Why do we have day and night?
As the Earth spins on its axis, the Sun always shines on one side giving us daylight. It is night on the shaded side. As the Earth continues to turn, the shaded side moves into the Sun’s light and the sunlit side turns away from the light. It takes 24 hours for the Earth to make one complete turn on its axis, and our clocks are based on this principle.
In the 1940s, people discovered that the Earth speeds up and slows down a little as it spins, although the reason for these changes is not fully understood. We have now developed atomic clocks that can measure time exactly.
Why do we have seasons?
We have seasons because the Earth is tilted on its axis. As the Earth moves around the Sun, the hemisphere tilted towards the Sun receives more sunlight and this is summer time. The days are longer and the weather is warm because of the extra sunlight. The hemisphere tilted away from the Sun receives less sunshine, has shorter days and is cooler – it is winter time. The area near the Equator is always exposed to the Sun’s rays, so it is warm all the year round. This means that there is little difference between the seasons.
