4 EARTH IS CLOSER TO THE SUN IN SUMMER

Most people know Earth doesn’t travel around the

Sun in a perfect circle, so it’s easy to see why some make the leap and assume that the seasons are caused by the distance to the Sun, but the idea doesn’t hold up when you think that the Northern and Southern Hemispheres experience summer at different times of the year. Earth’s orbit isn’t as elliptical as people imagine. Over the course of a year, the distance between Earth and the Sun varies by just 5 million kilometres (3.1 million miles) – that’s only about three per cent. What’s more, during winter in the Northern Hemisphere, we’re actually closer to the Sun than we are in summer.

The real reason for the seasons is the axial tilt of Earth. As the year progresses, light hits the Northern and Southern Hemispheres at proportionally different angles and for different amounts of time every day. During winter, the days are short and the light strikes the atmosphere at a low angle, glancing through the gases as it travels towards the surface and spreading out as it reaches the ground, distributing the energy. During summer the days are much longer and the sunlight hits Earth at a steep angle, taking a more direct path towards the floor and concentrating the energy into a smaller area.

1 December

In December the Northern Hemisphere tilts away from the Sun. Day lengths are shorter as a result.

2

Axial tilt

Earth’s axis points in the same direction. As the year goes by, different parts of Earth end up facing the Sun. 3 March and September In spring and autumn, the axis is lined up parallel to the Sun. The length of a day evens out.

4 June

The Northern Hemisphere receives direct sunlight and the days are longer, raising the temperature.