Day, night and the four seasons
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Explainer Video
Summary
Day, night and the four seasons
In a nutshell
When parts of the Earth face the Sun it is daytime. When they are in shadow, it is nighttime. One full day is . The Earth rotates on its axis as it orbits around the Sun which causes the seasons. When the North Pole is tilted towards the Sun, the northern hemisphere in summer and when it is tilted away, it is in winter.
Definitions
Key word | Definition |
| Orbit | The curved path which objects move around larger celestial objects in space |
| Northern hemisphere | North half of the Earth |
| Southern hemisphere | South half of the Earth |
| North/South Pole | Northern or southern points of the line which the Earth rotates upon |
| Axis | An imaginary line where the Earth appears to rotate around |
Day and night
Day is when the Sun appears in the sky and night is when it is not. It takes the Earth to complete one full rotation, which is how one full day (day and night) is defined.
One half of the Earth is always facing the Sun and one half is always in shadow. As the Earth rotates, different parts of the Earth face the Sun, which is daytime. Other parts will not face the Sun, which is nighttime.
The year and seasons
The Earth orbits around the Sun and one full orbit takes , which is one year. Over the course of a year, the seasons (winter, spring, summer and autumn) occur. They happen depending on if the Earth is tilting towards or away from the Sun.
This tilt means the North and South Pole are actually at an angle if you were to draw a vertical line through the Earth. In other words, the Earth spins on its axis.
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When the northern hemisphere is in winter, the North Pole is tilting away from the Sun. This means the southern hemisphere is in summer, as the South Pole is tilting towards the Sun.
Six months later, when the Earth has completed half of its orbit, the North Pole will now tilt towards the Sun. This means the northern hemisphere is in summer and southern hemisphere will be in winter. In between are spring and autumn.
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The Sun in the sky
The Sun appears to move in the sky, but it is actually the Earth rotating that causes this impression. The Sun rises in the east, and sets in the west. This is due to the direction in which the Earth is rotating.
During the summer, the Sun also appears higher in the sky This is because the Earth is rotating on its axis. During the summer in the UK, the North Pole will be tilted towards the Sun and in the winter it will be tilted away.
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The stars in the sky
At nighttime, the stars also appear to move, due to the Earth's rotation. During different seasons, the stars in the sky will change. This is because the Earth is now at a different point in its journey around the Sun. You are actually seeing a whole new set of stars!
FAQs - Frequently Asked Questions
How long is a day?
A day is 24 hours.
Why do we have seasons?
Seasons occur due to the Earth's tilt.
Why is there day and night?
Day occurs when part of the Earth faces the Sun. As the Earth rotates, that part will face away from the Sun causing nighttime.
Why do the Sun and the stars appear to move in the sky?
The Sun and stars appear to move in the sky because the Earth is rotating. The Sun and stars don't move much in comparison to the Earth.