Earth seasons

Why do we have day and night?

The Earth spins on its axis as it orbits the Sun. It takes 24 hours for the Earth to complete one spin on its axis. This period of time is called a day. The side of the Earth that faces the Sun is illuminated by the Sun. People who live on this side of the Earth have day. The other side of the Earth at this point is away from the Sun and people who live on this side have night.

Try this yourself!

1. Get a torch and a ball to find out why we get night and day.
2. Point the torch towards the ball and rotate it from left to right (west to east).                                                         

What do you see?

Answer - click here.

Why do we have seasons?

The Earth orbits the Sun once in about 365 days. This length of time is called a year.

The Earth’s axis is tilted, so as the Earth moves around the Sun, different parts of the planet get closer or further from the Sun.

The seasons: spring, summer, autumn and winter, are caused by the distance from the Sun due to the Earth’s tilt.

When the axis is tilted towards the Sun, that hemisphere experiences summer. When the axis is tilted away from the Sun, that hemisphere experiences winter.

At position A (left image), it is summer in the Northern Hemisphere and winter in the Southern Hemisphere.  At position B (right image), it is winter in the Northern Hemisphere and summer in the Southern Hemisphere.

• In UK the 21st of March represents our spring - from here on until 21st of June the day become longer and the nights shorter.
• Autumn begins on 22nd of September.  From here on until 21st of December the nights become longer and the days become shorter.
• On the 21st of March and 22nd of September the sun is directly over the equator - this is called equinox. 

Does the Sun and the stars move or is it just an illusion?

Well, if you look at the night sky, the stars seem to move in a circular path around the Pole Star, in the north of the sky.  Yet the Pole Star appears not to be in a fixed position.  This is because it is directly above the Earth's axis of rotation.  This apparent movement of the Sun and the stars is due to the rotation of the Earth on its axis.

Due to the Earth's anti-clockwise rotation, the Sun appears to:

• ’Rise’ in the EAST.
• ‘Set’ in the WEST, each day.
• The Sun is highest in the sky during midday. (1 pm in U.K. Summertime and 12 noon in winter.)
• The shadows caused by the Sun are always shortest at midday.
• During Summer the Sun rises very high in the sky.
• That is why the shadows are so short during summer.  (See animation below)