Understanding the Moon Phase Cycle

What is the length of time it takes for the moon to complete its eight-phase cycle?

What is the primary cause of the changes in the moon's appearance from Earth?

What is the term for the growing of the moon's image?

How many primary phases are there in the moon phase cycle?

What is the name of the first moon phase of the synodic month?

What is the result of the changes in the moon phase cycle on the ocean's tides?

When does the full moon occur in the moon phase cycle?

What is the position of the moon relative to the Earth and sun during a full moon?

What is the characteristic of the first quarter moon phase?

What is the shape of the shadow of the Earth on the moon during a crescent moon phase?

Which phase of the moon cycle occurs when most, but not all, of the moon is illuminated and visible from Earth?

What is the purpose of the lunar calendar in Chinese culture?

What is the name of the full moon in May in the US, based on Native and Colonial American traditions?

What is the characteristic of a lunar eclipse?

What is the impact of new moons and full moons on the oceans' tides?

The Moon Phase Cycle

The moon's appearance from Earth changes constantly due to its position relative to the Sun and Earth.
The cycle repeats every 29.5 days, which is the length of a synodic month.
The moon's image appears to grow from right to left and then shrink from right to left as it completes its orbit.

Phases of the Moon

There are 8 phases in the moon cycle: 4 primary and 4 secondary phases.
Primary phases are: New Moon, First Quarter, Full Moon, and Last Quarter.
Secondary phases are: Waxing Crescent, Waxing Gibbous, Waning Crescent, and Waning Gibbous.
Waxing refers to a growing moon image, while Waning refers to a shrinking image.

New Moon and Full Moon

The New Moon occurs when the moon is directly between the Earth and the Sun, with no sunlight reflected on the surface.
The Full Moon occurs when the moon is on the opposite side of the Earth from the Sun, with the entire moon visible from Earth.

Quarters

The First Quarter occurs when the moon is one quarter of the way through its cycle, with roughly one half of the moon illuminated on the right side.
The Last Quarter occurs when the left side of the moon is illuminated.

Crescent Moons

The Waxing Crescent occurs when a small portion of the right side of the moon is visible from Earth.
The Waning Crescent occurs when the left side of the moon is visible.

Gibbous Moons

The Waxing Gibbous phase occurs when most of the moon is visible, except a small portion on the left side.
The Waning Gibbous phase occurs when most of the moon is visible, except a small portion on the right side.

Moon Phase Traditions and Facts

Many cultures have traditions around the phases of the moon, such as the lunar calendar in China.
Some cultures give different names to each of the full moons, such as the Full Flower Moon in May.

Eclipses and Tides

A lunar eclipse occurs when the Earth's shadow completely blocks out the view of a full moon.
A solar eclipse occurs when a new moon is directly between the Earth and the Sun.
New moons and full moons can impact the oceans' tides, with the biggest variation between high and low tides occurring during these phases.

This quiz covers the basics of the moon phase cycle, including the eight phases that repeat during each synodic month. Learn how the position of the sun, moon, and Earth affect the appearance of the moon from Earth.