you will figure out why shadows have shapes at all.