How are shadows made?

The longer answer

Light cannot bend around things. It shoots out from the Sun, a lamp or a flashlight in straight lines, and when those lines hit something it cannot pass through, they stop. Everything behind that object stays darker.

The size of a shadow depends on where the light is. Move your hand close to a flashlight and it blocks a wide spread of light, so its shadow on the wall grows huge. Move your hand toward the wall and the shadow shrinks back to hand size.

Outside, the Sun does the same thing. When it is low in the morning and evening, your shadow stretches long across the ground. At midday, with the Sun high overhead, it shrinks to a small patch around your feet.

Three things to know

• Your shadow is longest in the early morning and late evening. A low Sun shines sideways, so your body blocks it in a long stripe. At midday your shadow shrinks to a puddle at your feet.
• The Moon makes shadows too, on a bright night. Moonlight is sunlight bouncing off the Moon. Under a full Moon you can see your own soft, pale shadow.
• A sundial tells the time with a shadow. As the Sun moves across the sky, a pointer's shadow swings around the dial and points to the hour.

Try it at home: a shadow monster game

1. In a dark room, shine a flashlight at a plain wall.
2. Hold your hand between the flashlight and the wall and make a shape.
3. Move your hand close to the flashlight. What happens to the shadow?
4. Now move your hand close to the wall. Can you make a monster, a dog or a bird?

Outside on a sunny day, mark the tip of your shadow with chalk in the morning and again at lunch, and compare.