What exactly is the shape of our earth: Circle, Round, Spherical, Geoid ?
What exactly is the shape of our earth: Circle, Round, Spherical, Geoid? This question in Geography has always created confusion. I remember, when I was in class II, my teachers taught me that the shape of our earth is round like a ball. After saying this, she draws a circle on the board. When I was in class V, a new teacher taught that the shape of earth is round like an orange. It is flat from top and bottom. But the globe which was in her hands was neither flat from the top nor from the bottom.
In senior classes
In class IX, a very senior teacher explained, that the shape of earth is not round like a ball but,, it is spherical. He was also holding a globe in his hands. By seeing the shape of it, I could not understand the difference between the shape of a ball and shape of globe. So, what is the actual shape?
What exactly is the shape of our earth?
Is it like a circle?
It can not be like a circle because a circle is defined as a two dimensional figure formed by a set of all those points which are equidistant from a fixed point in the same plane.
The fixed point is termed as the center of a circle.
So, we can say that circles are simply closed curves that are equidistant from a fixed center.
Moreover, the fixed point has to be of equal distance from all other points.
Some examples of circles in real life are cycle tires, wheels, camera lenses, steering wheels, buttons etc.
As the distance of poles and equator are not equal from the center of the earth, therefore it can not be a circle.
Is the shape of our earth round?
If the shape is not like a circle then can we call it to be round?
Circle is just a geometrical shape like square, triangle, rectangle etc.
There is no shape called “round”.
It is a noun that refers specifically to the shape.
For example “the ants are moving in a circle.”
Whereas, round is an adjective to describe something which is either circular (2D) or may be spherical (3D).
We can say a ring or a bangle is round.
At the same time we can also say that a football or a globe is round.
But, the earth’s shape is neither like a bangle nor like a football.
Therefore, we can conclude that the shape of our earth is not round.
Is it spherical in shape?
Something spherical is like a sphere in being round or more or less round.
So, sphere means which is more or less round from all sides.
For example both a basket ball and an apple are spherical even though they are never perfectly round.
Our earth is also not perfectly round from all sides, so if we call it spherical in shape, there is nothing wrong in it.
But, the two depressions formed at the poles and bulging at equator gives our earth a unique shape.
However, the earth’s shape seems like a sphere, although it is not perfectly spherical.
Therefore, even sphere is not the correct word for the earth’s shape.
Is the shape of our earth now Geoid?
It is very difficult to answer the question about earth’s shape.
There are several answers given by different scientists.
A Geoid is the irregular shaped “ball” that scientists use to calculate the depths of earthquakes.
It’s a new term used to describe the earth’s shape.
To some extent, Geoid shape is appropriate to use for the shape of our earth if not perfect.
Earth has huge mountains and deep oceans over it.
So, when we calculate distance from the center of the earth, at places there are deviations by 30 to 40 km.
Therefore, Geoid shape may be close to determine the shape of our earth but even this is not accepted by many.
Is it Oblate Spheroid?
What is oblate spheroid?
If you sit on a football, it get pressed from top and bottom and becomes bulgy at the center.
This type of shape is said to be oblate spheroid or oblate elliptical.
This shape is considered to be very close to the shape of the earth.
So, if someone asks you the exact shape of our earth, you may answer that it is Oblate spheroid or Oblate elliptical.
Have the teachers taught us the wrong shape ?
The answer is no.
Even today, teachers continue to teach in the same manner.
It is because, a student of class II can easily understand what is round by looking at the shape of a ball.
Similarly, when a child reaches in class V, his mental level increases and is able to imagine.
Therefore, when a teacher says that the shape of our earth is round like an orange, the child is in a position to understand.
In class IX, a child is able to understand and differentiate between between 2D and 3D shapes.
At this stage the teacher explains “that the shape of our earth is not round like a ball but,, it is spherical”.
After class IX, a child is no more dependent on the teacher (will google) to know about the shape of the earth.
Why do you think that the earth is suppressed from the top and bulgy at the equator?
One can easily understand this with an easy experiment.
Go to the bathroom.
Take a bucket half filled with water.
Now, dip your hands in “Water” and rotate it.
What do you see?
You will see that a depression is created at the center and the water expands sideways.
Exactly this is what happens in case of earth.
You see a depression at top and bottom, and bulgy at the center due to Centrifugal force .
Why It happens?
Our earth has a solid outer cover called the Crust.
Inside our earth things are still in liquid form.
So, when the earth rotates, the liquid present in the earth also rotates just like the water in a bucket.
This rotation of liquid creates a depression (like an orange) which can be seen at the poles बरमुडा त्रिकोण – .
As the water in the bucket expands sideways, similarly the liquid inside the earth also expands sideways making the earth bulgy near the equator.
Exact shape of our earth can not be defined.
There is no shape which resembles the actual shape of earth.
Inside our earth, things are not static which continuously creates disturbance inside and outside our earth.
Moreover, Volcanic eruptions, massive earthquakes, Tsunami , Tectonic Plate movement etc. keep on affecting the shape.
Therefore, the shape of our earth keeps on changing.
The latest shape of our earth described and acceptable is oblate spheroid or Oblate elliptical.