Shadow Clocks and Star Light: Graphing Earth's Patterns ✨ cross-curricular

Lesson Structure

Opening (5 minutes)

Stand at the front of the room and hold a pencil horizontally, then drop it. Ask: "Which way did it fall? Why?" Let 2-3 students respond. Then say: "Now imagine you're standing in Australia — on the other side of Earth. Which way would a dropped pencil fall for them?" Pause for discussion. Reveal: gravity always pulls toward Earth's center — down, from any point on the globe. Transition: "Gravity keeps us on Earth. Earth also moves in patterns that affect everything we see in the sky — shadows, day and night, even which stars are visible. Today we're going to find those patterns by graphing real data."

Main Activity (50 minutes)

Step-by-step instructions:

1. (8 min) — Gravity and Star Brightness: Build the Foundation. Write on the whiteboard: Why does the sun look so much brighter than other stars? Draw a simple diagram: Earth in the center, the sun close by, and 3-4 dots labeled "other stars" far away. Ask students to turn and talk: "What do you notice about the distances?" Debrief together. Write the key idea on chart paper: "The sun is a star. It looks brightest because it is closest to Earth. Other stars are so far away they look tiny and dim — but many are actually bigger and brighter than our sun." Connect back: gravity from Earth (directed down) keeps us in orbit around the sun, which is why we see it consistently.
2. (7 min) — Introduce Shadow Pattern Data. Tell students: "Scientists measured the shadow length of a 1-meter stick placed in the sun at different times during one day. I'm going to give you that data." Write the following data table on the whiteboard — students copy it into the Data Table section of their recording sheet:
   
   Time (Hour) / Shadow Length (cm): 7 AM = 95 cm | 9 AM = 55 cm | 11 AM = 20 cm | 12 PM = 8 cm | 1 PM = 18 cm | 3 PM = 52 cm | 5 PM = 90 cm
   
   Ask: "Before we graph, what do you predict the shape of the graph will look like?" Take 2-3 predictions aloud. Write them on the board to revisit later.
3. (15 min) — Graph Points on the Coordinate Plane. Model on the whiteboard: draw the first quadrant of a coordinate plane. Label the x-axis "Time (Hour of Day, 7–17)" and the y-axis "Shadow Length (cm, 0–100)." Show students how to convert time to a number: 7 AM = 7, 9 AM = 9, 12 PM = 12, 5 PM = 17. Plot the first point (7, 95) aloud, narrating: "I go to 7 on the x-axis first — that's the time. Then I go up to 95 — that's the shadow length. I put my dot there." Students then plot all 7 points independently on their own coordinate plane (Recording Sheet). Circulate and check that students are reading both axes correctly. Remind them: the ordered pair is always (x, y) — time first, then shadow length.
4. (8 min) — Connect the Dots and Describe the Pattern. Have students use a colored pencil to connect their points with a smooth curved line. Ask: "What shape does the line make?" (A U-shape or curved valley.) Ask: "When is the shadow shortest? Longest? Why?" Guide students to connect this to the sun's position: when the sun is highest in the sky (midday), shadows are shortest. When the sun is low (morning/evening), shadows are longest. Write on chart paper: "Shadow patterns repeat every day because Earth rotates in a predictable pattern — this is what causes day and night."
5. (7 min) — Seasonal Stars Discussion. Ask: "If Earth is always moving around the sun, does the nighttime side of Earth always face the same stars?" Let students discuss in pairs for 1 minute, then share out. Explain: Earth's orbit means we face different parts of the universe at different times of year — this is why some constellations only appear in summer and others only in winter. Draw a simple diagram: Earth at 4 positions around the sun, with arrows showing which direction is "nighttime sky" at each position. Students sketch this diagram in the "Seasonal Stars" box on their recording sheet and label it.
6. (5 min) — Anchor Chart: Patterns in Our Sky. As a class, build a 3-column anchor chart on chart paper. Columns: What We Observe | Caused By | Pattern It Makes. Rows to fill in together: (1) Shadows change length through the day / Earth's rotation / U-shape curve on graph; (2) Day and night / Earth's rotation / 24-hour cycle; (3) Different stars in winter vs. summer / Earth's orbit around the sun / Seasonal cycle; (4) Sun looks brighter than stars / Sun is much closer to Earth / Distance relationship. Students copy the completed chart into the Notes section of their recording sheet.

Closing (5 minutes)

Return to the predictions students made before graphing. Ask: "Were your predictions correct? What surprised you about the shape?" Have students write one sentence on the back of their recording sheet: "The pattern I found in the shadow data shows that..." Collect recording sheets as an exit ticket.

Quick Check: Ask these 3 questions verbally before dismissal:

• "Which direction does gravity always pull — and how do we know?" (Down, toward Earth's center — dropped objects always fall that way)
• "If Proxima Centauri is actually larger than our sun, why does it look like a tiny dot at night?" (It is enormously far from Earth compared to the sun)
• "On your graph, what does the lowest point of the U-curve represent?" (The shortest shadow, which occurs at midday when the sun is highest)