Day and Night

You get up in the morning, and it is bright outside. It is daytime You get up in the morning, and it is bright outside. It is daytime. Hours later, probably about the time you are having dinner, it is dark. It is nighttime. The pattern of day and night repeats day after day. Earth’s spinning causes the pattern of day and night.

Why are there day and night? An imaginary line, called Earth’s axis, runs through Earth from the North Pole to the South Pole.

Earth rotates, or spins, on its axis Earth rotates, or spins, on its axis. This motion is like that of a spinning top. It is the main reason why we have day and night. Earth rotates once every 24 hours. That 24-hour time period is one day.

At any time, half of Earth faces the sun. The part of Earth that faces the sun is lit and has daytime. The other half faces away from the sun. The part that faces away from the sun is dark and has nighttime.

Day and Night Cycle Video

At the start of each day, the part of the Earth you are on spins to face the sun. This time is sunrise. The sun appears to come up over the eastern horizon. The horizon is the line where the sky and Earth’s surface seem to meet. During the day, the sun seems to move across the sky from east to west.

As Earth continues to spin, the sun seems to move higher and higher in the sky. It rises all morning, until midday. Around noon, the sun is at its highest point in the sky for the day. In the afternoon, the sun seems to move lower and lower in the sky. It finally reaches and seems to fall below the horizon in the west. This time of day is sunset, the end of daylight. Your part of Earth then spins away from the sun. The sun seems to set in the west and night begins.

It looks as if the sun rises in the east, moves across the sky, and set in the west. However, the sun does not really rise in the east. It does not really move across the sky. The sun only seems to move that way because Earth rotates. If you stand in the middle of a room and slowly spin around, you will see the walls of the room move past you. You know that you are moving and the room is not. But it looks as if the room is moving around you.

After the sun sets, the sky is dark and you can see stars in the sky. During the night, most stars seem to move across the sky from east to west. The stars do not really move the way they seem to move. Like the sun, they seem to move that way because Earth is spinning on its axis. As Earth continues to spin, the sun will rise again the next morning. The cycle of day and night will repeat. A cycle is a set of events that happen over and over. Interactive Day and Night

Click here for more interactive videos Discussion Question: What would happen to day and night if Earth rotated faster? What would happen if Earth rotated more slowly?

Lesson Review Around what does Earth rotate? A. the sun B. its axis   A. the sun B. its axis C. the moon D. the horizon

2. How long does Earth take to rotate once?   A. 12 hours B. 20 hours C. 24 hours D. 36 hours

3. As Earth spins, the part facing the sun has   A. spring B. day C. night D. summer