What Causes the Seasons

As you have seen, the Earth is tilted and direct light
causes more heat than indirect light. Remembering your walk around the chair,
and how the tilt is at each point, can you work it out?

This is how it works. When the Northern hemisphere is
pointing at the sun, sunlight falls most directly on it. This is summer in the
Northern Hemisphere. As you get around to the side of the chair, neither
hemisphere is pointing toward the Sun. The light strikes both equally and
directly. However, as the orbit is elliptical, the Earth is further from the Sun
at this point so although the light is still direct, it is cooler, because of
the distance.

As the Earth moves around to the other side of the Sun
the Northern Hemisphere is tilted away from the Sun. Now the light falls
indirectly on it. It is winter. As it moves around to the fourth side, it the
light again falls directly on it, but it is further away, so it is warmer than
winter but cooler than summer.

Notice that the exact opposite is happening in the
Southern hemisphere. When the Northern Hemisphere has summer, the Southern
Hemisphere has winter, and the other way round. So, how do you decide which has
spring and which has fall? That is simple. Spring follows winter and fall
follows summer!



Earth’s Tilt

The effects of Direct and indirect Sunlight

Earth’s Orbit