The Earth’s Moon

Amazing Fact!

Many scientists believe the moon formed when a small planet crashed into the Earth. Rock and dust were thrown into space. Gravity pulled the rock and dust together to form the moon.

In space, the force of gravity causes smaller objects to orbit larger objects. Any object that orbits another object is called a satellite. The Earth is a satellite of the Sun. The Earth’s moon orbits the Earth, so the moon is a satellite of the Earth. It takes the moon about 27.3 days to revolve once around the Earth.

It also takes the moon about 27 days to rotate once on its axis. So, the side of the moon facing the Earth is always the same. On some nights, the moon appears in the sky as a bright circle. The moon appears bright because it reflects the light from the Sun. On other nights, the shape of the moon is different. The changing shape of the moon’s sunlit portion, as viewed from Earth, is called the phases of the moon.

As the moon orbits the Earth, part of the moon is lit up by the Sun while the other part is in darkness. The moon appears to change shape because the part of the moon lit up by the Sun changes as the moon orbits the Earth. When the whole side of the moon seen from Earth is lit up, we see a full, round moon. When only half of the side of the moon seen from Earth is lit up, we see the moon in the shape of a semi-circle.

What causes the phases of the moon?

AB Activities 7.2 – 7.3 Think Deeply

Why are we able to predict the shape the moon will appear in the sky?

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Learn the names of the different phases of the moon in a video on the NGScience website. QuickCode: H3C1