Why Earth Has Seasons
Written by Fraser Cain
Did you ever wonder, why does the Earth have seasons? What's happening to our planet so there are times when it's hotter and times when it's colder.
As you probably know, the Earth rotates in space – spinning like a top – is it orbits around the Sun. Imagine there's a line passing through the Earth, from the North pole to the South pole, and then out into space in both directions. This is called the axis of rotation.
And in the case of the Earth, axis of rotation is tilted. Instead of going directly up and down, compared to the axis of rotation for the Sun, the axis of rotation for the Earth is tilted at an angle of about 23.5°. This tilt makes all the difference to the climate here on Earth, and gives us seasons.
Now imagine Earth orbiting the Sun – a journey that takes one full year. During Summer in the northern hemisphere, Earth is tilted so that the North pole is pointed towards the Sun. And the South pole is pointing away from the Sun. This is when Earth is experiencing Summer for the northern hemisphere, and Winter in the southern hemisphere.
Then reverse the situation, so that Earth's North pole is tilted away from the Sun, and the South pole is tilted towards the Sun. Now it's Winter in the North, and Summer in the South.
Think about planets trying to get as much sunlight as possible from the Sun. They point the flat of their leaves so that they face the Sun directly. When sunlight falls on them at an angle, they don't get as much energy.
This is what's happening with the Earth. During the Summer for the northern hemisphere, light from the Sun is falling more directly onto the Earth and heating it up. In the southern hemisphere, light is falling at a very low angle and doesn't hit each part of the ground with as much energy.
And this is why Earth has seasons; because of the tilt of our axis of rotation.
Filed under: Astronomy
