Eratosthenes: A Great scientist and Astronomer

Eratosthenes, born in 276 BC in the town of Cyrene, was a very well-known Greek Scientist in his time. He was also an Astronomer, Geographer, Mathematician, and Poet. He was famous because it was considered that he was the first one to determine the circumference of the Earth. This theory of his was known as Eratosthenes Circumference of the Earth. The Eratosthenes Theory revolves around various facts such as determining the circumference of the earth and the sieve of Eratosthenes. Now, let’s learn more about the early life of Eratosthenes.

Education and Early life

Eratosthenes had gone to Athens for his further studies. He had earlier learned various skills such as reading, writing, arithmetic, and poetry since Cyrene was a cultural and learning hub during that time. Eratosthenes was taught Stoicism by none other than its founder, Zeno of Citium. He had also studied under the head of the Platonic Academy, which was Arcesilaus of Pitane. 

Eratosthenes wrote many poems, one of them was called Hermes, illustrating the life of the god, and the other called Erigone, describing the suicide of an Athenian woman named Erigone. The Pharaoh Ptolemy III made Eratosthenes a librarian in the Library of Alexandria, where he spent the rest of his life. He became a Chief librarian within five years and during his time at the library, he gave out various theories.  

Eratosthenes Circumference of the Earth

As Chief librarian in the library of Alexandria, He learned many fascinating things and one of them was understanding the Circumference of Earth. Eratosthenes had started to observe that during midday, walls in Cyrene cast no shadows since the sun was directly overhead whereas in Alexandria he could see small shadows on the walls.

Eratosthenes reasoned this study in his theory, The Eratosthenes theory, which states that:

• The shape of Earth was that of a sphere
• The Sun’s rays were termed to be parallel to one another when they reached the earth’s surface
• He measured the different angles of the shadow in Alexandria to No shadow in Cyrene, to find out the actual distance between Alexandria and Cyrene and learn how big Earth is. This was one of Eratosthenes’ methods

Eratosthenes, using the techniques of simple geometry, found that the distance from Cyrene to Alexandria was approximately one-fiftieth of the total distance around the planet. His maps said the distance between Alexandria to Cyrene was 5000 stades. Eratosthenes multiplied this figure by fifty , which resulted in 250,000 stades, He added 2,000 for correction and gave the theory that:

The Earth’s Circumference was equal to the distance of 252,000 stades at that time.

Eratosthenes’ Sieve

The Sieve of Eratosthenes helped in locating Prime Numbers. A prime number signified a number that cannot be reached by combining smaller numbers. The Greeks did not identify 1 as a prime number so the number 2 was considered the first prime number in the numeric system. The sieve of Eratosthenes was one of Eratosthenes’ methods which differentiated and separated a prime number from a composite number.

Beginning with the first prime number, which was number 2, The products of the composite numbers were received in a particular sequence until what was left were prime numbers in the “ sieve” or the number system. This innovation helped in making mathematical calculations much easier than before.

Eratosthenes’ Facts

There are certain unknown facts once ss related to Eratosthenes, which are as follows:

• Eratosthenes once saw the heavens seem to rotate once around the earth. Earth’s axis formed an imaginary line from the North pole and south pole to the center of the earth
• He was considered the first person to produce the first map in the world with the help of meridian lines, which were somewhat similar to the modern era latitudes and longitudes

• Eratosthenes’ theory was so prominent during those times that it led to the invention of the armillary sphere, which resulted in the most important instrument in the field of Astronomy for 1800 years and more to ascertain the positions of celestial objects

• Eratosthenes was the one who coined the term “ Geography” as we know it. This word came out of  “ Geo”, which meant earth in Greek and “ graphy”, which meant field of study in Greek

Eratosthenes died in 194 BC leaving behind a rich source of facts and theories, termed Eratosthenes’ theory and methods which were classified as Eratosthenes’ methods.

Conclusion

In this blog, we have learned about the early life and education of Eratosthenes, His theories on the circumference of the earth, known as Eratosthenes theory, his sieve, which was one of Eratosthenes’ methods, and various facts related to him. Still, some doubts may remain in the reader’s mind. To solve them, here is a dedicated FAQ section to help you clear all concepts related to Eratosthenes.