Science · The Sun, the Earth and the Moon

The Earth's rotation and day and night

Does the Sun really rise in the east and set in the west, or is it us who are turning? Discover how the Earth's rotation on its axis makes day and night, and why one turn takes about 24 hours.

15 min
1 simulation
Mini quiz

Updated: 15 October 2026

Preview

The question

Every morning the Sun rises in the east, and every evening it sets in the west. That is why, for thousands of years, people thought the Sun went around the Earth. But which one is really moving: the Sun, or you and the Earth under your feet? Would you believe that, as you read these lines, you are turning at hundreds of kilometres an hour?

Try it yourself

No account needed: change the values and check your answer. Some simulations ask for a prediction before they start; it doesn't matter whether it's right or wrong.

Number line

How many hours in one night and one day?

Drag the marker or move it with the arrow keys. When you are sure of the value, submit your answer.

Predict first

Which movement do you think produces one night and one day together?

It doesn’t matter whether you’re right; the simulation opens once you choose.

Lab

Foucault pendulum

Open full page in the Lab →

Fig. 1Foucault pendulum

The floor stays still; the plane of swing turns.

Pick a latitude, press play and watch the pins fall. Switch the view to see the same event through an eye that turns with the pendulum.

From space: the Earth and your latitudeLatitude 41.01°. The floor turns about the local vertical by sin φ of the Earth's spin.

Period T: 16.4 s
Turning per hour: 9.87°/h
Full turn: 36.5 h
Direction (from above): clockwise
Pins down: 0 of 36
Time passed: 0 min
Angle the plane has turned: 0.0°

Places

Latitude (south negative)

Pendulum length

Time speed

Learn

Progress is kept on this page only; no points are given.

1Predict
2Try
3Explain

If you shorten the wire from 67 m to 2 m, what happens to how fast the plane of swing turns each hour?

Purple: the plane of swing and the latest mark in the sandGold: the angle the plane has swept since the startThe numbers come from the model in this article: the Earth turns once in a sidereal day (23 h 56 min 4 s), the plane turns against the floor by 15.04° × sin φ an hour, and the period is T = 2π√(L/g) (g = 9.81 m/s²). The pins stand every 10°, the first one 5° from the starting plane; because the ball swings to both ends of the plane, they are all down once the plane has turned 180°. Changing the latitude starts the experiment again. The drawing is not to scale; when time is sped up, the swing is shown slowed down so the eye can follow it, and the true period is in the readout. The view from space shows only the floor turning about the local vertical (Ω · sin φ).

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Frequently asked

5 questions

Why do we have day and night?

Earth spins on its own axis. At any moment it is day on the half of Earth facing the Sun and night on the other half. As Earth keeps spinning, the place where you are moves from light into dark and back again.

Does Earth take exactly 24 hours to spin once?

A day measured by the Sun is 24 hours on average. Measured against distant stars, one full spin takes about 23 hours 56 minutes. The difference comes from Earth moving a little along its orbit in the same time.

Which way does Earth spin?

It spins from west to east. That is why the Sun seems to rise in the east and set in the west. Seen from above the North Pole, the spin is anticlockwise.

If Earth spins so fast, why can't we feel it?

A point on the equator moves at about 1,670 km per hour, but Earth spins very smoothly. What you feel is not speed itself but sudden changes in speed; on a smooth flight you do not feel the plane's speed either.

What is the difference between rotation and revolution?

Rotation is Earth spinning on its axis, which takes about a day and gives us day and night. Revolution is Earth travelling around the Sun, which takes about 365 days and sets the length of a year.