Moon Phases Explorer
Understand that the Moon does not make its own light: we see the sunlit half from different angles as it orbits Earth, giving eight repeating phases in about 29.5 days.
Before you try
What if the Moon stopped moving around Earth? Would it still change shape?
Try it out
Interactive activity
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What happened?
Move a control to see what changes and why.
Distances and sizes are squashed to fit the screen, and the tilt of the Moon’s orbit is drawn bigger than the real 5° so you can see it. The real orbit is also slightly oval.
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Try these ideas
- Find the day when the Moon is exactly half lit. Is it the first or last quarter?
- Press play and count how many days pass between two full moons.
- Go to full moon and switch to the side view. Does the Moon pass through Earth’s shadow?
- Turn on Eclipse and watch the Moon turn copper red.
Why it works
The Moon is a ball of rock that reflects sunlight. Half of it is always lit by the Sun, but as the Moon travels around Earth we see different amounts of that lit half. That is why it seems to grow (wax) and shrink (wane).
A full cycle (new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, waning crescent) takes about 29.5 days. In this simulator you drag through the days and see both a 3D view of the orbit and what someone on Earth would see in the sky.
Topics covered: moon phases, waxing, waning, lunar cycle, space for kids.
Check your understanding
Question 1 of 3
Why does the Moon look like it changes shape?
About how long does one full cycle of phases take?
At new moon, where is the Moon compared with the Sun and Earth?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Look at tonight’s Moon together. Can you match it to a day on the slider?
- Ask: if you stood on the Moon, would Earth also show phases?
- Keep a week-long Moon diary with quick sketches.
Related activities
- Solar System Orbit Explorer
- Rainbow and Light Refraction Lab
- Weather Maker
- Eclipse Shadow Lab: Solar and Lunar Eclipses
More for Class 3, Class 4, Class 5, Class 6 and Space.
Part of the learning path Space Explorer.