# Eratosthenes

276BCE

194BCE

Eratosthenes was a Greek mathematician who lived during the 3rd century BC. He was not only a mathematician but also an astronomer, geographer, and poet. One of his most famous contributions to mathematics is the Sieve of Eratosthenes, a method for finding all prime numbers up to a given limit. This concept involves systematically eliminating multiples of each prime number starting from 2, which ultimately reveals the prime numbers within the specified range.

Aside from his work on prime numbers, Eratosthenes is also known for his accurate calculation of the Earth's circumference.

Eratosthenes measured Earth?s circumference around 240 BC by comparing shadows. In Syene (modern Aswan), a well had no shadow at noon on the summer solstice, indicating the Sun was directly overhead. In Alexandria, 800 km north, a vertical stick cast a shadow, showing the Sun?s rays hit at an angle of about 7.2 degrees.

He reasoned that this angle corresponded to the arc between Alexandria and Syene, which is 1/50th of a circle (7.2 degrees is 1/50th of 360 degrees). Thus, the Earth?s circumference is 50 times the distance between the two cities, approximately 40,000 km.

cmglee, David Monniaux, jimht at shaw dot ca, CC BY-SA 4.0, via Wikimedia Commons

For students studying mathematics, learning about Eratosthenes can provide insights into the world of prime numbers and demonstrate the practical applications of mathematics in fields such as geography and astronomy. His contributions showcase the importance of critical thinking, problem-solving, and mathematical reasoning in exploring the mysteries of the universe.

Appreciate the work of Eratosthenes by trying some of the maths that this mathematician is known for.

There is an activity called Sieve of Eratosthenes that you could try right now. A self checking, interactive version of the Sieve of Eratosthenes method of finding prime numbers.

So there's no better time than the present to learn some mathematics from the past: let's Go!

Transum has many activities for the topic 'Angles' and recommends you try some of them.

Don't put off till tomorrow what you can do today: let's Go!

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