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The sun shines on the planet venus in space.
We all take it for granted, but do you really know the process behind night and day changes?

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The length of a day changes because the earth spins at a tilt. If the earth did not tilt, then the days would all be the same length and the sun would always be above the equator.

The earth rotates around a line approximately 23.5 degrees to the poles, so the position on the earth where the sun is directly overhead moves. The southern most line where the sun is directly overhead is called the Tropic of Capricorn and the northernmost line is the Tropic of Cancer.

The length of a day depends on where you are on the earth...
The length of a day depends on where you are on the earth; the extremes are found at the Poles. Due to the tilt of the earth, sometimes the North Pole points towards the sun, whilst the South Pole points away. This gives the North Pole 24 hours of daylight for about 6 months, whilst the South Pole is plunged into darkness.

After this, the North Pole tilts away from the sun. On the equator, the sun is always nearly overhead, so the days are more constant with approximately 12 hours of daylight and 12 hours of darkness everyday.

In the UK, the day length depends on where you are. As the UK is north of the equator, in the south there is less change, but most places still have a longest day of over sixteen hours, and a shortest of under eight.

The longest day is called the Summer solstice, and occurs on 21 June. On this day the sun is overhead at its nearest point to the UK, above the Tropic of Cancer. The shortest is on 21 December, when the sun is furthest away, over the Tropic of Capricorn.

The tilt of the earth not only gives us the changing day lengths, but the seasons as well.
The tilt of the earth not only gives us the changing day lengths, but the seasons as well. When the earth is tilted with the Northern Hemisphere pointing towards the sun, the sun's ray hit the UK more directly. A more intense sun gives days that are warmer, as well as longer. This is Summer.

When the earth is tilted away from the sun, the sunlight has to pass through more of the earth's atmosphere before it reaches the ground, so the sun is weaker. This gives the cold, short days of winter that are all too familiar in the UK, but at least we're not in the Arctic Circle preparing for 6 months of darkness.

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Key Points

• The length of a day changes because the earth spins at a tilt.
• The length of a day depends on where you are on the earth.
• The tilt of the earth also gives us our seasons.

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