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Thursday, July 09, 2020

A science teacher explains: Is the earth actually round in shape?

Many would argue that given its ever-changing topography due to natural and man-made factors the earth is flawed and cannot be considered as round.

Published: May 30, 2020 5:38:40 pm
parenting, shape of earth The earth has tried to lose its equatorial bulge. (Source: Getty Image)

By Rachna Arora

Is Mount Chimborazo in Ecuador the highest point on earth? Or is it Mount Everest? When compared at sea level, Mt Everest takes the top spot, but measured from the centre of the earth, Chimborazo would be about 2.13 km taller than Mt Everest. Yes, it is all relative!

Extending the above hypothesis, we can say that the earth is perfect though flawed. What we know is that earth is not round as a ball, but it bulges at the equator and is slimmer at the poles, making its shape an oblate spheroid. Yes, the father of Mechanics, Sir Isaac Newton with his unmatched understanding of forces was unsurprisingly the first to put forth the postulate attributing the equatorial bulge to rotation of the earth.

Next time you apply the Pythagoras theorem to simplify a numerical question, do pay a mental obeisance to him for his pioneering concept of establishing that earth is round and not flat, as most thought and thereby feared falling off the edge if they ventured too far.

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“The earth together with its surrounding waters must in fact have such a shape as its shadow reveals, for it eclipses the moon with the arc of a perfect circle,” said Nicholas Copernicus.

Whether it was by simple observations like visibility of different set of stars in the night sky depending on one’s location (pole star cannot be seen from the southern hemisphere) or nearly accurate measurement of the circumference of the earth by Eratosthenes (armed only with a stick and a brilliant mind), the ancient thinkers and observers without doubt established the spherical shape of the earth. The photographic proof arrived only after the launch of the artificial satellites in the mid-20th century.

To set doubts to rest, do observe the sunset from the base of Burj Khalifa. Then take the elevator to the top floor and you will see the sun set twice in a single day! This would not have been possible if the earth is not spherical.

Many would argue that given its ever-changing topography due to natural and man-made factors the earth is flawed and cannot be considered as round.

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The highest and lowest points from the sea level (Mount Everest and Challenger Deep in the Mariana Trench) have a difference of 19.8 km only which is insignificant as compared to dimensions of the earth. As rightly said, if the earth was scaled down to the size of a billiard ball, despite its surface imperfections, earth would be twice as smooth as the ball. No wonder it is lovingly called the Blue marble when viewed from space.

The earth has tried to lose its equatorial bulge. The difference of 21 km in the equatorial and polar radius is ever shrinking, since the poles have been rebounding after having lost the extra weight of ice from the Ice Age. However, this lasted until mid-1990 till this trend stopped. This might be the fallout of polar ice caps meltdown thereby draining the melted ice to the equator and thus putting the bulge back.

Mankind surely has come a long way from believing the earth is flat and supported by turtles, to venturing into, and understanding about the nooks and crannies of our planet but many challenges in the form of climate change and pandemics remain at large, which can be surmounted by the choices of our generation making earth a perfect abode for mankind.

(The writer is PGT- Physics at Shiv Nadar School, Noida.)

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