Why Do We Have Seasons

The year people finally bought the theory that the Earth revolves around the Sun and not vice-versa, which I believe was suggested by Nicolaus Copernicus sometime in the 16th Century, probably first sowed the seeds of the question.

Or at least the answer to the question. The answer is very simple: the Earth moves around the Sun alright, but its axis is tilted.

Why Do We Have Different Seasons on Earth

A tilted axis? Now we all know that the Earth rotates around its own axis and at the same time, revolves around the Sun. But unlike what most people may have pictured, the axis around which the Earth spins around isn't exactly vertical. The axis on the north pole remains tilted at an angle which is estimated to be around 23.5 degrees more than a perpendicular, and stays that way through the revolution path. So along the Earth's revolutionary path around the Sun, the northern hemisphere is closer to the Sun for sometime, and then when it completes half the revolution, the southern hemisphere comes closer to the Sun. So basically, the Earth's axis remains tilted in the same direction all through the revolution which causes the changes in seasons.

The catch here is that because of the tilted axis, the two hemispheres never have the same season at the same time. When one hemisphere has a particular season, the other hemisphere has a different season altogether. So now to study the different seasons, let us see the position of the Earth and the different seasons which the northern and southern hemispheres experience during different months of the year.

December - February
In these months, due to the tilted axis of the Earth, the southern hemisphere is closer to the Sun, while the northern hemisphere is farther from the Sun. Hence understandably, the southern hemisphere will be warmer. So the southern hemisphere will have the warm summer months during this period, while the northern hemisphere will have winter.

March - May
This is the first set of transitional, where the northern hemisphere starts coming closer to the Sun, and the southern hemisphere starts drifting away from the Sun. So it is like the warming up period in the northern hemisphere, which gets successively warmer, causing spring in countries in that hemisphere. The southern hemisphere on the other hand starts cooling down, causing autumn in countries in that hemisphere.

June - August
In the months between June to August the northern hemisphere starts coming closer to the Sun, with the axis at the north pole pointing towards it. The southern hemisphere on the other hand moves further away from the Sun, hence these months see the northern hemisphere having summers while the southern hemisphere countries having winter.

September - November
This is the second set of transitional months, where the northern hemisphere starts moving further away from the Sun while the southern hemisphere starts coming closer to the Sun. The countries in the northern hemisphere start cooling down, while the countries in the southern hemisphere start warming up. Hence during these months, the northern hemisphere experiences autumn, while the southern hemisphere countries see spring.

Being from the northern hemisphere, the first thing that came to my mind was whether the Santa Claus in Australia comes in beach wear! Because according to this explanation, it must be HOT in December in Australia!