Moon Phases for Kids: The 8 Phases of the Moon

Why does the Moon have phases?

The Moon doesn't make its own light. Like Earth, it's a ball lit by the Sun, so at every moment half of the Moon is in sunlight and half is in darkness.

The Moon travels around Earth about once a month. As it moves, we see its sunlit half from a different angle each night:

• When the Moon is between Earth and the Sun, its lit half faces away from us. We see the dark half, and the Moon seems to vanish: that's a new moon.
• When the Moon is on the far side of Earth from the Sun, we see the whole lit half: a full moon.
• In between, we see part of the lit half: crescents, quarters and gibbous moons.

That's the whole secret. The phase wheel above shows it from space: the inner ring is the Moon in its orbit, always half lit from the left, and the outer ring shows how each position looks from Earth. In the 3D view, you can fly around the Sun, Earth and Moon and watch a "view from Earth" picture change as the Moon moves.

The 8 phases of the Moon, in order

The four main phases (new, first quarter, full and third quarter) are exact moments that astronomers can time to the minute, like the times the U.S. Naval Observatory publishes. The four phases in between last several days each.

Words that describe the phases

Four words unlock every phase name:

• Waxing means growing. After new moon, the lit part gets a little bigger every night.
• Waning means shrinking. After full moon, the lit part gets smaller every night.
• Crescent is a thin curved sliver, less than half lit.
• Gibbous means bulging: more than half lit, but not full.

And quarter moons look half lit. They're called quarters because the Moon has traveled a quarter (first quarter) or three quarters (third quarter) of the way around its orbit since new moon.

A handy trick for the Northern Hemisphere: if the right side is lit, the Moon is waxing. Some kids remember it with "DOC": the growing Moon is lit on the right like the curve of a D, becomes a full O, then shrinks into a C lit on the left.

How long is the cycle?

From one new moon to the next takes about 29.5 days. That's where our word "month" comes from.

Oddly, the Moon only takes about 27.3 days to go once around Earth. The extra two days happen because Earth is also moving around the Sun. After one orbit, the Moon has to travel a little farther to line up with the Sun again.

Each night the Moon rises, on average, about 50 minutes later than the night before, because it moves about 12 to 13 degrees along its orbit each day.

Tonight's moon and the moon calendar

Under the phase wheel, the explorer works out tonight's moon right on your device: which phase it is, what percent of the face is lit, how many days it is into the cycle, and the dates of the next full and new moons. The calendar shows a little moon for every day of the month and marks the days of the four main phases. Use the arrows to look ahead to a birthday or back to a special night.

We calculate the Moon's position from the Sun's and Moon's positions in the sky using standard astronomy formulas, so the times match official tables to within minutes. Because it runs on your device, it uses your own clock and time zone.

The same side, always

The Moon spins once for every trip around Earth, so it always keeps the same face toward us. That's why the dark patches, the "man in the Moon," always look the same. The far side isn't permanently dark, though: it gets sunlight during our new moon, when the side facing us is dark. In the 3D view, notice that the Moon turns as it orbits, so the same side always faces Earth.

Moon phases and eclipses

Eclipses happen at special phases:

• A solar eclipse can happen only at new moon, when the Moon passes directly between the Sun and Earth and blocks the Sun.
• A lunar eclipse can happen only at full moon, when Earth is directly between the Sun and the Moon and Earth's shadow falls on the Moon.

We don't get eclipses every month because the Moon's orbit is tilted about 5 degrees compared with Earth's. Most months, the new and full moons pass a little above or below the line between Earth and the Sun.

Common mix-ups about moon phases

• "Earth's shadow makes the phases." No: the shadow only matters during a lunar eclipse. Phases are about our viewing angle.
• "The Moon only comes out at night." No: you can often see it in the daytime, especially near first and third quarter.
• "Everyone sees a different phase." No: the whole Earth sees the same phase on the same night. In the Southern Hemisphere it simply looks flipped left to right.

Moon phases activities for kids

1. Lamp and ball model. In a dark room, put a lamp on one side. Hold a ball at arm's length and turn slowly in a circle. Your head is Earth; watch the lit part of the ball grow and shrink through every phase.
2. Oreo phases. Scrape cream from cookie halves to make each of the 8 phases, then arrange them in order. It's a classic for a reason.
3. Moon journal. Sketch the Moon at the same time each evening for a month and compare it with the calendar above.
4. Printables. Use the moon phases chart as a reference, then try the moon phases worksheet with its word bank or the harder label the moon phases sheet.

Where moon phases fit in science

Moon phases usually come up in the early elementary grades, as children notice patterns in the sky, and again in middle school, when students model the Sun, Earth and Moon system to explain phases, eclipses and seasons. After the Moon, explore the whole solar system or learn facts about Earth.

For a complete science program, see our guide to the best homeschool science curriculum or browse science programs. Families can save favorites to a wishlist and check whether a scholarship in their state may help pay for them.