Understanding of the Earth: Shape, Size, Age, and Structure of the Earth’s Layers

Understanding Earth – Compared to other planets in the Milky Way Galaxy, Earth is the only planet that has life on it. In addition, the planet, which is nicknamed the “blue” planet, is included in the group of minor planets (terrestrial planets) – which are relatively small in size and mass – along with Mercury, Venus and Mars.

When compared to the vast universe, Earth is just an object too small to be seen. So small, the Earth looks like a single point that is very easy to lose sight of.

Even so, Earth has a uniqueness that does not exist on other planets. For example, on this planet there is water in three forms namely solid, liquid and gas. As a result, the planet we live in has oceans and polar ice.

It doesn’t stop there, on Earth there is also a continuous hydrological cycle such as rain, and the Earth’s surface will continue to change and experience rejuvenation all the time.

There are lots of interesting facts that are owned by our planet, Earth. Starting from the shape, size, age, rotation, revolution, to the various kinds of creatures that live in it. And in this article, Sinaumeds will find interesting facts that you might not know. Therefore, don’t skip anything , OK?

Earth’s Shape, Size, and Age

Earth shape

Since studying Geography at school, Sinaumeds must have known that the Earth is a planet with a spherical shape. And if measured more accurately, the shape is not perfectly round, but slightly oval like a chicken egg.

There is a lot of evidence that confirms this. For example, photographs taken from artificial satellites in outer space; time difference; the phenomenon of a ship sailing in one direction will return to its original place; and the fact that Sinaumeds would see the flag of the ship before his body when standing on the beach.

As stated in the book Earth and the Solar System written by Danang. This book discusses the solar system and the ins and outs of planet earth.

The shape of the earth which is like a chicken egg is also called a Geoid. Even more interesting, no other planet in the universe looks exactly like Earth. Sinaumeds also would not be able to equate the shape of the earth with any geometric shape.

Before arriving at the conclusion that the Earth is a Geoid, ancient humans had other theories that came from their imagination and observational abilities. The ancient Egyptians, for example, believed that the sky was a giant woman they called the goddess Nut.

This goddess Nut stretched out her arms and legs to the four corners of the world until they completely covered the earth. Then every morning, Nut would give birth to the sun and then be eaten again at night. Continue like that every day.

Meanwhile, the mainland is described as a god of the earth named Geb. The ancient Egyptians described geb as a man lying under the sky Nut.

It is different from the Babylonian civilization which divided the universe into three layers, namely the sky, the earth with a flat shape, then the water.

Slightly forward to 340 years BC, Aristotle is believed to be the first person to mention that the earth is round. This assumption is then supported by several facts resulting from his own observations.

After making observations, Aristotle realized that a lunar eclipse (full moon) was caused by the position of the Earth which is located between the Moon and the Sun. He also said the Moon’s shadow on the Earth’s surface always looks round. This fact can only happen if the Earth is spherical. If it were flat, the moon’s shadow should look oval except when it is above the crown.

So through this evidence, Aristotle then conveyed the idea that the earth is actually round. This idea was also agreed upon by philosophers after Aristotle, such as Euclid, Archimedes, Eratosthenes, and Aristarchus.

Earth Size

As humans who spend time on the surface of the Earth, we never see this planet as a whole. The view of the human eye has its own limit which is often referred to as the horizon.

Fortunately, humans managed to create a technology that allows us to see the entire planet Earth. The technology is called satellite. With the help of satellites, it was finally discovered that the circumference of the earth is 40,075 km. Very broad, right?

So, did Sinaumeds know that around 2,000 years ago there were humans who managed to measure the circumference of the earth with a simple stick? He is Eratosthenes, an ancient Greek mathematician who is also known as the father of Geography.

On a hot day, on June 21, 240 BC, Eratosthenes was in Siena–now Aswan. In this city he saw a well and realized that at the bottom of the well no shadow was formed at all.

Then he straightened a stick to make sure there was something strange in the city. After the stick was straightened, apparently no shadow was produced. At the same time, this oddity does not occur in the city of Alexandria–a city in Egypt which is about 843 km from Aswan.

