3D Chalk Hole Illusion

What you need

• Phone, 1, for photos (optional)
• Water, a splash, for cleanup (optional)
• Chalk, 6 to 8 sticks, including a dark one
• Broom, 1

How to do it

Grown-up prep: Pick a smooth, dry stretch of your own driveway or path, well away from cars and traffic. Stay nearby while kids draw and crouch.

1. Draw a rough oval on the pavement, about as wide as your arms.
2. Shade the far inside edge of the oval very dark.
3. Shade the near inside edge lighter.
4. Fill the middle with a medium shade to make it look deep.
5. Add bricks or cracks around the rim of the hole.
6. Stand at the near end and crouch so your eye is low.
   Ask: What do you think will happen to the hole when you look from this spot?
7. Now view your hole from that one spot. Does it look deep?
   Ask: What happens to the hole if you step to the side or stand tall?
8. Draw a box that looks like it sits on the ground.
9. Photograph a friend or a grown-up stepping over the box from the viewing spot. Ask for help if you need it
10. Now show your friends, or make more! What else could you make look real?
    Ask: What would you like to draw next to fool our eyes?

Play it again

• Floating ball: draw a ball with a shadow underneath so it seems to hover.
• Giant stairs: draw steps going down into a deep hole and shade each one.
• Photo gallery: make three illusions and take a picture of each one from its best spot.