Why does the length of daylight change during the year?

The pictures below show the changing length of daylight through the year. Play the animation to get a clear picture.

It's Winter
Longer night than day.

It's Spring
Equal day and night.

It's Summer
Longer day than night.

It's Autumn
Equal day and night.

Watch the animation for yourself.

With grateful thanks to whoever produced this excellent resource.
We hope you don't mind that we pulled the screen grabs as a teaching aid.

This site from the University of Manchester shows the same idea in a different way.
Click on the FULL SCREEN BUTTON

 

 

The earth is on a tilt 23.5 degrees to one side. This is what causes the difference in daylight hours and the seasons.

 

 

The Seasons

As you can see from this set of pictures, the world is on a tilt. It's the tilt that causes the change in seasons and the changing length of day and night.

Spring Equinox - Equal day and night.

Notice the tilt of the earth. It isn't tilting in or away from the sun so has no effect on the length of day, at this point in the earth's yearly orbit of the sun.

Summer Solstice

At this point in the orbit the earth's tilt means the sun is higher in the sky in the northern hemisphere. This is our summer when it's a lot warmer and the length of daylight is longer. Notice the North pole gets 24 hrs of daylight.

Autumn Solstice - Equal day and night.

Notice the tilt of the earth. It isn't tilting in or away from the sun so has no effect on the length of day at this point, in the earth's yearly orbit of the sun, which is why we get equal day and night.

 

Winter Solstice.

At this point in the orbit the earth's tilt means the sun is lower in the sky in the northern hemisphere. This is our winter when it's a lot colder and the length of daylight is shorter. Notice the North pole gets 24 hrs of darkness.

Watch the animation for yourself.

With grateful thanks to Pearson Inc for this excellent resource. We hope they don't mind that we pulled the screen grabs to help in our teaching.