Shadow Clock on the Sidewalk

What you need

• Sidewalk chalk, 3 colors
• Sunscreen, 1 bottle
• Water bottle, 1

How to do it

Grown-up prep: Pick a sunny paved spot away from the street and driveway traffic, ideally one that stays sunny all day. Plan three short visits: morning, lunchtime and mid-afternoon. Bring sunscreen, a hat and water, and keep each visit brief. Have the same person do the tracing each time if you can.

1. Find a flat, sunny spot on the pavement, far from the street.
2. Draw a big X on the pavement with chalk.
3. In the morning, stand on the X with your feet together, facing a landmark.
   Ask: Where is the sun right now: high up or low in the sky?
4. Hold very still while a helper traces your shadow. Mark the time inside.
5. At lunchtime, stand on the X again and trace your shadow in a new color.
6. In the afternoon, trace your shadow one more time and mark the time.
   Ask: Can you guess where this shadow will point before we trace it?
7. Step back and compare all three shadows. Which is longest? Which turned the most?
8. Now show your friends, or try again! Whose shadow clock will be the coolest?
   Ask: Who will you invite to make a shadow clock with you?

Play it again

• Tomorrow test: come back at lunchtime the next day and see if your shadow lands on yesterday's lunch outline.
• Pose parade: trace a shadow with arms up, then trace another with a funny pose, and compare.
• Hourly clock: add a new tracing every hour and see how far your shadow swings.