# What is the contributions of Eratosthenes?

## What is the contributions of Eratosthenes?

He invented the armillary sphere, a model of objects in the sky, in 255 BC. Additionally, he calculated the circumference of the Earth by incorporating the data of angle of elevation of the Sun at noon. Inclusion of Egypt in calculation of the circumference of the Earth was also his preference.

How did Eratosthenes measure the circumference of the Earth? He used geometry and ratios to determine the size of the Earth, by basing his calculations on observations of the sun.

Eratosthenes was the founder of scientific chronology; he endeavoured to revise the dates of the chief literary and political events from the conquest of Troy. Eratosthenes dated The Sack of Troy to 1183 BC. In number theory, he introduced the sieve of Eratosthenes, an efficient method of identifying prime numbers.

Eratosthenes also worked on prime numbers. He is remembered for his prime number sieve, the ‘Sieve of Eratosthenes’ which, in modified form, is still an important tool in number theory research. The sieve appears in the Introduction to arithmetic by Nicomedes .

The discipline of mathematics is not complete without Eratosthenes magnificent contribution to it. He was a close acquaintance of Archimedes and they often exchanged notes on several cross-disciplinary areas of math. He invented the armillary sphere, a model of objects in the sky, in 255 BC.

Eratosthenes will always be remembered for the calculation of the Earth’s circumference circa 240 BC, using trigonometry and knowledge of the angle of elevation of the Sun at noon in Alexandria and Syene (now Aswan, Egypt).

Archimedes, (born c. 287 bce, Syracuse, Sicily [Italy]—died 212/211 bce, Syracuse), the most famous mathematician and inventor in ancient Greece. Archimedes is especially important for his discovery of the relation between the surface and volume of a sphere and its circumscribing cylinder.

Eratosthenes then measured the angle of a shadow cast by a stick at noon on the summer solstice in Alexandria, and found it made an angle of about 7.2 degrees, or about 1/50 of a complete circle. He realized that if he knew the distance from Alexandria to Syene, he could easily calculate the circumference of Earth.

Several astronomers and mathematicians before and after Eratosthenes tried to accurately measure the circumference of the Earth, but is was Eratosthenes that came through. He found the circumference of the Earth to be nearly 250,000 stadia (25,000 miles). Eratosthenes also contributed to geographic source of the river.

Quick Guide – Eratosthenes’ Greatest Achievements Eratosthenes produced a reliable, logical method to discover prime numbers: The Sieve of Eratosthenes. In an updated form, this is still important in modern number theory. In about 240 BC Eratosthenes calculated Earth’s size with good accuracy.

How did Eratosthenes contribute to geology?

Eratosthenes made major contributions to geography. He sketched, quite accurately, the route of the Nile to Khartoum, showing the two Ethiopian tributaries. He also suggested that lakes were the source of the river.