In Alexandria, sticks standing upright cast shadows as they always did. Eratosthenes then questioned this, how could there be a shadow on a stick erected in Alexandria, while in the city of Aswan there was none?

Armed with high curiosity, he did not waste this opportunity to measure the circumference of planet Earth. From the results of his measurements, Eratosthenes found the size of the earth to be 46,250 km.

When compared with the results of the modern measurements mentioned earlier, the results of Eratosthenes’ measurements were only 15% off. In other words, the results of calculations using curiosity and a stick are not much different from those produced by satellite technology. Moreover, he did it 2,000 years ago, when science was not very developed.

Thanks to the experiments he did, Eratosthenes recorded his name as the first person to successfully measure the circumference of the earth.

Earth Age

The total population of the Earth is now almost touching the figure of 8 billion people. Of these, perhaps only a handful do not have a birth certificate – the official document that records the first day a person lives.

Through the deed, we can know how long we have lived. Unfortunately there is no certificate that records the age of this blue planet. Fortunately, scientists never stop looking for answers to the question “how old is the earth?”.

Over the last 400 years, thousands of scientists have attempted various ways to predict the age of the Earth. Some use changes in sea level, sea salinity (saltiness), or the time it takes for the Earth/Sun to display temperature.

Unfortunately, all of these methods are still unreliable. This is because there are many other things that might affect the calculation results. For example, the issue of sea level, which fluctuates and falls, or something else.

After that, scientists try to estimate the age of the Earth by examining the rocks on the Earth’s surface. However, plate tectonics has never stopped changing the Earth’s crust, so it is certain that the rocks present in the planet’s early days have been lost.

The oldest rock ever found on Earth is near the Great Slave Lake, northwestern Canada, called Acasta Gneiss. Its age is estimated at 4.03 billion years. In addition, there are many more rocks with ages > 3.5 billion years on all continents, including:

  • The Isua Supracrustal Rocks in Greenland are 3.7 billion – 3.8 billion years old
  • Rocks in Swaziland that are estimated to be 3.4 – 3.5 billion years old
  • Rock in Western Australia with an age of 3.4 billion to 3.6 billion years.
  • The zirconium crystals found by a group of researchers in Australia are about 4.3 billion years old.

Maybe for you, all these discoveries are enough to answer questions about the age of planet Earth. But not for scientists. They have not given up and are trying to take advantage of more sophisticated technology in this 20th century.

Scientists are using the technology to improve radiometric dating processes and work out the age of rocks. They examined some of the elements present in a rock. Then calculate the initial number of radioactive elements and how long it will take for the elements to decay.

Now, from these latest methods, scientists then believe that the current age of the Earth is around 4.54 billion years!

Earth’s Rotation and Revolution

Earth Rotation

Maybe Sinaumeds once asked why there should be day and night? What makes day and night exist? Or why during the day there is sun, but it disappears when night comes? The answer to these three questions is only one, namely because the earth rotates on its axis or the earth’s rotation.

To complete one rotation / rotation, our planet takes approximately 23 hours 56 minutes 4 seconds or what we usually call one day. Interestingly, no human can feel its rotation directly. How did it happen?

Because there is earth’s gravity which is in charge of pulling all objects on the surface towards the center of gravity of the earth. So Sinaumeds could not feel the earth’s rotation. Even so, we can still see the impact of the earth’s rotation directly, including:

Impact of Earth’s Rotation

There is day and night. Because the earth rotates, one side automatically faces the sun and the other does not. This is what causes day and night.
The apparent daily movement of the sun or the movement of the sun from east to west. If you pay attention, it seems that the sun circles the earth every day, when in fact it is the earth that moves from west to east. While the sun remained silent in its place.

There is a time difference. There are currently 24 time differences on planet Earth, this number is obtained by dividing the longitude every 15°. Therefore, the center of time is Greenwich City which is at 0° longitude or known as Greenwich Mean Time (GMT). In Indonesia itself there are 3 divisions of time, firstly West Indonesia Time (WIB), then Central Indonesia Time (WITA), and East Indonesia Time (WIT).

