Earth's rotation: day & night

In the morning the Sun rises, in the evening it disappears again. It looks as if the Sun were travelling across the sky. In reality the Sun stays where it is, and the Earth turns beneath it. This turning around its own axis is called the Earth's rotation, and it is the reason there is day and night at all.

A spinning top in space

The Earth turns like a giant spinning top around an imagined line, the axis. For one full turn it needs about 24 hours, that is one day. The side that is facing the Sun has day. The side turned away from the Sun lies in the dark and has night. Because the turning never stops, day and night take turns without a pause.

From east to west

The Earth turns from west to east. That is why we see the Sun appear first in the east and set in the west in the evening. Someone living far in the east sees the sunrise earlier than someone in the west. Places at the equator race through space the fastest, because on one turn they cover the longest way: about 40,000 kilometres in a day, which is roughly 1,670 kilometres per hour. You feel none of it, because the air, the sea and you yourself all turn along at the same steady pace.

Why there are time zones

Because only one part of the Earth ever faces the Sun, it is not noon everywhere at the same time. When the Sun stands high in our sky, it is deep night on the other side of the Earth. So that clock time matches the Sun's position, the Earth has been divided into 24 time zones, one for each hour of the day. From one zone to the next the time usually jumps by exactly one hour. If you travel far east you set your clock forward, if you travel west you set it back. Otherwise your clock would say noon while the Sun is already setting.