WHY ARE THERE SEASONS?

HELLO PEOPLE!

Spring,
Summer,
Autumn,
Winter!

Which is your favorite season?

In today’s lesson, we discussed on the topic “Why are there seasons?”. We read through the notes Miss Lin gave to us and tried to understand it by discussion it in our little groups. The groups than sent a representative to share on what they have discussed on. However, during the first round of sharing, the explanations were rather superficial they touch briefly on the tilt of axis and the revolution of Earth around the sun. However, the explanations had no direct link to why seasons existed.

In my opinion, I feel that the main reason why such superficial answers were given was due to the fact that we were unable to visualize this system actually works. We managed to do a better job when Miss Lin gave us a second chance to relook into our explanations.

First we must know that the Earth spins on a tilted axis (23.5˚ from the plane of orbit of the Earth) about once every 24 hours. Without this tilt, no matter how the Earth revolves around the sun, there will be no seasons as every point of the earth will not experience any change of intensity of sunlight. All seasonal changes are driven by changes in the amount of the Sun's energy. This is one of the most important reasons for seasons.

In addition to the earth rotating around its axis, the Earth completes one revolution around the sun about once every 364 1/4 days. The diagram above illustrates the various positions of the earth around the sun. The darker part of the globe represents the part of the earth that does not receive sunlight while the brighter part of the globe represents the part of the earth that receives sunlight at that period of time. The red line on the globe represents the equator. This equator will divide the earth into halves, North and South Hemispheres.

Why is the equator the hottest?
Although every part of Earth which is facing the sun receives the same amount of light rays, the rays at the poles are spread out over a larger surface area compared to equators. Therefore, the intensity of light rays is greater at the equator. Refer to Figure 1.

Figure 1.



At 1, December 21-22, the southern hemisphere experience the longest day as it has the maximum tilt towards the sun. This means that it will receive a great amount of insolation and it will be warmer. On the other hand, the northern hemisphere experience the shortest day as it has the maximum tilt away from the sun. This means that it will receive a small amount Hence the North Hemisphere will experience winter while the South Hemisphere will experience summer.

At 2, March 21-22, the hours of day and night gradually become the same. Therefore, this means that the temperature is generally the same in the two hemispheres. Due to the fact the number of hours spent during the day in the South Hemisphere is shorter compared to that of the season prior to it, the temperature will drop. On the other hand, the North hemisphere generally becomes warmer. Hence, the North hemisphere will experience spring while the South hemisphere will experience autumn.

Okay, so here’s the main gist of the lesson. : )
Jia you for assessment week! XD
<3 Melissa-Raye Teo