MOON

Circling round Earth once a month, the Moon is our planet’s only natural satellite. As the Moon orbits Earth, our view of it constantly changes, following a cycle known as the PHASES OF THE MOON. Like Earth, the Moon is made up of rock, but is only about a quarter as big across. Because it is so small, its gravity is low (about one-sixth of Earth’s), and it has no atmosphere.

Table 12. ESSENTIAL DATA

Diameter at equator3,476 km (2,160 miles)
Average distance from Earth384,400 km (238,900 miles)
Orbital period27.32 days
Rotation period27.32 days
Time to go through phases29.3 days
Mass (Earth=1)0.01
Gravity (Earth=1)0.17
Average surface temperature-20°C (-4°F)

THE MOON IN ECLIPSE

Two or three times a year the Moon enters the shadow Earth casts in space. This happens when the Sun, Earth, and Moon line up and is called a lunar eclipse. During a total eclipse, when the Sun, Earth, and Moon line up exactly, the Moon does not disappear but takes on a reddish hue as it is lit by light from the Sun that is bent by Earth’s atmosphere.

THE LUNAR SURFACE

From Earth, we only ever see one side of the Moon – the near side. The dark areas are great dusty plains, called maria (seas). The bright areas are highlands hundreds of kilometres across and covered with craters. The hidden far side of the Moon is more heavily cratered, but has no large seas.

PHASES OF THE MOON

Over a month we see the Moon appear to change shape. These different shapes, or phases, occur because, as the Moon circles Earth, we see more or less of the half of its surface that is lit by the Sun. The Moon takes 29.53 days to go through its phases.

THE LUNAR CYCLE

With the Moon directly between Sun and Earth, the side facing us is dark. We call it a New Moon. As the Moon moves on, we see more and more of its face lit up, until we see it all at Full Moon. Afterwards, we see less and less until it disappears at the next New Moon.

Copyright © 2007 Dorling Kindersley

highlights

Top 10 Sweet 16 Birthday Gifts
Your daughter's sweet 16 is a big milestone in her life. Celebrate this special occasion with one of these top gifts for girls turning 16.

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, brought to you by Galactic Hot Dogs.

Printable Lists of the Top 100 Baby Names
Need help with baby name ideas? Use our printable list of the top 100 girl names and top 100 boy names of 2015 to help you brainstorm and narrow down your favorites.

Registered for Kindergarten — Now What?
Wondering what to do now that you've signed your child up for kindergarten? Try our award-winning Kindergarten Readiness app! This easy-to-use checklist comes with games and activities to help your child build essential skills for kindergarten. Download the Kindergarten Readiness app today!

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Facebook icon Follow Us on Pinterest

editor’s picks