KS3 · Physics

The spinning Earth

Every sunrise you've ever watched was really you, turning round to face the Sun.

Follow one place through one spin

1Sunrise: turning into the light2Midday:facing theSun3Sunset: turning out of the light4Midnight:facing away

Stage 1 of 4: Sunrise: turning into the light. paused

Sunrise: turning into the light · 1/4scrub one spin →

The spin carries your town out of the half of the Earth facing away from the Sun and into the half facing it. For you, the Sun comes into view: sunrise.

The Earth spins on its axis, an imaginary line through the North and South Poles, once every 24 hours. The Sun stays where it is. One trip round this loop is one full spin, and the moving dot is your town. (The axis is tilted, too. Hold on to that: the tilt matters later, when you learn about the seasons.)

Watch out: At every moment, half the Earth is having day and half is having night. When it's night where you are, the Sun is still shining. It's just lighting the other half of the Earth.

What causes night?

Four explanations, one right answer

It's the middle of the night and dark outside. Four friends each explain why.

Which is closest to what you think right now?
How sure are you?

The Sun's path across the sky

?

Reason it through

If the Sun isn't moving, why does it seem to rise in the east and set in the west?

Link 1 of 4

First link · your turn

Start with the spin. Which way does the Earth turn?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Two motions at once

SpinvsOrbit

The Earth spins and orbits at the same time. Don't mix them up.

Focus

What the Earth moves around

Spin

Its own axis, an imaginary line through the Earth

Orbit

The Sun, on a path that is almost a perfect circle

The insight

Spinning is turning on the spot; orbiting is travelling right round something else.

How long one takes

Spin

24 hours

Orbit

365.25 days (365 and a quarter)

What one gives us

Spin

One day

Orbit

One year

Does it cause day and night?

Spin

Yes. It turns each place into and out of the Sun's light.

Orbit

No. It takes a whole year, far too slow for a night every 24 hours.

Predict, then check

We've drawn the Earth as a ball all lesson. How do we actually know?

A boat sails straight out to sea, further and further away. Just before it disappears completely, which part of it has already gone from view?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Why we get day and night, and why the Sun only seems to move.

What you need to know

  • The Earth is roughly spherical, and there is evidence for it, such as a boat's bottom disappearing over the horizon before its top.
  • The Earth spins once every 24 hours on its axis, the imaginary line it spins around. The axis is tilted.
  • The half of the Earth facing the Sun has day; the half facing away has night. The spin carries each place through both once every 24 hours.
  • The Sun appears to rise in the east and set in the west because the Earth spins anticlockwise (seen from above the North Pole).
  • One spin takes one day (24 hours); one orbit of the Sun takes one year (365.25 days).

The big picture

The Earth is a roughly spherical planet that spins on its axis, an imaginary line it turns around, once every 24 hours. The half facing the Sun has day and the half facing away has night, so each place turns into the Sun's light, out of it and back again once every 24 hours. From the ground, that spin makes the Sun appear to rise in the east and set in the west, though it is really the Earth moving. The Earth also orbits the Sun, and one orbit takes 365.25 days: a year.

Key points

1The Earth is roughly a sphere.
2An axis is the imaginary line a spinning object spins around, and the Earth's axis is tilted.
3One spin of the Earth takes 24 hours, and that is why one day-night cycle takes 24 hours.
4Day is the half facing the Sun; night is the half facing away.
5Day and night are not caused by the Moon, by the Sun moving, or by the Earth's orbit.
6The Sun only appears to move from east to west: seen from space, it is the Earth turning.
7An orbit is the Earth's path round the Sun, and one orbit takes 365.25 days: a year.

Worked example

Problem

A town is halfway through its daytime. How long will it be until the town is halfway through its night? And how long until it is halfway through its daytime again?

⚠ Watch out

Saying the Sun 'goes down behind the Earth' at night. The Sun doesn't go anywhere. Your half of the Earth has spun round to face away from it.

🧠

Memory hook

Spin for a day, orbit for a year, and the Sun stays put while we do the turning.

✓

Check yourself

When it is night where you live, is the Sun shining on the Earth anywhere? Explain where, using the words 'spin' and 'half'.

Flashcards

(15)
What shape is the Earth?
Roughly spherical: shaped like a ball (a sphere).
A boat sails out to sea. Which part vanishes first, and what does that show?
The bottom goes before the top, because the Earth's surface curves between you and the boat. It's evidence the Earth is a sphere.
Apart from the boat, what other evidence shows the Earth is a sphere?
Travel continuously in one direction and you come back to where you started; the curve can be seen from high aircraft and spacecraft; Earth's shadow on the Moon looks curved; photos from spacecraft show a round Earth.
What is an axis?
The imaginary line that a spinning object spins around.
How long does the Earth take to spin once on its axis?
24 hours: one day.
What is special about the Earth's axis, and why will it matter later?
It is tilted. The tilt is important when you learn about the seasons.
Which half of the Earth has day, and which has night?
The half facing the Sun has day, because it gets the Sun's light. The half facing away has night.
Why does one day-night cycle take 24 hours?
In one 24-hour spin, a place turns into the Sun's light, out of it and back again.
Name three things that do NOT cause day and night.
The Moon covering the Sun, the Sun moving behind the Earth, and the Earth's orbit of the Sun.
Which way does the Earth spin?
Anticlockwise, seen from above the North Pole.
Where does the Sun appear to rise and set?
It rises in the east, moves across the sky in a curve, and sets in the west.
Does the Sun really move across the sky during the day?
No. It only appears to. From space you'd see the Earth rotating in front of the Sun: the same motion from a different viewpoint.
In the lamp model of day and night, what do the lamp, the person and the turning stand for?
The lamp is the Sun, the person is the Earth, and turning slowly anticlockwise on the spot is the Earth's spin.
What is an orbit?
The path the Earth takes around the Sun: almost a perfect circle, with the Sun at the centre.
How long does one orbit of the Sun take, and what do we call it?
365.25 days (365 and a quarter days). We call it one year.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

Learning with Lightbulb is opening soon

You can use this lesson now. Join the waitlist and we'll let you know when the full Lightbulb experience is ready.

Keep me posted

More KS3 Physics topics

See the full KS3 Physics curriculum →

How this lesson was checked. This KS3 Physicslesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.