The Moon's Amazing Phases
The Moon changes shape in the sky over about a month, moving through eight distinct phases. It isn't actually changing shape at all — what changes is how much of its sunlit half faces Earth.
What Causes the Moon's Phases?
The Moon doesn't make its own light. Instead, we see the Moon because it reflects sunlight. As the Moon orbits (goes around) the Earth, we see different amounts of the sunlit part of the Moon. That's what creates the phases.
The Phases of the Moon
Here's a quick guide to the main Moon phases. Each phase lasts for a few days:
- New Moon: The Moon is between the Earth and the Sun, so the side facing us is not lit. We can't see the New Moon.
- Waxing Crescent: A tiny sliver of the Moon becomes visible. "Waxing" means it's growing.
- First Quarter: We see half of the Moon lit up.
- Waxing Gibbous: More than half of the Moon is lit, and it's still growing.
- Full Moon: The entire side of the Moon facing Earth is lit up.
- Waning Gibbous: More than half of the Moon is lit, but now it's shrinking ("waning").
- Third Quarter: We see half of the Moon lit up again, but the opposite side from the First Quarter.
- Waning Crescent: A tiny sliver of the Moon is left, and it's getting smaller.
The eight names always come round in the same order, and then start again from the beginning. Put them back into that order.
- Full Moon
- New Moon
- Third Quarter
- First Quarter
- Waning Crescent
- Waxing Crescent
- Waning Gibbous
- Waxing Gibbous
Try This: Moon Phase Chart
Track the Moon's phases for one month: go outside at night and draw what you see. Here's what you'll need:
- Paper
- Pencil or pen
- A clear view of the sky at night
Steps:
- Every night, look at the Moon.
- Draw what you see on your paper. Try to get the shape right.
- Write the date next to your drawing.
- After a month, look at your chart. Can you see the different phases?
Why This Works
By observing the Moon each night, you'll see how the amount of sunlight we see on the Moon's surface changes over time. Tracking the phases helps you understand the Moon's orbit around Earth and how the Sun's light creates the different shapes we see.
The Sun lights one half of the Moon, and it is the same half all month long. The Moon never changes shape. What changes is where the Moon is standing in its circle around Earth, and so how much of that lit half is pointing our way. The eight phases are eight places on one circle, not eight Moons.
Next time you look up, remember: the Moon itself isn't changing. Only your view of its sunlit half is.