Why Does the Moon Change Shape

The Moon does not actually change shape. It is always a round ball. But from Earth, it looks like it changes from a thin sliver to a full circle and back again. This happens because we see different amounts of the Moon's sunlit half as it orbits the Earth.

How Moon Phases Work

The Sun always lights up half of the Moon, just like it lights up half of Earth. As the Moon moves around the Earth, we see different parts of its sunlit side. When the Moon is between Earth and the Sun, we see the dark side. This is a new moon. When Earth is between the Moon and the Sun, we see the full sunlit side. That is a full moon.

The Monthly Cycle

It takes about 29.5 days for the Moon to go through all its phases. The Moon grows from new moon to full moon. This is called waxing. Then it shrinks from full moon back to new moon. This is called waning. The phases are new moon, crescent, quarter, gibbous, and full moon.

Fun Facts

• The same side of the Moon always faces Earth because the Moon rotates at the same speed it orbits.
• A blue moon is the name for the second full moon in a single month.
• The Moon reflects only about 12 percent of the sunlight that hits it.

Did You Know?

During a lunar eclipse, the Earth's shadow falls on the Moon and can make it look red. This is sometimes called a blood moon. The red color comes from sunlight bending through Earth's atmosphere!