Deflection of wind direction or Coriolis effect. Because the earth rotates on its axis, the winds that should move from the poles to the equator turn. To the north of the earth, the winds turn right and to the south of the earth, to the left.

Earth Revolution

Simply put, the earth’s revolution is the process of the earth’s rotation around the sun for approximately 365 ¼ days or 1 year. Every planet in the Milky Way Galaxy also revolves around the sun, really.

Uniquely, all planets have their own elliptical plane (path around the sun) due to the sun’s gravitational force. So between one planet and another planet will not collide.

The Influence of the Earth’s Revolution

  1. The apparent annual motion of the sun. Every December 22 to June 21, the northern hemisphere will be more inclined towards the sun. Meanwhile, from June 21 to December 22, the southern hemisphere is more inclined towards the sun.
  2. The difference between the length of day and night. You may have felt the sun setting a little longer than usual. For example, at 18:05 the sun, the sky still looks bright, even though it is usually getting dark. This phenomenon occurs because of the earth’s revolution. Usually in December, the southern part of the earth experiences longer heat. Vice versa.
  3. There are seasonal differences. Because the south is more inclined to the sun in December, this part is experiencing summer. And in the north actually experience winter. Conversely, in June, the north will experience summer and the south will experience winter.

It turns out that the rotation and revolution of the earth are mentioned by Allah SWT in the Al-Qur’an Surah Luqman verse 29 which means:

“Have you not seen that Allah causes the night to enter into the day and causes the day to enter into the night and He causes the sun and the moon to subside, each running for an appointed time. Indeed, Allah is All-Seer of what you do.” Luqman 31:29 ).

In addition, there are many other verses that explain about this planet where we live. If Sinaumeds wants to know more deeply, please read the book Earth and Space Sciences: Science and Al-Qur’an Studies written by Wiji Aziiz Hari Mukti, M.Pd. Si.

Structure of the Earth’s Layers

Earth, as the only planet that can be inhabited by living things, apparently has 4 layers, like the layers of onion skin. One of the benefits of these layers is to protect all living things on the surface from the high temperatures that exist in the earth’s core. The following is a brief explanation of the four layers:


The earth’s crust is the outermost layer of the earth which is thinner in size than the other layers. This section is divided into two categories, namely oceanic crust (oceans) and continental crust (land).

Even though it is called thin, the thickness of the earth’s crust actually reaches tens of kilometers, you know! Oceanic (oceanic) crust is 6 to 11 kilometers thick, while continental (land) crust is about 30 to 70 kilometers thick.

To learn more about the oceans and land, you can read it in the book Geomorphology by I Gede Sugiyanta.


Earth’s Blanket (Mantle)

The earth’s blanket is the layer that wraps around the earth’s core and is the thickest layer with a thickness of about 2,900 kilometers. Like the Earth’s crust, the mantle is also divided into two categories, namely the outer mantle and the inner mantle.

The outer mantle is from 10 to 300 kilometers thick below the Earth’s surface. The temperature in this layer ranges from 1,400° to 3,000° Kelvin. As a result of this high temperature, the metals in it harden.

Furthermore, in the second or inner mantle, the thickness reaches 300 to 2,890 kilometers with a temperature of around 3,000° Kelvin. In this layer, the existing metals have started to melt.

Earth’s Core

This earth is a liquid layer that has a thickness of about 2,266 kilometers and is located at a depth of 2,900 kilometers from the bottom of the earth’s crust to the center of the earth. The core of the earth is divided into two, namely the outer core and inner core.

The outer core is a layer with temperatures ranging from 4,300° Kelvin at the outermost and 5,000° Kelvin at the closest to the inner core. Thanks to this unusually high temperature, this layer is virtually in the form of a fluid with a low viscosity.

Meanwhile, the inner core is the deepest layer of the earth with a solid spherical shape and has a radius of about 1,220 kilometers. The inner core layer is the hottest layer with temperatures reaching 5,500° Kelvin.

Thus the review of the Earth that we need to know. Sinaumeds can get recommended Earth-related books at sinaumedia.com. Sinaumedia always provides the best products so that Sinaumeds has #MoreWithReading information.