Groundhog Day Science: Does a Shadow Predict the Weather? (Shadow Activity for Grades 1–2)

Every February 2, people watch to see whether a groundhog sees its shadow. It’s folklore, and a fun starting point for a real science question: what do shadows actually tell us?

Fact or folklore?

Start by sorting statements. Which are facts we can check, and which are stories?

• “A shadow is made when something blocks light.” (Fact: you can test it.)
• “A groundhog can predict six more weeks of winter.” (Folklore: it’s a tradition, and its track record isn’t good.)
• “Shadows are longer in the morning than at noon.” (Fact: you can measure it.)

This is a gentle first lesson in asking “How do we know?”, a habit that serves students all the way through science.

Measure a shadow three times in one day

You need a plastic bottle (filled with sand or water so it doesn’t blow over), sidewalk chalk, yarn and scissors.

1. Choose a sunny spot. Mark an X with chalk and stand the bottle on it.
2. At about 9 a.m., trace the shadow with chalk and measure its length with a piece of yarn. Cut the yarn to match, and tape it on a chart.
3. Repeat at about noon and 3 p.m., without moving the bottle.
4. Compare the three pieces of yarn.

The shadow is longest when the Sun is low (morning and late afternoon) and shortest when the Sun is high. Notice it also moves: the Sun appears to move across the sky, so the shadow swings the other way.

No sun, or too cold to go out? Use a flashlight held low and then high over a toy. Low gives a long shadow, high gives a short one, which models the Sun.

Why it happens

Light travels in straight lines. An object blocks it, and the dark shape behind is the shadow. When the light comes from low in the sky, the shadow stretches out along the ground. When the light comes from overhead, the shadow shrinks.

The shadows themselves don’t tell you about next month’s weather. They tell you about where the Sun is.

Questions to ask

• What stayed the same? (The bottle, the spot.)
• What changed? (The time of day.)
• Why do you think the shadow got shorter?
• Could a shadow tell us the weather? What evidence would we need?

Resources

Our free Groundhog Day Shadows pack for Grades 1 and 2 includes a reader, a class graph, a puppet activity, a short emergent-reader book and an answer key. For a full lesson, try Why is my shadow long in the morning? from the Light and Shadows unit. Sign up for three lessons free.