Measure the Moon

What You Need:

• Paper clip
• Clear night when the moon is low in the sky

What You Do:

1. Help your child unbend the paper clip, then twist it into a U shape.
2. When the moon is low in the sky, go outside and have him hold the paper clip at arm’s length in the direction of the low, large-looking moon. Show him how to use the paper clip like a pair of calipers, bending it so the tips are touching the top and bottom of the moon to record its apparent diameter.
3. Wait an hour or more for the moon to climb higher in the sky.
4. Go back outside and have your child hold her paper clip calipers at arm’s length again. What does she see? The moon should fit within the paper clip exactly.

If your kid liked this activity, try exploring other optical illusions by checking out a book on optical illusions from the library or researching them online.