It seems to us that Earth stands quite stable(稳定的). But it is really m all the time. It turns around a make-believe line through its centre. We c this make-believe line Earth’s axis(轴). The t ends of Earth’s axis are its poles. It t Earth 24 hours to travel around its axis once. We look at the sun and say it ‘rises’ and travels across the sky, but the sun doesn’t really do s . It is the turning of E that makes us feel that the sun were moving across the sky. We can’t see the Earth is moving b everything on Earth is turning around it. As Earth moves around every 24 hours, the first half of Earth faces the sun and then the other h 8 . When our half of Earth is f 9 the sun, we say it is day. When our half is a from the sun, we say it is night. It is the turning of Earth that tells us when to get up and when to go to bed.