Thursday, February 1, 2018

Earth's Tilt - The Reason For Change In The Seasons

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Summer-Fall(Autumn)-Winter-Spring-all-seasons
Summer, Fall (Autumn), Winter, Spring
Credit: Woot Shirts
Nearly every living being (whether human or lion or bacteria or ant) is aware of the fact that What Season Is? In fact, even if we just talk about humans only, a human being can divide one year up to four seasons such that: Summer, Fall (Autumn), Winter, Spring. Well, we can divide years in so many different ways. Like in my country ( I AM FROM INDIA ); according to Hindu Calender, a year is divided into six seasons or (Ritu) such that each season has a fixed 2-month time span of the 12-Month Hindu Calendar.

According to the Hindu Calendar, the six seasons or Ritu are Vasanta (spring), Greeshma (summer), Varsha (monsoon), Sharad (spring), Hemanta (early winter), and Shishira (prevernal or late winter).


What Is The Reason For Change In the Seasons?

In a modern world, everyone is quite aware of the scientific fact that earth revolves around the sun in an elliptical model or Heliocentric Model according to the Kepler's Laws Of Planetary Motion. So as a result, one might logically assume that our planet's changing distance from the sun (when the earth is close to the sun its summer, or when the earth is far away from the sun its winter) is the reason for change in the seasons; but sadly it is not correct explanation for the reason for the change in the seasons. Though it has some effects on different seasons on earth but not the effective or sole reason for the justification for the reason for the seasons.

Earth's Tilt Is The Reason For Change In The Season !!

Earth's-Obliquity
Earth's axial tilt (obliquity) is currently about 23.4°
Credit: Wikimedia Commons

The reason for the season is Earth's Tilt (Earth's axis of rotation) relative to its orbital plane while traveling in a loop (elliptical) around the sun every year. The angle of Earth's Tilt is approximately 23.4 degrees. In astronomical world, Earth's Tilt is also known as "Obliquity". The hemisphere (northern or southern) which is tilted toward the sun experiences summer and the hemisphere which is tilted away from the sun experiences winter; ( which we will talk in the later section). 


What Is The Reason For Earth's Axial Tilt?

The correct reason behind the Earth's Tilt is still a puzzle to solve. There are so many controversial or hypothetical theories related to the Earth's Axial Tilt, but none of them is satisfactory. One theory suggests that; during the early age of our solar system when our planet earth (during its young age) collided with some early heavenly body which later became the moon of our planet Earth. And as a result of that collision, there is an axial tilt on earth of 23.4 degrees.

On the other hand, some scientists suggest that planet earth may have tilted itself to gain its ecological balance. One mindful person can regard that both of the above theories are just theoretical and even may be hypothetical because when that happened we were not there. All we can do is argue!!


Who Discovered the Earth's Tilt?

The Earth's Axial Tilt or Obliquity is surprisingly known for a very long time. According to the historical scientific writings; if we go back to the scientific timeline, the earth's tilt had been logically calculated in Ancient India and China around 1100 BC. Later in 1437, Ulugh Beg of Samarkand, Uzbekistan who was Astronomer, a mathematician as well as the Sultan confirmed the earth's Obliquity as 23°30′17″ (23.5047°).

Later in the modern world or western world, the first accurate calculation of earth's tilt was calculated by a Danish Astronomer and a nobleman Tycho Brahe in the late 1500s. And by using his calculations, observations and written works; Johannes Kepler developed his set of planetary law which in today's world is known as Kepler's Laws Of Planetary Motion.


How Season Changes Due To Earth's Tilt To Different Hemisphere

Earth's-Tilt -The-Reason-For-Change-In-The-Seasons
Illumination of Earth at each change of astronomical season
Credit: Wikimedia Commons

It is a world-recognized fact that is if divide our sphere (planet earth) what we get is two hemispheres that are commonly known as The Northern Hemisphere and The Southern Hemisphere. As we discussed in the earlier section that, the hemisphere which is tilted toward the sun during a specific period of time experiences summer and longer days; and the hemisphere which is tilted away from the sun experiences winter and shorter days. Due to the cyclic rotation of the earth around the sun, the hemisphere tilted toward or away from the changes simultaneously.


Likewise, when the northern hemisphere is tilted toward the sun, it experiences the warm weather, summer as well as the longer day (daylight); while on the other hand at the same time southern hemisphere is experiencing the cold weather, winter as well as the shorter day and vice versa. During may, June and July, Northern Hemisphere experience summer; and during November, December and January,  Southern Hemisphere experience summer.

So from above observation, we can conclude that due to the Earth's Tilt, "northern hemisphere's summer solstice = southern hemisphere's winter solstice". In simple words, when there is summer in the northern hemisphere, at the same time there is winter in the southern hemisphere or vice-versa.

As far as equator is concerned; there is no change in the season because each day sunlight strikes the equator at the same angle. In simple words; every day of the year, equator receives 12 hours of sunlight. 

ON that note, I can say that I have tried to give an overview of Earth's Tilt - The Reason For Change In The Seasons within my reach. If there is any suggestion, I am all ears. Feel free to comment.
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 Don’t Believe It As I Said Till You Yourself Believe It First – Gautama Buddha
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