1 . Have you ever wanted to travel in space? In a way you already do, because you live on Earth, and Earth is a planet floating in space.    1     They are a whole family of planets that scientists call our solar system.

The word “solar” means “having to do with the Sun”.The planets in our solar system all circle the Sun in paths called orbits.    2     It doesn't take them as long to travel around the Sun.Planets farther from the Sun have longer orbits.It takes Earth about 365 days—one year—to travel around the Sun.

    3     They all spin, or rotate.It takes Earth 24 hours, or one day, to spin around one time.As Earth spins, the parts that face the Sun are lit up—it is daytime there.The parts that face away from the Sun are dark－it is nighttime.

If you could visit the other planets, you would find some strange and surprising worlds.Some are dry and rocky, while others are balls of swirling gases with solid centers.Some planets are much hotter than Earth－so hot that nothing can live there.    4     Other planets are far away from the Sun.They are very, very cold—colder than any place on Earth.

    5     It is not too hot and not too cold.Earth has water to drink and air to breathe.Earth is the only planet in our solar system where plants and animals and people can live.