Question

What is the reason for the seasons? Explain fully why different hemispheres experience opposite temperatures at some times of the year and similar temperatures at others. Identify the months when these events occur.

Answer 1

First of all, we must know that the rotational axis of earth is not purely vertical. It is tilted from the vertical by an angle of around 23.5 degrees. This is the main reason why we have different seasons in different region of earth ( namely, Northern and southern hemispheres)

Most of the people think that we get seasons because earth is rounding the sun and when it is far away from sun, it's winter on earth and when it is closer to sun, it is summer. However, this is totally wrong and can be proved wrong by the fact that on 4th of July, earth is at its farthest point from sun and we all know how hot it is in July in northern hemisphere.

Therefore, earth's inclination is the principal reason of different seasons.

Here is a diagram

In the figure above,

In June, the Northern Hemisphere faces the Sun, and North experience summer and have longer days. In December, the Southern Hemisphere faces the Sun and is illuminated more directly and north is cold. In spring and autumn ( march 21 and september 21) , the two hemispheres receive more equal shares of sunlight.