Earth’s Orbit and Seasons

Earth’s Axis

The Earth has an imaginary pole that goes through its centre, through the North and South poles. This imaginary pole is called Earth’s axis. As you can see by the image below, the axis is slightly tilted, at around 23.4 degrees.

The Earth’s spin is the rotation of Earth around its own axis, rotating counter-clockwise.

Day and night

When a planet spins once on its axis, this is how we define a ‘day’. So, it takes Earth 24 hours for Earth to make a complete turn on its axis. The sun does not light up the whole Earth at once, it does one half at a time. This is why we have light and darkness, day and night. It will be daytime on the side of the Earth facing the Sun and night time for the side of the Earth facing away from the Sun.

During the year, we can have different lengths of daytime. In the summer, daytime is the longest, but in the winter, daytime is the shortest. In summer, the sun rises higher in the sky than it does in winter.

Earth Orbiting the Sun

A year for a planet is the time it takes for it to go around the Sun completely. So, it takes the Earth 365 days to orbit the Sun and the orbit is in an elliptical shape. Actually, it takes Earth around 365.25 days for Earth to orbit the Sun, which is why every 4 years there is a leap year. In a leap year there is an extra day.

Different planets in our solar system take different amounts of time to orbit the Sun. For example

  • Mercury takes 88 days to orbit the Sun
  • Earth takes 365 days to orbit the Sun
  • Mars takes 687 days to orbit the Sun

Earth’s Seasons

We experience seasons because the Earth is tilted on its axis, and the Earth’s orbit is elliptical.

Different angles that the Sun’s rays hit the Earth result in different amounts of heat.

The four seasons are:

  • Winter
  • Spring
  • Summer
  • Autumn

December – Around this time and along with June, Earth is at the position of the orbit furthest from the Sun. At this point Due to the Earth’s tilt, the north is tilted away from the sun and the south is tilted towards the sun. This means it is winter in the north and summer in the south.

March – The Earth moves further around its orbit. At this point, it is spring in the north and autumn in the south.

June – Around this time and along with December, Earth is at the position of orbit furthest from the Sun. This time, the north is tilted towards the Sun and the south is tilted away from the Sun. Which means it is summer in the north and winter in the south.

September – As the Earth moves further round, it is autumn in the north and spring in the south.

The equator is an imaginary line around the middle of the planet, midway between the North Pole and the South Pole. Wherever the Earth is in orbit, the Sun hits the equator at around the same angle each time. Which means the equator doesn’t experience seasons.

In the UK

  • When the Northern hemisphere is tilted towards the Sun, it is summer.
  • When the northern hemisphere is tilted away from the Sun, it is winter.