MS-ESS1-1ESS1.B: Earth and the Solar System — scale, properties, and motions of objects in the solar system. Eclipses arise from the geometric relationship among the Sun, Earth, and Moon. SP2: ModellingScience Practice 2: Developing and using models — students manipulate a physical model of the Sun-Earth-Moon system to test conditions for solar and lunar eclipses. SP4: Analyzing DataScience Practice 4: Analyzing and interpreting data — students observe outcomes across multiple conditions and identify the pattern that produces an eclipse.

Spatial ReasoningSpatial manipulation of a 3D orbital geometry builds mental models that text alone cannot — direct manipulation of the SVG model activates visuospatial processing. (Hegarty & Waller, 2005) Productive StruggleStudents who discover the eclipse condition through trial and error show deeper conceptual retention than those who are told the answer. (Kapur, 2016 — Productive Failure) Guided InquiryStructured challenges with feedback scaffold inquiry while keeping cognitive load manageable — key for middle school learners. (Kirschner et al., 2006)

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Simulation

Eclipse Alignment

Can you create an eclipse by lining up the Sun, Earth, and Moon?

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Driving Question

Why does the Moon reach new moon and full moon every month, but eclipses only happen sometimes?

Mission Briefing

What You Need to Know First

Before you touch the controls, read these three facts. They are the rules of the simulation.

Solar Eclipse

New Moon + Node

The Moon must be between the Sun and Earth — that is a new moon. It also must be near a node, the point where its tilted orbit crosses Earth's orbital plane. Both must be true at the same time.

Lunar Eclipse

Full Moon + Node

Earth must be between the Sun and Moon — that is a full moon. The Moon must also be near a node so Earth's shadow actually reaches it. Phase alone is not enough.

Most Months

Shadow Misses

The Moon's orbit is tilted about 5 degrees relative to Earth's orbital plane. Most new and full moons, the Moon is slightly above or below the plane — and the shadow passes without hitting.

The core idea: A new moon or full moon is not enough. The Moon also has to be near a node.

Lab

Eclipse Alignment

Use the controls below to set up the Sun-Earth-Moon system. Adjust all three dials and watch the result change in real time.

🔒 Unlock the three observation cards above to begin the lab.

Eclipse Type

Moon Phase

Moon Height

👆 Select an eclipse type, moon phase, and moon height to begin.

Guided Challenges

Three Challenges

Use the lab controls above to solve each challenge. Read the goal, set the controls, and watch the result. You can revise as many times as you like.

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Solar Eclipse

Lunar Eclipse

Why Not Every Month?

Challenge 1

Create a total solar eclipse.

Think carefully: which phase puts the Moon between the Sun and Earth? And where does the Moon need to be in its orbit for the shadow to actually connect?

Solar Eclipse Achieved

New moon + near a node = the Moon's shadow reaches Earth. Both conditions had to be true at the same time.

Challenge 2 Locked

Create a lunar eclipse.

This time Earth casts the shadow. Which phase puts the Moon on the far side of Earth from the Sun? What else has to be true?

Lunar Eclipse Achieved

Full moon + near a node = Earth's shadow falls on the Moon. The Moon had to be on the far side of Earth and near the orbital plane.

Challenge 3 Locked

Create a month with no eclipse.

The right phase is there — but the shadow still misses. Show what happens most months when the Moon is above or below the orbital plane.

No Eclipse Month Achieved

Even with the correct phase, the Moon's tilted orbit causes the shadow to miss. Most months work this way.

Discovery Summary

What You Found Out

Three things the lab just showed you. Each one connects to a challenge you solved.

Moon Phase✓

In Challenge 1 you needed a new moon — the only phase that puts the Moon between the Sun and Earth.
In Challenge 2 you needed a full moon — the only phase that puts Earth between the Sun and Moon.
Quarter moon failed both. The geometry has to be right from the start.

Orbital Nodes✓

In Challenge 3 the phase was correct — but the shadow still missed.
The Moon's orbit is tilted about 5 degrees, so it usually passes above or below the orbital plane. The shadow misses Earth or the Moon entirely.
Eclipses only happen when the Moon is near a node — one of two places where its orbit crosses the plane.

Shadow Zones✓

Even when an eclipse happens, not everyone sees the same thing.
The umbra is the darkest part of the shadow — observers inside it see a total eclipse.
The penumbra is the outer shadow — observers there see only a partial eclipse.
Your location relative to the shadow determines what you experience.

The big takeaway: Moon phase creates the possibility. Node alignment makes the eclipse happen.

Phase 3

Deep Time

What looks permanent in the sky is only temporary on geologic time scales. The Moon is slowly drifting away from Earth — and that quietly changes what eclipses look like.

Ready

Model note: This animation compresses hundreds of millions of years into a few seconds. Dates are estimates based on the Moon moving away from Earth about 3.8 cm per year.

Ready to begin

A 10-second journey through deep time

Watch how the Moon’s slow outward drift quietly transforms what eclipses look like across millions of years.

Check Your Understanding

Checkpoint

5 questions about eclipse alignment, moon phase, orbital tilt, nodes, and shadows.

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