Earth and Space: Day and night
Objectives
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Use the idea of Earth’s rotations to explain day and night
Use the idea of Earth’s rotations to explain the apparent movement of the Sun
Plenary
Using the plenary sheet, pupils should label the Sun (largest), Earth (middle sized) and Moon
(smallest).
Lighting up the Earth
Ask the pupils to suggest why it can be day in the UK but night in New Zealand. Darken the
classroom and shine a torch from a distance onto a globe.
Explain that the Earth rotates on its axis. Stick a marker on the globe over the UK and with a
pupil holding the torch still, slowly rotate the globe. Different parts of the globe are
illuminated at different times. As the UK enters into the light, this is day. When the UK is
directly under the sun’s light, this is noon. When the UK moves out of the light, this is night.
Pupils must note:
The rotation of the Earth causes us to experience day and night.
With the globe aligned such that it is noon in the UK (marker directly under light), pupils
should identify a country experiencing early morning, a country experiencing late evening
and a country experiencing night. Suggestions may be checked against a world clock.
Movement of the sun
With a demonstration using the globe and torch, clarify that the Sun stays still while the Earth
orbits it, rotating on its axis. If the Sun stays still, why does it look like it moves across the
sky during the day?
EXPERIMENT: Pupils should prepare sheets of paper with thin slits cut out (see fig. 1). This
represents what we can see from Earth’s surface. Holding their sheets up to their eyes, they
should align themselves so the torchlight is just visible at the ‘East’ end. With the torch
remaining still, pupils should slowly rotate towards the East. Although the torch is still, it
appears to move from East to West.
This is similar to what we see on the surface of the rotating Earth while the Sun remains still.
Pupils must note:
The Sun appears to move across the sky due to the rotation of the Earth.
Fig. 1: Sheet with a slit for ‘sun movement’ activity
Possible extra-curricular questions
Does the moon also rotate?
The moon also rotates, but it rotates such that the same side always faces Earth. This is
called synchronous rotation.
Why do we only see the moon at night?
This is not necessarily true. Sometimes we can see the moon during the day; it depends on
what point in the lunar cycle you are observing the moon.
Why do we get seasons?
The Earth is not upright when it rotates; it is tilted at a slight angle. This means that at
different times in the year, different parts of the Earth are tilted towards or away from the
Sun. An area experiences summer when it is tilted towards the Sun and winter when it is tilted
away from the Sun.
Do other planets experience day and night?
Yes. The length of a day is different on other planets. When a planet rotates more quickly, it
experiences shorter days.
Why can’t we feel the Earth rotating?
We can’t feel the Earth rotating because we are rotating at the same pace as our surroundings. To see
that the Earth is rotating, you have to look at other objects in space, such as the Sun.