How do we know?
↻ One of the pages with a moving picture
A swinging ball showed that it is Earth that turns.
- Earth is always spinning, like a top.
- One full spin takes about 24 hours: one day and one night.
- The Sun lights up only the half of Earth that faces it.
- When your side turns away from the Sun, your sky gets dark. It’s night!
In 1851 Léon Foucault hung a heavy ball on a long wire, a swinging pendulum. Slowly, its swing seemed to turn. Really, Earth was turning underneath it.
He first showed his famous pendulum at the Paris Observatory in France, and people could watch Earth spin without leaving the room.
The same spin makes the Sun seem to cross the sky. The Sun is not moving around us: we are turning past it.
Wow number
1,000 mph is how fast Earth’s middle, the equator, spins. Just over 1,000 miles per hour!
Myth or fact?
The Sun moves across the sky because it goes around Earth. Myth. Earth’s spin only makes the Sun look like it moves.
At the South Pole there is just one sunrise a year. Fact. And just one sunset!
Think about it
When you go to bed, who on the other side of the world might be waking up?
Where in the world?
Utqiaġvik, Alaska where in summer the Sun stays up for 84 days without setting. Léon Foucault first showed his pendulum at the Paris Observatory in France — 71.2906° N, 156.7886° W.
Where these facts come from
Every number on page 10, and who measured it
This page tells us Earth spins once about every 24 hours, and how fast.
What Is Earth? (Grades 5-8) — NASA, the U.S. space agency
nasa.gov/learning-resources/for-kids-and-students/what-is-earth-grades-5-8
We checked it on 31 October 2026
This page tells us Utqiaġvik, Alaska, goes 84 days in summer without a sunset.
Months in the Midnight Sun — NASA, the U.S. space agency
science.nasa.gov/earth/earth-observatory/months-in-the-midnight-sun-154342
We checked it on 31 October 2026
This page tells the story of Foucault's swinging pendulum in Paris.
Earth Rotates — The American Physical Society, a big group of physics scientists
aps.org/apsnews/2007/02/foucault-earth-rotates
We checked it on 31 October 2026
This page tells us the South Pole has just one sunset a year.
Sunset at the South Pole signals 6 months of darkness — NOAA, the U.S. weather and ocean agency
noaa.gov/stories/sunset-at-south-pole-signals-6-months-of-darkness
We checked it on 31 October 2026
Has this changed?
Earth has spun for a very long time, so this answer is not going to change.
A day is not exactly the same length forever: very slowly, Earth’s spin is changing. But for you the sky will go dark tonight, just like yesterday.
Words from this page
- pendulum
- A weight that hangs from a wire and swings back and forth.
- equator
- The imaginary line around the middle of Earth, halfway between the poles.
Try it!
Build a clock out of a stick and its shadow.
1. On a sunny morning, push a stick into the ground in an open spot. 2. Every hour, put a pebble at the tip of its shadow. 3. Never look straight at the Sun!
What happens: the shadow swings around as the day goes by. The Sun seems to move because we are spinning.
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