Earth's Spin Makes Day Turn Into Night
Nova the astronomy guide stands on a rooftop at dusk, actively spinning a glowing globe with one hand while the other points at the orange horizon where the Sun is sinking, as the first stars begin to appear overhead.
- Explain why the Sun appears to rise in the morning and set in the evening.
- Identify that Earth rotates once every 24 hours, causing day and night.
- Compare what the side of Earth facing the Sun experiences versus the side facing away.
- Predict which part of Earth will next move into sunlight as the planet keeps spinning.
- Describe rotation as a spin on an axis, using the globe model as evidence.
Key terms
- Rotation
- When Earth spins around like a top.
- Axis
- The imaginary line Earth spins around.
- Daytime
- The bright side facing the Sun.
- Nighttime
- The dark side away from the Sun.
Earth Spins Like A Top
Earth is always spinning, just like a top going around and around. We call this spinning rotation. Earth turns around an imaginary line through its middle called its axis. It takes 24 hours, which is one whole day, to spin all the way around one time. You are spinning too, but it feels still because everything turns together.
Where The Light Falls
Think of a flashlight shining on a ball. Only the part the light touches is bright. The side of Earth facing the Sun gets sunlight and has day. The side turned away is dark and has night. As Earth keeps spinning, your town turns into the light for sunrise and away from the light for sunset.
Worked examples
Your town spins to face away from the Sun. What happens?
- The Sun cannot shine on your side anymore.
- Your side of Earth is now in shadow.
Answer: It becomes nighttime in your town.
Activity
Spin the globe slowly and watch which side faces the Sun lamp — drag the globe to rotate Earth and see day and night change across the surface.
Practice
Explain why we have day and night each day.
Tell how long Earth takes to spin around once.
Common mistakes to avoid
- Clouds make the night darkNight comes when your part of Earth spins away from the Sun.
Check your understanding
What causes day and night on Earth?
Your friend in Australia is having lunchtime right now. What time of day is it most likely to be for someone living in the United States at that same moment?
How long does it take Earth to complete one full rotation?
Recap
Earth spins on its axis one full time every 24 hours. The side facing the Sun has day, and the side turned away has night.
Reflect
Why are people across the world awake while you sleep?