Anyone else been asked “why do we have seasons” by their children (or asked themselves for that matter)? Well, here’s the answer…
If you imagine a stick going from the North Pole through the Earth and out at the South Pole, then it takes 24 hours for our planet to spin around this central stick or axis – in other words, a day. The Earth takes 365.24 of our days to move around the Sun and end up back where it started. This is our calendar year.
We divide the year into seasons, and it is the Earth’s movement around the Sun during the course of the year which causes them. Let’s go into this in a little more detail…
The central axis (our imaginary stick) around which Earth spins is actually tilted at 23.5 degrees. This means that the Earth is always pointing to one side as it orbits the Sun (in other words, it’s a bit wonky!). For example, when the North Pole is tilting or leaning towards the Sun, that hemisphere receives more sunlight (summer). At that interval, the southern hemisphere is pointing away from the Sun meaning it is their winter. Conversely, 6 months later when the North Pole and its hemisphere are tilting away from the Sun it receives less direct sunlight and it is winter. Spring and autumn occur in between.
To demonstrate this very simply, if you tilt a pen towards a football – and imagine that the nib is the North Pole and the ball the Sun – when the nib is facing the ball it is summer there. If you then walk 180 degrees (half way) around the ball without changing the position of the pen, the nib is now facing away and it is winter.
So the basic answer to why do we have seasons is because the Earth is tilted!
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