# How to Find the Radius of the Earth?

## The Radius of the Earth

If we talk about the earth then we can say that Earth is the nearly spherical ball and the only known planet of the solar system on which life exists. In addition, Earth is not completely round and it’s in the shape of an orange. In this topic, we are going to discuss the various things that help us to find the radius of the earth.

### What is Earth?

The Earth is the third planet of our solar system and galaxy known as Milky Way. Furthermore, it is the only known planet where life exists. Also, the earth provides a protective environment for living things. So, they can exist in this suitable environment.

Besides, the distance between the sun and the earth is also a factor that supports life on earth.

### What is the Radius of the Earth?

Radius refers to a line that connects to the centre point of a circle to any point on its outside layer. In simple words, radius refers to that line, which originates from any point of the circle and touches the centre point the circle.

Most noteworthy, if we double the radius (the diameter of the circle) then it divides the circle into two equal halves. Also, the diameter is the maximum distance between the two points of the circle.

### What Does the Earth Look Like?

If we talk about the appearance of the earth from the outer space then we see a blue planet with white whirls and areas of yellow, green, brown, and white.

In addition, the blue area is water (oceans and seas), the white whirls are clouds and yellow, brown, and green are landforms.

Besides, the white area is the snow caps or north and south poles (Antarctica and Arctic). Also, the equator is the imaginary line that divides the earth into two equal halves.

Furthermore, the southern half of the planet is Southern Hemisphere and the north half is the Northern Hemisphere. Most noteworthy, the north most point is the North Pole and the southernmost point is the South Pole.

### How to Find the Radius of the Earth?

During the 3 century, B.C. Eratosthenes was able to mathematically calculate the diameter of the earth by comparing the difference in the angle of the sun’s rays at different geographic points. He was the first person that was able to calculate the radius of the earth.

In addition, he was able to determine the circumference of the earth because he knew the distance between the two locations (Syene {present day Aswan, Egypt} and Alexandria). Furthermore, with the circumference, he drives the diameter and radius.

For measuring the radius of the earth compute the circumference of the earth. Do this by taking the example of Eratosthenes and find the distance and angle between two locations.

Since the distance between the two locations can be an arc measurement of the 360-degree circle. The arc in the Eratosthenes case was of 7.2 degrees and the distance between the two locations is 787 kilometre.

So, for him the following relationship between objects will apply: 7.2 / 360 = 787 / x.

Here x is the circumference of the earth. On solving the circumference of the earth we get 39,350 kilometres.

So the radius of the earth will be

Circumference = 2πr
39,350 = 2 × 3.14 × r
r = 39350/ 6.28 = 6267 kilometer.

### Solved Question for You

Question. Which of the following is not required to find the radius of the earth?

A. The distance of two location
B. Pie (π)
C. Circumference

Answer. The correct answer is option A. Because the distance between two locations relates to the circumference of the circle.

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